Case Reports for Species & Habitats on the Initial Draft

OSPAR Commission, 2008: Case Reports for the OSPAR List of Threatened and/or Declining Species and Habitats __________________________________________________________________________________________ Nomination The majority occur along the Mid-Atlantic ridge Seamounts between Iceland and the Hayes fracture zone EUNIS Code: A6.72 (Gubbay, 2002). National Marine Habitat Classification for UK & The enhanced currents that occur around seamounts provide ideal conditions for suspension Ireland code: Not defined feeders. Gorgonian, scleratinian and antipatharian corals may be particularly abundant, and other suspension feeders such as sponges, hydroids and ascidians are also present. Concentrations of commercially important fish species, such as orange roughy, aggregate around seamounts and live in close association with the benthic communities (Gubbay, 2002). Geographical extent OSPAR Regions; I, IV,V Biogeographic zones: 1,2,3,21,22,25 Region & Biogeographic zones specified for decline and/or threat: I, IV,V Seamounts are undersea mountains which are typically cone shaped, rising steeply from the seabed, but which do not emerge above sea level. They can be very large features, and more than 100km across the base. They often occur in chains or clusters, which are probably linked to seafloor hotspots and associated volcanic activity. Geological studies indicate that they have been generated along the Mid-Atlantic Ridge for the past Location of seamounts in the North Atlantic 35 million years, although some, such as the (from Epp & Smoot, 1989) seamounts around Rockall Bank and between the south-west corner of Rockall and the Charlie-Gibbs fracture zone may have formed before then (Epp & Smoot, 1989). Definition for habitat mapping The majority of the seamounts in the OSPAR Seamounts are defined as undersea mountains, Maritime Area lie along the Mid-Atlantic Ridge with a crest that rises more than 1,000 metres (MAR) between Iceland and the Hayes fracture above the surrounding sea floor (Menard, 1964 in zone. There are also groups of seamounts some Rogers, 1994). Seamounts can be a variety of distance from the MAR to the south west of the shapes, but are generally conical with a circular, Rockall Bank, west of Portugal on the Madeira-Tore elliptical or more elongate base. Seamounts are Rise , and the Milne seamounts to the east of the volcanic in origin, and are often associated with MAR (Gubbay, 1999). seafloor ‘hot-spots’ (thinner areas of the earth’s crust where magma can escape). Seamounts, Application of the Texel-Faial criteria often with a slope inclination of up to 60°, provide a Seamounts were nominated in a joint submission by striking contrast to the surrounding ‘flat’ abyssal three Contracting Parties citing decline, sensitivity, plain. Their relief has profound effects on the and ecological significance with information also surrounding oceanic circulation, with the formation provided on threat. The nomination was for of trapped waves, jets, eddies and closed Region V. circulations known as Taylor columns (Taylor, 1917 in Rogers, 1994). Seamounts occur frequently Decline within the OSPAR Maritime Area. Analysis of narrow beam bathymetric data by the US Naval Consideration of decline is most relevant to the Oceanographic office from 1967-1989 identified biological communities associated with seamounts more than 810 seamounts within the North Atlantic. rather than the physical structure of the feature 251 OSPAR Commission, 2008: Case Reports for the OSPAR List of Threatened and/or Declining Species and Habitats __________________________________________________________________________________________ itself. There are documented cases of extensive rays, tuna and swordfish. The ecological importance damage to seamount communities in some parts of of seamounts for top predators is emphasised by the world (eg. Butler et al., 2001; the fact that some far-ranging pelagic species WWF/IUCN/WCPA 2001) but limited information concentrate their mating and spawning in such specific to seamounts in the OSPAR Maritime Area places. Two examples are the pelagic armorhead (Pentaceros wheeleri) and the scalloped Sensitivity hammerhead (Sphyrna lewini) (Boehlert & Sasaki, 1988). An example in the OSPAR Area is the Seamount habitats are very sensitive to the physical Formigas Bank in the south eastern part of the impact of trawling and to the removal of benthic and Azores which appears to act as a feeding ground pelagic key species by commercial fisheries. Being and possibly a fish spawning and nursery area for isolated and confined to small areas, seamount many species as suggested by the groups of small habitats and faunas will be able to recover only over cetaceans such as bottlenose dolphin, common long time periods by the sporadic re-colonisation dolphin, spotted dolphin and pilot whales as well as from nearby seamounts and shelf areas. Where this captures of loggerhead turtles recorded in the area. is not possible, as in the case of endemic species, disturbance might lead to extinction. The benthic fauna are dominated by suspension feeders some of which are typically restricted to the Many of these species have life-history strategies seamount environment. They are characterised by that make them particularly sensitive to exploitation. high levels of endemism, which suggests limited The orange roughy Hoplostethus atlanticus is reproductive dispersal. Sampling of the benthic probably the best known as it is slow growing and, seamount fauna in the SW Pacific, for example, with an estimated life span of more than 100 years, suggests that some of these species are notably one of the longest lived fish species (Allain & localised. Somewhere between 29-34% of the Lorance, 2000). Orange roughy tend to form species collected during 23 cruises to the region are discrete and dense aggregations around seamounts believed to be new to science and potentially from which high catch rates can be obtained, endemic to these seamounts (Richer de Forges et fisheries can rapidly deplete the stocks. Deep water al., 2000). Less is known about the level of corals and sponges are also found on seamounts endemism on seamounts in the North East Atlantic. and are very sensitive to physical damage caused by fishing gear. The concentration of commercially valuable fish Ecological significance species around seamounts is well documented. Fishes such as the orange roughy and some Seamounts are a distinct and different environment deepwater oreos appear to be adapted to life in this from much of the deep sea. They act as ‘islands’ for environment, their substantial aggregations epibenthic and pelagic faunas, have a high rate of supported in the otherwise food-poor deep sea by endemic species, are used as ‘stepping stones’ for the enhanced flow of prey organisms past the the transoceanic dispersion of shell species and as seamounts (Koslow & Gowlett-Holmes, 1998). reproduction/feeding grounds for migratory species (eg. Richer de Forges, 2000) Their steep slopes, Apart from these general characteristics of which are often current-swept, and the seamounts that make them ecological significant predominance of hard exposed rock surfaces there are also unique situations which make some provides a marked contrast to the characteristically even more significant. One example is the João de flat and sediment-covered abyssal plain. Their Castro bank which is the only known example of a profile and elevation from the surrounding seafloor shallow water hydrothermal vent seamount in the also affects the circulation of water in the area, for NE Atlantic. Its uniqueness and rare fauna example by deflecting currents as well as leading to assemblages mean it might have an important role the formation of trapped waves, jets and eddies as a ‘stepping stone’ for species colonising the (Rogers, 1994). Azorean islands. Studies of the pelagic communities above Threat seamounts reveal both qualitative and quantitative The biological resources of seamounts have been differences when compared to the surrounding the targets of intensive exploitation, as they support water. The biomass of planktonic organisms over commercially valuable fish, shellfish and corals. seamounts is often higher than surrounding areas, This has created serious problems as resources which, in turn, become an important component of have been fished before there is a reasonable the diet of fish and top predators such as sharks, understanding of the biology of the species being 252 OSPAR Commission, 2008: Case Reports for the OSPAR List of Threatened and/or Declining Species and Habitats __________________________________________________________________________________________ targeted, no formal stock assessment and no Landings records from the commercial fisheries that quotas. The result has been over-exploitation and operate on seamounts are another source of major crashes in various stocks (eg. Koslow & information about seamount fauna however as this Gowlett-Holmes, 1998; Koslow et al., 2001; is pooled it is rarely possibly to distinguish Lutjeharms & Heydorn, 1981). There is no information for individual seamounts. This also published information on whether crashes have also makes it difficult to show the level of fishing effort on occurred on NE Atlantic seamounts but there are particular seamounts. certainly anecdotal reports of sites being fished out and vessels moving to new areas to sustain their Changes in relation to natural variability fishing activity as seamounts beyond the EEZ of the Little is known

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