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The Offshore Marine Environment of , Atlantic: Scientific Review and Assessment

Report to the RSPB by -Scope Marine Environmental Consultants

October 2015

Front cover: Blue Prionace glauca. This open is one of the shark species to be caught as by the commercial longline fishery targeting species in the mid-Atlantic. [Image: https://upload.wikimedia.org/wikipedia/commons/e/ea/Prionace_glauca_1.jpg].

The Offshore Marine Environment of Ascension Island, South Atlantic:

Scientific Review and Conservation Status Assessment

Author: Robert Irving

Principle Consultant Sea-Scope Marine Environmental Consultants

www.sea-scope.co.uk

This report should be cited as: Irving, R.A. 2015. The offshore marine environment of Ascension Island, South Atlantic: scientific review and conservation status assessment. Report to the Royal Society for the Protection of (RSPB) by Sea-Scope Marine Environmental Consultants. 115 pp. The Offshore Marine Environment of Ascension Island, South Atlantic

Contents

Executive summary ...... iii 1. Introduction ...... 1 1.1 Ascension Island - geographical context ...... 1 1.2 Ascension’s nearshore marine biodiversity ...... 2 1.3 Island governance and history ...... 3 1.4 Proposals for a ...... 4 1.5. The scope of this report ...... 5 2. Collation of scientific knowledge ...... 7 2.1 An overview of the geophysical and oceanographic context ...... 7 2.2 Commercial species ...... 11 2.3 Non-commercial fish species...... 16 2.4 and rays ...... 23 2.5 Cetaceans ...... 29 2.6 ...... 32 2.7 ...... 36 2.8 Marine molluscs and other invertebrates ...... 40 2.9 ...... 43 2.10 Deep-sea and pelagic biodiversity ...... 49 2.11 Oceanic microflora / microfauna ...... 53 3. Conservation needs and threat assessment ...... 54 3.1 The sustainability of high fisheries ...... 54 3.2 Offshore impacts on species also found inshore ...... 57 3.3 Conservation needs of the wider pelagic environment of the ...... 59 4. Conclusions ...... 61 4.1 Sources, quality and extent of information ...... 61 4.2 The marine biodiversity importance of Ascension’s offshore waters ...... 61 4.3 The main threats to maintaining and enhancing the offshore marine biodiversity .... 62 4.4 What would a no-take MPA protect and secure? ...... 62 4.5 What are the main data gaps to fill? ...... 63 5. References ...... 64 6. Bibliography ...... 72 Appendix: Species of ‘game ’ and ‘deep water fishes’

i The Offshore Marine Environment of Ascension Island, South Atlantic

ii The Offshore Marine Environment of Ascension Island, South Atlantic

Executive summary

 The waters surrounding Ascension Island, extending to the 200 nautical mile (370 km) limit of the (EEZ) (an area of 445,390 km2), are currently being proposed (by the RSPB and others) as a large-scale Marine Protected Area, where no extractive activities (particularly ) would be permitted. However, the proposal includes a recreational and sport fishing zone extending from 0 – 12 nautical miles (22 km) around the island (forming an area of approximately 2,400 km2), where local fishing activity would be permitted. If implemented as proposed, the outer, fully protected ‘Ocean Sanctuary’ would cover approximately 443,000 km2 of ocean surrounding the island.  Relatively little is known about the marine life which inhabits the surface waters, the mid-depths and the ocean floor of this vast area, on account of the paucity of research which has been conducted around Ascension over the years. Most research has been undertaken on key species of conservation concern such as turtles and seabirds. Information on commercial fish species is poor, largely reliant on data from catch landings as well as on-board observers on fishing vessels. Considerably more is known about the inshore area than further offshore, particularly following a recent Initiative project which has been investigating shallow water biodiversity (Brickle et al., 2013). Overall, levels of scientific knowledge are similar to the amount of information available for the UK Overseas of the .  The Ascension Island EEZ is on the southern edge of the main fishing grounds for . This is the primary target species of a commercial longline fishery, mainly undertaken by Taiwanese and Japanese vessels. , , blue and sailfish (as well as other species) are also taken, though in smaller quantities. Recent stock assessments for the ICCAT region (that is, the whole of the , the Mediterranean Sea, the Black Sea and the Baltic Sea) indicate that catches of bigeye tuna and swordfish are considered sustainable1 (within the fishery as a whole), and probably those of yellowfin tuna too (Reeves & Laptikhovsky, 2014). However, it is apparent that regional stocks of blue marlin and sailfish are currently being over-fished (Reeves & Laptikhovsky, 2014). Specific stock assessments of Ascension tuna and billfish populations have not been carried out.

 The greatest cause of conservation concern relating to the fishery is the number of sharks that are being caught as bycatch, particularly the whose conservation status is near- threatened. Incidental catch rates of seabirds, turtles and cetaceans are considered to be ‘very low’, but still take place. From research published in 2009, based on observations made on board Taiwanese tuna longline vessels whose area of operation included Ascension’s waters between 2002 to 2006, 35% of the total tuna catch consisted of bycatch fish species, most notably blue sharks (52%), other shark species (11%) and other fish species (37%). For the period from 2011 to 2013, the bycatch of blue sharks caught from the Ascension ‘area’ (larger than just the EEZ) amounted to an average of 463 tonnes/year.

 Ascension is the largest nesting site for endangered turtles in the South Atlantic. Every 3-4 years, these turtles leave their feeding grounds off the coast of to travel to Ascension to breed, a distance of 2300 km. Numbers of nests on the island’s sandy beaches have been steadily increasing since a ban on commercial harvesting was introduced 70 years ago, together with legal protection. Since monitoring of nest sites began in 1977, the average number of green clutches deposited annually has increased six-fold, from 3,700 to 23,700 (Weber et al., 2014). At

1 Note that the term ‘sustainable’ is used here in a commercial fishery sense only, whereas current populations of these species are likely to have declined considerably from their naturally occurring, pre-commercial fishing population sizes.

iii The Offshore Marine Environment of Ascension Island, South Atlantic

the end of the nesting season, adults migrate back to Brazil. With effective protection and monitoring in place at Ascension, the main threat to these turtles is now considered to be from fishing gear closer to the Brazilian coast.  Ascension Island is one of the world’s most important tropical breeding sites and the most important in the tropical Atlantic. In addition to the island’s own endemic species of , there are 10 other seabird species which breed around the island’s fringes, numbering in excess of 400,000 individuals2, with many concentrated on the offshore stack of Boatswainbird Island. Several of these species, fitted with tracking devices, have been found to forage over hundreds of kilometers of ocean. The endemic Ascension frigatebird, whose conservation status is Vulnerable, spends much of its time at sea, with individuals being found to venture as far as the coast of West .  A total of 5 species of cetacean have been recorded from within Ascension Island’s EEZ. This is probably an underestimate of the true figure, as most sightings have come from the island’s nearshore waters where there is greater boat/ship traffic and more opportunity to make sightings. A small group of humpback visit the island each year around September/October and though they have young with them, it is unclear whether they use the island’s waters as a calving and breeding area. It is postulated that they would have migrated from the cool waters of the Falklands or even the Antarctic.  12 species of shark have been recorded from within the EEZ, together with giant and the smaller devil ray. Of the shark species, the scalloped hammerhead is regarded worldwide as being endangered. In parts of the Atlantic Ocean, scalloped hammerhead populations have declined by over 95% in the past 30 years on account of it being targeted by commercial fishing operators for its highly prized fins. Galapagos sharks are the most frequently encountered shark species in the island’s nearshore waters and they are occasionally taken by local sports fishing vessels. Populations of this shark at other sites within its range have come under pressure from targeted fishing, bycatch by commercial longline operators and the species’ slow reproductive rate. News of their total (believed to have been a result of overfishing - see Luiz & Edwards, 2011) from St Paul’s Rocks, a small archipelago of barren islets lying to the north-west of Ascension on the Mid-Atlantic Ridge, where they were once very numerous, makes for a salient lesson in the management of these apex predators in the waters surrounding remote, offshore islands and seamounts.

 Within the extent of the EEZ are three distinct seamounts which rise to between 316 m and 70 m of the surface. These undersea mountains can provide great insights into patterns of marine biodiversity. They may vary greatly in their biodiversity, can have a high degree of endemism, may be centers of speciation, and may act as "stepping stones" for the dispersal of coastal species. The three within the Ascension Island EEZ have been little studied, although recent video footage by National Geographic from a deep-water ROV deployed on the Grattan (approximately 250 km to the south-east of Ascension) has confirmed the presence of a number of fish species which were thought endemic to Ascension and/or St Helena.  Very little information exists on the EEZ’s deep sea (i.e. marine life living on the below 100 m depth) which is largely unstudied and a major gap in knowledge. A total of just 26 species of ‘deep water fishes’ are listed as occurring at Ascension.  Several of Ascension’s seabird species rely, indirectly, on the presence and behaviour of tuna (and other large fish species) in to catch their prey (Au & Pitman, 1988). Tuna species, particularly

2 Note, however, that once the island’s seabird populations were considerably larger than present day populations, with declines probably being caused by human and cat (now both stopped), and, more arguably, by the diminution of prey availability caused by the depletion of large fish (tuna and billfish, in particular) by the fishing industry.

iv The Offshore Marine Environment of Ascension Island, South Atlantic

yellowfin Thunnus albacares, in pursuance of their own prey, tend to drive smaller to the surface. In the case of flyingfish, they are likely to glide above the surface of the sea during these chases in order to escape being caught by the tuna. Flyingfish form the principal diet of both and , which they obtain near or above the sea surface (Oppel et al., 2015). Sooty terns are also reliant upon large schools of surface-swimming tuna to drive their prey within reach (Au & Pitman, 1988). Thus, in order to maintain healthy populations of these seabirds, there is heavy reliance on the presence of tuna schools within their foraging ranges.

 At present, there are no large-scale, benthic or pelagic reference areas (i.e. areas where extractive human activities have been banned, allowing the enclosed ecosystems to function entirely naturally) anywhere in the tropical Atlantic. The UK has led the way in promoting such scientific reference areas further south in the Atlantic at South Orkney in 2009 and along the length of the Antarctic peninsula in 2012. The creation of a MPA at Ascension would provide such a reference area, a major sanctuary of global significance in an ocean where a considerable number of apex predators such as tuna, billfish and sharks are removed by commercial fishing operators.

v The Offshore Marine Environment of Ascension Island, South Atlantic

Abbreviations & explanations of terms used in the text

AIG Ascension Island Government bathy-pelagic The , part of the that extends from a depth of 1000 m to 4000 m below the ocean surface. It lies between the meso-pelagic above, and the abysso-pelagic below. CITES Convention on International Trade in of Wild Fauna and Flora CMS Convention on the Conservation of Migratory Species of Wild EEZ Exclusive Economic Zone (formerly Exclusive Fisheries Zone, EFZ). Extends out to 200 nm (370 km) from the island’s coastline. ICCAT International Commission for the Conservation of Atlantic Tuna, the Regional Fisheries Management Organisation responsible for the conservation and management of tuna and tuna-like species in the Atlantic. IUCN International Union for the Conservation of Nature IUU Illegal, Unreported and Unregulated fishing longline A of fishing gear in which individual baited hooks on short branch lines are attached to long main lines. They can be fished at or near the surface, as is the case in the Atlantic tuna fishery, or on the sea bottom. meso-pelagic Also known as the twilight zone, the meso-pelagic is that part of the pelagic zone that extends from a depth of 200 to 1000 metres below the ocean surface. MPA Marine Protected Area pelagic Living in the , i.e. away from the bottom, and frequently near the surface. ROV Remote Operated Vehicle RSPB Royal Society for the Protection of Birds, a UK charitable Non-Governmental Organisation (NGO) seamount An underwater mountain rising from the ocean seafloor that does not reach to the water's surface (sea level), and thus is not an island. Seamounts are typically formed from volcanic activity. UK of Great Britain and UNCLOS United Nations Convention on the Law of the Sea

vi The Offshore Marine Environment of Ascension Island, South Atlantic

1. Introduction

At 7° 57′ S, 14° 22′ W, Ascension Island lies almost midway between the continents of and Africa in the South Atlantic Ocean. The nearest land to Ascension is the similarly diminutive island of St Helena which lies some 1100 km to the south east (Fig. 1). Ascension, therefore, has the peculiar distinction of being one of the most remote islands in the world. It is part of the United Kingdom Overseas Territory of St Helena, Ascension and . The island of Ascension exists as the visible pinnacle of a massive submarine volcano which erupted from the Mid-Atlantic Ridge some one and a half million years ago. It now lies approximately 145 km to the west of the Ridge, 1500 km from the coast of to the north east, and 2300 km from the coast of Brazil which lies due west. Much of the island’s surface is still pock-marked by volcanic peaks, craters and vast flows of unvegetated , solidified into extremely hard rock formations. Although there have been no eruptions since the island was permanently inhabited in 1815, physical textures suggest that the most recent deposits erupted less than 500 years ago (Faneros & Arnold, 2003).

Fig. 1. Map showing the location of Ascension Island in the South Atlantic Ocean. The 200 nm EEZ is shown in red.

1.1 Ascension Island - geographical context

The island is almost triangular in outline, being 14 km across from east to west and 11.2 km from north to south. Its land area of 97 km2 is entirely volcanic in origin, with much of it, particularly to the north and the east, remaining as bare rock outcrops with massive lava flows and ash cones (Figs. 2 & 3). The highest point of the island is the peak of Green Mountain which stands at 859 m above sea level. The coastline varies from dramatic 200 m high cliffs at the south-east corner, to gently shelving sandy bays along the west coast, separated by a multitude of small knobbly headlands and rock outcrops.

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Fig. 2. Satellite view of Ascension Island. Fig. 3. Map of Ascension. Note the presence of Satellite Image (c) Space Imaging. Boatswainbird Island, the larger of the two ‘stacks’ close to the eastern promontory.

1.2 Ascension’s nearshore marine biodiversity

Ascension’s marine life is poorly studied. Much more information is known about the shallow sublittoral zone around the island than is known about the deeper, offshore waters. Scuba surveys have documented the dominant sublittoral substrata to be of volcanic rock and sand (AIG, 2014). Underwater rock formations consist of bedrock reefs, vertical cliffs and steep boulder slopes, as well as a variety of caves, canyons and lava tubes. There are also gently shelving areas of coarse sand and maerl cobbles, particularly on the western side of the island, though their inherent instability means they support a depauperate, albeit distinctive, and plant community (AIG, 2014).

Unlike most tropical islands, Ascension has no coral reefs. Instead, the nearshore marine life is characterised by an abundance of fish, a largely cryptic and nocturnal invertebrate fauna, and a striking scarcity of erect, benthic macroalgae (Irving, 2013). Rock surfaces are frequently covered by encrusting and erect calcareous red (Lithothamnia sp.). These appear to be the only forms of seaweed which can survive the attention of the large numbers of grazing fish and sea urchins (Irving, 1989). Over 100 species of seaweed have been recorded from the shallow sublittoral (Price & John, 1980; Tsiamis et al., 2014) but these, together with a variety of sessile invertebrates, are often hidden away in crevices inaccessible to grazing organisms. Although abundant, fish diversity is low when compared to other tropical Atlantic islands. A total of 133 ‘coastal’ fish species have been recorded in Ascension waters, representing a unique assemblage of western, eastern and amphi-Atlantic species (Wirtz et al., 2014). The fish fauna is dominated by very large numbers of the black triggerfish Melichthys niger. Large pelagic fish such as yellowfin tuna Thunnus albacares, rainbow runner Elagatis bipinnulata and galapagensis also venture into the shallow sublittoral zone to feed on inshore species such as Melichthys niger (AIG, 2014).

There is a UK Darwin Initiative project currently underway entitled the Ascension Island Marine Sustainability (AIMS) project. The project aims to increase Ascension Island’s marine biodiversity knowledge and fisheries science capacity substantially, informing the development of the Biodiversity Action Plan for marine taxa, and providing the science base needed for sustainably managed inshore

Page 2 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic and offshore fisheries (AIG website, 2015). The project is being carried out with primary partners at SAERI (the South Atlantic Environment Research Institute based in the Falklands), and with input from RSPB (Royal Society for the Protection of Birds), BAS (British Antarctic Survey) and SMSG (Shallow Marine Survey Group). This project follows another Darwin-funded project in 2012 which assessed the nearshore marine biodiversity and initiated inventories of invertebrates, the fish fauna and algae (http://www.smsg-falklands.org/blog/2012/06/15/marine-biodiversity-survey-of-ascension-island). Water temperature in the shallow sublittoral is relatively warm and stable, ranging between approximately 22-24 ° C in September/October and 28-29 ° C in March/April (AIG Conservation, unpublished data). Tidal range is small (0.8m) and average wave height does not exceed 2m. Few areas could be regarded as even moderately sheltered, although wave and current action is strongest along southern and eastern shores exposed to the prevailing south-easterly trade winds. The trade winds and westward flowing surface currents have a pervasive effect on the oceanography of the shallow sublittoral zone, with a clear east-west gradient in temperature and salinity (AIG, 2014).

1.3 Island governance and history

The three island UK Overseas Territories of Ascension, St Helena and Tristan da Cuhna are overseen by a Governor (based in St Helena), although Ascension has its own island-based Administrator. Officially there are no permanent residents living on the island: all personnel are ‘temporary’ (although depending on their contracts they may in practice remain on the island for many years) and are either employed or are spouses or partners of employees. The main employers on the island are the Ascension Island Government (AIG), the (RAF), the Air Force (USAF) (responsible for building the island’s airstrip during WWII), the British Broadcasting Corporation (BBC) and the Composite Signals Organisation (CSO), amongst others. An elected Island Council advises the Governor on laws, policies and the government’s annual budget. The UK Government remains responsible for Ascension Island’s external relations, defence and internal security. Since April 2002 the island’s revenue has derived from locally raised taxes, import duties, the sale of philatelic stamps and (from October 2010 to December 2013) the sale of fishing licences. The island was discovered by the Portuguese ‘empire builder’ Afonse du Alberquerque in 1503 on Ascension Day. Being dry and barren it was of little use to the East Indies fleets. So it remained uninhabited until Emperor I was incarcerated on St Helena in 1815 when a small British naval garrison was stationed on Ascension to deny it to the French. The island was designated “HMS Ascension”, a “Stone sloop of War of the smaller class” (http://www.ascension-island.gov.ac/the- island/history). By Napoleon’s death in 1821 Ascension had become a victualling station and sanatorium for ships engaged in the suppression of the slave trade around the West African coast. In 1823 the island was taken over by the . It remained under the supervision of the British Board of Admiralty until 1922, when it was made a Dependency of St Helena. AIG’s Conservation Department is responsible for the management of the island’s waters, extending to the limit of the EEZ. Despite the UK Government having certain on-island responsibilities, the island’s waters are not included within the geographical remit of the European Union’s Common Fisheries Policy. The island, similar to other UK Overseas Territories, has its own distinct fisheries management regime (Appleby, 2015). The Wildlife Protection Ordinance was recently updated in October 2013 “to protect and preserve the wildlife and of Ascension” (AIG website, 2015), and covers marine species and too. The Ordinance confirms that Fishing Limits extend to the limit of the island’s (i.e. 200 nm or 370 km); that Prohibited Areas and/or Closed Seasons may be established to protect particular species; and that there is a list of named species (“wildlife products”) which are protected by the Ordinance (see Table 1 below).

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Table 1. Schedule of “wildlife products” as listed in the Wildlife Protection Ordinance, 2013.

Reptiles Green turtle Chelonia mydas Bottlenose dolphin Tursiops truncatus Hawksbill turtle Eretmochelys imbricata Fish Birds shark Rhincodon typus Ascension Island frigate Fregata aquila Manta rays Manta spp. Masked Sula dactylatra Ascension scorpionfish Scorpaena ascensionis Sula leucogaster Resplendent angelfish Centropyge resplendens Red- footed booby Sula sula Ascension hawkfish Amblycirrhitus earnshawi (aka Wideawake Onychoprion fuscatus Lubbock’s gregory (aka Stegastes lubbocki tern) Yellowtail damselfish) Fairy tern (aka ) Gygis alba St Helena Thalassoma sanctaehelenae Anous minutus Ascension wrasse Thalassoma ascensionis Anous stolidus Ascension goby Priolepis ascensionis Red- billed tropic bird Phaethon aethereus St Helena butterflyfish Chaetodon sanctaehelenae Yellow- billed tropic bird Phaethon lepturus Bicolour butterflyfish Prognathodes dichrous (aka hedgehog butterflyfish) Storm petrels Oceanodroma spp. St Helena sharpnose Canthigaster pufferfish sanctaehelenae Marmalade razorfish Xyrichtys blanchard

Various highly migratory species which occur within the island’s EEZ, such as Atlantic sailfish, albacore and yellowfin tuna, are included within Annex I of the 1982 United Nations Convention on the Law of the Sea (UNCLOS). St Helena and its Dependencies (via the UK) are signatories to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the Convention on the Conservation of Migratory Species of Wild Animals (CMS). Much of Ascension Island, as well as Boatswainbird Island (a seabird-dominated rock off the main island’s east coast – see Fig. 3), are currently designated as Important Bird Areas by Birdlife International. The island’s own National Protected Areas Regulations 2014 provide for the establishment of protected areas, the protection of named species within these areas, and the restriction of all forms of development within these areas. The regulations also prohibit access to without a permit.

1.4 Proposals for a Marine Protected Area

The RSPB has been working to establish a large Marine Protected Area (MPA)3 around Ascension Island, extending out to the limit of the EEZ, since 2013. Declaration of such an MPA would be by the Governor. In their manifesto commitments for the general election in May 2015, the UK Conservative Party (who subsequently won the election) stated that “we will designate a further marine protected area at Ascension Island, subject to the views of the local community”. In 2010, the UK Government declared a very large MPA around the Chagos archipelago in the (another UK Overseas Territory) (Sheppard et al., 2012), and has recently declared its intention to establish an MPA around the Pitcairn Islands in the South Pacific (Dawson, 2015), covering an area of 835,000 km2.

3 The term ‘Marine Protected Area’ can be interpreted in various ways. In the context used here, essentially, it would mean the prohibition of extractive activities within 12 nm to 200 nm of the island.

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The RSPB (2014) believes that the creation of a large scale, fully protected no-take MPA extending from 12 nm to 200 nm offshore (the extent of Ascension’s Exclusive Economic Zone) – an area of over 443,000km2 - represents “the best opportunity to protect the biodiversity of Ascension’s waters and contribute to the conservation of the pelagic ecosystem of the tropical Atlantic”. Sport fishing activities would be permitted to continue within an inner area (approximately 2,400 km2), extending from the coast to 12 nm offshore. The RSPB list a number of reasons to support their proposal for a MPA around Ascension (J. Hall, pers. comm.):  It is one of the most important tropical seabird islands in the world, where RSPB removed feral cats over ten years ago.  RSPB has been working in partnership with the Ascension Conservation Department ever since, and were extremely concerned by the poorly managed Taiwanese long-lining fishery which was opened in Ascension’s waters in 2010.  RSPB believe that marine protection builds upon their historic seabird conservation agenda and offers the best future opportunity for Ascension’s community and marine environment.  Ascension lies in productive waters and so has a high biodiversity value marine environment worthy of protection, not just for seabirds and the megafauna which remains (such as very large blue marlin), but also to enable the recovery of species such as sharks, which are widely reported on-island to have been greatly reduced or to have disappeared almost entirely.  Finally, Ascension represents one of the only places in the tropical Atlantic where ecosystem-scale protection is possible, due to the paucity of EEZs in this region. The island currently has no specific marine protected areas, although approximately 0.45 km2 of sandy, sublittoral habitat adjacent to major nesting beaches are included in Nature Reserves designated under the National Protected Areas Order 2014 and National Protected Areas Regulations 2014. These are primarily intended to protect the mating and inter-nesting habitat of the internationally important green turtle population, with restrictions on development and access by certain types of water craft (AIG, 2015a).

1.5. The scope of this report

1.5.1 The purpose of the study

This report has been commissioned by the RSPB with the following purpose:

To complete a scientific review and conservation status assessment of the offshore marine environment (12 nm – 200 nm) around the UK Overseas Territory of Ascension Island in order to inform scientifically rigorous conservation management. To collate all known scientific information about the offshore marine environment into one report, highlighting species richness, known population trends, and existing or potential future threats. Given the limited data available, it is envisaged that information and inferences will need to be drawn from research conducted within both Ascension’s nearshore environment and the regional high seas, or other best available evidence and proxies as appropriate. It will use this information to evaluate the conservation needs of Ascension’s marine environment.

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1.5.2 Methodology used

The study has been purely desk-based with no visit to the island. However, e-mail communication with members of staff of the AIG Conservation Department (Dr Nicola Weber and Dr Judith Brown) has been most informative and helpful. The author has had access to their database of scientific literature relating to the island’s marine environment, which has proved a most useful starting point. Further reference material has come from the RSPB’s own digital ‘Ascension library’. In addition to these sources, specific papers have been tracked down via the internet. The author visited Ascension 30 years ago as a member of a 5-week long diving expedition to the island.

A comprehensive bibliography of scientific papers relevant to the offshore environment has been compiled, which is included as Section 6 to this report.

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2. Collation of scientific knowledge

For the purposes of this review, information has been gathered from a variety of sources, most particularly scientific papers and reliable internet sites. When used, these sources have been acknowledged in the text and listed under References (section 4). There is also a much larger Bibliography (section 5), which includes all references which have been sourced for possible use for this review. These have been arranged by subject.

2.1 An overview of the geophysical and oceanographic context

2.1.1 Geophysical context

Understanding the formation of the ocean floor The Atlantic Ocean is the Earth’s youngest ocean. It has been formed by the separation of the continents of the Americas and those of Africa and Eurasia. The Mid-Atlantic Ridge is located at the juncture of crustal plates that form the floor of the Atlantic Ocean. It is considered a "slow-spreading" ridge (the ridges in the Pacific are faster-spreading), at a rate estimated to be approximately 1-5 cm/yr. Running along the crest of the ridge is a long rift valley that is about 80 to 120 km wide. This contains the zone of seafloor spreading, in which molten magma from beneath the Earth’s crust continuously up, cools, and is progressively pushed away from the ridge’s flanks (Fig. 4).

Fig. 4. A topographic section of the Mid-Atlantic Ridge. The high flanks on both sides of the rift valley are shown in red. The highest areas are red and the lowest areas are blue. The rift valley is a linear low-lying area between the flanks of the ridge. A Fracture Zone, running at right-angles to the Ridge, is visible at the top of the image. The large features are covered with smaller-scale features that might be considered "texture". Image: Kenneth C. Macdonald & Paul J. Fox (UCSB).

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Although this seafloor spreading process occurs steadily over geologic time (tens or hundreds of thousands of years), on a day-to-day basis the formation of oceanic crust happens in fits and starts - small earthquakes occur as the plates break while pulling apart; some blocks of rocks are pushed up and some drop down; magma is squeezed through the fractures in the rocks and may extrude on the seafloor to form small volcanic cones; and time may pass with very little noticeable change in the landscape (http://earthguide.ucsd.edu/mar/intro2.html). The spreading centres themselves form broad central ridges that sink steadily with age and distance, starting at about 2,500 m water depth and sinking to typical open ocean depths of 4,000 meters. This unevenness of spreading and plate creation usually produces volcanic ridges and fault-bounded hills that may rise up several hundred metres above the surrounding seafloor.

A major 240 km offset of the rift valley is made by the Ascension Fracture Zone, some 50 km north-east of the actual island of Ascension (van Andel et al., 1973). It is possible to trace this Fracture Zone topographically from the Pernambuco in the west, across the Mid-Atlantic Ridge, and along most of the Guinea Ridge to the east, a total length of 4400 km (see Fig. 14 in section 2.9). The rift valley just south of the Ascension Fracture Zone reaches depths of 3600 m, remains uncut by offsets for at least 50 km and is bordered by several parallel ridges on either side (Faneros & Arnold, 2003). In geomorphological terms, the island is an intra-plate volcanic island and is located 90 km west of the Mid-Atlantic Ridge (Fig 5). However, the above sea portion of the island accounts for less than 1% of the volcano’s total volume (Nielson & Sibbett, 1996), with the 60 km basal diameter lying in 3,200 m depth of water. Seismic activity still continues near the Ascension volcano, being concentrated on the Mid-Atlantic Ridge and the Ascension Fracture Zone. Minor earthquakes occur nearly every other day though all are centered outside the Ascension volcano. A study by Hansen et al. (1996) recorded a range of earthquake magnitudes from 0.4 to 4.2. They were shallow events, with hypocentres ranging in depth from 500m to 2500m.

2.1.2 Oceanographic context

The Mid-Atlantic Ridge divides the Atlantic Ocean longitudinally into two halves. Its presence has a major influence on the circulation of near-bottom water masses (Tomczak and Godfrey, 1994). Deep Fracture Zones (such as the Ascension Fracture Zone) which run at right-angles to the Ridge, provide routes for bottom water to pass from one side of the ocean to the other (Levin & Gooday, 2003).

The main current which affects Ascension, for the most part, is the South Equatorial Current (Fig. 6). This flows close to the surface from east to west and, along the , may reach speeds in excess of 1 m/s. However, the island is also affected from time to time by the usually deeper-flowing (and colder) Atlantic Equatorial Undercurrent (also known as the Southern Equatorial Counter-Current), which flows from west to east. The interaction of these two currents can give rise to localised turbulence, gyres and eddies which combine with upwellings in nearshore waters caused by the seabed topography, giving rise to considerable mixing of the water types in the vicinity of Ascension (AIG, 2012). This mixing is responsible for the higher levels of productivity around the island than one might expect to see in otherwise typically oligotrophic waters.

Close to the ocean floor, the water is never still, because tidal forces move water at all ocean depths. As a result, the water bathing all sessile sea-bed organisms slowly changes, bringing food and removing wastes. These ocean floor currents are not uniform however, and their dynamics will change with the presence of localised features such as canyons, abyssal hills and seamounts.

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Fig. 5. 3D bathymetric views and a plan view (lower left), showing the distinctive nature of the Ascension volcano (marked ‘AI’) arising from the deep ocean floor surrounding it, and its relationship to the Mid-Atlantic Ridge (MAR). Taken from the Recommendations of the Commission on the Limits of the in regard to the Submission made by the United Kingdom of Great Britain and Northern Ireland in respect of Ascension Island on 9 May 2008.

Fig. 6. Generalized circulation map depicting the major currents in the Atlantic. NAG, North Atlantic Gyre; AEU, Atlantic Equatorial Undercurrent; SAG, South Atlantic Gyre; CAR, Current; GS,Gulf Stream; CC, Canary Current; GC, Guinea Current; NEC, North Equatorial Current; SEC, South Equatorial Current; BR, BrazilCurrent; BEN, Benguela Current. (After Muss et al., 2001).

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2.1.3 Ocean floor habitats

The deep Atlantic Ocean floor is covered by sediments deposited by volcanic processes, by turbidity currents and related gravity-driven processes, by bottom currents and by pelagic sedimentation (Emery & Uchupi, 1984). Sediments become progressively finer with increasing depth and distance from land, with deposition rates being higher in the central parts of the Atlantic. Over much (67%) of the Atlantic

Ocean, the surface sediments are carbonate oozes (CaCO3 content 30–50%) (as opposed to siliceous oozes, more prevalent closer to the polar regions), with a mean particle size of <100 mm; a sand-sized fraction consisting predominantly of planktonic foraminiferan tests; and an organic-carbon content generally <0.5% (Emery & Uchupi, 1984).

Sediment primarily accumulates in local depressions along the steep, rugged Mid-Atlantic Ridge terrain. Seafloor sediments thicken away from the Mid-Atlantic Ridge, with those near the Ascension volcano ranging from 250 m to 340 m thick. They continue to thicken to the west and, within the Ascension Fracture Zone, may accumulate to being as much as 530 m thick locally (Faneros & Arnold, 2003). At a more local level, the surface of the sedimentary ooze will display signs of animal life with features such as pits, burrows, mounds, tracks, fecal casts and resting traces. Many of these result from movement, burrowing, feeding, defecation or dwelling/construction by benthic invertebrates and fishes. Such traces of animal activity (or lebensspuren, as they are known) often provide the main evidence for the presence of large organisms on abyssal plains and elsewhere in the deep sea, and may be particularly useful for quantifying buried mega-infauna (i.e. large animals living within the sediments). These organisms, which are very difficult to sample using conventional methods, potentially play a major role in deep-sea community ecology and in the structuring of the deep-sea sedimentary environment (Faneros & Arnold, 2003).

2.1.4 Physical conditions on the ocean floor

Whilst the deep-sea floor is an extreme environment, it is also a physically stable environment. At depths below about 800 m, water temperature remains remarkably constant, at about 2°C on the abyssal plain. These cold temperatures reduce chemical reaction rates and have a bearing on the pace of life on the sea floor. Pressure increases by 1 atmosphere for every 10 m of depth. Pressure can affect deep sea organisms physiologically (high deep sea pressures oppose the secretion of gas) and biochemically (because the performance of proteins (e.g. enzymes) and (e.g. cell membranes) changes with pressure). Salinity at these depths is likely to be ‘normal’ for seawater, i.e. at about 35 parts per thousand. Dissolved oxygen is carried to the deep-sea floor by the descent of surface waters. The water overlying most of the deep-sea floor is saturated with oxygen or nearly so (5–6 ml/l) and so is not a limiting factor for the majority of organisms. Certain conditions though will reduce oxygen concentration to levels that are problematic for organisms (Thistle, 2003). One occurring within the Ascension EEZ is likely to be organic material (e.g., faecal pellets) falling from the euphotic zone, being decomposed by aerobic bacteria and then consumed by as it sinks. This will contribute to an oxygen sink in the mid-water zone. Where ocean floor currents are locally enhanced, eddies can develop and sediment resuspension is likely to occur. These episodic events, termed ‘abyssal storms’, can erode and re-deposit several centimeters of sediment within a short period.

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The following sections (2.2. to 2.8) set out what is known about the marine life which inhabits the offshore waters around Ascension Island – commercial fish species, non-commercial fish species, sharks and rays, cetaceans, turtles, seabirds, and molluscs and other invertebrates. Wherever possible, a description is given of the known range of a species, its population size worldwide (and whether this is increasing or decreasing), its conservation status and any threats it might face. Further information is then given, where known, with regard to its status within the Ascension Island EEZ.

2.2 Commercial fish species

The species of fish which occur within Ascension’s EEZ can be divided into two groups: migratory and resident. Resident species tend to be found in the shallower waters close inshore. Of a total fish fauna of 173 species, Wirtz et al. (2014) list 133 as being ‘coastal’ species. These species and recruit locally with populations rarely being supplemented by fish migrating from more remote stocks (Armstrong & Reeves, 2015). Migratory species, on the other hand, are likely to originate from spawning and recruitment beyond the 200 nm EEZ. Large pelagic species that are migratory and of commercial interest include various tuna (bigeye and yellowfin in particular) and billfish (particularly swordfish, though also sailfish and blue marlin). Other migratory species more likely to be caught by sports fishermen include , rainbow runner and dolphinfish.

Bigeye tuna is the main target species for commercial fishing fleets operating in the mid-Atlantic, utilising longlines. It would appear from data reported to the International Commission for the Conservation of Atlantic Tuna (ICCAT) on catch rates per area that the Ascension EEZ is on the southern and western edges of the main fishing grounds for bigeye tuna. Most fishing activity is towards the edge of the EEZ, particularly in the northern part, but there is marked seasonal and annual variation in this (Reeves & Laptikhovsky, 2014). The fishery in the Ascension EEZ is highly seasonal, with the highest catches over December-January and negligible catches over July-September (Reeves & Laptikhovsky, 2014). Table 2 lists ten species of fish which are known to be of commercial interest and which are known to occur within the Ascension EEZ. The following brief descriptions are given for those species of conservation concern (i.e. they are Endangered or Near Threatened) or which are mainly targeted by commercial fisheries.

Bigeye tuna Thunnus obesus Bigeye tuna can grow up to 2.5 m in length and weigh up to 180 kg. The species is distributed throughout the Atlantic Ocean between 50°N and 45°S. It tends to be found in greatest numbers where the water temperature is between 17° and 22°C (Froese & Pauly, 2015). Variation in occurrence is closely related to seasonal and climatic changes in surface temperature and . Bigeye tend to swim deeper than other tuna species and show substantial vertical movements in the water column (Reeves & Laptikhovsky, 2014), descending into deeper water at daybreak and returning to surface waters at dusk. The IUCN Red List status for Bigeye tuna is ‘Vulnerable’. This is largely due to the fact that there has been an estimated global decline of 42% of the stock over the 15 year period from 1992-2007 (Collette et al., 2011d).

This is the main target species for commercial fishing vessels using longlines within the Ascension EEZ, accounting for between 74-82% of the total catch. Ascension lies close to the southern and western edge of the main fishing areas, and only in the peak season of December to January does the Ascension area become relatively important. The reported 2012 catch from the Ascension EEZ was 1,543 tonnes, which amounts to 2.2% of the total catch from this stock in 2012 (Reeves & Laptikhovsky, 2014).

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Yellowfin tuna Thunnus albacares The yellowfin is one of the larger tuna species, reaching a maximum length of 2.2 m and a maximum weight of 180 kg. This species is found worldwide in tropical and subtropical seas. It is fast-growing, widely-distributed and highly productive. Within the Atlantic, tagging data show that trans-Atlantic migrations occur, and the yellowfin tuna from the entire Atlantic are considered to be part of a single stock (Collette et al., 2011b). The most recent assessment of this stock in the Atlantic was conducted in 2008 (ICCAT 2009). This paints a confusing picture: recent trends have differed between the western and eastern Atlantic, with the overall catches in the west declining by 26% since 2006. In the eastern Atlantic, on the other hand, catches have increased by 23% since 2006, mainly due to substantial increases in purse seine effort. The IUCN Red List status for yellowfin tuna is ‘Near Threatened’ (Collette et al., 2011b).

Longline catches of yellowfin tuna from the Ascension EEZ comprise only a small percentage of the total catch: the reported catch from the EEZ in 2012 was 65 tonnes which compares with a total catch of 101,866 tonnes (or 0.06%) (Reeves & Laptikhovsky, 2014). This species is also caught by angling boats from Ascension as part of the recreational fishery (Wirtz et al., 2014). Ascension’s sports fishing business managers report that yellowfin tuna catches were decreasing over time, but over the last two years they have increased rapidly over all size ranges, with more large fish being caught in particular. This pattern was noted by other boat operators and may be related to an overall increase in stock abundance in the South Atlantic (Armstrong & Reeves, 2015).

Albacore Thunnus alalunga Albacore is a relatively small temperate species of tuna. It grows to an average length of 1.4 m and a weight of 60 kg. The species is present in all , though it is not found close to the surface between 10 ° N and 10 ° S. This species can be confused with juvenile bigeye tuna, which also has very long pectoral fins, but with rounded tips. The IUCN Red List status for albacore has changed from ‘Near Threatened’ in 2011 to ‘Least Concern’ in 2015 (Collette et al., 2011c & 2015). This is despite an estimated 37% decline globally in spawning stock biomass across all stocks over the past 20 years (1987–2007). In 2010 the stock in the South Atlantic was considered to be in a “slightly overfished state”, but it is not currently being fished above maximum sustainable yields (Collette et al., 2011c). Ascension lies at the northern extent of the albacore’s range in the South Atlantic, so is well outside the main area for the albacore fishery. Catches within the EEZ were very low: during 2012 they amounted to just 0.12% of the total catch (Reeves & Laptikhovsky, 2014). Wirtz et al. (2014) comment that albacore are rarely caught by angling boats, typically during the winter when water temperatures are lower.

Atlantic bluefin tuna Thunnus thynnus

Bluefin tuna grow to an average length of 2.5 m and may weigh over 250 kg. The species’ distribution is restricted to the wider Atlantic region (including the Mediterranean Sea). Its population has undergone major declines since the 1960s due to high fishing pressure. Its range has shown larger contractions (minus 46% since 1960) than any other pelagic species (Collette et al., 2011a). The IUCN Red List status for Atlantic bluefin tuna is ‘Endangered’, the highest category for any fish species listed in this report. This is largely due to the

Page 12 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic most recent Red List assessment (undertaken in 2010) showing global declines in populations, most noticeable of 51% over the past 39 years of the Eastern Atlantic stock. The Western Atlantic stock has also shown severe declines in the past and has not yet recovered (Collette et al., 2011a). This species has been recorded from Ascension (Wirtz et al., 2014), though no information is provided on where, regarding distance from shore or depth of water. It is not targeted commercially (it is not listed as a commercially-fished species by Reeves & Laptikhovsky, 2014), although it is possible individuals may be taken as bycatch on longlines.

Swordfish Xiphias gladius

Swordfish may grow to over 3.0 m in length and weigh over 600 kg. The species is pandemic, being found in the Atlantic, Indian, and Pacific Oceans in tropical, temperate and sometimes cold waters. The Atlantic population comprises two stocks that are genetically distinct: South Atlantic and North Atlantic. The South Atlantic stock has been overfished in the past, but an assessment of stock levels in 2011 show levels to have stabilized (Collette, 2011e). Worldwide, their status is considered to be Least Concern. A total catch of 116.2 tonnes of swordfish was reported by vessels licensed to fish within the EEZ during 2012. This amounts to 1.14% of the estimated catch from the stock as estimated by ICCAT (Reeves & Laptikhovsky, 2014). Swordfish is a relatively recent new species to have been caught by sports anglers at Ascension (Wirtz et al., 2014). Nightime is the best time to catch swordfish.

Sailfish Istiophorus albicans Sailfish may grow to over 3.0 m in length and weigh up to 58 kg. Wirtz et al. (2014) list the Indo-Pacific sailfish Istiophorus platypterus as being a previously unrecorded species for the island. Some authors recognize Istiophorus platypterus (Shaw 1792) as a single worldwide species (as has been the case historically), while others now recognize the occurrence of another species of sailfish in the Atlantic, Istiophorus albicans, with I. platypterus just being present in the Indo-Pacific. In this report, the author has opted for the species name, I. albicans.

As sailfish favour coastal waters rather than the open oceans they are primarily caught by coastal artisanal and recreational fishing vessels, with vessels operating longlines further offshore taking them occasionally as bycatch. Evidence from tagging studies indicates that they move shorter distances than other billfish species (Reeves & Laptikhovsky, 2014). ICCAT note concerns about the quality of catch data for sailfish, with substantial problems with under- reporting of catches (Reeves & Laptikhovsky, 2014). This problem may also be apparent at Ascension, with virtually zero catches reported between 1999 and 2011, but then with catches thereafter, including a reported 21.3 tonnes in April 2013 (Reeves & Laptikhovsky, 2014). It appears as though Ascension lies on the south-western edge of the main distribution area for sailfish.

Blue marlin Makaira nigricans The , which can grow to 5.0 m in length and weigh as much as 650 kg, has a distribution restricted to the Atlantic Ocean. Interestingly, females may grow up to four times as large as males. It is considered to be one of Ascension’s iconic species and a sought-after catch for sport anglers. However, Armstrong & Reeves (2015) reported that the island’s sport fishing business managers noted that the annual number of blue marlin they have caught was around 120 when they

Page 13 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic started fishing in 2000, but in subsequent years has declined rapidly (112, 73, 34, 20 then 9 per year thereafter). The sport fishing managers considered that there were 10-year cycles in peaks in catches, though this has yet to be proven. In March 2013, a British angler visiting Ascension caught the fourth largest blue marlin specimen ever to have been caught in the Atlantic, weighing in at 600 kg and measuring 6 m in length – see photo on right. It would appear that Ascension lies on the south-western edge of the main distribution of this species. Commercial vessels licensed to fish within the Ascension EEZ during 2012 reported a total catch of 11.3 tonnes of blue marlin (Armstrong & Reeves, 2015).

Other marlin species The record-breaking blue marlin. Metro, 7th March 2013 Istiompax indica is one of the largest marlin species, growing to 4.5 m and weighing up to 750 kg. It occurs primarily in the tropical Pacific and Indian Oceans, though a few stray individuals are known to travel around the Cape of Good Hope into the Atlantic. Although a total catch of 12 tonnes of black marlin was reported from commercial vessels licensed to fish within the Ascension EEZ during 2012 (Armstrong & Reeves, 2015), there are no records of black marlin being caught in Ascension waters as yet (Wirtz et al., 2014). Atlantic white marlin Kajikia albida is caught from time to time around Ascension by recreational anglers (Wirtz et al., 2014). It is also occasionally caught by commercial vessels from the ICCAT area within which the Ascension EEZ lies, though because of difficulties with identification (it can be confused with another species of marlin known as the roundscale spearfish Tetrapturus georgii) total catch data and stock assessments are uncertain (Armstrong & Reeves, 2015).

Note also that blue shark Prionace glauca and shortfin mako (shark) Isurus oxyrinchus may also be targeted by certain fisheries interests (see Reeves & Laptikhovsky, 2014, p14).

A search of the on-line FishBase database (www..org), using the terms ‘Ascension Island’ and ‘pelagic’, returned ‘0’ results. However, there were returns for the search terms ‘game fish’ and ‘deep water fish’ (see Table 3, section 2.3). Further illustrative information on all open water ‘game fish’ species (as listed by FishBase) and all ‘deep sea’ fish species (as listed by FishBase) is provided in the Appendix at the back of this report. This has been included as readers of this report may be unaware of what many of these fishes look like and of their worldwide distributions.

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Table 2. Species of fishes known to be caught by commercial fishing vessels licensed to fish within the Ascension Island EEZ. (See also Table 13, p 54).

Species Common name IUCN Red Reference Notes Featured List in Appendix

Scombridae

Thunnus thynnus Atlantic bluefin tuna EN Wirtz et al., 2014 Very rarely caught at Ascension. Split into eastern (Europe, Mediterranean & NW Africa) & western (E coast of USA) stocks which can mix.

Thunnus albacares Yellowfin tuna NT Wirtz et al., 2014; Reeves & According to recent stock assessments, this species is being fished  Laptikhovsky, 2014 sustainably. Catches of this stock within the EEZ constitute a very low proportion of the total catch (Reeves & Laptikhovsky, 2014).

Thunnus alalunga Albacore LC Wirtz et al., 2014; Reeves & Very rarely caught at Ascension.  Laptikhovsky, 2014 Thunnus obesus Bigeye tuna VU Wirtz et al., 2014; Reeves & Recent stock assessments indicate this species is being fished  Laptikhovsky, 2014 sustainably (Reeves & Laptikhovsky, 2014).

Katsuwonus pelamis Skipjack tuna LC Wirtz et al., 2014 Fishing pressure “not negatively impacting the population at present”. 

Xiphiidae Xiphias gladius Swordfish LC Wirtz et al., 2014; Reeves & Recent stock assessments indicate this species is being fished Laptikhovsky, 2014 sustainably (Reeves & Laptikhovsky, 2014). Istiophoridae Kajikia albida Atlantic white marlin VU Wirtz et al., 2014; Reeves & Rarely caught at Ascension. Laptikhovsky, 2014 Makaira nigricans Blue marlin VU Wirtz et al., 2014; Reeves & Indications that this stock is currently being over-fished (Reeves & Laptikhovsky, 2014 Laptikhovsky, 2014). Istiophorus albicans Sailfish LC Wirtz et al., 2014; Reeves & Indications that this stock is currently being over-fished (Reeves &  Laptikhovsky, 2014 Laptikhovsky, 2014). Refered to by Wirtz et al. (2014) as I. platypterus.

Tetrapturus pfluegeri Longbill spearfish LC Wirtz et al., 2014 Rarely caught at Ascension.

CR Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD NE Not Evaluated

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2.3 Non-commercial fish species

‘Non-commercial’ is a broad and rather arbitrary category of dividing up a very large number of fishes belonging to numerous families. In order to provide some ecological basis for the category, those species listed in Table 3 have been divided into four groupings:

 Species likely to be found on the seabed, in deep water or associated with seamounts;  Species likely to be found in mid-water;  Species likely to be found close to the surface;

 Species ‘co-habiting’ with others;

Note that there is a further category of ‘deep water’ fishes which includes those species considered to be true bathypelagic fishes (i.e. they inhabit the zone between 1000 m – 4000 m deep). These are included in section 2.10. The St Helena deepwater scorpionfish nigropunctatus was first described from St Helena (where it was considered endemic), though its range has since been extended to the nearby Bonaparte seamount (Edwards, 1993), Grattan seamount (Trunov, 2006), St Peter and St Paul Archipelago (Vaske et al., 2008) and now from Ascension (Wirtz et al., 2014). This extension of a species’ geographical range is likely to be the case for several species, as more exploratory work of the biodiversity of seamounts takes place in future. Grattan seamount rises to just 70 m below the surface. It is therefore not surprising to find a number of species of fishes present close to the plateau on the top of the seamount that are reef fishes rather than deep water forms. An example of such species is the Bicolour or Hedgehog butterflyfish Prognathodes dichrous (Fig. 7). Only two butterflyfish species have been recorded from Ascension Island (the other being the St Helena butterflyfish Chaetodon sanctaehelenae – Fig. 8) and both are also present at St Helena. Both species are endemic to these two islands, though the former has also now been recorded from Grattan seamount (see section 2.9).

Fig. 7. Bicolour butterflyfish Fig. 8. St Helena butterflyfish Prognathodes dichrous. Photo : Chaetodon sanctaehelenae. John Taylor, 1985. Photo : Robert Irving, 1985.

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Aquarists, individuals who keep reef fishes as pets or educators who display them to members of the public, have a particular affection for butterflyfish as they are often very attractive and make pretty, eye- catching subjects for home and public aquariums. It has been interesting to come across an article on the internet by an aquarist enthusiast on the fish life of the Grattan seamount. He states, “Indeed, at least in the context of the aquarium trade, Ascension Island is home to some of the rarest fish species that are no longer available in the current day. In the old days, Centropyge resplendens [Resplendent angelfish], Chaetodon sanctaehelenae [St Helena butterflyfish] as well as Prognathodes dichrous [Bicolour butterflyfish] were the main players coming out of that little mount of sea rock. Endemism is also high with interesting species such as Priolepis ascensionis [Ascension goby], Amblycirrhitus earnshawi [Ascension hawkfish] and Xyrichtys sanctaehelenae [Yellow razorfish] just to name a few.” There is still a demand for endemic species of fishes, taken as live specimens from the wild, with rare species changing hands for considerable sums of money. Certain species, but by no means all, have been successfully bred in captivity, which then lessens the need to take specimens from the wild. Fortunately, these species are now on the prohibited list of the island’s Wildlife Protection Ordinance (2013), so it is illegal to remove them from Ascension’s waters.

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Table 3. List of non-commercial fish species known to inhabit the offshore waters within the Ascension Island EEZ. Note that the Appendix to this report provides further information on certain open water and deep water species (as indicated in column on the right).

Species Common name IUCN Red Reference (listed by) Notes Featured List in Appendix

Species likely to be found on the seabed, in deep water or associated with seamounts

Gymnothorax vicinus Purplemouth moray NE Wirtz et al., 2014 To 145 m depth. A benthic and solitary species inhabiting rocky shores and reefs where water is clear. Most active at night. (Fishbase).

Trachinocephalus myops Snakefish NE Wirtz et al., 2014 Burrows into sandy substrata, from 3–388 m. Listed by Fishbase as Synodus myops.

Saurida brasiliensis Brazilian lizardfish NE Wirtz et al., 2014 From 18–410 m depth, though usually from 50–198 m. Found close to seabed. Found on the outer continental shelf. (Fishbase).

Diretmoides pauciradiatus Longwing spinyfish NE Wirtz et al., 2014 From 0-600 m depth. eaters, with young near the surface  and older adults often descending to below 1,000 m depth.

Fistularia petimba Red cornetfish NE Wirtz et al., 2014; Trunov, 2006 From 10-200 m. Doubtful record for Ascension (Wirtz et al., 2014) but recorded from Grattan seamount (Trunov, 2006).

Pontinus nigropunctatus St Helena deepwater LC Wirtz et al., 2014; Trunov, 2006 From 146-183 m depth. Recorded from Grattan seamount (Trunov, scorpionfish 2006) and now from “close to Ascension” (Wirtz et al., 2014).

Scorpaena grattanica Grattan scorpionfish NE Wirtz et al., 2014; Trunov, 2006 From 120-170 m depth. To date, this species is endemic to Grattan seamount, and was first described by Trunov (2006). (See also Fig. 20).

Holanthias fronticinctus St Helena seaperch NE Wirtz et al., 2014 Recorded from 120 m depth at Grattan seamount and also from “close to Ascension” (Wirtz et al., 2014). Previously considered endemic to St Helena and nearby Bonaparte seamount. However, there is some disagreement as to this ID, as video footage of the fish has it being identified as the Ascension swallowtail H. caudalis.

Serranus sanctaehelenae St Helena comber NE Wirtz et al., 2014; Trunov, 2006 Recorded from both Ascension (Wirtz et al., 2014) and Grattan seamount (Trunov, 2006). Endemic to St Helena, Ascension and Grattan seamount.

Prognathodes dichrous Bicolour or Hedgehog LC Wirtz et al., 2014; Trunov, 2006 A reef-associated species, but included here as has been recorded butterflyfish from Grattan seamount (Trunov, 2006). Endemic to St Helena, Ascension and Grattan seamount.

Cookeolus japonicus Longfinned bullseye NE Wirtz et al., 2014 From 40-400 m depth (usually, 165-200 m). Recent new record from Ascension; also recorded from Grattan seamount (Wirtz et al., 2014).

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Species Common name IUCN Red Reference (listed by) Notes Featured List in Appendix

Promethichthys Roudi NE Wirtz et al., 2014 From 80-800 m depth (Usually 300-400 m). Found at continental  prometheus slopes, around oceanic islands and submarine rises. Migrate to midwater at night. Feed on fish, cephalopods and . (Fishbase).

Ruvettus pretiosus Oilfish NE Wirtz et al., 2014 From 100-800 m depth (usually 200-400 m). Usually over the continental shelf, sometimes in oceanic waters down to 800 m. Migrates far offshore. Pelagic. Feeds on fish, crustaceans and . (Fishbase). New record for Ascension (Wirtz et al., 2014).

Species likely to be found in mid-water

Coryphaena equiselis Pompano dolphinfish LC Wirtz et al., 2014 From 0-400 m depth. Highly migratory species. Primarily an oceanic species but may enter coastal waters. Usually forms schools. Follows boats and may be found under floating objects. Feeds on small fishes and squid. (Fishbase). Wirtz et al. (2014) qualify that this record needs confirmation.

Coryphaena hippurus Common dolphinfish LC Wirtz et al., 2014 Highly migratory species. Adults are found in open waters but also near the coast. Form schools. Feed on almost all forms of fish and zooplankton; also takes crustaceans and squid. (Fishbase).

Caranx bartholomaei Yellow jack NE Wirtz et al., 2014 Adults prefer offshore reefs and open marine waters. Generally solitary but sometimes seen in small groups. Feed on small fishes. (Fishbase). A new record for Ascension (Wirtz et al., 2014).

Caranx crysos Blue runner LC Wirtz et al., 2014 A schooling species, from 0–100 m depth. Of commercial interest  (particularly off the US eastern seaboard). Found both inshore and offshore. Associated with Fish Aggregating Devices (FADs).

Caranx fischeri Longfin crevalle jack NE Wirtz et al., 2014 Inhabits the subtropical waters of the east Atlantic Ocean. Mostly found inshore, though appears to be able to travel long distances. Only recently (2007) separated from C. hippos.

Caranx latus Horse-eye jack NE Wirtz et al., 2014 From 0–140 m depth. A pelagic schooling species normally found  near offshore reefs. (Fishbase).

Caranx lugubris Black jack NE Wirtz et al., 2014 From 12–354 m. restricted to clear oceanic waters. Not commonly  Trunov, 2006. found in shallow banks. Sometimes seen near drop-off at outer edge of reefs. (Fishbase). Also recorded from Grattan seamount (Trunov, 2006).

Decapterus macarellus scad NE Wirtz et al., 2014 From 40–400 m depth. Adults prefer clear oceanic waters, frequently  around islands. Feed mainly on zooplankton. (Fishbase).

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Species Common name IUCN Red Reference (listed by) Notes Featured List in Appendix

Decapterus punctatus Round scad NE Wirtz et al., 2014 From 0–100 m depth. A shoaling species, generally near the bottom. They feed on planktonic invertebrates, primarily , but also on gastropod larvae, and pteropods. Spawning occurs well offshore year-round. Caught commercially and used for bait. (Fishbase).

Elagatis bipinnulata Rainbow runner NE Wirtz et al., 2014 From 0–150 m depth. Inhabits both coastal and offshore areas. Attracted to FADs. Highly migratory (Fishbase). Known to venture into inshore waters to feed on inshore species such as Melichthys niger (AIG, 2014).

Pseudocaranx dentex White trevally NE Wirtz et al., 2014 From 10–238 m depth (though usually 10-25 m). Adults form schools  at the surface, mid-water and close to the seabed. Associated with reefs. (Fishbase).

Selar crumenophthalmus Bigeye scad NE Wirtz et al., 2014 From 0–170 m (though usually 0–10 m). Adults prefer clear oceanic waters around islands. Individuals travel in compact groups of hundreds of thousands of fish. Mainly nocturnal in habit, they disperse at night to feed on small , benthic invertebrates, and forams when inshore, and zooplankton and fish larvae when offshore. (Fishbase).

Seriola rivoliana Longfin yellowtail NE Wirtz et al., 2014 From 5–245 m (though usually 30–35 m). Adults are benthopelagic in outer reef slopes and offshore banks to 160 m or more. They form small groups. Young often seen around floating objects. (Fishbase).

Seriola dumerili Greater amberjack NE Wirtz et al., 2014 From 1-360 m (though usually 18-72 m). Adults found on deep seaward reefs, feeding primarily on fishes such as the bigeye scad, though also on invertebrates. Small juveniles associate with floating plants or debris in oceanic and offshore waters. (Fishbase).

Trachinotus ovatus Pompano NE Wirtz et al., 2014 From 50–200 m depth. Typically more of a reef species, often in  small shoals. (Fishbase).

Uraspis helvola Whitetongue jack NE Wirtz et al., 2014 From 50-300 m. Adults benthopelagic in sandy bottoms at the foot of  the edge of outer reefs, either singly or in small shoals. (Fishbase).

Species likely to be found close to the surface

Tylosurus sp. Hound needlefish Wirtz et al., 2014 Fishbase lists the Hound needlefish Tylosurus crocodilus crocodilus  ( Belonidae) as being present at Ascension. However, Wirtz et al. (2014) list Tylosaurus sp., and state “it is currently unknown if the western Atlantic T. acus (Lacepède, 1803) or the eastern Atlantic T. rafale Collette & Parin, 1970 is present at Ascension”. Wirtz et al.

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Species Common name IUCN Red Reference (listed by) Notes Featured List in Appendix

(2014) point out that the species Tylosaurus imperialis (Rafinesque, 1810) was split into several subspecies, which have subsequently been raised to species level. This needlefish is large, growing up to 1.5 m long.

Platybelone trachura Ascension keeled NE Wirtz et al., 2014 Endemic to Ascension and St Helena islands. needlefish

Cheilopogon Bennett's flyingfish LC Wirtz et al., 2014 Found on both sides of the Atlantic, particularly around islands. pinnatibarbatus Feeds on zooplankton and small fishes.

Cheilopogon exsiliens Bandwing flyingfish NE Wirtz et al., 2014

Cypselurus cyanopterus Margined flyingfish NE Wirtz et al., 2014

Exocoetus volitans Tropical two-winged NE Wirtz et al., 2014 Feed mostly on small crustaceans and other planktonic animals. flyingfish Preyed upon by swordfish, and many other larger pelagic fishes (Fishbase).

Hirundichthys rufipinnis Redfin flyingfish NE Wirtz et al., 2014 From an original description by Kner & Steindacher (1867) of a fish taken “from the south-west of Ascension”.

Scomberescox saurus Atlantic saury NE Wirtz et al., 2014 From 0-30 m. Oceanic, schooling and gregarious. Feeds on zooplankton and fish larvae. Preyed upon by fish, including tunas, marlin and . (Fishbase). However, Wirtz et al. (2014) states that the identification of this species requires verification, as the recorded species for St Helena has now been changed to Nanichthys simulans (Edwards & Glass, 1987).

Species ‘co-habiting’ with others

Echeneis naucrates Live sharksucker NE Wirtz et al., 2014 Most abundant in warm waters. Coastal as well as oceanic. Often found free-swimming in shallow inshore areas and around coral reefs. Attaches temporarily to a variety of hosts including sharks, rays, large bony fishes or sea turtles, whales and dolphins. (Fishbase).

Remora albescens White suckerfish LC Wirtz et al., 2014 Host specific on manta rays, but occasionally attaches to sharks (including Whale sharks). Often occurs inside chamber and mouth of host. Rarely free-swimming. (Fishbase).

Remora remora Sharksucker NE Wirtz et al., 2014 Usually associated with sharks but also attaches itself to other large fishes (including manta rays) and sea turtles. May be found in gill chambers, fins and body surface. Sometimes free-swimming. Feeds

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Species Common name IUCN Red Reference (listed by) Notes Featured List in Appendix

on parasitic copepods. (Fishbase).

CR Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD Data Deficient NE Not Evaluated

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2.4 Sharks and rays

Shark fisheries have rapidly expanded all over the world during the last three decades, so that today several species are threatened. A number of local have already taken place, and a considerable decrease in abundance has been observed for most species (Séret, 2005). The continuing demand related to the production of medicinal products for the Asian market, as well as the consumption of , together with the high prices of these products, are the main drivers of this fishery. The function of sharks, as top predators at the end of the food chain, is however essential to maintain the balances and the genetic quality of prey populations. The collapse of shark stocks, beside the loss of biological diversity, represents a real threat to the sustainability of marine ecosystems.

All species of sharks and rays which have been recorded from within the Ascension EEZ are listed in Table 4. Those regarded as being Endangered or Near-threatened on the IUCN Red List of Threatened Species are discussed in more detail below.

2.4.1 Endangered species

Just one species of shark considered to be Endangered has been reported from Ascension’s offshore waters and that is the scalloped hammerhead Sphyrna lewini, though its presence has only recently been recorded (Wirtz et al., 2014).

Scalloped hammerhead Sphyrna lewini

The scalloped hammerhead is a coastal pelagic species, found in warm temperate and tropical coastal waters all around the globe between latitudes 46° N and 36° S. It has been recorded down to depths of at least 275 m, though is most often found above 25 m. During the day, scalloped hammerheads tend to be found closer to shore whilst at night they hunt further offshore. Adults occur alone, in pairs or in small schools, while young sharks occur in larger schools. Adults spend most of the time offshore in midwater, though females will migrate to the coastal areas to have their pups.

Research has shown that in parts of the Atlantic Ocean, scalloped hammerhead populations have declined by over 95% in the past 30 years in several areas of its range, including , the northwest and western central Atlantic and Brazil. This led in 2007 to the status of this shark species being raised from Near Threatened to Endangered (Baum et al., 2007). Among the reasons for this decline are over-fishing and the rise in demand for shark fins. This species' fins are highly valued compared to other species (because of their high fin ray count) and they have been heavily targeted in some areas (Baum et al., 2007). All life-stages are vulnerable to capture as both target and bycatch in fisheries: large numbers of juveniles are captured in a variety of fishing gears in nearshore coastal waters, and adults are taken in gillnets and longlines along the coastal shelf and offshore in oceanic waters. It is reported that at Ascension, groups of these sharks used to be seen at certain places close to the coast, though they are rarely seen at these sites any longer.

The scalloped hammerhead is a member of the family Sphyrnidae, which is listed on Annex I, Highly Migratory Species, of the UN Convention on the Law of the Sea.

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2.4.2 Near Threatened species

Four of Ascension’s shark species are considered to be Near Threatened according to the IUCN Red List of Threatened Species.

Blue shark Prionace glauca The Blue shark is an oceanic and epipelagic shark found worldwide in deep temperate and tropical waters, from the surface to about 350 m depth. They feed on squid primarily but will also take pelagic octopuses, a large number of bony fishes, small sharks and occasional sea birds. Whale and porpoise blubber and meat have been retrieved from the stomachs of some captured specimens. Blue Sharks are highly migratory with complex movement patterns. There tends to be a seasonal shift in population abundance to higher latitudes associated with oceanic convergence or boundary zones as these are areas of higher productivity. Tagging studies of blue sharks have demonstrated extensive movements in the Atlantic with numerous trans-Atlantic migrations which are probably accomplished by swimming slowly and utilising the major current systems (Stevens, 2009). Records from the Atlantic show a regular clockwise migration within the prevailing currents (Compagno, 1984). Although Blue shark appear abundant in areas where they are found, and they are fast-growing and fecund (maturing in 4–6 years and producing average litters of 35 pups), there is concern over the numbers which are being caught (an estimated 20 million individuals annually), mainly as bycatch. This quantity is considered unsustainable (Stevens, 2009) and hence its Near-threatened status. (See also section 3.1.1). However, this ‘near-threatened’ status is now being questioned: Reeves & Laptikhovsky (2014), reviewing recent ICCAT assessments, state that “Atlantic Blue Shark are classified into Northern and Southern stocks. In both cases, although the assessments are highly uncertain they indicate that for both stocks the biomass is above that which would support MSY and that they are currently harvested below the fishing mortality that would lead to MSY. This suggests that the current level of exploitation is sustainable.”

Galapagos shark Carcharhinus galapagensis The Galapagos shark has a widespread, but patchy distribution, occurring at many widely separated island and some coastal sites in the Pacific, Atlantic and Indian Oceans (Bennett et al., 2003). They are capable of crossing open oceans between islands and individuals have been reported at least 50 km (31 miles) from land. The primary food of Galapagos sharks are benthic bony fishes (including , sea bass, flatfish, flatheads, and triggerfish) and octopuses. They also occasionally take surface-dwelling prey such as mackerel, flyingfish, and squid. As the sharks grow larger, they are reported to consume increasing numbers of elasmobranchs (rays and smaller sharks, including of their own species) and crustaceans. At Ascension, they are known to venture into inshore waters to feed on inshore fishes, such as the plentiful blackfish Melichthys niger. The Galapagos shark is classified globally on the IUCN Red Data List as Near Threatened, primarily because populations at many sites may be subject to high levels of fishing pressure (e.g. tuna longline fisheries, targeted drop-line fishing) and due to its slow reproductive rate (Bennett et al., 2003). The population of Galapagos sharks at Ascension is also likely to be influenced by catches from nearshore recreational/-based angling. In 1985, this was the most numerous shark species seen close to the island by divers, particularly off the east side of the island around Boatswain Bird Island (R. Irving, pers. obs.). More recently, Tim Hook, a knowlegeable Ascension angler (as reported by Wirtz et al., 2014), states that large groups of dozens of differently sized individuals may be seen on occasion. The current sport-fishing world record for this species (at 140 kg) is from Ascension Island (Wirtz et al., 2014).

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Tiger shark Galeocerdo cuvier

This large (>5.5 m long), omnivorous shark is common worldwide in tropical and warm-temperate coastal waters. It is a relatively fast growing and fecund species. This species of shark is caught regularly in target fisheries and as bycatch. The fins, skin and liver oil from Tiger Sharks are all considered to be of high quality and can fetch good prices. Tiger sharks are taken as bycatch in a variety of fisheries including tuna and swordfish longline fisheries, particularly those operating on, or close to, the continental and insular shelves. There is evidence of declines for several populations where they have been heavily fished, but in general they do not face a high risk of extinction. However, continued demand, especially for fins, may result in further declines in the future (Simpfendorfer, 2009). This species has probably the most diverse diet of any shark species. Prey includes numerous bony fish, sharks, rays, turtles, sea birds, seals, dolphins, sea snakes, cephalopods, crabs, lobsters, gastropods and jellyfish. They consume carrion and readily take baited hooks. Tiger sharks also have a propensity to consume "garbage" of human origin, including plastics, metal, sacks, kitchen scraps and almost any other item discarded in the sea (Randall, 1992). In Georgetown, Ascension, there are photographs of large specimens (500+ kg) caught in the past on display in the Saints Bar Club (Wirtz et al., 2014). Tim Hook states, “[Tiger sharks] are only around for 2 or 3 months (starting November/December). They arrive at the same time as the first Green turtles but only stay for about half of the turtle season.” Tiger sharks have been seen cruising shallow beaches at night, presumably searching for Green turtles (Wirtz et al., 2014).

Bluntnose sixgill shark Hexanchus griseus The Bluntnose Sixgill Shark is wide ranging, although patchily distributed, in boreal, temperate and tropical seas. It occurs from the surface to at least 2,000 m, on continental and insular shelves and upper slopes (including seamounts). It feeds on a wide variety of animals including other sharks, skates, rays, chimaeras, dolphinfish, small swordfish and , herring, halibut, turbot, gurnards and anglerfish, as well as many types of invertebrates including squid, crabs, sea cucumbers and (Cook & Compagno, 2005). Adults tend to follow diurnal patterns of vertical distribution, sitting deep on the bottom by day and coming toward or to the surface at night to feed.

Due to its broad depth range and relative sluggishness, this shark has often been captured incidentally in fisheries for other species. It is taken by handline, longline, gillnet, traps, trammel net, and both pelagic and bottom-trawls. It appears to be very vulnerable to overfishing, unable to sustain intensive, targeted fisheries for long periods, and hence its Near threatened status (Cook & Compagno, 2005). At Ascension, this species is only caught at night, frequently near the pipeline deepwater mooring off Georgetown. The current sport-fishing world record for this species is from Ascension, at 589 kg (Wirtz et al., 2014).

Whale shark Rhincodon typus

The whale shark is the world’s largest living fish, growing up to about 14 m long and weighing in the region of 25 tonnes. It is also one of the most charismatic and unmistakable animals in the sea. This enormous filter-feeding elasmobranch, with its unique checkerboard pattern of spots and stripes, inhabits all tropical and warm temperate seas. They are known to migrate considerable distances, on occasion to places where they can aggregate in large numbers. Ascension Island does not appear to be such an aggregating location, with just lone individuals observed from time to time within the EEZ. However, tracking studies have followed female whale sharks from the Caribbean region into the open Atlantic and it has been suggested that these sharks may be seeking a suitable place in the tropical mid-Atlantic to give birth (Heuter et al., 2013).

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Table 4. Species of sharks and rays (class ) present within the Ascension Island EEZ.

Species Common name IUCN Red Reference Notes List

Rhincodontidae

Rhincodon typus whale shark VU Wirtz et al. 2014;

Alopiidae

Alopias supercilliosus bigeye thresher shark VU Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Lamnidae

Isurus oxyrinchus shortfin mako shark VU Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Carcharhinidae

Prionace glauca blue shark NT Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Carcharhinus galapagensis Galapagos shark NT Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Carcharhinus obscurus VU Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Galeocerdo cuvier NT Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Sphyrnidae

Sphyrna lewini scalloped hammerhead EN Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Hexanchidae

Hexanchus griseus bluntnose sixgill shark NT Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

Dalatiidae

Isistius brasiliensis Cookie cutter shark LC Fishbase

Heteroscymnoides marleyi Longnose pygmy shark LC Fishbase

Squalidae

Euprotomicrus bispinatus pygmy shark LC Reeves & Laptikhovsky, 2014; Wirtz et al. 2014

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Species Common name IUCN Red Reference Notes List

Myliobatidae

Manta birostris Giant manta VU Wirtz. et al., 2014 Manta sp. are listed as a protected species under AIG Ordinance. In other parts of the world, manta rays are frequently caught as bycatch by tuna fisheries. However, they are not reported as a bycatch species within the Ascension EEZ. Manta rays are known to be under threat worldwide.

Mobula tarapacana* Devil ray DD Wirtz. et al., 2014; J.Brown (pers. comm.) Wirtz et al. (2014) list ‘Mobula sp.’ though J. Brown (the island’s Fisheries Officer) has confirmed it as being M. tarapacana.

CR Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD Data Deficient NE Not Evaluated

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Other shark species A number of other shark species are known to occur within the ICCAT area, but whose presence has still to be confirmed within Ascension EEZ waters. These are: Sandbar shark Carcharhinus plumbeus, Longfin mako shark Isurus paucus, Night shark Carcharinus signatus, South Atlantic Carcharhinus falciformis, Porbeagle Lamna nasus, and Oceanic whitetip shark Carcharinus longimanus.

The Oceanic whitetip shark is worthy of further mention. This species was once described as “nearly ubiquitous in water deeper than 180 m and above 20°C” is now only occasionally recorded (Baum & Myers, 2004), It was once the most common shark throughout the warm-temperate and tropical waters of the Atlantic (Baum et al., 2006).

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2.5 Cetaceans

Our knowledge of cetacean species within Ascension’s offshore waters is patchy to say the least. Only five (possibly six) species are known to occur, though the true number is likely to be more than this. By means of comparison, within the eastern tropical Atlantic region, which extends from Mauritania south to Angola, at least 34 cetacean species have been recorded (Weir & Pierce, 2013). Offshore records within Ascension’s EEZ are likely to have come from ship-borne observers, with inshore records either being taken from smaller craft or from the island’s cliffs. Occasionally, as has been the case with the Gervais beaked whale specimens, individuals have been found washed up on the shore, either dead or dying. Ascension Island Conservation Department staff and volunteers have been monitoring whales and dolphins in the waters around Ascension Island since 2001. Inshore sightings have been primarily of bottlenose dolphins. This work is ongoing and the data collected are submitted into the Conservation Department’s GIS system for future reference.

Table 5. Cetacean species recorded from within the Ascension Island EEZ.

Species Common name IUCN Reference Notes Red List (see notes below)

Delphinidae

Tursiops truncatus Common bottlenose dolphin LC 1 Listed under AIG Wildlife Protection Ordinance, 2013

[Stenella attenuata] [Pan-tropical spotted dolphin] 2 Uncertain as to whether S. attenuata is present or not due to possible confusion with S. Stenella frontalis Atlantic spotted dolphin DD 2 frontalis.

Balaenopteridae

Megaptera novaeangliae Humpback whale LC 1

Physeteridae

Physeter macrocephalus Sperm whale VU 2

Ziphidae

Mesoplodon europaeus Gervais’ beaked whale DD 1

CR Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD Data Deficient

1: Whales and Dolphins of Ascension Island. Leaflet & poster produced by the Ascension Island Government (no publication date given). Available on-line at: http://www.ascension-island.gov.ac/wp-content/uploads/2013/01/ whales-and-dolphins-leaflet.pdf 2: Notes accompanying the Ascension Island stamp set Whales and Dolphins, issued 23 March 2009. Available on-line at: http://www.the-islander.org.ac/artc_6352_ALL_2916_1.html.

Common bottlenose dolphin Tursiops truncatus

Common bottlenose dolphins are distributed worldwide throughout tropical and temperate inshore, coastal, shelf, and oceanic waters. A recent minimum worldwide estimate of their abundance has been given as 600,000 individuals (Hammond et al., 2012). Bottlenose dolphins consume a wide variety of

Page 29 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic prey species, mostly fish and squid though they may also eat shrimps and other crustaceans (Hammond et al., 2012). Within Ascension’s nearshore waters, bottlenose dolphins are considered ‘resident’ as they are present throughout the year and may be seen all around the coastline, though particularly off the island’s east coast. Recent studies have shown there to be two types of bottlenose dolphins worldwide, forming distinct ‘inshore’ and ‘offshore’ groups. Those at Ascension are probably offshore dolphins, as these are usually the ones that take up residency around offshore islands (Hammond et al., 2012). Offshore individuals tend to be slightly larger, darker and have proportionally shorter fins and beaks than inshore individuals.

Atlantic spotted dolphin Stenella frontalis [Pantropical spotted dolphin Stenella attenuata] Whilst the Pantropical spotted dolphin Stenella attenuata has been reported as being seen in Ascension’s waters, there is some uncertainty as to whether or not this is a correct identification. The Atlantic spotted dolphin Stenella frontalis appears very similar to the Pantropical spotted dolphin and their shape is often described as an intermediate between a Bottlenose and a Pantropical spotted dolphin (Hadoram & Jarrett, 2006). The colouration and patterns vary with age, lifestage and geographic location, so it becomes very difficult to tell the two species apart. Atlantic spotted dolphins are usually found in groups of fewer than 50 individuals, but have been occasionally seen in larger groups of around 200 animals. The inshore/coastal pods usually consist of 5-15 animals. Atlantic spotted dolphins are sometimes associated with other cetacean species such as bottlenose dolphins. The smaller and less-spotted forms that inhabit more pelagic offshore waters and waters around oceanic islands are less well known in their habitat requirements (Jefferson and Schiro 1997). Pantropical spotted dolphins often occur in groups of several hundred to one thousand animals. They are considered quite gregarious, often schooling with other dolphin species. Although specific migratory patterns haven't been clearly described, they seem to move inshore in the autumn and winter months and offshore in the spring. They feed primarily on mesopelagic cephalopods and fishes. No information specific to spotted dolphins recorded within the Ascension EEZ has been discovered.

Humpback whale Megaptera novaeangliae Seven major breeding stocks of Humpback whale are now recognized worldwide (Reilly et al., 2008). Two of these occur in the Southern Atlantic: Stock A (Southwest Atlantic): coast of Brazil; and Stock B (Southeast Atlantic): coast of West Africa from the Gulf of Guinea down to South Africa. It is uncertain from which stock the small number of whales which regularly arrive at Ascension in September/October are from. The Stock A population was reduced to a few hundred animals by the 1960s, being targeted by Antarctic whaling operations centred on South Georgia, though it has now recovered to number over 6,500 (Reilly et al., 2008). The Stock B population was similarly depleted during the first half of the 20th century by large catches in its wintering grounds off Gabon, Congo, Angola, and western South Africa, though its numbers have also recovered (Reilly et al., 2008). Humpback whales are known to undertake long migrations between breeding grounds in tropical coastal waters in winter, to feeding grounds in middle and high latitudes. The Ascension humpbacks may well have traveled from the or even further south from the coastal waters of Antarctica, a distance in the region of 7-8,000 km. Humpback whale calves have been seen at Ascension too, but it is not known whether or not they have been born within Ascension’s waters.

Sperm whale Physeter macrocephalus

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It is not that surprising to find sperm whale as a cetacean species that has been recorded from within Ascension’s EEZ. The habitat of the sperm whale is the open sea and they can be found in almost all marine waters worldwide, deeper than 1,000 m, that are not covered by ice (Taylor et al., 2008a). Their current Red List status is Vulnerable, owing to the fact that their population worldwide is proving very slow to recover the losses inflicted from the days of commercial whaling. Within the Atlantic Ocean, sperm whales tend to be sighted nearer to the continental margins of the ocean than close to the centre. It would therefore be unusual for there to be many sightings of sperm whales around Ascension.

Gervais’ beaked whale Mesoplodon europaeus At one time thought to be restricted to the North Atlantic, this species is probably continuously distributed in deep waters across the tropical and temperate Atlantic Ocean, both north and south of the Equator. It has been described as a ‘naturally rare’ species (Taylor et al., 2008b), and its Red List status reflects this: Data Deficient. The species prefers deep waters based on the presence of prey from such habitats in stomach contents and a lack of sightings near shore (Mead, 1989). Gervais’ beaked whales are known to feed primarily on squid, although some fish may be taken as well. In 1980, three individual Gervais’ beaked whales stranded at Ascension in quick succession (AIG cetacean leaflet). These were the first records of this species outside the North Atlantic (Mead, 1989). A fourth animal stranded in March 2002. It is unclear why these strandings happened. Other strandings of beaked whales elsewhere (including Gervais’ beaked whale) have been linked to disorientation thought to have been caused by loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Taylor et al., 2008b). However, it is not known if this was the cause of these strandings.

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2.6 Turtles

Turtles are a very ancient group of , whose collective ancestry can be traced back 100 million years in the fossil record. There are seven species alive today. Marine turtles can be found in all oceans of the world except for the polar regions. They are generally found in the waters over continental shelves. After taking to the water for the first time, males will not return to shore again. During the first three to five years of life, marine turtles spend most time in the pelagic zone, floating in seaweed beds. Green sea turtles in particular are often found in Sargassum beds, a brown seaweed in which they find shelter and food. Two species of turtle frequent the nearshore waters around the island: the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata. Green turtles are far more numerous than hawksbills at Ascension and use the island’s sandy beaches for egg-laying, particularly those on the west side of the island. Whilst hawksbill turtles are regularly observed in the nearshore waters, they do not come ashore to nest. The hawksbill turtles seen are probably sexually immature juveniles.

Table 6. Species of marine turtles recorded from within Ascension Island’s EEZ.

Species Common name IUCN Red List Reference

Cheloniidae

Chelonia mydas Green turtle EN Listed in Appendix I of CITES Listed in Appendices I & II of CMS Inter-American Convention for the Protection and Conservation of Sea Turtles AIG Wildlife Protection Ordinance, 2013 Green Turtle Species Action Plan (AIG, 2015a)

Eretmochelys imbricata Hawksbill turtle CR Listed in Appendix I of CITES Listed in Appendices I & II of CMS Inter-American Convention for the Protection and Conservation of Sea Turtles AIG Wildlife Protection Ordinance, 2013

Dermochelyidae

Dermochelys coriacea Leatherback turtle VU Listed in Appendix I of CITES Listed in Appendices I & II of CMS Inter-American Convention for the Protection and Conservation of Sea Turtles Memorandum of Understanding Concerning Conservation Measures for Marine Turtles of the Atlantic Coast of Africa

CR Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD Data Deficient

Green turtle Chelonia mydas The green turtle grows up to 1.5 m in length and up to 300 kg in weight (AIG, 2015a). The natural lifespan is thought to be about 80 years. It has a circumglobal distribution, occurring throughout tropical and, to a lesser extent, subtropical waters. Whilst the population at Ascension appears to be doing very well (a six-fold increase in the number of egg clutches deposited over 36 years, from approximately 3,700 to 23,700 clutches – Weber et al., 2014a), elsewhere the picture has not been so positive. Extensive subpopulation declines have been reported in all major ocean basins over the last three generations as a result of overexploitation of eggs and adult females at nesting beaches, juveniles and adults in foraging areas, and, to a lesser extent, incidental mortality relating to marine fisheries and degradation of marine and nesting habitats (Seminoff, 2004). Consequently, the IUCN Red List of Threatened Species conservation status is set at Endangered.

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Since the discovery of the Ascension Island in the sixteenth century, the green turtle population has been subjected to several centuries of exploitation for its meat. This intensified to a commercial scale following permanent settlement of the island by the British in 1815, resulting in a severe depletion of the population (Broderick et al. 2006). Harvesting had largely ceased by the 1930s when the operation became uneconomical, and green turtles were legally protected in 1944 (Weber et al., 2014a). The green turtle is a highly migratory species. For those returning to Ascension to nest and mate (both females and males make the journey), they would have swum from coastal feeding areas off the coast of Brazil, a distance of approximately 2,400 km, to reach the island (Mortimer & Portier, 1989). This is a remarkable feat of navigation within the animal kingdom, with apparently very few clues to assist them find their destination. Foraging areas for adult green turtles from Ascension are off the Brazilian coast between Rio de Janeiro and Forteleza. Juvenile green turtles originating from Ascension are even more widely distributed, having been identified at foraging grounds along a 6000 km stretch of South American coastline from northern to the Caribbean (Naro-Maciel et al., 2012). The adults are predominantly herbivorous with a diet composed largely of seaweed and seagrass. During their journey to Ascension, their nesting period and their return journey, they fast (or only eat very little). These journeys are repeated every 3-4 years. The green turtle nesting period on Ascension occurs between December and June. Hatchlings and small juveniles are epipelagic omnivores and are thought to associate with floating vegetation and other debris entrained in ocean currents (Witherington et al., 2012). The first five years of their lives are spent in the open ocean and individuals are rarely seen. Indeed, what happens to individuals during these ‘lost years’ has long been a mystery for turtle biologists. One of their main predators during this time are probably sharks – tiger sharks Galeocerdo cuvier are known to patrol Ascension’s shallow waters at night during the nesting season (Wirtz et al., 2014). It has been estimated that, for the species as a whole, as few as 1% of hatchlings are likely to reach sexual maturity (20+ years) (Hammerschlag et al., 2015). Recent work has investigated the ‘lost years’ conundrum of the green turtle using predictions of transport within an Atlantic Ocean circulation model (Putman & Naro-Maciel, 2013). Utilising known ocean current circulations, dispersal simulations were carried out using ‘virtual particles’, released at both known nesting sites and foraging areas, which were then tracked.

Fig. 9. Predicted distribution of 13,500 particles tracked forwards in time from their release at Ascension Island. (L) particle density counted daily; (R) mean age in years of particles. Taken from Putnam & Naro-Maciel (2013).

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Fig. 9 shows the results of virtual particles being released from Ascension. It is clear to see that the particles are taken in a westwards and south-westwards direction from the island towards the South American coast, as one would expect. What is intriguing is to see that, by years 3-4, a considerable density remains in the central Southern Atlantic, eventually traveling past the southern tip of Africa and into the Indian Ocean. However, this model is predicting entirely passive drifting and takes no account of a turtle’s ability to actively swim. It is unclear how long hatchlings may spend in Ascension’s nearshore waters before embarking on their journey westwards to the Brazilian coast. During their journey, they are likely to spend most of their time close to the surface, to satisfy breathing requirements and also as it is likely to be the safest zone for them to occupy. For post-nesting adults fitted with tracking devices, their journey back has been shown to take a route that is almost due west from Ascension to the ‘bulge’ of the Brazilian coast, followed by a period of extended coastal travel to their final destination (AIG, 2015a).

Hawksbill turtle Eretmochelys imbricata Far less is known about the hawksbill turtles that visit Ascension than for green turtles. The hawksbill turtle has a circumglobal distribution in tropical waters of the Atlantic, Indian and Pacific Oceans but has undergone dramatic reductions in population size across its range due to overharvesting for meat, shells and eggs (Mortimer & Donnelly, 2008). It is only recently that any scientific studies have been undertaken on the population of hawksbill turtles that occur around Ascension. Putman et al., (2014) conclude that 85% of hawksbills observed in Ascension Island’s waters originate from nesting populations in north-eastern Brazil, with the remainder linked to smaller rookeries in West Africa (e.g. São Tomé and Principe) and potentially even the Indian Ocean. By tagging individual turtles over the past ten years (2003-2013), Weber et al. (2014b) found that there was a mean minimum residence time of 4.2 years (range: 2.8–7.3 yr) and a mean growth rate of 2.8 cm/yr. They concluded that Ascension serves as a mid-Atlantic developmental habitat for benthic-feeding, juvenile hawksbill turtles on extended oceanic migrations before recruiting to their adult foraging grounds, likely to be located in Brazil or tropical West Africa.

Leatherback turtle Dermochelys coriacea Leatherback turtles are known to undertake long-distance, transoceanic migrations (Hays et al. 2004). However, little was known of their migrations in the South Atlantic until 2006 when reports were received of individuals which had been tagged in Gabon, West Africa stranding on the eastern shoreline of South America. More recently, it has been shown that individuals travel in the opposite direction too (Almeida et al., 2014): a tagged individual from a nesting beach in SE Brazil has turned up on a beach in Namibia. The presence of leatherback turtles within Ascension’s EEZ has only recently been confirmed. Fossette et al. (2014) assessed known interactions of leatherback turtles with vessels between 1995 and 2010 (see Fig. 10). The figure shows where high-fishing-pressure areas overlapped with leatherback habitat use. It shows that within the Ascension EEZ there was both medium (high fishing pressure/medium turtle use – shown in orange) and high (high fishing pressure/high turtle use – shown in red) susceptibility of longline by-catch of leatherbacks.

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Fig. 10. Long-term susceptibility of leatherback turtle to bycatch in longline fisheries. This map shows where high-fishing-pressure areas overlapped with leatherback habitat use, between 1995 and 2010, in the Atlantic Ocean. Three classes were defined: low (high fishing pressure/low turtle use), medium (high fishing pressure/medium turtle use) and high susceptibility (high fishing pressure/high turtle use). Nine main high-susceptibility areas were identified (nos 1–9 on the map). These areas occurred both in international waters and in the EEZs of 12 countries (in dark grey) fringing the Atlantic, including Ascension Island (United Kingdom; ‘UK’, no. 7). Dashed grey lines represent the limits of national EEZs. Broken lines represent latitudes 10° N and 10° S. Taken from Fossette et al., 2014.

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2.7 Seabirds

Ascension Island is the most important seabird breeding site in the tropical Atlantic, supporting approximately one million nesting seabirds of 11 different species (Table 7) (Oppel et al. 2015). Prior to 1815 (when the British established a permanent garrison on the island), the island was uninhabited and many species bred all around the main island’s coast and even on the low-lying plains. However, both humans (in harvesting eggs) and feral cats (taking chicks) have decimated numbers of several species, and driven most to breed in Fig. 11. on nest, Boatswainbird the relative safety of the offshore stack of Island. Photo: R. Irving, 1985. Boatswainbird Island. Feral cats were successfully eradicated in 2006 (Ratcliffe et al., 2010) and since then a number of species have successfully started to breed back on the mainland. It has recently been shown by Croxall et al. (2012) that, worldwide, seabirds are more threatened than other comparable groups of birds and that their status has deteriorated faster over recent decades. The principal current threats at sea are posed by commercial fisheries (through competition and mortality on fishing gear) and pollution, whereas on land, alien invasive predators, habitat degradation and human disturbance are the main threats.

Table 7. Breeding seabirds on Ascension Island/Boatswainbird Island.

Species Common name IUCN Population estimates (Oppel et al., 2015) Red List Fregata aquila Ascension Island frigate bird VU Approx. 20,000 individuals (Ratcliffe et al., 2008)

Sula dactylatra Masked booby LC Approx. 4,600 individuals

Sula leucogaster Brown booby LC Approx. 500 individuals Sula sula Red-footed booby LC Approx. 50 individuals Onychoprion fuscatus Sooty tern (aka Wideawake Approx. 350,000 individuals (Hughes et al., LC tern) 2012) Gygis alba Fairy tern (aka White tern) LC

Anous minutus Black noddy LC Anous stolidus Brown noddy LC Phaethon aethereus Red-billed tropic bird LC Approx. 100 Phaethon spp. (both Red-Billed and White-tailed) Phaethon lepturus White-tailed tropic bird (aka LC yellow-billed tropic bird) Oceanodroma spp. Storm petrels _ An IUCN Red List status is not possible when no specific species is identified. See also Table 9. Oceanodroma castro Madeiran storm petrel (aka LC band-rumped storm petrel)

CE Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD Data Deficient

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Ascension frigatebird Fregata aquila

The Ascension frigatebird is the island’s only endemic species of bird. It is classified by IUCN’s Red List of Threatened Species as being Vulnerable (BirdLife International, 2012). Ascension frigatebirds have been found to forage over a wide expanse of open ocean, incorporating much of the Territory’s 200 nm EEZ and beyond into international waters (AIG, 2015b). The average foraging trip of a breeding adult lasts 2-3 days and extends to a maximum distance of 200-300 km from the island. However, displacements of over 1000 km have been recorded. Juveniles and non-breeding adults are even more wide-ranging, occasionally appearing as vagrants along the coast of tropical West Africa (Ashmole et al., 1994) and even as far north as (Wallbridge et al., 2003). Ascension frigatebirds are pelagic surface-feeders and generally forage far from land over open ocean (AIG, 2015b), probably in association with cetaceans and tuna schools that drive smaller prey species within reach (Au & Pitman, 1988). Their diet appears to be more conservative than that of other seabirds at Ascension Island, consisting almost entirely of of the genera Exocoetus, Cypsilurus and Hirundichthyes (Stonehouse & Stonehouse, 1963). All prey is taken in flight as frigatebirds cannot normally take off from the water. During certain seasons, small groups can also be observed feeding on sea turtle hatchlings and sooty tern chicks over land. of other seabirds is known to occur but is not thought to form a significant part of the species’ diet (Ashmole et al., 1994). All of the other seabird species listed in Table 7 are known to forage in the waters of the EEZ.

Masked booby Sula dactylatra Masked boobies nesting at Ascension Island forage over a wide expanse of open ocean, although predominantly within the island’s 200 nm EEZ. On average, the foraging trips of breeding birds extend to a maximum of 140 km from the Island, although occasional displacements of over 300 km have been recorded (Oppel et al., 2015). Flying fish feature prominently in their diets, though at least 11 prey species have been identified in regurgitates at Ascension Island, including large numbers of juvenile redlip blennies atlanticus (Dorward, 1962). Masked boobies are amongst the most pelagic species of the family, preferring to forage over deep water (Schreiber & Clapp, 1987), often in association with subsurface predators such as dolphins and yellowfin tuna Thunnus albacares (Au & Pitman, 1988). They obtain most of their prey by plunge diving from a height of 10-30 m (AIG, 2015c), though they are only able to access prey within the top two metres of the water column (Weimerskirch et al., 2009).

Sooty (Wideawake) tern Onychoprion fuscatus

Sooty terns are the most numerous seabird breeding on Ascension (AIG, 2015d), with as many as 350,000 birds (175,000 nests) breeding each season (Hughes et al., 2012). However, historically, Hughes (2014) estimates that the breeding population numbered approximately 2.8 - 3 million birds between 1877 and 1958, prior to a decrease in prey availability linked to the rapid expansion in commercial long-lining for tuna in the tropical Atlantic Ocean. The foraging distribution of sooty terns during the breeding season is not known (AIG, 2015d). Between breeding seasons sooty terns are pelagic and highly migratory, seldom approaching land. Tracking studies suggest that Ascension birds predominantly forage far to the north of the Island during the non- breeding phase, exploiting the productive waters of the equatorial central Atlantic.

Sooty terns are highly pelagic and are generally only found close to land around breeding periods. Their diet consists mainly of small pelagic fish and squid caught at or near the surface of the ocean (Ashmole, 1963). Sooty terns rely heavily upon prey driven within reach by small, surface-schooling

Page 37 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic tuna such as skipjack Katsuwonus pelamis and yellowfin Thunnus albacares and are seldom seen feeding independently of them in oceanic waters (Au & Pitman, 1988).

Table 8 lists migrant (non-breeding) seabird species which have been recorded within 200 nm of Ascension (Bourne & Simmons, 1998).

Table 8. Migrant (non-breeding) seabird species recorded within 200 nm of Ascension. Unconfirmed/dubious sightings have been left out. After Bourne & Simmons (1998). Common name Scientific name Position seen / Notes 10.5°S 16.1°W (180 nm SSW Ascension) Originally called a Herald petrel subspecies, but now split into Trinidade petrel Pterodroma arminjoniana 3 separate species (Brooke, 2004). Only breeds on Islands off the coast of Espírito Santo, Brazil. One on board HMY Britannia at 12.5°S 09.4°W (24Jan1957); 05.6°S 15.0°W, 200 nm north (01Feb1985); 70 nm north Bulwer’s petrel Bulweria bulwerii (16Apr1986); 10.0°S 10.0°W, 150 nm SE (17Nov1988); from North Point (17Nov1988); and (31Oct1997) Seen twice at sea, 1957-59; and offshore (Apr1977); two Large skua Catharacta sp. (18Feb1987); 3 miles off Geordetown (18Sep1993); 06Nov1996; and going south (10Oct1997). One at 04.5°S 15.5°W (16Feb1983); 05°11′S 14°52′W Pomarine skua Stercorarius pomarinus (29Nov1983); 05.6°S 15.0°W (10Feb1985) – all about 200 nm north of Ascension. One harrying black noddies offshore (Dec1993). Two at 10.5°S 16.1°W, 180 nm SSW (02Oct 1982); three 70 nm to north (08May1984); three at 05.2°S 14.9°W, 200 nm to Arctic skua Stercorarius parasiticus north (29Nov1983); at least four 200 nm to north (23Nov1988); mup to 37 daily offshore (20-24Nov1988); one chasing noddies off North Point (11Mar1990). 11 at 10.5°S 16.1°W, 180 nm SSW (02Nov1982); four 02.8°S Long-tailed skua Stercorarius longicaudus 17.9°W (23Nov1988); pale immature heading south (16Oct1989) 19 at 10.5°S 16.1°W, 180 nm SSW (02Noc1982); one at 08.4 Arctic tern Sterna paradisaea °S 13.1°W offshore (19Nov1988).

Hughes et al. (2014) have recently analyzed a series of seabird sightings data (of both resident and migratory birds) from 1957 to 2011 and have concluded that there appears to be an area to the north- west of Ascension which is favoured by various species which they have called an ‘assembly site’ (Fig. 12). The two main findings of their study are that (1) waters to the north-west of Ascension Island are more highly used by pelagic seabirds than those to the south or the east of the island; and (2) the assembly site that they have identified for seabirds is partly within the EEZ of Ascension Island. They also state that “Seabird assembly sites can be explained by food availability and we predict that the waters in local areas along the South Equatorial Current in the NW segment may be more productive for seabirds that forage at higher trophic levels than the waters elsewhere in the tropical Atlantic Ocean”.

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Fig. 12. At-sea sightings of one or more seabirds of the same species in the middle of the tropical Atlantic Ocean between 1957 and 2011 (inclusive). The four sighting classes were defined as ‘low’ (0-4 sightings), ‘medium’ (5-9 sightings), ‘high’ (>90th percentile) and ‘potential assembly sites’ (highest number of sightings). Taken from Hughes et al., 2014. [Note that the grey circle denotes the limit of the study area in question, which was considerably larger than the 200 nm EEZ limit around Ascension].

Hughes et al. (2015) also list the species of seabirds which had been recorded on two or more occasions in the vicinity of the ‘assembly site’ to the N-NW of the island, together with their general breeding locations (Table 9).

Table 9. Pelagic seabird species recorded on two or more occasions in the assembly site at 14–16°W and 4–6°S N–NW of Ascension Island, South Atlantic, together with their breeding locations. After Hughes et al., 2015.

Arctic Antarctic Mid-latitude Tropical Islands Long-tailed Jaeger Great Shearwater Cory’s Shearwater Red-footed bobby Stercorarius longicaudus Puffinus gravis Calonectris diomedea Sula sula Parasitic Jaeger Sooty Shearwater Leach’s Storm Petrel Masked Booby Stercorarius parasiticus Puffinus griseus Oceanadroma leucorhoa Sula dactrylatra Pomarine Skua White-bellied Strom Petrel Bulwer’s Petrel Ascension Frigatebird Stercorarius pomarinus Fregetta grallaria Bulweria bulwerii Fregata aquila Arctic Tern Wilson’s Storm Petrel Common Tern Red-Billed Sterna paradisaea Oceanites oceanicus Sterna hirundo Phaethon aethereus Sooty Tern Onychoprion fuscatus Black Noddy Anous minutus Brown Noddy Anous stolidus Band-rumped Storm Petrel Oceanodroma castro

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2.8 Marine molluscs and other invertebrates

2.8.1 Marine molluscs The phylum has both terrestrial and marine representatives and includes slugs and snails (which together make up about 80% of all known mollusc species), bivalves and cephalopods, the last group including octopuses, and cuttlefishes. Cephalopods, particularly the squids, form an important part of the diet of several seabird species. Very little is known of the molluscan fauna in the waters surrounding Ascension; considerably more is known of the nearshore molluscan fauna (for instance: Rosewater, 1975). The accepted way of obtaining mollusc specimens on the sea bed for identification purposes has been by using a deep sea dredge. The author has only come across one expedition which used such a dredge off Ascension – the of 1872-1876. The ship HMS Challenger called by at Ascension towards the end of her epic 4½ year scientific cruise around the world in March 1876. The dredge samples obtained (as included in a subsequent paper by Edgar in 1890 entitled On the marine mollusca of Ascension Island) came from “420 fathoms [768 m] off the west side of Ascension Island”, though the exact latitude and longitude is not recorded. Nine species of mollusca were recorded by Smith (1890) from the dredge sample, out of a total of 42 species recorded “from Ascension” (Table 10).

Table 10. List of mollusca which have been recorded from Ascension Island’s ‘offshore’ zone (i.e. not from shallow, nearshore waters, typically less than 50 m depth).

Species Notes Species (as originally recorded) (as recognized currently) Gasteropoda (sic) Eulima chyta Watson, 1883 Eulima chyta Watson, 1883

Rissoa (Setia) tenuisculpta Name changed to Cingula tenuisculpta (in Talassia tenuisculpta Watson Rosewater, 1975) and now to Talassia (Watson, 1873) tenuisculpta (Watson, 1873)

Rissoa (Setia) triangularis R. Name now changed to Setia triangularis Setia triangularis (Watson, Boog Watson, 1886 (Watson, 1886) 1886) Basilissa oxytropis Watson, 1879 This is no longer a recognised species. The ? ‘closest’ species name is Basilissa alta var. oxytoma Watson, 1879, which is now renamed as Hadroconus altus (Watson, 1879) Utriculus oryctus Watson This is no longer a valid , and the species ? is not recognised at all. Rosewater (1975) lists this species as Retusa orycta (R. Boog Watson, 1883), but this species too is no longer recognised. Cylichna cylindracea (Pennant, Cylichna cylindracea 1777) (Pennant, 1777) Scaphopoda

Dentalium entalis var. agile Dentalium entalis is listed as a species in its own Antalis entalis (Linnaeus, right and as having three variants. Var. agile is 1758). not one of these variants. Dentalium entalis has now been renamed as Antalis entalis (Linnaeus, 1758). Listed by Rosewater (1975) as Dentalium (Antalis) agile M. Sars, 1872

Pelecypoda [Bivalvia]

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Species Notes Species (as originally recorded) (as recognized currently) Cryptodon sp. There were 38 species belonging to the genus ? Cryptodon in 1890. The genus no longer exists, with all species being allocated to various other genera.

Nuculana jeffreysi (Hidalgo, The genus Nuculana still exists (originally ? 1877) encompassing over 200 species and sub- species!) though there is no record of jeffreysi as being one of its species.

The nearshore molluscan fauna is listed by Rosewater (1975), and features 89 species. Amongst these are a number of pelagic species which would certainly be found offshore as well as closer to the shore. The violet Janthina janthina (Linnaeus, 1758) is one such, first being collected from the nests of sooty terns. It is concluded that these birds are likely to have picked up the snails far out to sea and carried them to shore as food. Janthina janthina is found worldwide in the warm waters of tropical and temperate seas, floating at the surface by means of a special ‘raft’ they create out of air bubbles. These snails are therefore part of the pleuston, organisms living on or at the very surface of the water. They are pelagic, drifting on the surface of the ocean, where they feed upon pelagic hydrozoans, especially the by-the-wind sailor Velella velella and the Portuguese man o' war Physalia physalis. The common octopus Octopus vulgaris (Fig. 13) has been recorded from Ascension in nearshore waters (Rosewater, 1975). “Dredged in 20-30 fathoms [36-54 m]”. This particular specimen was taken on the Challenger expedition at the same time as the dredged material, though all cephalopod specimens for the entire voyage of HMS Challenger were described by Hoyle (1886) rather than by Smith (1890).

Fig. 13. Common octopus Octopus vulgaris, photographed at Ascension by John Taylor in 1985 as part of ‘Operation Origin’, a diving expedition to catalogue the island’s nearshore habitats and species.

Other cephalopod species (particularly squid) are also likely to feature within the offshore waters of the EEZ, particularly deep water pelagic (i.e. mostly meso-pelagic) species. Many of these species reside in the depths during daylight hours but will migrate to the surface during darkness to feed on planktonic organisms near the surface. Several seabird species present on Ascension include these deep-water cephalopods in their diet, and it should be possible to identify the partially digested remains of the

Page 41 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic cephalopods from the stomach contents of these birds. The beaks of the cephalopods take a long time to digest and it is possible to identify a cephalopod species from just its beak.

2.8.2 Other marine invertebrates The biota of the deep seafloor features many other invertebrate species, but as far as the author has been able to ascertain, no published reports have been produced on any such studies. However, besides molluscs, it is likely that sessile organisms would include various sponges, anemones, corals, sea fans and sea whips, bryozoans and sea squirts. Mobile species would probably feature various worms, crustacea, sea cucumbers, brittlestars and starfish. See also section 2.10.1.

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2.9 Seamounts

It is thought there may be as many as 100,000 seamounts (which rise at least 1,000 m) scattered throughout the world’s oceans, but only 0.4% (~400) of these have actually been explored and of these, only 100 have been sampled in any detail. Deep-sea scientists have recently catalogued over 30,000 seamounts for the internationally collaborative CenSeam project (Census of Seamounts) which began in 2005 as part of the larger Census of Marine Life project. Seamounts are considered to be important for several reasons:  They provide excellent case studies for the understanding of marine biodiversity patterns. Seamounts vary greatly in their biodiversity; they may have a high degree of endemism; they may act as centres of speciation; and they may provide a role as "stepping stones" for the dispersal of coastal species.  They are areas of high production that support commercially important fisheries and, particularly in the Pacific Ocean, coral mining.  They are fragile ecosystems that must be managed carefully and with good scientific information in order to prevent habitat damage. At least five distinct seamounts have been identified within the Ascension EEZ. The small amount of research that has been carried out on investigating them has tended to concentrate on their topography and not so much on their ecology. Consequently, the generalized description of seamounts given here is not specific to the Ascension EEZ seamounts, although much of it will be relevant. As a result of their very nature in forming very large, prominent structures on the sea floor, seamounts can have a considerable influence on the oceanic conditions found in their vicinity. They can affect oceanic currents resulting, amongst other things, in local concentrations of plankton which in turn attract species that graze on it. They have been shown to act as highly effective natural aggregating devices for tuna and other migratory species, primarily for feeding but also possibly for breeding too. They also may serve as way stations in the migration of whales and other pelagic species. Each may host elevated concentrations of biological diversity (compared with the surrounding sea floor) and each is likely to have its own unique ecosystem.

No two seamounts are the same: each will have its own set of physical features and conditions, which in turn affect the marine life associated with it. Differences in seabed morphology will influence hydrodynamic flow patterns and therefore the deposition of sediment and organic matter ( et al., 2010). Complex current patterns can also influence sea life above them. Strong localized currents and upwellings can lead to increased concentrations of plankton over seamounts and this, combined with the constant influx of prey organisms, means that they can attract large numbers of fish. Thus, the physical presence of seamounts has been shown to support relatively large planktonic and higher consumer biomass when compared to surrounding ocean waters, particularly in oligotrophic oceans (as is the case within the Ascension EEZ).

Some seamounts have been shown to support high levels of biodiversity and unique biological communities. In some instances high levels of endemic species (only found at that locality) have been found. Seamounts may act as regional centers of speciation, stepping stones for dispersal across the oceans and refugia for species with a shrinking range. Cetaceans, sharks, tuna, and cephalopods all congregate over seamounts to feed, and some seabirds have been shown to be more abundant in the vicinity of shallow seamounts.

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Fig. 14. Bathymetric profile across the central Atlantic Ocean, showing the location of Ascension Island in relation to the ocean basin margins and the Mid-Atlantic Ridge. Vertical exaggeration 1:150. Adapted from the Submission made by the United Kingdom of Great Britain and Northern Ireland to the Commission on the Limits of the Continental Shelf in regard to Ascension Island on 9 May 2008.

2.9.1 Physical descriptions of seamounts within the Ascension EEZ

Of the five distinctive seamounts present within the Ascension EEZ, three have their summits less than 320 m from the sea surface (Fig. 15 and Table 11). Two of these have been named (Gratton and Harris Stewart), while the third still awaits to have a name recognised by the Undersea Feature Names Gazetteer (http://www.ngdc.noaa.gov/gazetteer/) of the General Bathymetric Chart of the Oceans. The summits of the other seamounts remain in deep water (i.e. greater than 800 m from the surface).

Fig. 15. The location of three of the main seamounts within the Ascension Island EEZ. Note that Ascension itself is in the exact centre of the EEZ circle. (Courtesy of Ascension Island Government Conservation Department). The local bathymetry for Grattan Seamount is shown in Fig. 16, and that for the Harris Stewart Seamount in Fig. 17 below. Grattan Seamount is also referred to in the literature as the Grattan Bank,

Page 44 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic as it can be seen there is another smaller seamount lying close to the west of the main one, with a distinct ‘valley’ between them.

Table 11. Distinctive seamounts within the Ascension Island EEZ.

Name of seamount Location Shallowest point / ref.

9° 44′ S 12° 49′ W 72 m below surface (Edwards, 1993); 70 m (Hect & Grattan (260 km SE of Ascension Is.) Malan, 2007) 8° 28′ S 16° 58′ W Harris Stewart 265 m below surface (Hect & Malan, 2007) (305 km WSW of Ascension Is.)

Unnamed* 90 km E of Grattan Seamount 316 m below surface (Reeves & Laptikhovsky, 2014)

Unnamed 7° 50’ S 14° 35’ W 800 m below surface (Faneros & Arnold, 2003) (“Northern”) (20 km NW of Ascension)

Unnamed 8° 57’ S 14° 38’ W 1500 m below surface (Faneros & Arnold, 2003) (“Southern”) (116 km SW of Ascension) * It is possible that this seamount is the one known elsewhere as ‘Circe’.

Fig. 16. Seabed beathymetry in the vicinity of Grattan seamount. Image taken from internet site: http://earthref.org/cgi- bin/sc.cgi?id=SMNT-097S-0128W

One of the Ascension angling boats (Shy III) travelled to the Grattan Bank in March 2006 and reported their catch by means of an on-line blog (http://www.marlinnut.com/forums/t4903/). Captain Ian Carter reported “small yellowfin tuna, small billfish, small wahoo and a large blue marlin; and at deeper depths caught grouper, bullseye, oilfish, black jacks and small sharks.” He supposed that “…this was the first time a sport boat had ever been there.”

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Fig. 17. Seabed beathymetry in the vicinity of Harris Stewart seamount. Image taken from internet site: http://earthref.org/cgi- bin/sc.cgi?id=SMNT-085S-0170W

Fig. 18. Sun-illuminated (i.e. viewed from Fig. 19. Sun-illuminated bathymetry for an directly overhead) bathymetry for an unnamed seamount (“Southern”), lying unnamed seamount (“Northern”), lying just to approximately 116 km south-west of the north-west of Ascension). The shallowest Ascension. It is approximately 19 km long by part of the seamount is approximately 800 m 9 km wide. The base is in a water depth of below the surface, the deepest part being at 3,200 m and the summit at 1,500 m. [Image about 3,600 m depth and with a basal taken from Faneros & Arnold, 2003]. diameter of 16 km. [Image taken from Faneros & Arnold, 2003].

Faneros & Arnold (2003) named the two seamounts they investigated (Figs. 18 & 19) “Northern” and “Southern” for simplicity’s sake. They concluded that the Northern Seamount’s close proximity to the

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Ascension volcano, the correlation of the seamount’s summit with the northwest trending ridge of Ascension, and the overlapping relationships deposits with the basal portion of the Ascension volcano suggests that the seamount originated as Ascension flank eruptions. With regard to the Southern Seamount, the orientations of it to the ridge and graben structures that so closely parallel the Mid- Atlantic Ridge, indicates that the Southern Seamount probably originated from Mid-Atlantic Ridge volcanic processes, as apposed to hot-spot related processes suggested for Ascension Island (Faneros & Arnold, 2003).

A further, named seamount (Stvor Guyot) is present between the Ascension Fracture Zone and the Bode Verde Fracture Zone to the south, approximately 930 km ESE of Ascension (and thus outside the EEZ).

2.9.2 Ecological description of seamounts within the Ascension EEZ

During the course of his research for this review, the author has only come across one paper written on a biological subject matter for any of the seamounts within the Ascension EEZ, and that has been on the fish fauna of the Grattan Bank (Trunov, 2006). Trunov (2006) describes fish samples that were taken during Russian research cruises from 1973-1975 which visited a number of seamounts in the mid-Atlantic, collected by seine nets of pelagic and bottom trawls. He provides no description of the other marine life encountered nor of any of the habitats. He describes one species new to science and named Scorpaena grattanica, a species of scorpionfish (Fig. 20). The international Census of Seamounts project has led to many new discoveries in the deep oceans from all parts of the globe, but particularly in the Pacific Ocean. Even before the project, any ecological investigation of a seamount was likely to come up with numerous species new to science. De Forges et al. (2000) reported on the discovery of more Fig. 20. Scorpaena grattanica, a new species of than 850 macro- and megafaunal species scorpionfish (Family ) from Grattan Seamount, described and illustrated by I.A. Trunov from seamounts in the Tasman Sea and (2006). southeast Coral Sea, of which 29–34% were new to science and potential seamount endemics. They proposed that the low species overlap between seamounts in different parts of the region indicated that the seamounts in clusters or along ridge systems function as ‘island groups’ or ‘chains,’ leading to highly localized species distributions and apparent speciation between groups or ridge systems that is exceptional for the deep sea. Their results have substantial implications for the conservation of this fauna, which is threatened by fishing activity. With regard to seamounts present in the mid-Atlantic, Edwards (1993) points out that a number of the seamounts in the region are likely to act as stepping stones in the distribution of their fish faunas (Fig. 21). Several species originally thought to be endemic to a restricted location or locations have now been found to have wider ranges, although these are still restricted to their own isolated seamounts or island fringes. Wilson & Kaufmann (1987) estimated the endemism of fishes and invertebrates on seamounts as 12% and 15% respectively, though De Forge et al. (2000) reported their investigations of SW Pacific seamounts to indicate endemism levels as high as 22-36%. Clearly, it is highly likely that these levels of endemism will fall as more studies are undertaken on seamount ecology, or at least the range over which their endemicity extends will increase.

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Fig. 21. Map of central South Atlantic area between the islands of Ascension and St Helena to show locations of shallow (< 200m deep) seamounts. (Based on British Admiralty Chart 4007.) (After Edwards, 1993).

More recently, in 2011, a National Geographic expedition obtained ROV video footage of the marine life associated with the plateau of the Grattan Seamount. This was the first time video had been obtained from the site (http://www.expeditions.com/blog/2011/11/21/first-look-at-a-tropical-seamount-2/). The plateau appeared covered with various species of coral, anemones and numerous fishes. Of the fishes, two species proved to be of particular interest: the Bicolour butterflyfish Prognathodes dichrous (only previously recorded from, and thus an endemic of, St Helena and Ascension); and a small anthias, the Ascension swallowtail Holanthias caudalis (known only from Ascension) though misidentified initially as the very similar St Helena basslet H. fronticinctus. So these findings fit in with the ‘stepping stone’ hypothesis, extending the known range of both of these endemic species.

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2.10 Deep-sea and pelagic biodiversity

2.10.1 Benthic communities of the deep sea

For animals of the deep-sea floor, geographical patterns in the distribution of species (or higher taxa) and the causes of those patterns are not well known. This situation arises, in part, because of the great mismatch between the vastness of the habitat and the small amount of sampling that has been done. In addition, large numbers of species are present in the deep sea, most of which are undescribed. Further, the number of specialists who can provide identifications or taxonomic descriptions is small and is decreasing (Thistle, 2003). Compared with the North Atlantic, the deep-sea benthos of the Equatorial Atlantic, and that of the South Atlantic, is poorly known. Most studies have concerned the abundance, diversity and distribution of particular groups, such as ascidians (Monniot, 1979), protobranch bivalves (Allen & Sanders, 1996) and echinoderms (Sibuet, 1979).

The organisms which constitute the benthic communities can be separated by their chosen method of feeding. Deposit feeders (such as various worm-like animals including polychaetes, oligochaetes, nemerteans, echiurians and sipunculids) ingest sediment. Suspension feeders feed on material they collect from the water column, intercepting epibenthic plankton, particles raining from above, and particles that have been resuspended from the seabed. These can be divided into active suspension feeders (e.g. barnacles and sponges); and passive suspension feeders (e.g. crinoids, some holthurians, some ascidians). Carnivores/predators (which will include many of the demersal fishes) select and consume living prey. In the food-poor deep sea prey are rare, so the time between encounters with prey will be long compared to that needed to subdue and ingest a prey item once encountered. That leaves detritivores and the specialised carcass feeders: at peak abundance around a fish carcass, tens of fishes, hundreds of amphipods, and hundreds of brittlestars may be present (although these peaks are not simultaneous). These abundances are many times greater than abundances in the background community, so carcasses will cause local concentrations of individuals (Thistle, 2003). Rocky outcrops that rise above the sediment ooze, or offer sheer or overhanging faces which avoid having particulate matter accreting on them, provide a firm foothold for the attachment of sessile organisms. These will include deep sea corals, such as gorgonian branching corals and sea whips, erect and branching sponges, sea anemones and erect bryozoans. Associated mobile benthic megafaunal organisms will include various starfish and brittlestars, holothurians, crabs and shrimps, and gastropod molluscs; macrofaunal organisms consist primarily of polychaetes, bivalve molluscs, and isopod, amphipod, and tanaid crustaceans; and finally the meiofauna consists of primarily of foraminifers, nematodes, and harpacticoid copepods.

2.10.2 Demersal communities

Very little information is known about the communities inhabiting the demersal zone close to the ocean floor within the EEZ. They are likely to feature deep-sea demersal fishes, certain species of shark, cephalopods and, from time to time, transitory visitations by sperm whale. Those fishes which have been recorded, or are expected to be recorded, within this zone are presented in Table 12, with further information summarised in the Appendix. A query of the FishBase on-line database (using the search terms ‘Ascension Island’ and ‘deep water’) revealed 26 species likely to inhabit this zone within the EEZ.

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2.10.3 Mid-water pelagic communities Pelagic communities that inhabit the water column itself range in size from the great whales to minute crustaceans. They include nektonic organisms (i.e. those that can swim against currents if need be) such as cephalopods (octopus and squid) and mesopelagic fishes; and planktonic organisms (i.e. those whose movements are heavily influenced by currents) such as medusa, ctenophores, doliolids and siphonophores. Many of these species will undertake vertical migrations through the water column, a pattern often dictated by movements of zooplankton. However, the diversity, abundance and distribution of pelagic organisms inhabiting this zone is very poorly known, despite this ecosystem being by far the largest on Earth!

The decomposition of organic matter, together with animal respiration, reduces the oxygen concentration in the water column, producing an oxygen-minimum layer in mid-water, usually between 300m and 1000m depth. Recent research into this Oxygen Minimum Zone (OMZ), which in the eastern tropical Atlantic is at around 400 m depth, has found that this zone has been expanding at a rate greater than that seen elsewhere, leading to a habitat reduction for large, active predatory fish such as marlin (http://www.mbari.org/expeditions/GOC15/Leg2/ February25.html).

2.10.4 Near-surface communities Little information is available on near-surface oceanic communities. The Ascension region appears to be sandwiched between two areas of primary production: the Eastern Tropical Atlantic (to the east and north) and the South Atlantic Tropical Gyre (to the south and west). Some areas correspond, in broad terms, to areas where the food supply to the benthos is seasonally pulsed, others to areas where the benthic food supply is more continuous. Recent work by Hughes et al. (2014) indicates an area to the north-west of Ascension which they have termed an ‘assembly site’ and which appears to be favoured by foraging seabirds. It is possible this could indicate a particularly productive area of sea, fed by upwelling currents and generating denser quantities of primary producers (i.e. phytoplankton) than surrounding areas. However, this suggestion remains speculative until further research work can be undertaken.

The upper layers of the ocean support the whole range of ecological producers and consumers, ranging from phytoplankton and zooplankton, through various swimming invertebrates and open ocean fishes, to predatory sharks and cetaceans. Table 3 (section 2.2) lists various open water fishes present within the Ascension EEZ; Table 4 (section 2.3) lists those sharks and rays which may be encountered; and Table 5 (section 2.4) lists the cetaceans. The three species of turtle (Green, Hawksbill and Leatherback) which are on migration routes when passing through the offshore area of the EEZ, should also not be forgotten.

2.10.5 Non-biological deep sea resources Whilst the Pacific Ocean tends to be better known for its manganese nodules than the Atlantic, such nodules do exist on the seafloor of the Atlantic though in discrete regions. Manganese nodules are composed of a mixture of iron and manganese oxides and were first recovered from the Atlantic near the during the Challenger Expedition (1872-1876). They are most extensively developed in the Argentine, Brazil and Cape Basins in the South Atlantic and in the Sargasso Sea in the North Atlantic. These Atlantic nodules have a somewhat lower manganese content (16%) and higher iron content (21%) than those in the Pacific and Indian Oceans (Brown et al., 1989). Despite their presence in the Atlantic, and even their association with seamounts, it is thought unlikely that they would be present within the Ascension EEZ and highly unlikely, if present, to be there in commercially viable quantities. For many years the technology was not available to extract manganese nodules in commercially viable quanitites, but the hardware and techniques are now being developed for experimental extraction projects to begin.

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Table 12. Fish species thought to inhabit ‘deep waters’ within the Ascension Island EEZ. Species Common name IUCN Reference Notes Appendix Red List Dalatiidae Euprotomicrus bispinatus Pygmy shark LC Wirtz et al., 2014  Isistius brasiliensis Cookie-cutter shark LC Fishbase (DW)  Herpetoichthys regius Ornate snake NE Wirtz et al., 2014 Also recorded by Trunov (2006) as Ophichthus regius from Grattan seamount. Cetomimidae Ditropichthys storeri NE Fishbase (DW)  Derichthyidae Derichthys serpentinus Narrownecked oceanic eel NE Wirtz et al., 2014  Nemichthyidae Nemichthys scolopaceus Slender snipe eel NE Wirtz et al., 2014 Platytroctidae Barbantus elongatus NE Wirtz et al., 2014  Astronesthes caulophorus NE Fishbase (DW)  Astronesthes micropogon NE Fishbase (DW)  Astronesthes niger NE Fishbase (DW)  Chaudiolus minimus NE Fishbase (DW)  Echiostoma barbatum Threadfin dragonfish NE Fishbase (DW)  Eustomias intermedius NE Wirtz et al., 2014 affinis Günther’s boafish NE Fishbase (DW)  Giganturidae Gigantura chuni Gigantura NE Wirtz et al., 2014  Gigantura indica Telescopefish NE Wirtz et al., 2014  Lampridae Lampris guttatus Opah NE Wirtz et al., 2014  Myctophidae Notolychnus valdiviae Topside lampfish NE Fishbase (DW)  Diretmidae

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Diretmoides pauciradiatus Longwing spinyfin Fishbase (DW) Diretmus argenteus Silver spinyfin NE Fishbase (DW)  Zenionidae longipinnis NE Wirtz et al., 2014  Diplospinus multistriatus Striped escolar NE Fishbase (DW)  Gempylus serpens Snake mackerel NE Fishbase (DW)  Lepidocybium flavobrunneum Escolar NE Fishbase (DW)  Nealotus tripes Black snake mackerel NE Fishbase (DW)  Promethichthys prometheus Roundi escolar NE Wirtz et al., 2014 Symphysanodontidae Symphysanodon berryi Slope bass NE Fishbase (DW)  Trichyuridae Aphanopus intermedius Intermediate scabbardfish NE Wirtz et al., 2014 

CE Critically Endangered EN Endangered NT Near Threatened VU Vulnerable LC Least Concern DD Data Deficient NE Not Evaluated

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2.11 Oceanic microflora / microfauna

The tropical ocean region is made up of oligotrophic waters characterized by low primary productivity and consequently a low secondary productivity (Melo et al., 2014). Despite low densities, tropical zooplanktonic communities have as their primary characteristic a high species richness, which in turn results in a large network of trophic interactions in which this community participates (Piontkovski & Landry, 2003). Within this complex network of interactions, copepods play a significant role in the transfer of energy and organic material from primary producers to the higher trophic levels in pelagic ecosystems, accounting for as much as 80% of the biomass of planktonic metazoans in the marine environment. Copepods are considered the most abundant and diverse components of mesozooplankton in marine environments and the most important secondary producers in marine food webs. Variations in the abundance, distribution and interactions within the community of planktonic copepods are strongly related to the hydrographic characteristics of the marine environment. The presence of islands and seamounts is responsible for variations in the hydrodynamics of the environments where these features occur, generating a diversity of physical and ecological processes which in turn influence the structure of several local communities (Genin 2004) and promote the creation of unique habitats for many species.

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3. Conservation needs and threat assessment

3.1 The sustainability of high seas fisheries

The main target species of the longline fishery, whose distribution encompasses part of the Ascension Island EEZ, is bigeye tuna Thunnus obesus. This longline fishery operates over a wide area of the tropical Atlantic (Reeves & Laptikhovsky, 2014). Other species have also been targeted, most notably swordfish Xiphias gladius, yellowfin tuna Thunnus albacares, blue marlin Makaira nigricans and sailfish Istiophorus albicans (platypterus). Reeves & Laptikhovsky (2014), in their review of fisheries management for Ascension Island waters, concluded that the relevant stocks for bigeye tuna and for swordfish were currently being fished sustainably. The stock assessment for yellowfin tuna was more uncertain but they concluded that it was probably being fished sustainably. However, there were indications that the stocks for both blue marlin and sailfish were currently being overfished (Table 13). The longline method of fishing that is used by vessels operating in the tropical mid-Atlantic (undertaken mostly by vessels from Taiwan and Japan) involves the use of longlines. The longline consists of a main line to which baited hooks are attached at intervals by means of secondary branch lines (sometimes called snoods). These are short lengths of line, attached to the main line using a clip or swivel, with a single hook at the other end. Longlines are classified mainly by where they are placed in the water column. Those used in the vicinity of Ascension tend to be set at depths greater than 100 m (J. Brown, pers. comm.). Huang (2013) describes the fishing gear used on the Taiwanese vessels as follows: “The bigeye tuna vessels deploy 3,000 hooks per set. The main line (monofilament nylon) is 90 to 150 km long. Secondary branch lines are about 40-50 m in length and have light sticks connected to the 4.2-inch J hooks. Squid, mackerel and milkfish are used as bait. The vessels spend 6-9 hours setting lines and approximately 12-19 hours hauling.”

Table 13. Reported total catches by species and entry year for licensed vessels fishing in the Ascension EEZ, 2011 to 2013 (from Reeves & Laptikhovsky, 2014). Year: 2011 2012 2013 No. of trips: 176 99 91 Tuna Bigeye 2,972.3 1,543.3 1,503.5 Yellowfin 144.9 64.6 75.6 Albacore 67.6 29.6 37.8 Billfish Swordfish 199.4 116.2 218.2 Black Marlin 30.3 12.0 5.9 Striped Marlin 11.6 0.4 2.1 Blue Marlin 100.5 11.3 22.6 Sailfish 0.0 5.7 35.1 Other 224.5 120.9 121.2 Total 3,751.1 1,904.0 2,022.1 Estimated value (£1,000) 14,245.4 7,265.6 7,616.0

3.1.1 The ‘problem’ of bycatch

The term ‘bycatch’ can be broadly defined as “the incidental capture of non-target species”. Bycatch may be discarded (i.e. thrown back into the sea either alive or dead) or it may be retained on board the vessel if it has value and if it is allowed to be landed back at port (i.e. within a size limit or a quota allowance).

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Longline fishing results in significant bycatch. In order to assess this problem, Taiwan was required to initiate an observer programme in 1999 (Huang, 2011). Not all of the Taiwanese vessels have observers on board however – details of the coverage are given by Huang (2011). Typically, about 5% of vessels will have observers on board4, which means that 95% will not and their catch data will simply be written down into logbooks. Logbook information has been recognised as notoriously unreliable, usually involving significant under-reporting and incorrect species identification, meaning that accurate estimates can only be achieved through programmes that use well-trained observers (Paleczny et al., 2015; Baum et al., 2003). Another problem with the catch data that are recorded for these longline vessels has been that it is not always noted whether or not the vessel has been fishing within the Ascension EEZ.

Huang et al. (2009) include information on bycatch species for the period 2002-2006. In terms of the proportion of the total catch that could be assigned as bycatch, their ‘other’ category (i.e. non- commercial fish species) amounted to 35.1% of the observed catch. Of this ‘other’ category, 51.6% was Blue shark, 10.8% was other sharks, and the remaining 37.6% was other fish species. The ‘other’ category figure of 35.1% for the period 2002-2006 had apparently fallen to between 6.0% and 6.3% for the period 2011 to 2013, as reported by vessels in the Ascension EEZ (Reeves & Laptikhovsky, 2014). Reeves & Laptikhovsky (2014) point out that this suggests sharks, and particularly Blue sharks, are likely to be a major component of the ‘other’ catch category within the Ascension EEZ (Table 14). As shark-finning is illegal in Taiwan (Reeves & Laptikhovsky, 2014), the presumption is that catches of sharks are taken for human consumption or possibly as trade in other countries. Other shark species of particular concern that are caught by commercial longlining vessels as bycatch in Ascension include Galapagos sharks, bigeye thresher sharks and oceanic whitetip sharks.

Table 14. Estimated species composition of sharks and other fish in catches by vessels licensed to fish within the Ascension EEZ, 2011 to 2013 (from Reeves & Laptikhovsky, 2014). [Note that these figures do not relate to actual catches within the EEZ]. Catches reported in the ‘other’ category are first “raised” to account for presumed discarding using the specified raising factors, then the species compostion of the raised estimates is obtained using the bycatch rates given in Huang et al. (2009).

Year: 2011 2012 2013 Catch of ‘other’ fish as reported 224.5 t 120.9 t 121.2 t Raising factor 5.86 5.53 5.85 Raised estimate of ‘other’ fish caught 1,316.6 t 668.3 t 709.7 t Estimated catch of Blue Shark 678.9 t 344.6 t 366.0 t Estimated catch of other sharks 142.5 t 72.4 t 76.8 t Estimated catch of other fish species 495.1 t 251.3 t 266.9 t

The extraction of sharks by longlining has been identified as being a significant factor in the changes which have befallen the pelagic fish community in the Pacific since the 1950s, when industrial fishing commenced (Ward & Myers, 2005). It was found that, since the start of fishing, a major shift in size composition, species abundance and community biomass took place. The largest and most abundant predators, such as sharks and large tunas, suffered the greatest declines in abundance (21% on

4 Taiwan initiated their fisheries observer programme in 1999 (Huang, 2011). The average coverage achieved over 2002 to 2006 was 5.3% of trips in all Atlantic tuna longline fisheries. The number of vessels participating in these fisheries varies from year to year. In 2006, there were 15 vessels fishing for Bigeye tuna; in 2007, this increased to 60 vessels; and in 2012, 75 Taiwanese vessels were authorised to fish for Bigeye tuna and 59 for Albacore (ICCAT, 2014).

Page 55 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic average). Ward and Myers (2005) also found striking reductions in mean body mass. For example, the mean mass of blue shark Prionace glauca was 52 kg in the 1950s compared to 22 kg in the 1990s. The estimated abundance of this species was 13% of that in the 1950s. Overall, the biomass of large predators fell by a factor of 10 between the periods. Of the three possible explanations put forward to explain these data (fishing, environmental variation, and sampling bias), available evidence indiated fishing to be the most likely cause for the observed patterns. Of course, the Pacific is not the Atlantic, and there will be differences in fleet sizes and catch effort, but there are some lessons which should be taken into consideration when appraising longlining in the Atlantic. There are two main factors which make assessing the impact of commercial fisheries on the pelagic communities of the Ascension EEZ so difficult. Firstly, there is no observer category for fishing which takes place solely within the EEZ; and secondly, both target species (i.e. tunas, swordfish, blue marlin, sailfish etc,) and bycatch species (sharks, other non-commercial fish species, turtles etc.) are mobile and may swim freely in or out of the EEZ on routes which may vary from year to year depending on environmental conditions. In order to try to minimize the quantity of bycatch that is caught, a number of adaptations have been shown to have succeeded in some longline fisheries. Such mitigation techniques include the use of weights to ensure the lines sink quickly; the deployment of streamer lines around the vessel when deploying baited longlines to scare away birds; setting lines only at night in low light (to avoid attracting birds); limiting fishing seasons to the southern winter (when most seabirds are not feeding young); and not discharging offal while setting lines. For the Taiwanese longline fishing fleet, Huang (2011) provides information on the mitigation measures that have been introduced to address bycatch issues. These include measures to promote the live release of sharks, seabirds and turtles; the prohibition of shark finning; and the prohibition of retaining on board oceanic whitetip, hammerhead or bigeye thresher sharks. Huang (2011) also notes that the Taiwanese have also conducted research on such measures as using circle hooks as a means of reducing bycatch of species such as turtles, though it was concluded that no significant difference was seen between the use of J-hooks and circle hooks for sea turtle bycatch. Apart from certain shark species (blue shark, Galapagos shark, bigeye thresher shark and oceanic whitetip shark) and certain other fishes, the impact of bycatch on turtles, seabirds and cetaceans appears to be ‘very low’, according to Reeves & Laptikhovsky (2014). For instance, from data published by Huang et al. (2009) and interpreted by Reeves & Laptikhovsky (2014), the annual catch of seabirds across the whole Taiwanese fleet in the tropical tuna industry was estimated at 20 birds per year for the period 2002 to 2006. Similarly for turtle bycatch during the same period (2002-2006), between latitudes 0 ° and 10 ° S and by interpreting data from Huang et al. (2009) and Huang (2013), Reeves & Laptikhovsky (2014) estimate the annual catch of turtles within this latitude range as being 100 per year. Of these, they state, 60 would be Leatherbacks and one a Green turtle. Around 40% would be released alive. For cetacean bycatch, Huang et al. (2009) noted that, for the period 2002 to 2006 for the Taiwanese fleet fishing in the Atlantic with observers on board, a total of 27 individual cetaceans were captured, and that most captures were made in the tropical zone. No further information is given on these individuals.

3.1.2 The attraction of seamounts to high seas fisheries

Seamounts seem to favour aggregations of marine predators (tunas, dolphins, seabirds) in their vicinity (Morato et al. 2008; Pitcher et al. 2007). They have been identified as hotspots of pelagic biodiversity in the open ocean (Samadi et al., 2006), though the evidence for this is not as clear as first seemed (Clark et al., 2010).

Biological communities on seamounts face a number of threats from human activities. The most widely known of these is fishing, especially trawling, although in recent years the potential has increased for

Page 56 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic exploitation of mineral resources too (more so in the Pacific however, than in the Atlantic). Seamount communities are extremely vulnerable to the impacts of fishing: their limited fixed habitat, the extreme longevity of many species (of the order of 100 years and more – see Table 15 below), and the apparently limited recruitment between seamounts, all compound the uncertainty of recovery from trawling, which sweeps away the benthic epifaunal community as a bycatch (De Forges et al., 2000). In the 1970s, extensive trawling began on seamounts as fleets discovered large aggregations associated with them (Clark et al. 2007). Orange roughy Hoplostethus atlanticus have been targeted on seamounts worldwide, with roundnose grenadier Coryphaenoides rupestris being a major seamount fishery in the North Atlantic. Smaller fisheries for Beryx splendens, mackerel, and black cardinalfish Epigonus telescopus have occurred in the mid-Atlantic and elsewhere. Few of these large- scale seamount trawl fisheries have proved sustainable, with many showing a boom-and-bust pattern (Vinnichenko, 2002). Many deep-sea commercial species have characteristics that generally make them more vulnerable to fishing pressure than shallower shelf species (Clark et al., 2010). They can form large and stable aggregations over seamounts for spawning or feeding, which enables very large catches and rapid depletion of stock size. Biological factors such as longevity, low fecundity, and slow growth rates make recovery from fishing impacts slow. Seamount fisheries have typically proven difficult to research and manage sustainably. Once overexploited, it is uncertain if deep-sea fisheries on seamounts can recover, and irregular recruitment levels may be a key factor (Clark, 2001).

Many seamount taxa are extremely long-lived and grow very slowly, especially those forming biogenic habitats (some scleractinian corals) and those adding structural complexity (e.g., large erect anthipatharian and gorgonian corals, sponges, and crinoids) (Table 15). Some of these low-productivity components of benthic ecosystems on seamounts can therefore be expected to have less capacity to absorb human disturbance and take much longer to recover than their shallower, more productive counterparts (Clark et al., 2010).

Table 15. Examples of age estimates of seamount invertebrate megabenthos (from Clark et al., 2010). Faunal group Age (years) Method Reference Glass sponge 440 Ring count Samadi et al. 2007 Stalked crinoid 340 14C dating Samadi et al. 2007 Zoanthid (Gerardia spp.) 400–900 14C dating Roark et al. 2006 Zoanthid (Gerardia spp.) 1800 14C dating and ring count Rogers et al. 2007 Gorgonian coral 67–2377 14C dating Roark et al. 2006 coral 35–197 14C and 120Pb dating Rogers et al. 2007 Biogenic habitat (accumulated) 1000–50,000 U/Th dating Rogers et al. 2007

3.2 Offshore impacts on species also found inshore

3.2.1 Foraging seabirds

The number of seabirds caught by incidental capture in pelagic longlines is thought to be very low (Yeh et al., 2013), probably because of the preference for active prey with the consequence that they do not generally pursue fishing vessels in search of discards (Huang, 2011). Several of Ascension’s seabird species however rely, indirectly, on the presence and behaviour of tuna (and other large fish species) in order to catch their prey (Au & Pitman, 1988). Tuna species, particularly yellowfin Thunnus albacares, in pursuance of their own prey, tend to drive smaller pelagic fish to the surface. In the case of flyingfish, they are likely to glide above the surface of the sea during these chases in order to escape being caught by the tuna. Flyingfish, particularly of the genus

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Exocoetus, form the principal diet of both boobies and frigatebirds, which they obtain near or above the sea surface (Oppel et al., 2015). Sooty terns are also reliant upon large schools of surface-swimming tuna to drive their prey within reach (Au & Pitman, 1988). Consequently, there is heavy reliance on the presence of tuna schools within the foraging ranges of these seabirds.

Atlantic stocks of large tuna species have declined by an estimated 50–80% over the past 50 years and there is some evidence of impacts on Ascension’s seabirds (Hughes, 2014). It would appear that fisheries for the Atlantic yellowfin and bigeye tuna are currently regarded as sustainable by the regional regulator (ICCAT, 2014), though it is known that there has been a long term decline in their populations since the 1960s (Cullis-Suzuki & Pauly, 2010). Indeed, this period of decline corresponds to an apparent collapse in the size of the Ascension Island sooty tern population by almost 90% (Hughes, 2014). A dietary shift in chick provisioning also appears to have occurred during this period, with a significant decline in the proportion of fish and a corresponding increase in the proportion of squid, which has a lower nutritional value (Hughes, 2014). Again, overfishing has been implicated in this shift, with a decline in the availability of small fish driven to the surface by schooling tuna during the day forcing terns to switch to alternative food items, such as squid that tend to be active on the surface at night (Hughes, 2014). If tuna stocks continue to be overfished, impacts on the remaining sooty tern population are likely to be significant (AIG, 2015d). As pointed out in the Species Action Plans for the Ascension frigatebird, the masked booby and the sooty tern, any further depletion of tuna stocks as a result of overfishing would therefore be expected to have severe consequences in terms of reduced food availability and diminished breeding success (AIG, 2015b). It has been proposed that the importance of Ascension as a seabird breeding station relates to its position within a zone of elevated productivity driven by the westward flowing South Equatorial Current (Scullion, 1990). Any changes in current strength and position as a result of climate change could therefore have significant impacts on the productivity of the marine ecosystem and food availability for seabirds at Ascension Island. Indeed, mass seabird breeding failures periodically occur at Ascension Island and there is circumstantial evidence to suggest that these are related to climate anomalies such as the El Niño Southern Oscillation (AIG, 2015b).

3.2.2 Sharks

Following the advent of tagging studies, many shark species have been found to be highly migratory, traveling long distances during their lifetimes. These include tiger shark (max. recorded distance between tagging and recovery of tag of 3,430 km), bigeye thresher shark (2,767 km), shortfin mako (3,433 km), dusky shark (3,800 km). Galapagos sharks are also known to be capable of crossing open oceans between islands, with individuals being reported at least 50 km from land.

No definitive population assessments of shark species known to occur within the Ascension EEZ have been undertaken. However, it is apparent that large numbers of sharks are taken as bycatch during longlining operations. Blue shark, shortfin mako, and bigeye thresher shark are all classed as being ‘most vulnerable stocks’ within the ICCAT area (Reeves & Laptikhovsky, 2014). Bigeye thresher sharks are also known to be significant to Taiwanese fisheries, which land about 220 metric tons annually. (Joung et al. 2005).

The Galapagos shark is the most common shark species seen in the nearshore waters around Ascension. Anecdotal evidence suggests their numbers are thought to be increasing again, having been depleted for a number of years. The shark has a widespread but patchy worldwide distribution, occurring at widely separated islands and some coastal sites in the Pacific, Atlantic and Indian Oceans (Bennett et al., 2003). In 1982, it was reported as being a “very common species” at St Paul’s Rocks, a small archipelago of barren islets on the Mid-Atlantic Ridge to the north-west of Ascension at 00°55′N; 29°21′W (Edwards & Lubbock, 1982). Indeed, the shark population was described as being “one of the densest shark populations of the Atlantic Ocean”, consisting largely of Galapagos Carcharhinus

Page 58 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic galapagensis and silky Carcharhinus falciformis sharks (Edwards & Lubbock, 1982). However, for the past decade, no sharks have been observed around the islets despite the occurrence of several diving expeditions, and the population of Galapagos sharks there is now recognised as being extinct (Luiz & Edwards, 2011). The sharks’ demise is the result of intense fishing pressure by commercial fishing vessels operating around the islets throughout the year. The persistence of occasional individuals of the once locally common silky shark in the vicinity of the archipelago, as a result of constant immigration of this oceanic species from outside the area, suggest that the population might recover if the present fishing pressure was removed (Luiz & Edwards, 2011). This episode should be borne in mind when considering not only Ascensions’ shark populations but also those of neighbouring seamounts.

3.2.3 Turtles

Incidental capture in fisheries constitutes a major source of mortality for marine turtles worldwide and may affect green turtles, both in their coastal foraging habitats and during oceanic migrations. The migration route between Brazil and Ascension Island traverses an area of intensive pelagic longlining for tuna and billfish (AIG, 2015a). Although thousands of marine turtles die as a result of long-lining activities worldwide, green turtles account for a relatively small proportion of this total (Angel et al., 2014), with most studies in the southern and central Atlantic reporting a by-catch rate of 0-13 individuals per million hooks (Sales et al., 2008; Coelho et al., 2013). The herbivorous diet and predominantly coastal distribution of adult green turtles probably explain this reduced susceptibility, although specific data from along oceanic migration routes where risks may be elevated is lacking. In contrast, by-catch rates of green turtles in coastal trawl and net fisheries in the south-west Atlantic are substantial ( et al., 2013; Gallo et al., 2006) and may impact both adults and juvenile stages originating from Ascension Island.

3.3 Conservation needs of the wider pelagic environment of the tropical Atlantic

From studies that have been undertaken on Ascension’s nearshore marine wildlife, it is apparent that their origins derive from both sides of the Atlantic. This is likely to be the case with a number of deep sea species too. The predominant current affecting the island flows from east to west, leading to the expectation that there should be more species whose geographical spread extends further to the east than to the west. However, this is not necessarily the case. The growing use of mitochondrial DNA as a research tool investigating speciation may well determine many new species or species groups, as well as extending the known ranges of other species (e.g. Muss et al., 2001). Ascension’s marine wildlife represents a unique mix of eastern and western Atlantic biodiversity.

3.3.1 The need for a Reference Area within the tropical Atlantic system As far as the author is aware, there are no large-scale benthic or pelagic ‘reference areas’ within the tropical Atlantic. Reference areas provide extensive areas of ocean that are free from commercial fishing operations, and thus provide an opportunity for comparing fished and non-fished ecosystems. Without such areas for comparative purposes, it is not possible to assess properly the impact which extractive fishing activities might be having on individual species or certain habitats. Reference areas also provide scientists with an opportunity to undertake monitoring of natural variability and long-term change within ecosystems in areas free of the disturbances caused by human activities.

The UK has led the way in promoting the establishment of such scientific reference areas. Indeed, having a reference area was one of the main justifications behind the UK’s successful Commission for

Page 59 of 115 The Offshore Marine Environment of Ascension Island, South Atlantic the Conservation of Antarctic Marine Living Resources (CCAMLR) proposal to create the South Orkney MPA in 2009 (http://archive.ccamlr.org/pu/E/e_pubs/cm/11-12/91-03.pdf). The area in question, the South Orkney Islands southern shelf, was acknowledged “as being of high conservation importance, and representative of key environmental and ecosystem characteristics in the region”.

Other reference areas have also been proposed around the Antarctic landmass. In 2012, the UK proposed the establishment of a network of scientific reference areas along the length of the Antarctic peninsula in areas where ice sheets collapse. Other reference areas were also being proposed at the time by , and the United States for areas of the Antarctic coastal shelf over which they had jurisdiction.

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4. Conclusions

4.1 Sources, quality and extent of information

 This Review provides a comprehensive assessment of what is known about the offshore marine environment surrounding Ascension Island in the South Atlantic. Sources have included peer-reviewed literature and grey literature, expert opinion and personal experience.

 Where known, species inventories have been presented, with notes on their conservation status, worldwide distributions and local importance.  Most information is known about the island’s resident seabird populations and the annual visits of nesting green turtles, both of which make use of the island’s offshore waters. Data are available on the taking of commercial fish species (particularly of tuna and billfish species), though often these data derive from areas which extend beyond the 200 nm limit of the island’s EEZ. Far less is known about pelagic, non-commercial fish populations (including sharks), offshore cetaceans, benthic invertebrates and the deep-sea benthos in general.  Much of the fisheries data will have come from logbooks, which are known to be of dubious accuracy.  A similar review of marine environmental knowledge was undertaken by the author in 2012 for the Pitcairn Islands, another UK Overseas Territory in the South Pacific (Irving & Dawson, 2012). There was a similar lack of information available for much of the islands' offshore area (extending to the 200 nm EEZ limit), with much more information being available for the nearshore area, as has been the case with Ascension. The Pitcairn Islands also lie at the very fringes of the range of tuna (yellowfin, bigeye, skipjack and albacore) and certain billfish (blue and striped marlin), and there had been commercial fishing licenses sold to Korean and Japanese fishing concerns in the past.

 Given the lack of good quality, local data and an apparent dearth of knowledge overall, the precautionary principle should be adopted wherever possible.

4.2 The marine biodiversity importance of Ascension’s offshore waters

 The geographical location of the island, almost mid-way between the continental land masses of West Africa and that of Brazil in South America, is largely responsible for the mix of species which are present in its waters, some of which have origins on the west side and some on the east side of the South Atlantic. Other physical factors which give rise to the unique set of conditions which influence the island’s waters include the shifting location of influencing ocean currents; the unusual bathymetry of the seabed and its proximity to the Mid-Atlantic Ridge and associated deep-sea features; and the lack of reef-building corals surrounding a tropical island.  Those species of greatest conservation interest include the endemic Ascension frigatebird (recently discovered to venture as far as the coast of West Africa on its foraging flights); a very large sooty tern population; the second largest nesting population in the Atlantic of endangered green turtles; a juvenile population of critically-endangered hawksbill turtles; a small, over- wintering population of humpback whales; and a resident population of oceanic bottlenose dolphins.  The Ascension Island EEZ features a number of prominent seamounts, the shallowest of which rises to within 72 m of the surface. Seamounts are typically associated with increased densities of marine life, particularly of sessile invertebrates (such as sponges and fan corals), and mobile

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echinoderms, molluscs and crustacea. The fish fauna will also be richer on the slopes of these seamounts. Seamounts also have the ability to act as ‘stepping stones’, providing opportunities for certain species to expand their ranges.

4.3 The main threats to maintaining and enhancing the offshore marine biodiversity

 Licensed commercial fishing by foreign vessels has been permitted to take place within the island’s EEZ over recent years. Even though the island’s EEZ lies at the southern and western edge of the main fishery area, catch returns have shown that considerable numbers of tuna species and billfish species are extracted, together with certain oceanic shark species and other species of lesser value to the vessel operators.  As well as the extraction of targeted species (typically of apex predators), a wide range of species are caught incidentally as bycatch, including sharks and other non-target fish species and, to a lesser extent, seabirds.  A recent paper (Paleczny et al., 2015) has shown a global decline in seabirds over the period between 1950 and 2010 of 69.7%. The cause of the estimated overall decline in seabird populations is likely to be a suite of threatening human activities, such as introduced species at nesting colonies (e.g., , cats), entanglement in fishing gear at sea, pollution, direct exploitation (harvesting chicks, eggs, adults) etc., with overfishing of food sources by humans being one of the main categories.  A number of Ascension’s seabird species (particularly masked boobies and sooty terns) have been shown to favour certain areas of the EEZ during their foraging flights from the island. It has been postulated that these may be areas where there are concentrations of surface fish species, possibly being driven to the surface by schools of tuna preying upon them too. Continuous removal of tuna may well lead to these ‘hotspots’ being reduced in importance, requiring the seabirds to expend greater amounts of energy seeking out suitable prey.

4.4 What would a no-take MPA protect and secure?

 A no-take MPA would provide a ‘reference area’ in the tropical Atlantic Ocean, where no other such reference area exists. Within this reference area, no commercial fishing would be undertaken, and thus no extraction of apex predators. This would allow the ecosystem within the EEZ to resort gradually to its non-fished, natural state.  A no-take MPA would ensure that seamounts could remain in a pristine condition, allowing their unique marine life to continue to flourish. This assumes that they have not been subject to commercial bottom fishing with nets (which would have adversely affected sessile faunal communities) or to large-scale long-line or net fisheries (which could well have taken out many of the apex predatory species).

 A no-take MPA would prevent extractive operations other than fishing (such as deep sea mining) from taking place.  A no-take MPA, extending from the 12 nm limit to the extent of the EEZ at 200 nm, would allow for the continuation of sports fishing (sea angling) and for the extraction of other marine life (such as spiny lobsters) from within the 12 nm limit. However, these activities require on-going monitoring to ensure that over-exploitation does not result, particularly regarding the selective

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extraction of the largest individuals. It is reassuring to note that inshore fishing licensing is being brought in by the AIG Conservation Department.

4.5 What are the main data gaps to fill?

 It is clear from the findings of this Review that our knowledge of the offshore environment around Ascension Island would benefit from further research studies (as indicated below).

 In recent years, the development of tracking devices which can be fitted to animals without apparent ill-effect or change in behaviour patterns has increased our knowledge of the range of certain species dramatically. For the first time, we have been able to track an individual animal, be it a seabird, turtle or cetacean, beyond the horizon and for days at a time as well. Our understanding of how these animals utilize the offshore waters around the island would benefit from many more such studies, especially in the case of the island’s seabirds, the three species of turtle known to be present, various tuna species, humpback whales and even whale sharks and other shark species.  The possible between tuna populations (when near the surface) and the island’s seabird populations is of great interest and would benefit from further research. Research into the behaviour of tuna within Ascension Island’s EEZ would help to establish more precise population movements, the timing of migrations, and whether more resident populations exist that can be effectively protected at a local level.  Deep-sea researchers should be encouraged to look at the marine life inhabiting the numerous seamounts and deep-sea trenches and canyons which are present within the EEZ and about which we know very little.  Species identification – e.g. spotted dolphins Stenella spp.? Are these Atlantic spotted dolphins or Pan-tropical spotted dolphins? Which species of petrels are present?

 Humpback whales – can it be determined if they belong to Stock A (western South Atlantic) or Stock B (eastern South Atlantic)? We would then know where they spend their summers. How many individuals visit Ascension and are they the same individuals year on year? Does Ascension act as a calving and nursery area for them?  Encouraging members of the local community to assist with tagging large game fish and shark species, in order to determine their ranges.

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5. References

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Padula, V., Wirtz, P. and Schrödl, M. 2014. Heterobranch sea slugs (Mollusca: ) from Ascension Island, South Atlantic Ocean. Journal of the Marine Biological Association of the United Kingdom, 1-10. available on CJO2014. doi:10.1017/S0025315414000575. Pawson, D.L. 1978. The echinoderm fauna of Ascension Island. Smithsonian Contributions to the Marine Sciences, 2: 1-31. Pelembe, T.J. 2005. Commercial Fishing Ascension Background Brief. Perrin, W.F. 1985. The former dolphin fishery at St Helena. Report of the International Whaling Commission, 35: 423-428. Petit, J. and Prudent, G. 2010. Climate Change and Biodiversity in European Union Overseas Entities. IUCN report. 192 pp. Piontkovski, S., Williams, R., Ignatyev, S., Boltachev, A. and Chesalin, M. 2003. Structural-functional relationships in the pelagic community of the eastern tropical Atlantic Ocean. Journal of Plankton Research, 25(9): 1021- 1034. Price, J.H. & John, D.M. 1977 Subtidal Ecology in Anitgua and Ascension A Comparison. Proceedings of the 11th Symposium of the Underwater Association at the British Museum, 111-133. Price, J.H. and John, D.M. 1980. Ascension Island A survey of inshore benthic macroorganisms, communities and interactions. Aquatic Botany, 9: 251-278. Rocha, L.A., Bass, A.L., Robertson, D.R. and Bowen, B.W. 2002. Adult habitat preferences, larval dispersal, and the comparative phylogeography of three Atlantic surgeonfishes (Teleostei: Acanthuridae). Molecular Ecology, 11(2): 243-251. Rosewater, J. 1975. An annotated list of the marine mollusks of Ascension Island, South Atlantic Ocean. Press. Rudorff, C.A.G., Lorenzzetti, J.A., Gherardi, D.F.M. and Lins-Oliveira, J.E. 2009. Application of remote sensing to the study of the pelagic spiny lobster larval transport in the tropical Atlantic. Brazilian Journal of Oceanography, 57: 7-16. Samadi, S., Bottan, L., Macpherson, E., Richer de Forges, B., Boisselier, M-C. 2006. Seamount endemism questioned by the geographical distribution and population genetic structure of marine invertebrates. Marine Biology, 149:1463–1475. Smith, E.A. 1890. On the marine mollusca of Ascension Island. Proceedings of the Zoological Society of London, April 1, 1890: 317-322. Stock, J.H. 1996. Origin of the non-marine aquatic fauna of St. Helene and Ascension. Proceedings of the 2nd Symposium of Fauna and Flora of the Atlantic Islands, 5: 455-462. Trunov, I.A. 2006. Ichthyofauna of seamounts around the island of Ascension and St Helena Island. Journal of Ichthyology, 46(7): 493-499. Tsiamis, K., Peters, A.F., Shewring, D.M., Asensi, A.O., Van West, P. and Küpper, F.C. 2014. Marine benthic algal flora of Ascension Island, South Atlantic. Journal of the Marine Biological Association of the United Kingdom, 1-8. http://www.journals.cambridge.org/abstract_S0025315414000952 van Andel, T.H., Rea, D.K., von Herzen, R.P and Hoskins, H. 1973. Ascension Fracture Zone, Ascension Island and the Mid-Atlantic Ridge. Geological Society of America Bulletin, 84(5): 1527-1546. Watson, R.B. 1879. Mollusca of H.M.S. Challenger Expedition. Journal of the Linnean Society, Zoology, 14: 692— 695.

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Appendix Ascension Island ‘Game Fishes’ (as included within the on-line database ‘Fishbase’)

Tylosurus crocodilus hound needlefish

Authority: (Péron & Lesueur, Order: Family: Belonidae 1851)

Depth range: 0 – 13 m Max. length: 150 cm Max. weight: 6.4 kg No map available Description: Reef-associated. A pelagic species found on seaward reefs. Solitary or in small groups. Feeds on fishes. Feared by fishers because they can cause puncture wounds with their sharp snouts when jumping out of the water, e.g. when alarmed or attracted to lights at night.

Notes pertinent to Ascension: Tylosaurus sp. recorded by Wirtz et al. (2014), Map: Fishbase Picture: J-C Baur but as yet it is currently unknown whether it is the western Atlantic T. acus or the eastern Atlantic T. rafale which is present at Ascension. Wirtz et al. (2014) Distribution: Western Atlantic: New , USA to Brazil. Eastern Atlantic: Fernando do not list T. crocodilus. Poo, , Liberia, and Ascension Island; from and Guinea; and Cape Verde.

Reference(s): Fishbase 02Feb14 (‘game fishes’); Wirtz et al., 2014. IUCN Red List status: Not Evaluated

Caranx crysos blue runner

Authority: (Mitchill, 1815) Order: Perciformes Family:

Depth range: 0 – 100 m Max. length: 70 cm Max. weight: 5.1 kg

Description: Reef-associated. A schooling species generally not far from the coast. Juveniles often found in association with floating Sargassum. Adults feed on fishes, shrimps, and other invertebrates. They spawn offshore from

January through August. Eggs are pelagic.

Notes pertinent to Ascension: Map: Fishbase Picture: JE Randall

Distribution: Eastern Atlantic: Senegal to Angola, including the western Mediterranean, St. Paul's Rocks and Ascension Island. Reported from Mauritania. Western Atlantic: Nova Scotia, Canada to Brazil, including the Gulf of Mexico and the Caribbean. Also found in Argentina. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014. IUCN Red List status: Least Concern

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Caranx latus horse-eye jack/yellowjack/big-eye jack

Authority: , 1831 Order: Perciformes Family: Carangidae

Depth range: 0 – 140 m Max. length: 101 cm Max. weight: 13 kg

Description: A pelagic schooling species, usually found on offshore reefs. Feeds on fishes, shrimps and other invertebrates. Eggs are pelagic. The adult horse-eye jack commonly swims with others in a school, either as one species or mixed with crevalle jack.

Notes pertinent to Ascension: Map: Fishbase Photo: Estrada Anaya

Distribution: Circumtropical (Atlantic, Indian & Pacific Oceans). Commonly found in the subtropical Atlantic Ocean from and the northern Gulf of Mexico and south to Rio de Janeiro. In the eastern Atlantic, it is found from St. Paul's Rocks to Ascension Island and, rarely, the in the Gulf of Guinea. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Caranx lugubris black jack/black trevally

Authority: Poey, 1860 Order: Perciformes Family: Carangidae

Depth range: 12 – 354 m Max. length: 100 cm Max. weight: 18 kg (usually 24 – 65 m) Description: An oceanic and insular species, very much restricted to clear oceanic waters. Sometimes seen near drop-off at outer edge of reefs. Occasionally forming schools. Feed on fishes at night. Eggs are pelagic. The black jack inhabits deep reefs and reef drop offs, also being common around oceanic seamounts.

Notes pertinent to Ascension: The species was initially named Caranx Map: Fishbase Photo: JE Randall ascensionis by Georges Cuvier in 1833. Distribution: Circumtropical (Atlantic, Indian & Pacific Oceans). Western Atlantic: Bermuda and the northern Gulf of Mexico to Brazil. Eastern Atlantic: , , St. Paul's Rocks, Ascension Island, Cape Verde, and Gulf of Guinea. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

87 The Offshore Marine Environment of Ascension Island, South Atlantic

Decapterus macarellus

Authority: (Cuvier, 1833) Order: Perciformes Family: Carangidae

Depth range: 0 – 400 m Max. length: 46 cm Max. weight:

Description: Pelagic-oceanic. Adults prefer clear oceanic waters, frequently around islands. Sometimes they are found near the surface, but generally caught between 40 and 200 m depth. Usually seen as fast moving schools along the reef edges near deep water. They feed mainly on zooplankton.

Eggs are pelagic.

Notes pertinent to Ascension: Photo of species taken by T. Hook at Map: Fishbase Photo: JE Randall Ascension (Wirtz et al., 2014). Distribution: Circumglobal. Western Atlantic: Nova Scotia, Canada and Bermuda to approximately Rio de Janeiro, Brazil. Appears to be absent from the Gulf of Mexico. Eastern Atlantic: St. Helena, Ascension, Cape Verde, and Gulf of Guinea; Azores and Madeira. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Pseudocaranx dentex white trevally

Authority: (Bloch & Order: Perciformes Family: Carangidae Schneider, 1801) Depth range: 10 – 238 m Max. length: 122 cm Max. weight: 18.1 kg

Description: Reef-associated. Adults occur in bays and coastal waters. Schools are found at the surface, in mid-water and on the bottom and are often associated with reefs and rough bottom. Feed on plankton by ram- filtering and suction feeding and on bottom invertebrates. Eggs are pelagic. One of the best table fish 'being indeed the salmon of St. Helena'.

Notes pertinent to Ascension: Map: Fishbase Photo: A Carvalho Filho

Distribution: Western Atlantic: North Carolina, USA and Bermuda to southern Brazil. Eastern Atlantic: Mediterranean, Azores, Madeira, the Canary Islands, Cape Verde, Ascension and St. Helena Island. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

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Trachinotus ovatus pompano

Authority: (Linnaeus, 1758) Order: Perciformes Family: Carangidae

Depth range: 50 – 200 m Max. length: 70 cm Max. weight: 2.8 kg

Description: Pelagic-neritic. Adults are moderately common in shallow water in areas of surge. Found in clear waters. Form schools. Small specimens are regularly caught at night from steep rocky shores. Adults feed on small crustaceans, molluscs and fishes.

Notes pertinent to Ascension: Map: Fishbase Photo: R Freitas

Distribution: Eastern Atlantic: Bay of Biscay, British and Scandinavian waters (rare vagrant) to Angola, including the Mediterranean Sea and offshore islands. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Uraspis helvola whitetongue jack

Authority: (Forster, 1801) Order: Perciformes Family: Carangidae

Depth range: 50 – 300 m Max. length: 58 cm Max. weight:

Description: Reef-associated. Adults are benthopelagic in sandy bottoms at the foot of the edge of the outer reefs, continental coasts and around islands. Solitary or forming small schools.

Notes pertinent to Ascension: Photo of this species taken at Ascension by T. Map: Fishbase Photo: unsw.discoverlife.org Hook (Wirtz et al., 2014). Distribution: Circumglobal. Southeast Atlantic: St. Helena and Ascension islands.

Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

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Promethichthys prometheus roundi escolar

Authority: (Cuvier, 1832) Order: Perciformes Family: Gempylidae

Depth range: 80 – 800 m Max. length: 100 cm Max. weight: ?

Description: Benthopelagic. Found on continental slopes, around oceanic islands and submarine rises. Migrate to midwater at night. Feed on fish, cephalopods and crustaceans. Eggs and larvae are pelagic.

Notes pertinent to Ascension: Map: Fishbase Photo: PMN Cambraia Duarte

Distribution: Tropical and warm temperate waters of all oceans. Subtropical; 50°N - 36°S, 180°W - 180°E. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Istiophorus albicans Atlantic sailfish

Authority: (Latreille, 1804) Order: Perciformes Family: Istiophoridae

Depth range: 0 – 200 m Max. length: 315 cm Max. weight: 58.1 kg

Description: Pelagic-oceanic. Usually found in the upper layers of warm water above the thermocline, but also capable of descending to rather deep water. Often migrate into nearshore waters. Occasionally form schools or smaller groups of 3 to 30 individuals, but often occur in loose aggregations over a wide area. Feed mainly on small pelagic fishes but also takes bottom-dwelling organisms.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014); instead, they Map: Fishbase Photo: E Baumeier have listed the Indo-Pacific sailfish Istiophorus platypterus. Some authorities believe these two species are one and the same. Distribution: Atlantic Ocean: in tropical and temperate waters approximately 40°N in the northwest Atlantic, 50°N in the northeast Atlantic, 40°S in the southwest Atlantic, and 32°S in the southeast Atlantic. Highly migratory species.

Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

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Katsuwonus pelamis skipjack tuna

Authority: (Linnaeus, 1758) Order: Perciformes Family: Scombridae

Depth range: 0 – 260 m Max. length: 110 cm Max. weight: 34.5 kg

Description: Pelagic-oceanic. Found in offshore waters; larvae restricted to waters with surface temperatures of 15°C to 30°C. Exhibit a strong tendency to school in surface waters with birds, drifting objects, sharks, whales. Feed on fishes, crustaceans, cephalopods and molluscs; cannibalism is common. Spawn throughout the year in the tropics. Eggs and larvae are pelagic. Preyed upon by large pelagic fishes.

Notes pertinent to Ascension: Only recently recorded from Ascension. Photo Map: Fishbase Photo: R Freitas of this species taken at Ascension by T. Hook (Wirtz et al., 2014). Distribution: Cosmopolitan in tropical and warm-temperate waters. Highly migratory species. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Least Concern

Thunnus alalunga albacore (tuna)

Authority: (Bonnaterre, Order: Perciformes Family: Scombridae 1788)

Depth range: 0 – 600 m Max. length: 140 cm Max. weight: 60.3 kg

Description: Pelagic-oceanic. abundant in surface waters of 15.6° to 19.4°C. Known to concentrate along thermal discontinuities. Form mixed schools with skipjack tuna Katsuwonus pelamis, yellowfin tuna Thunnus albacares and bluefin tuna T. maccoyii. Schools may be associated with floating objects, including sargassum weeds. Feed on fishes, crustaceans and squids. Eggs and larvae are pelagic.

Notes pertinent to Ascension: Caught by game fishers at Ascension, though Map: Fishbase Photo: C Archambault no photo (Wirtz et al., 2014) Distribution: Cosmopolitan in tropical and temperate waters of all oceans but not at the surface between 10°N and 10°S. Often confused with juvenile Thunnus obesus which also have very long pectorals but with rounded tips. Highly migratory species.

Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Near Threatened

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Thunnus albacares yellowfin tuna

Authority: (Bonaterre, 1788) Order: Perciformes Family: Scombridae

Depth range: 1 – 250 m Max. length: 239 cm Max. weight: 200 kg

Description: A pelagic-oceanic species occurring above and below the . They school primarily by size, either in monospecific or multi- species groups. Larger fish frequently school with porpoises, also associated with floating debris and other objects. Feed on fishes, crustaceans and squids. Eggs and larvae are pelagic.

Notes pertinent to Ascension: Photo of this species taken at Ascension by T. Map: Fishbase Picture: iotc.org Hook (Wirtz et al., 2014). Distribution: Worldwide in tropical and subtropical seas. Highly migratory species.

Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Near Threatened

Thunnus obesus bigeye tuna

Authority: (Lowe, 1839) Order: Perciformes Family: Scombridae

Depth range: 0 – 250 m Max. length: 250 cm Max. weight: 210 kg

Description: Pelagic-oceanic. Occur in areas where water temperatures range from 13°-29°C, but the optimum is between 17° and 22°C. Variation in occurrence is closely related to seasonal and climatic changes in surface temperature and thermocline. Juveniles and small adults school at the surface in mono-species groups or mixed with other tunas, may be associated with floating objects. Adults stay in deeper waters. Eggs and larvae are pelagic. Feed on a wide variety of fishes, cephalopods and crustaceans during the day and at night.

Notes pertinent to Ascension: Photo of this species taken at Ascension by T. Map: Fishbase Photo: culture.teldap.tw Hook (Wirtz et al., 2014). Distribution: Atlantic, Indian and Pacific: in tropical and subtropical waters. Highly migratory species. Reference(s): Fishbase (‘game fishes’); Wirtz et al., 2014 IUCN Red List status: Vulnerable

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Ascension Island ‘Deep Water Fishes’ (as included within the on-line database ‘Fishbase’)

Ditropichthys storeri

Authority: Goode & Bean, Order: Family: Cetomimidae 1895 Cetomimiformes Depth range: 650 – 3400 m Max. length: 13 cm Max. weight: ?

Description: Juveniles (less than 3.5 cm) were captured in shallower depth range (650-877 m). Larger specimens appear to dwell deeper.

Notes pertinent to Ascension: Map: Fishbase Drawing: shows typical fish in this family. Distribution: Circumglobal. Atlantic Ocean: between 41°N-43°S, in the eastern Atlantic it is found south of Canary Islands to east of Ascension Island; in the western Atlantic it is known from the USA to Argentina. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Euprotomicrus bispinatus pygmy shark

Authority: Quoy & Gaimard, Order: Squaliformes Family: Dalatiidae 1824 (?Squalidae)

Depth range: 0 – 1800 m Max. length: 31 cm Max. weight: ?

Description: Epi-, meso-, and perhaps bathypelagic at 1->400 m. Occurs at or near the surface at night, descending to below 400 m (possibly as deep as 1,800 m) during the day. Feeds on squid, bony fishes, and crustaceans. Ovoviviparous, with 8 young per litter, size at birth between 6 and 10 cm. Caught with dip-nets and buckets at night

Notes pertinent to Ascension: Map: Fishbase Drawing: FAO

Distribution: Circumglobal: In subtropical to temperate waters. Southeast Atlantic: near Ascension Island, east of Fernando de Noronha Island, and west of Cape of Good Hope, South Africa. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Least Concern

93 The Offshore Marine Environment of Ascension Island, South Atlantic

Isistius brasiliensis cookie cutter shark

Authority: Quoy & Gaimard, Order: Squaliformes Family: Dalatiidae 1824 Depth range: 0 – 3700 m Max. length: 56 cm Max. weight: ?

Description: Epi- to bathypelagic. Makes diurnal vertical migrations from below 1,000 m in the day to or near the surface at night. Travels long vertical distances in excess of 2,000 to 3,000 m on a diel cycle. Feeds on free-living deepwater prey such as large squid, gonostomatids, crustaceans, but is also a facultative ectoparasite on larger pelagic animals such as wahoo, tuna, billfishes, and cetaceans. Specialized suctorial lips and a strongly modified pharynx allow it to attach to the sides of it prey.

Notes pertinent to Ascension: Not listed by Wirtz et al., 2014. Map: Fishbase Photo: Wikipedia

Distribution: Circumtropical. Western Atlantic: Bahamas and southern Brazil. Eastern Atlantic: Cape Verde, Guinea to Sierra Leone, southern Angola and South Africa, including Ascension Island. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Least Concern

Derichthys serpentinus narrow-necked oceanic eel

Authority: Gill, 1884 Order: Anguilliformes Family: Derichthyidae

Depth range: 0 – 2000 m Max. length: 40 cm Max. weight: ?

Description: Meso- to bathypelagic. Feeds on small fishes and crustaceans.

Notes pertinent to Ascension: Map: Fishbase Drawing: Canadian Museum of Nature Distribution: Circumglobal: In tropical to temperate waters. Eastern Atlantic: one confirmed record near Ascension Island. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

94 The Offshore Marine Environment of Ascension Island, South Atlantic

Diretmoides pauciradiatus Longwing spinyfin

Authority: Order: Beryciformes Family: Diretmidae

Depth range: 0 – 600 m Max. length: 37 cm Max. weight: ?

Description: Bathypelagic. Juveniles tend to stay near surface while adults may descend to 1000 m. Adults are plankton-eaters.

Notes pertinent to Ascension: Wirtz et al. (2014) lists this species but not Map: Fishbase Photo: Ramjohn, D.D. Diretmus argenteus, which is listed by Fishbase. Distribution: Eastern Atlantic: Guinea Bissau to Angola. Western Atlantic: eastern Florida, Gulf of Mexico, the Caribbean and northern Brazil. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Diretmus argenteus silver spinyfin

Authority: Johnson, 1864 Order: Beryciformes Family: Diretmidae

Depth range: 0 – 2000 m Max. length: 28 cm Max. weight:

Description: Bathypelagic. Juveniles are found from near surface to about 250 m to more than 1,000 m. Largest adults may be benthopelagic. Adults are plankton-eaters.

Notes pertinent to Ascension: Wirtz et al. (2014) does not list this species but Map: Fishbase Photo: P. Wirtz lists Diretmoides pauciradiatus, known as the longwing spinyfish. Distribution: Circumglobal: In tropical to temperate waters. Eastern Atlantic: Iceland and British Isles to South Africa including Canary Islands and Ascension Island. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

95 The Offshore Marine Environment of Ascension Island, South Atlantic

Diplospinus multistriatus striped escolar

Authority: Maul, 1938 Order: Perciformes Family: Gempylidae

Depth range: 50 – 1000 m Max. length: 33 cm Max. weight: ?

Description: Benthopelagic. Oceanic, migrating upward at night to 100 to 200 m (Ref. 6181). Probably forming schools during daytime (Ref. 6181). Feed on crustaceans and small fish.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014) Map: Fishbase Drawing: FAO

Distribution: Atlantic, Indian and Pacific: in central water masses. Rather rare, but relatively abundant in the northwest and southeast Atlantic. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Lepidocybium flavobrunneum Escolar

Authority: (Smith, 1843) Order: Perciformes Family: Gempylidae

Depth range: 200 – 1100 m Max. length: 200 cm Max. weight: 45 kg

Description: Occurs mainly over the continental slope, down to 200 m and more. Migrates upward at night. Feeds on squid, crustaceans and a wide variety of fishes. Flesh oily and may have purgative properties. Sometimes caught by tuna long-liners.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Photo: Cambraia Duarte, P.M.N.

Distribution: Tropical and temperate seas of the world. Eastern Atlantic: known from 13°N off Guinea to Lobutu, Angola. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

96 The Offshore Marine Environment of Ascension Island, South Atlantic

Gempylus serpens snake mackerel

Authority: Cuvier, 1829 Order: Perciformes Family: Gempylidae

Depth range: 0 – 600 m Max. length: 100 cm Max. weight: ?

Description: Pelagic, strictly oceanic and usually solitary. Adults migrate to the surface at night while larvae and juveniles are found near the surface during the day. Feed on fishes, cephalopods and crustaceans.

Notes pertinent to Ascension: Map: Fishbase Photo: Cambraia Duarte, P.M.N.

Distribution: Worldwide in tropical and subtropical seas. Adults also often caught in temperate waters. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Nealotus tripes black snake mackerel

Authority: Johnson, 1865 Order: Perciformes Family: Gempylidae

Depth range: 914 – 1646 m Max. length: 25 cm Max. weight: ?

Description: Oceanic, epipelagic to mesopelagic, migrating to the surface at night. Feeds on myctophids and other small fishes, squid and crustaceans.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Photo: JAMARC

Distribution: Atlantic, Indian and Pacific: in tropical and temperate waters.

Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

97 The Offshore Marine Environment of Ascension Island, South Atlantic

Gigantura chuni Gigantura

Authority: Brauer, 1901 Order: Aulopiformes Family: Giganturidae

Depth range: 500 – 3000 m Max. length: 15 cm Max. weight: ?

Description: The common name for this order is the Telescopefishes. This peculiar-looking fish have eyes which protrude on stalks. They also have a long, ribbon-like tailfin.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Image: (from Wikipedia entry)

Distribution: Atlantic, Indian and Pacific: mainly in tropical areas.

Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

Gigantura indica Telescopefish

Authority: Brauer, 1901 Order: Aulopiformes Family: Giganturidae

Depth range: 500 – 2000 m Max. length: 20 cm Max. weight: ?

Description: The species is rare. Inhabits deep water. Famous for its bizarre shape and unusual eyes.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing:

Distribution: Circumglobal: In tropical to subtropical waters. Deep sea.

Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

98 The Offshore Marine Environment of Ascension Island, South Atlantic

Lampris guttatus Opah

Authority: (Brünnich, 1788) Order: Lampriformes Family: Lampridae

Depth range: 100 – 500 m Max. length: 200 cm Max. weight: 270 kg

Description: Oceanic and apparently solitary. Epi- and mesopelagic. Feeds on midwater fishes and invertebrates, mainly squids (Ref. 6737). Occasionally taken as a by-catch of tuna fisheries.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Image: Mincarone, M.M.

Distribution: Worldwide in tropical to temperate waters. Western Atlantic: Grand Banks and Nova Scotia (Canada) to Florida (USA), Gulf of Mexico and the West Indies up to Argentina. Eastern Atlantic: Norway and Greenland to Senegal and south of Angola. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Notolychnus valdiviae topside lampfish

Authority: (Brauer, 1904) Order: Family: Myctophidae Myctophiformes Depth range: 25 – 700 m Max. length: 6 cm Max. weight: ?

Description: High-oceanic, epipelagic and mesopelagic. Found between 375- 700 m during the day and between 25-350 m at night. Size stratification with depth during the day only. Feed on copepods, conchoecid ostracods and euphausiids.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: SFSA

Distribution: Worldwide distribution in tropical, subtropical and temperate waters. Eastern Atlantic: west of British Isles and Bay of Biscay to South Africa. Western Atlantic: Canada to Argentina.

Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

99 The Offshore Marine Environment of Ascension Island, South Atlantic

Nemichthys scolopaceus Slender snipe eel

Authority: Richardson, 1848 Order: Anguilliformes Family: Nemichthyidae

Depth range: 258 – 4337 m Max. length: Max. weight: ?

Description: Occur in midwater, usually below 400 m. Feed on crustaceans while swimming with its mouth open. Mesopelagic and bathypelagic.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: from Wikipedia.org

Distribution: Worldwide in tropical and temperate seas. Western Atlantic: Nova Scotia, Canada and northern Gulf of Mexico to Brazil. Eastern Atlantic: Spain to South Africa. Reference(s): Fishbase (‘deep water fishes’); IUCN Red List status: Not Evaluated

Barbantus elongatus elongate searsid

Authority: Krefft, 1970 Order: Osmeriformes Family: Platytroctidae

Depth range: 1800 - 2000 m Max. length: 18 cm Max. weight: ?

Description: Bathypelagic

Notes pertinent to Ascension: Map: Fishbase Drawing: Typical representative of this family. Distribution: Eastern Atlantic: slopes of St. Helena, Ascension and Mid- Atlantic ridge.

Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

100 The Offshore Marine Environment of Ascension Island, South Atlantic

Astronesthes caulophorus

Authority: Regan & Order: Family: Stomiidae Trewavas 1929 Depth range: 100 m - ? Max. length: 26 cm Max. weight: ?

Description: Oceanic-mesopelagic.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: SFSA

Distribution: Eastern Atlantic between 23°30'N and 24°S.

Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Astronesthes micropogon

Authority: Goodyear & Gibbs Order: Stomiiformes Family: Stomiidae 1970 Depth range: 120 – 600 m Max. length: 8 cm Max. weight: ?

Description: Bathypelagic. Fairly common in deep oceanic waters, usually living deeper than 500 m during the day. Smaller individuals migrate to the near-surface or even surface waters at night. Feeds on midwater fishes and crustaceans.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing shows representatives of this family.

Distribution: Eastern Atlantic: Morocco south to Namibia. Western Atlantic: USA to the Caribbean Sea including the Gulf of Mexico; from French Guiana to Brazil. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

101 The Offshore Marine Environment of Ascension Island, South Atlantic

Astronesthes niger

Authority: Richardson, 1845 Order: Stomiiformes Family: Stomiidae

Depth range: unknown Max. length: 16 cm Max. weight: ?

Description: Bathypelagic. An oceanic and mesopelagic species usually found deeper than 500 m during the day. Feeds on midwater fishes and crustaceans. Most common species taken in surface nets at night.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: Canadian Museum of Nature

Distribution: Atlantic Ocean: through most of the Atlantic, from about 43°N to 36°S, but absent in the west from 5°N to 20°S. Elsewhere, Indian Ocean. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Chauliodus minimus

Authority: Parin & Novikova, Order: Stomiiformes Family: Stomiidae 1974 Depth range: Unknown Max. length: 15 cm Max. weight: ?

Description: Bathypelagic, collected offshore in the Atlantic.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Photo: L.G. Fischer

Distribution: Eastern Atlantic: Congo south to Angola. Western Atlantic: Brazil south to Argentina. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

102 The Offshore Marine Environment of Ascension Island, South Atlantic

Echiostoma barbatum threadfin dragonfish

Authority: Lowe, 1843 Order: Stomiiformes Family: Stomiidae

Depth range: 30 – 4200 m Max. length: 37 cm Max. weight: ?

Description: Meso- to abyssopelagic.

Notes pertinent to Ascension: Wirtz et al. (2014) does not list this species but Map: Fishbase Drawing: SFSA does list Eustomias intermedius, known as the intermediate dragonfish. Distribution: Eastern Atlantic: Portugal to South Africa except the Gulf of Guinea. Western Atlantic: USA south to Argentina, including the Gulf of Mexico and the Caribbean Sea. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Eustomias intermedius

Authority: Clarke, 1998 Order: Stomiiformes Family: Stomiidae

Depth range: 632 – 640 m Max. length: Max. weight: ? No map available Description: Pelagic-oceanic. Deep water.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: shows typical fish in this family. Distribution: Atlantic Ocean

Reference(s): Fishbase (‘deep water fishes’); IUCN Red List status: Not Evaluated

103 The Offshore Marine Environment of Ascension Island, South Atlantic

Stomias affinis Günther’s boafish

Authority: Günther, 1887 Order: Stomiiformes Family: Stomiidae

Depth range: 0 – 3182 m Max. length: 22 cm Max. weight: ?

Description: Bathypelagic. Some individuals may migrate to the surface at night. Feed mainly on myctophids.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Photo: F. Welter-Schultes

Distribution: Circumglobal in tropical and subtropical waters. Eastern Atlantic: Mauritania south to Angola. Also across the Atlantic between 0 and 20°N, extending to 35°N and 39°S in the western part (USA to Argentina). Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Symphysanodon berryi Slope bass

Authority: Anderson, 1970 Order: Family: Perciformes Symphysanodontidae

Depth range: 101 – 406 m Max. length: 13 Max. weight: ? cm

Description: Bathydemersal – inhabits rocky bottoms.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: FAO

Distribution: Western Central Atlantic: from off North Carolina and Bermuda to northern South America (including West Indies, Gulf of Mexico, and Caribbean Sea); off Ascension Island; South Atlantic, from localities well north of St. Helena Island and west of the Island of Pegalu. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

104 The Offshore Marine Environment of Ascension Island, South Atlantic

Aphanopus intermedius Intermediate scabbardfish

Authority: Parin, 1983 Order: Perciformes Family: Trichiuridae

Depth range: 300 – 1350 m Max. length: 100 cm Max. weight: ?

Description: Benthopelagic. “Of no fisheries interest”.

Notes pertinent to Ascension: Not listed by Wirtz et al. (2014). Map: Fishbase Drawing: FAO

Distribution: Atlantic Ocean: in moderately warm and tropical waters. In the eastern Atlantic, it is found off western Sahara, Congo and Angola, from Sierra Leone submarine rise and Pilberry Seamount. Reference(s): Fishbase (‘deep water fishes’) IUCN Red List status: Not Evaluated

Zenion longipinnis

Authority: Kotthaus, 1970 Order: Family: Zenionidae

Depth range: 200 – 450 m Max. length: 11 cm Max. weight: ?

Description: Bathydemersal.

Notes pertinent to Ascension: Map: Fishbase Drawing: shows typical fish in this family.

Distribution: Eastern Atlantic: Mauritania to Angola, Ascension and St. Helena Islands. Western Atlantic: off northeast Florida, the Bahamas, Gulf of Mexico, Caribbean to southern Brazil. Reference(s): Fishbase (‘deep water fishes’); Wirtz et al., 2014 IUCN Red List status: Not Evaluated

105