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Home , Deep sea fish, Demersal fish, Kingklip, Ocean fisheries, Pelagic fish, Spiky oreo

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C3. DEEPWATER by Ross Shotton * insufficient for . Thus in deeper layers depend on organic material convected downward; this can happen in various THE DEEPWATER HABITAT ways. Dead and sink, and The deep- are the largest habitat on earth. though much is consumed as it sinks, sufficient The area over 4000 m in depth covers 53 percent of it enters the deepwater to sustain much of the of the ’s surface or 38 percent of the world’s deepwater . Many species undergo surface. The continental slopes alone occupy extensive diel vertical migrations, feeding near 8.8 percent of the world’s surface, compared to the surface and descending during the day, 7.5 percent for the and shallow presumably to avoid predation in the surface seas (Merrett and Haedrich 1997). The deep-sea waters. In this way, surface production is can be classified into four zones: the cascaded through progressively deeper layers mesopelagial is uppermost and ranges from 200 though the concentration of organic material to 1 000 m; the bathypelagic occupies the 1 000– decreases exponentially with depth. Organic 4 000 m depth zone; the abyssopelagic goes from material from large carcasses sinking to the 4 000 to 6 000 m and the mentioned seafloor, e.g. dead , and sulpha-based for completeness, is the habitat of the deep organic production associated with deep-sea trenches (See Figure C3.1). From a demersal seafloor hot-water vents are of relatively minor , the deepwater region can be taken as the importance. continental slopes, starting at the shelf break and It is now known that seasonal effects in the corresponding to the mesopelagic and surface layers are transferred into even the deeper bathypelagic and , beneath, the continental rise regions of the so that despite the physical which extends down to the abyssal planes at uniformity of the deep oceans, an annual around 6000 m. Complicating this picture are the production signal exists resulting in seasonal existence of features that may rises migrations and reproductive cycles in deep-sea thousands of metres above the surrounding fauna. areas–, or form regions of “hills” or knolls. WHAT ARE THE DEEPWATER The main rarely extends below ? 1200 m; below this the falls to around 2ºC and even lower in areas where water Given the continuity of the oceans as an masses sink, such as the Weddel Sea and high- , any depth-based zonation will be latitude areas in the NE Atlantic. Active current arbitrary. Some workers use 500 m as the start of effects are encountered to at least mid-slope the deepwater habitat, others consider deepwater depths of about 800 m, a result of eddies and turbulence caused by Figure C3.1. Depth Zones of the Oceans the poleward flow of western boundary currents. Wind-driven surface currents can also cause mid-depth of water and species and down welling of surface waters and species. On the seabed, bottom-sea friction can cause cross-shelf water movement and vertical movement of water. No light penetrates beyond 1 000 m and even at depths of 150 m light intensity is reduced to 1 percent of that at the surface

189 fishes to be those living at depths greater than continents and oceanic ridges has resulted in 400 m - no rigid definition of what are deepwater regional differences that are believed to have fishes has been found to be always acceptable. arisen from continental drift and subsequent However, deepwater fishes can be categorized ocean formation. Another important feature of into mesopelagic, bathypelagic and benthopelagic deepwater fishes is that much remains unknown– categories. Mesopelagic and bathypelagic species new discoveries continue, e.g. recently that of a are true , generally of small adult size 4.5 m 750 kg (megamouth shark) and a six- and unlikely to be exploited on a commercially gilled ray, both representing new taxonomic scale. Mesopelagic fishes, such as lantern fishes families. Indeed, deepwater elasmobranchs are (Myctophidae) and cyclothonids (Gonosto- one of the groups of particular conservation matidae) live beneath the to concern even when not exploited, given their low approximately 1000 m depth. Bathypelagic fishes numbers, their late maturity, low fecundity and live below 1000 m and are usually highly adapted intermittent . to life in a food-poor environment. The Though there have been some traditional benthopelagic species live on, or close, to the deepwater fisheries (the drop line fishery for bottom, a zone now known to be differentiated in black scabbard fish (Aphanopus carbo) in its biological characteristics. Madeira and the Azores is one of the more Here, deepwater species are defined as those interesting), the most important commercially are beyond and below the depth of the continental those that are harvested by . Many of shelf, i.e. those inhabiting the continental slopes these occur in association with sea mounts and and below. The behavioural characteristics of seafloor ridges while others have been taken at many “deepwater” species further complicate a shallower depths in the past but has search for an easy and useful definition. Many extended in to deeper waters as deepwater fishing deepwater species migrate toward the surface at technology has improved and stocks have been night returning during the day thereby forming a fished down at shallower depths. trophic link between surface waters and the Important species that form deepwater benthopelagic fishes when these latter prey upon aggregations include fish returning from the surface layers. Other (Hoplostethus atlanticus) and the oreos fishes make this diel migration themselves, (Allocyttus spp., spp. Pseudocyttus feeding in the surface layers and then descending, spp., etc), which are often fished together, presumably to avoid being eaten themselves. alfonsinos (Beryx spp.) in lower latitude fisheries, Some species only inhabit deepwaters in their ( eleginoides) adult stage, and may be exploited during both in fisheries, pelagic armourhead their shallow - and deepwater phases - (Pseudopentaceros wheeleri) and various species complicating the interpretation of whether such of Scorpaenidae found on both of North catches be defined as deepwater or not. America. The first existing deepwater demersal species Away from seamounts, Gadiforme fishes such as were present around 80 million years ago and, in the Macrouridae predominate. These species too order of their occurrence in the fossil record, tend to be slow growing but are not so “extreme” were the Holosauridae, Bythitidae, Ophidiidae in their characteristics as those species associated (cusk and brotulas), Macrouridae (rat-tails with fisheries. Other species that may and ), Scorpaenidae (rockfishes), be included in this group are sablefish Trachichthyidae, and most recently, (Anoplopoma fimbria), Greenland Notocanthidae and Moridae (morid ) (Reinhardtius hippoglossoides), morids (Andriyashev, 1953). Because the demersal (Moridae), cusk-eels (Brotulidae) and fishes are distributed according to depth, those (). Some of these species were inhabiting the slope and rise are spread along thought by many to be unmarketable but with ribbon-like bathymetric-defined regions around effective marketing and careful processing the perimeters of the oceans. Where deepwater (failure to properly remove all surface waxes pelagic species impinge on these habitats feeding from orange roughy fillets during processing can opportunities are created for both groups. cause diarrhoea) even the sceptics have been While most of these families occur world-wide, surprised at the market penetration that has been the existence of deepwater basins bounded by the achieved by many deepwater species.

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Orange roughy Their eggs float near the sea surface and the larvae also inhabit surface waters. In Australian Figure C3.2 - Annual nominal catches ('000t) waters, spiky oreo are more abundant at of Orange roughy 10 0 intermediate depths (600-800 m) and , 90 Atlantic in deeper waters (900-1 200 m). Both species are 80 Indian benthopelagic feeders consuming salps, 70 Pacific 60 , fish and . 50 40 Management of these fisheries on the high seas is 30 confounded by lack of obtaining required data. 20 Ageing data from and New Zealand 10 0 indicate that the maximum age for smooth oreo is 1975 1980 1985 1990 1995 2000 86 years and 153 years for black oreo. Natural Source FAO mortality for smooth oreo has been estimated at 0.063 yr-1 and 0.044yr-1 for black oreo. Estimates The Orange Roughy (Hoplostethus atlanticus) from New Zealand indicates “MSY” to be of the (Figure C3.2), is a Trachichthyidae found in the order of 1.6 percent of B if the population is not North and south Atlantic, Southern , 0 to be reduced to a of less than 0.2 B0 , New Zealand sea, South Pacific. It (probability <0.2). For operational reasons, where is caught at depth over 800 m by fisheries that they are managed at all, smooth, black and spiky often target spawning aggregations associated oreos may be managed as a single stock with the with seamounts. The fraction of the resource dangers this implies (Annala, Sullivan & O’Brien present in other areas is unknown. 1999). The slow growth and exceptional longevity of this species means that fisheries have depended Alfonsinos on serial stock depletion. Recruitment appears to be episodic and high market demand stimulates Figure C3.4 - Annual nominal catches ('000t) of Alfonsinos exploitation. Rates of sustainable exploitation 16 14 may be ≈5 percent of virgin biomass. This Atlantic + Mediterranean species exists as national, transboundary, 12 Indian straddling and high seas stocks. High sea 10 Pacific management is confounded by the difficulty of 8 obtaining required data. 6 4 Oreo dories 2 0 Figure C3.3 - Annual nominal catches ('000t) 1975 1980 1985 1990 1995 2000 of Oreo dories Source FAO 50 45 Atlantic 40 Indian The Alfonsinos (Beryx splendens), (Figure C3.4) 35 Pacific are Bericidae that have a circumglobal 30 distribution though they are generally not present 25 20 in the northeast Pacific. They inhabit the outer 15 shelf (180 m) and slope to at least 1 300 m depth, 10 probably moving further from the bottom at 5 night. Beryx splendens are caught in mid-water 0 1975 1980 1985 1990 1995 2000 trawls over shallower seamounts, underwater Source FAO ridges and on the slope edge between 300 and 500 m. The juveniles are pelagic. Genetic The Oreo dories (Allocystus spp. Neocystus spp. analysis suggests that there is, or has been, gene and Pseudocustus spp.) (Figure C3.3), are flow at the inter-oceanic scale and that this fishes Oreostomadidae found close to the sea bed in have an ocean-wide population structure. There deepwater and form large shoals over rough may be a Southern Ocean pool of juveniles that grounds near seamounts and canyons. The recruit northwards creating single genetic stocks juveniles are pelagic and inhabit oceanic waters. of black and smooth oreo, but discrete ecological They tend to be dispersed over smooth grounds. stocks with restricted post-recruitment dispersal

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(Lehodey, Grandperrin & Marchal 1997, Smith fast and significant. For example, resources of 2000). toothfish in Prince Edward Islands (South ) have been reduced only a few percent of the pre- These species have a maximum recorded age of exploitation level. 17 years and become sexually mature at about 4 years of age. Natural mortality is estimated to be around 0.23. They thus offer most chance of Pelagic Armourhead sustaining deepwater fisheries that target them. Figure C3.6 - Annual nominal catches ('000t)

Little is known about the local area stock 0.5 of Pelagic Armourhead structure of these species and it is believed, e.g. 0.5 that the New Zealand fishery may be exploiting a 0.4 0.4 wider South Pacific stock (Annala, Sullivan & Atlantic, Southeast 0.3 Indian, Western O’Brien 1999). 0.3 0.2 Pacific, Southwest Toothfish 0.2 0.1 Figure C3.5 - Annual nominal catches ('000t) 0.1 of toothfish 0.0 60 1975 1980 1985 1990 1995 2000 Source FAO 50 Atlantic Indian 40 Pacific Pelagic Armourhead (Pseudopentaceros

30 wheeleri), (Figure C3.6) are Pentacerotidae that inhabit Sea mounts, especially in the North 20 Pacific but also other ocean areas which are 10 caught by bottom trawl over seamounts. 0 Their fishery well illustrates the possible fate of 1975 1980 1985 1990 1995 2000 Source FAO seamount fisheries. Japanese and Russian vessels began trawling in the Emperor Seamount chain Toothfishes (Dissostichus spp.), (Figure C3.5) and the Northern Hawaiian Ridge areas in 1969. are Notothenidae that have a circumpolar The total catch for the Russian vessels is not distribution within Antarctic and Southern Ocean known but is estimated at over 133 400t in the waters. Patagonian toothfish (D. eleginoides) are period 1967–1977. Between 1969 and 1977, the found around southern South America and Japanese sent two to five trawlers a year to this (D. mawsoni) occurs in high area and averaged catches of 22 800–35 100t a latitudes, more currently in the Pacific region. year. Ninety percent of the catch were pelagic The two species overlap between 60°S and 65°S armourhead. After catches fell to 5 800 - 9 900t and both occur to depths of 3 000 m. The between 1977 and 1982. The once dominant northern limit for most populations of Patagonian pelagic armourhead have been replaced by toothfish is 45°S, except along the Chilean and alfonsino (Beryx splendens), though the alfonsino Argentinean coasts where they may extend north stocks have never been as large as the pelagic in deeper colder water. Significant populations of armourhead they followed and there is no Patagonian toothfish exist in the waters of, and evidence that either of the will recover adjacent to, the various sub-Antarctic islands and to levels that will be commercially viable in the in the waters of Chile, Argentina, Uruguay and near future. Peru. The problem of illegal, unregulated and Hoki unreported fishing (IUU), while considerably Hoki (Macruronus novaezelandiae), (Figure reduced during the 2003-2004 (6 342t in C3.7) is a benthopelagic Macruronidae that Statistical Area 41 and 3 701t in Area 87), usually lives near the bottom, but form mid-water remains the major concern. Further, catches of aggregations for spawning. Large adult fish toothfish reported as taken outside of the generally occur deeper than 400 m, while CCAMLR management area, are believed by juveniles may be found in shallower water. Mid- many to have been harvested from stocks within water trawl fisheries target aggregations near the management area. Past declines in toothfish canyons that are often close to coasts in areas of stocks targeted by IUU fishing fleets have been narrow continental shelves.

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Figure C3.7 - Annual nominal catches ('000t) characteristically modified in deepwater fishes. 900 of hoki In the absence of light most deep-sea fish are 800 black or red as this wave length is highly Atlantic 700 Indian attenuated in seawater and such fish effectively 600 pacific have black colour. Despite the lack of light, 500 deepwater fish often have large and unusual 400 retinal and lens to detect the ambient 300 light, which usually arises from on 200 10 0 prey, predators or co-specifics. Many deepwater 0 species have reduced muscle and bone mass, 1975 1980 1985 1990 1995 2000 which gives them near : those Source FAO that prey by slowly cruising have swimbladders capable of excreting gas despite the ambient Stock structure is often uncertain and thus the hydrostatic pressures of about 400 atmospheres matching of TACs to the areas of fisheries is a present at great depths (Marshall 1954, 1979). concern; in some areas of seal and other non-target species is a problem. Management Deepwater species too, must successfully , experience in at least some jurisdictions indicates grow and return to the area of the adult habitat. that this resource can be sustainably managed, The extreme conditions of the deep-sea are though in the major global fishery for this reflected in the variety of reproductive strategies species, in New Zealand, the TAC is changed that exist. Low population sizes not withstanding, from time to time as the size of the hoki stocks hermaphroditism, extreme varies and has fluctuated over the last 15 years and unbalanced sex ratios occur. Despite the between 200 000 and 250 000t. In 2004, the TAC fewer species found in the deep-seas, they was reduced to 100 000t as the spawning stock display a variety of reproductive strategies has declined – caused, it is believed, by ENSO- ranging from strongly K-selected species, which related oceanographic events. may be semelparous (e.g. Coryphaenoides armatus, a widely occurring macrourid), through Other species ovoviparous and oviparous species to those that are strongly r-selected. It is believed that A further suite of deepwater, or at least slope successful year classes may be intermittent, and species, have been the target of fisheries in many many deepwater species may spawn only tropical regions. These can be targetted by small- periodically over the years. scale deepwater fisheries usually along the shelf break and shelf slope wherever the continental A number of tactics have been adopted to reduce shelf is relatively narrow and the fishing grounds dispersion of eggs. The buoyant eggs of the wide are accessible to fishermen using small fishing spread and deepwater macrourids bear sculptured boats. The principle species consist of members patterns that slow their ascent, an not of the Lutjanidae, Serranidae, and Carangidae present in species of this family living in families and mostly importantly include the shallower waters. Eggs of Hoplostethus Eteline snappers (e.g. Etelis coruscans and atlanticus are initially buoyant and later sink and E. carbunculus) and the jobfishes (e.g. probably finish their development on the Pristomopoides filamemtosus, P. typus and seafloor, so facilitating their retention to their P. multidens). These fisheries are particularly adult habitat. important to small island states that often have few other resources though they are also widely found along the continental margins of many continents in tropical and sub-tropical A major determinant of fishery productivity is the areas. growth rate of the fish and invariably, the size distributions of fish populations that are usually negatively skewed. However, bimodal size LIFE-HISTORY CHARACTERISTICS distributions have been found for some OF DEEPWATER FISH deepwater species and one explanation for this is Not surprisingly, given the characteristics of their that because of their unproductive habitat, habitat, colouration, structure, musculature, deepwater species are obliged to put their surplus and swimbladder form and eyes are production into somatic growth to achieve an

193 optimal foraging size and only then do they reaches about 40 cm and 2 kg in size though the allocate surplus energy to reproduction. maximum size varies with region. Specialized aimed-trawling techniques have developed as at No matter the reason, it is clear that many first massive catches from spawning aggregations deepwater species grow slowly, so slowly in fact could be taken in minutes resulting in split that determination of their actual age remains ends and lost catches. The species is sensitive to difficult and age determination has been approaching objects (an adaptation to avoid contentious. For some species, particularly predation by sperm whales?) so that acoustic orange roughy (Hoplostethus atlanticus), the assessment using towed bodies containing the appropriate ageing technique has been acoustic transducer has proved difficult in some vigourously contested, and depending on the areas. Maximum sustainable levels of assumptions that were asserted, the species could exploitation of orange roughy may be as low as have had a potential longevity ranging from 21 to 5-10 percent of unfished biomass, i.e. M ~ 0.04. >100 years; current thinking now accepts the Accumulating evidence indicates that few of hypothesis that these fish grow to relatively old these fisheries are being exploited sustainably ages, with the maximium > 100 years. and it remains uncertain what ongoing yields will Many deep-sea fisheries biologist have concluded be. Smaller stocks usually do not escape that it is not meaningful to talk about deepwater depletion once they become targetted, however, fisheries in terms of sustainable fisheries, so slow there is conflicting evidence that other stocks are the growth rates of many of these species, a have proven more resilient to overexploitatin that characteristic that is compounded by their expected, possible because (a) fishing disperses apparently episodic recruitment. In such fisheries the fish before the stock is fished down and, if the resource consisted of widely-separated age- (b) because of episodic spawning. In this case, classes that are fished to very low levels of where fishing depends on spawing aggregations abundance, stock recovery arising from good not all of the stock may be vulnerable to capture recruitment may only be possible in generation in any one year as not all spawn each year terms greater that those of . (Butterworth and Brandão 2005). A Trichiurid fishery, which exploits Aphanopus DEEP-SEA FISHERIES carbo, is a rare example of a deepwater fishery that, because it has traditionally used hook and Until most recently, the great depth of the deep- line gear, has proved sustainable over a period of sea has made it difficult to exploit, and the about 150 years. Adults of this species are existence of relatively more abundant resources benthopelagic living in the deep range 400- in shallower seas have meant that there was little 1 600 m. The species ranges from Greenland to incentive to fish in such difficult-to-exploit the Canary Islands and on both sides of the mid- regions. Few deepwater fisheries are of long Atlantic ridge. This deepwater species grows standing and those that are the Portuguese rapidly and has longevity of around 8 years. (Madeira) line fishery for However, as for orange roughy, the usual (Aphanopus carbo) and Pacific Island fisheries ominous signs are now evident for this fishery. for snake (Gempylidae) and cutlass Catch increased from 1 100t in 1980 to 3 000t in fish (Trichiuridae) were initially exploited by 1992 and gear efficiency has increased through artisanal fisheries whose effects upon the the introduction of monofilament lines and a resources were sustainable. large increase in the number of hooks per line set, Well known among recently developed now 4 000–5 000 per line. deepwater fisheries is that of the orange roughy, a The Macroudidae are another group whose species that inhabits slope waters, those of members are widespread and in particular seamounts and the seafloor, most notably around locations, abundant. They are typical pelagic New Zealand and Southeast Australia where this “cruisers” and inhabit the mid- to upper region of commercial fishery initially began; interestingly, the continental slope. In the North Atlantic orange roughy was first described from the fisheries exist for Macrourus berglax and Azores. The fishery later spread to the Walvis Coryphaenoides rupestris, which use bottom Ridge in the Southeast Atlantic (Namibia), the trawls initially fishing in depths of 600–800 m, Southwest Indian Ocean and a small fishery and more recently to 1 500 m. However, exists in the of Biscay. This long-lived fish experience in these fisheries off

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Figure C3.8 - Annual nominal catches southern Indian characteristically ('000t) of Deepsea species at depths of 800 m commonly target orange 7 000 roughy (Hoplostethus atlanticus), black oreo Atlantic & M editerranean (Allocyttus niger), spiky oreo (Neocyttus 6 000 Indian rhomboidalis) and smooth oreo (Pseudocyttus Pacific 5 000 maculatus). When fishing at depths of ≈400 m, these vessels would commonly harvest alfonsino 4 000 (Beryx splendens), boarfish (Pseudopentaceros

3 000 richardsoni), cardinalfish (Epigonus telescopus) and bluenose (Hyperoglyphe antartica). 2 000 Such fisheries may have little bycatch (and thus 1 000 ), i.e. the fisheries could be considered “clean” in that few non-targeted species are 0 1950 1960 1970 1980 1990 2000 taken. However, unskilled operators, who snag Source FAO the bottom, can cause significant damage to the . And, lost catch from burst codends shows the all-too-familiar pattern of total results in fishing mortality that is rarely recorded. allowable catches tracking declining trends in reported landings. Coryphaenoides rupestris In these fisheries, traditional tools of fisheries have a potential longevity of 70 years, through in management, e.g. those that assume annual the NE Atlantic, fish ages are usually of 20–30 recruitment and a functional stock-recruitment years. Thus, as for other deepwater species, relationships may fail so badly that using them Macrourids exhibit the characteristics of many may endanger ensuring of the deepwater fisheries that render them particularly resources, rather than conserving them. Although susceptible to . characteristically deepwater resources are harvested by trawling, from a management The are a highly evolved group perspective, the fishing tactics have more in that are not usually associated with deepwater common with purse seining. Fishing may be done fisheries, but important fisheries for members of on acoustic marks, especially in the case of this group occur in both the North Atlantic and orange roughy fisheries or by extended tows as North Pacific Oceans. In the Atlantic, the best when targeting alfonsino. known has been that for Greenland Halibut (Reinhardtius hippoglosoides) on the continental When fishing for orange roughy catch success slope depths. This fish had an average size of critically depends on crew skills and the success around 1kg up until the mid-1980s, but has since of fishing tactics rather than, e.g., the dimensions declined to around 200g in the early 1990s. of the . In recording fishing effort, the main requirement is to know if the net was a Figure C3.8 represents the evolutioncaptures of bottom or pelagic trawl, and in the latter case, if the deep-sea species listed in table C3.1. Some of it was fished “hard-down” and if the gear these species however can also be captured in performed as intended, i.e. was the tow other fisheries and there is no possiblility to “successful” even if no fish were caught. Related determine which portion comes from deep-sea to this are fishing tactics in the presence of other fishing. These statistics only reflect the amount vessels. Vessels with crews with inferior skills of deep-sea species catches reported to FAO by often trailed better performing vessels relying on member countries. No information is available to them to locate concentrations of fish. In these attribute the changes in 1979 and 1998 to an cases, complex gaming behaviour on the part of increase of actual catches or a better reporting. the skipper could result further complicating interpretation of vessel operating success. While RESOURCE MANAGEMENT ISSUES (CPUE) remains one of the most useful indices of stock status, as noted, in The biological features of deepwater species that these vulnerable fisheries, its undue emphasis it may be caught by the same fisheries are varied could well be misleading, if not dangerous. and require that appropriate management strategies are adapted. Different species A further complication of deepwater research, complexes may occur in the same general area especially on the high seas, is the provision of but at different depths. For example, in the data that are essential for resource management

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Table C3.1 Species of deepwater fish recorded in the FAO Reported Landings Database

ARISTAEIDAE Plesiopenaeus edwardsianus Scarlet GERYONIDAE Geryon quinquedens Red Lithodes aequispina Golden king crab Crustaceans LITHODIDAE Paralomis spinosissima Antarctic stone crab PANDALIDAE Pandalus spp Pandalus SOLENOCERIDAE Pleoticus robustus Royal red shrimp Callorhinchus capensis Cape elephantfish CALLORHINCHIDAE Callorhinchus milii Ghost shark Callorhinchus spp Elephantfishes , etc. Chimaeriformes Chimaeras, etc. monstrosa Rabbit fish CHIMAERIDAE Hydrolagus novaezealandiae Dark ghost shark Hydrolagus spp Ratfishes Chondricthyans HEXANCHIDAE Hexanchus griseus Bluntnose sixgill shark Bathyraja meridionalis Bathyraja meridionalis RAJIDAE Bathyraja spp Bathyraja rays Centroscymnus coelolepis Portuguese dogfish Centroscymnus crepidater Longnose velvet dogfish SQUALIDAE Somniosus microcephalus Greenland shark Somniosus pacificus Pacific sleeper shark ARGENTINIDAE Glossanodon semifasciatus Deep-sea smelt Beryx spp Alfonsinos BERYCIDAE Centroberyx affinis Redfish BRANCHIOSTEGIDAE Branchiostegidae CAPROIDAE Caproidae Boarfishes Hyperoglyphe Bluenose warehou CENTROLOPHIDAE Seriolella caerulea White warehou CHLOROPHTHALMIDAE Chlorophthalmidae Emmelichthyidae Bonnetmouths, rubyfishes EMMELICHTHYIDAE Emmelichthys nitidus Cape bonnetmouth EPIGONIDAE Epigonus spp Cardinal fishes Brosme brosme Cusk Micromesistius australis Southern GADIDAE Micromesistius poutassou Blue whiting Molva dypterygia Blue ling Molva molva Ling Lepidocybium flavobrunneum Escolar Rexea solandri Silver gemfish GEMPYLIDAE Ruvettus pretiosus Oilfish Thyrsitops lepidopoides White snake GERYONIDAE Geryon spp Geryons MACRORAMPHOSIDAE Macroramphosus scolopax Longspine snipefish Coryphaenoides rupestris Roundnose grenadier Lepidorhynchus denticulatus Thorntooth grenadier MACROURIDAE Macrouridae Grenadiers, rattails Macrourus berglax Roughhead grenadier Macrourus spp Grenadiers Macruronus magellanicus Patagonian grenadier Teleosteans MERLUCCIIDAE Macruronus novaezelandiae Macruronus spp Blue grenadiers Antimora rostrata Blue antimora MORIDAE Mora moro Common mora Lampanyctodes hectoris Hector's MYCTOPHIDAE Myctophidae Dissostichus eleginoides Patagonian toothfish NOTOTHENIIDAE Dissostichus mawsoni Antarctic toothfish blacodes Pink cusk- Genypterus capensis Kingklip OPHIDIIDAE Genypterus chilensis Red cusk-eel Genypterus maculatus Black cusk-eel Genypterus spp Cusk-eels Oreosomatidae Oreo dories PENTACEROTIDAE Pseudopentaceros richardsoni Pelagic armourhead PLEURONECTIDAE Reinhardtius hippoglossoides Greenland halibut Polyprion americanus Wreckfish POLYPRIONIDAE Polyprion oxygeneios Hapuku wreckfish SCORPAENIDAE Scorpaena scrofa Red scorpionfish STERNOPTYCHIDAE Maurolicus muelleri Silvery lightfish Harpadon nehereus Bombay-duck Hoplostethus atlanticus Orange roughy TRACHICHTHYIDAE Trachichthyidae Aphanopus carbo Black scabbardfish Lepidopus caudatus Silver scabbardfish TRICHIURIDAE Trichiuridae Hairtails, scabbardfishes Trichiurus lepturus Largehead hairtail TRIGLIDAE Pterygotrigla picta Spotted gurnard

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FAO 2001, 2002). The operators of many high maturity, use of conventional limit spawning seas fishing vessels have no flag-responsibility to biomass reference levels, few stocks may remain report their catches, fishing effort or area of which can satisfy these demands and should they operations. And, when catches are landed in do so, harvest rates may have to be in the order of foreign countries, from a data recording five percent of virgin biomass. Third, stock perspective, this situation is exacerbated. An recovery times may be of the order of decades, example of such a fishery is that of the North perhaps beyond normal commercial (and Pacific pelagic armourhead (Pseudopentacerus political) time horizons. Fourth, even if there wheeleri). No trace of this fishery is to be found were agreement on management objectives and in the FAO Nominal Catches and Landings harvest control functions, in many instances Database, the largest and most comprehensive neither the management regimes nor regulatory global record of fish catches, despite this fishery mechanisms exist to ensure compliance with any being reported as reaching a level or 200 000t per management plan. These are the challenges that year! Likewise, the FAO database in the period must be addressed if the world’s deepwater up to 2000 reports explicit landing of orange resources are not to disappear as contributors to roughy from only three countries; however, welfare. informal contacts through working groups shows that at least seven countries have harvested this OPERATIONAL MANAGEMENT: species from the Indian Ocean. In some cases this lack of information is a consequence of national THE ASSESSING AND MANAGING OF laws regarding confidentiality of information. EXPLOITATION OF DEEPWATER Characteristically only few vessels, or even one, FISHERIES may participate in seamount-based fisheries This section is drawn from the report of the FAO within a management region, which if stock- Workshop on the Assessment and Management based may consist of a single seamount. And, of Deepwater Fisheries, University of Otago, national laws often prevent governments from Dunedin, New Zealand, 27–29 November 2003 releasing information that identifies the (FAO 2005) operations of a single vessel or company. This can create an insurmountable barrier to effective The estimation of abundance resource management. The estimation of the abundance of deepwater fishery resources has many of the characteristics MANAGEMENT OBJECTIVES: of those for more traditional shelf stocks but IS “SUSTAINABLE YIELD” other attributes are unique to deepwater species. A PRACTICAL GOAL? Some deepwater species, such as orange roughy, Management for sustainable yields, as a have low productivity, are highly aggregating, management objective, has been increasingly are often, but not exclusively, found around criticized in “conventional” fisheries for nearly underwater features, and that they react to survey two decades as numerous fishery administrations and fishing gear not just at the time of capture but have struggled to implement such a management also over longer periods. The reasons for paradigm. As a consequence, the management aggregating behaviour (e.g. suitable conditions or emphasis has changed towards the use of learned behaviour) remain uncertain and more reference points as simpler, more tractable and research on fish behaviour is highly desirable. more useful tools. In a complementary and more However, the low productivity in deepwater may complex development is the emerging demand not be universal. Some "deepwater" species for “ecosystem” management. When considering (particularly those with long pelagic phases, the circumstances of many deep-sea fishes, it is strong diurnal migration patterns, or preferred clear that major challenges arise in adapting such depths above about 800 m) have moderate levels models, if indeed they can be adapted to deep-sea of productivity. fishery situations. First, “sustainability” may be Egg surveys, methods often used for shallow an irrelevant or at least unusable management water stocks, may peform poorly in estimating concept in fisheries where the resources have abundance for a variety of reasons, among which episodic and unpredictable recruitment, no matter are the highly localized spawning behaviour (e.g. the spawning stock size. Second, for those orange roughy) of some species while others (e.g. species with low growth rates and late sexual some oreos and boar fish) may have wide-region

197 panmictic spawning behaviour. Trawl and considerable advances are being made in this acoustic surveys are potentially the most useful direction. methods for estimating abundance and both can be used to obtain relative abundance indices, Biology, age and growth although the use of acoustics is difficult even for Management of deepwater species is complicated relative abundance estimation when the target by the wide variability in their biological species is also associated with other species characteristics. Many species have high during the survey period. Both methods present longevity, slow growth rates, high age at maturity problems with respect to the estimation of and low fecundity and many, but not all, absolute abundance. For acoustics assessment, deepwater species have relatively low annual difficulties include identification of the values of production to biomass ratios. For such stocks, species-specific backscattering cross section this means that sustainable yield levels are areas and target species identification. For trawl relatively low, and recovery from depleted states surveys, estimating the vulnerability to capture can be slow. (i.e. survey catchability) is problematic. Routine data collection and analysis is essential The use of remotely operated vehicles and for effective management and should not be autonomous underwater vehicles has potential for restricted to the needs for immediate stock use in abundance estimation, or in experiments to assessment purposes. Biological characteristics estimate vulnerability to capture by trawls but (e.g. size-at-maturity) can change as fish stock further development is needed. But, methods size changes so such characteristics need to be based on developments in technology will require monitored as ancillary inputs to evaluating stock advances in the understanding of fish behaviour status. Density dependent effects need to be (natural and in response to fishing and research considered in the , as estimates vessels and gear). In particular, further work is of catchability, maturity, growth rates, spawning needed on factors influencing aggregating success and other factors may change. Stock behaviour and such underwater technology may structures of most deepwater species are offer opportunities in this respect. generally poorly known and their depth means Additional issues concern those relating to that direct methods to monitor distribution and identifying stock structure, stock distribution and movements (such as by tagging) can rarely be movement. Obtaining some form of relative or applied. absolute abundance estimates may be feasible, Fish population parameters are often poorly but their validity will depend on appropriate known, and variable. And complicating the use of survey designs that take account of underlying spawning models is that several deepwater distributions and movements. As yet, it appears species (e.g. orange roughy and hoki) do not that there is no single best way to estimate spawn each year. This means that reliance upon abundance and that use of a range of methods gonad stage data to determine age at maturity, or will offer the best way forward. In some areas, the maturity ogive, may be misleading. In the trawl and acoustic surveys are in regular use and case of orange roughy, there is a transition zone the estimates and indices derived are used in in the that appears to mark the onset of stock assessments with varying degrees of spawning. However, the frequency of spawning success, but this often depends on the availability is important, in terms of the proportion of the and quality of other data sources. population available to the fishery or the biomass The costs of deepwater fishery resource surveys survey each year, particularly if the proportion is high and commonly the cost-benefit of surveys varies between years. Stock-recruitment is a consideration in deciding on best ways relationships, and levels of recruitment, are forward in any particular circumstance. poorly known for most, if not all, deepwater Dedicated research cruises provide the best species. Yet this is important for understanding means of providing abundance estimates, and can changes in stock size, and for the management of often undertake a wider range of associated work sustainable fisheries. at the same time. However, the use of industry- Chemical and radiometric methods have based surveys (especially acoustic surveys) is improved confidence in the interpretation of providing useful inputs for stock assessments and otolith rings of deepwater species and improved age-method validation. In the absence of initial

198 data, general age and growth estimates may be - age data. available from other areas or fisheries. Ageing Although age information is essential for for production estimation is still needed, estimating population productivity, it is less however, in the major fisheries. important to devote resources to ageing stocks for There is a pressing need to try to understand the which age and growth information already exists ecological processes affecting biological for other stocks of the same species. Knowledge variability for without this, predictive modelling of fish ages (which enables estimation of growth can be misleading. At the least, consideration rates, natural mortality, and sometimes should be given to trophic interactions and links recruitment) was crucial for determining between deepwater demersal fish and the sustainable yields for orange roughy fisheries mesopelagic energy source. when they were first initiated. But, it was not until a validated ageing system was developed Assessment of eepsea fisheries that it became evident that orange roughy had unusually low growth rates, low natural A number of key data gaps and data needs exist mortality, high age at maturity and high for reliable assessments of deepwater species. longevity. Ageing of other orange roughy Three, in order of priority are: populations has demonstrated some differences in - Catch data at the minimum, it is essential to these life history parameters, but such differences know the amount and location of fisheries may be insufficient to justify initiation of major catches. This needs to be collected at an research initiatives on ageing, particularly if appropriate spatial scale given the localized resources are limited. It may be better to give aggregations formed by many deepwater higher priority to other data needs, such as the species. It would also be useful to collect data need for abundance indices, and simply adopt the on length frequency distributions of target age-length keys, growth parameters and natural species, and catches of by-catch species. mortality estimates from other similar stocks. - Valid indices of relative abundance–preferably, Finally, to satisfy objectives that are often these should be fishery-independent but, mandated by international agreements or national realistically, they are likely to be fishery- policy, it may be necessary to augment existing, dependent commercial catch rates. It is or to set up new, programmes to provide data on extremely difficult to develop “valid” ecosystem considerations, such as bycatch interpretations of the indices at the beginning of species, other associated species, and the effects a fishery; however, programmes should be of fishing on habitat. In multi-species fisheries developed to collect data on relevant factors for which it is extremely difficult to obtain such as the relationship between commercial species-specific data on catch and abundance, CPUE and abundance, selectivity by fisheries, these may need to be assessed and managed as stock boundaries, migration patterns, and the species assemblages, with application of the dynamics of aggregating behaviour. precautionary approach with regards to setting catch or effort limits. - Estimates of absolute abundance–ultimately, these are needed to estimate long-term sustainable yields. They can be obtained either Management concerns of deep-sea fisheries from a fishery-independent survey that provides estimates of absolute abundance (e.g., Biological reference points an acoustic survey) or an assessment model that Options for reference points include frameworks estimates absolute abundance based on catch based on control rules using target and limit and relative abundance. reference points and management procedures that Other data needs that may be crucial for some consider the assessment and management stocks, and will almost always improve the systems in concert using various performance accuracy and precision of assessments if measures to evaluate outcomes. In general, the available, include: use of evaluation approaches to derive robust management procedures is desirable; however, in - relative or absolute estimates of recruitment; the case of many information poor fisheries the - the relationship between stock size and feasibility of doing this is questionable. For many recruitment; and low-productivity stocks, target biomass levels

199 used for management purposes vary from about Precautionary approach 30 percent to 55 percent or higher of the unexploited level and rather than setting targets, a The approach of treading carefully and restricting catches in early phases of deepwater fisheries is more useful approach may be to concentrate on well supported. In New Zealand, new orange avoiding a lower biomass (typically 20 percent of roughy fisheries are voluntarily capped at 500 t unexploited) with a high probability (typically while information is gathered. The Commission 90 percent). Depending on the uncertainty inherent in any assessment and projection, the for Conservation of Antarctic Marine Living implied target biomass would vary but would Resources (CCAMLR) does not allow new fisheries unless they are explicitly allowed and likely fall within the range of typically adopted involve permit conditions such as mandatory data targets. In this regard though, some collection procedures. Although there is growing consider fishing mortality reference points to be a superior approach. support for such approaches, still, rapid declines in biomass of low productivity stocks occurs as Ecosystem approach to fisheries the initial of the resources have, almost invariably, been overestimated. management

Even in deepwater fisheries, the single most ECOSYSTEM CONSIDERATIONS OF important first step in moving towards an ecosystem approach to is THE DEEP-SEA ENVIRONMENT to get single-species fishing mortality under Given its great depth, extent and, until only the control and reduce it to appropriate levels. For most recent years, its low to non-existent visible this to happen, assessment and management of profile, it is unsurprising that the environment of marine resources must be better integrated with the deep-sea has escaped concern. But, much appropriate management frameworks that ensure evidence now shows that human activity is single stock management is successful while degrading the deep-sea floor and along with it the considering wider environmental or ecosystem habitat of the fish that live there. Major causes of issues. this damage the physical impact by trawls on benthos (Koslow et al. 2000) and ocean dumping Data-poor situations of sludge residuals from the processing of sewerage; of growing concern is In many deepwater fishery situations, there may exploration activities, and potentially in the be little or no information available to set initial future, mineral extraction. catches, assess stock status or estimate reference points. Adaptive management may be useful but Deep-sea surveys have shown the existence of there is often tension between adaptive deepwater in the North Atlantic, North management procedures that probe for Pacific, south of Australia, about New Zealand information (and therefore require that catches be and almost certainly they will occur elsewhere. In high enough (or low enough) to create contrast in the North Atlantic, the dominant Lophelia data sets) and the adoption of a precautionary occurs in depths between 200-1 000 m and grows approach, which would suggest low catches for at a rate of about 1 mm per year. The highest low productivity stocks. Evaluated (adaptive) reefs have measured 35 m, implying an age of management procedures may also be problematic 8500 years and the largest Lophelia reef are more if the information that is accrued shows that the than 13 km long and reach 400 m in width. Off assumptions used in management and resource , corals are found far from in modelling are untenable and must be re- depths > 200 m. Here, species known to exist evaluated. In these situations meta-analyses may include Paragorgia arborea (Gorgonacea), provide a means of garnering the maximum which can be up to five metres in height and possible benefit from the dispersed global data on Primnoa resedaeformis (Paragorgia), which, deepwater stocks, fisheries and associated fishermen report, grows in dense patches where habitats. Such an analysis could provide a means is has not been removed by demersal trawling. for setting initial catch limits for new fisheries as Such reefs provide shelter for marine fishes, a basis for adaptive and/or precautionary which in the NE Atlantic include commercial management. species such as redfish, saithe, cod, ling and tusk. The reefs have traditionally been rich fishing

200 grounds for longline and gillnet fisheries and Butterworth, D.S. & Brandão, A. 2005. experimental fishing has shown the occurrence of Experiences in Southern Africa in the productive fishing grounds in relation with the Management of Deep-sea Fisheries. In presence of bottom corals. Evidence is emerging Proceedings of the Conference on Management that the maintenance of bottom habitat corals and Governance of Deepwater Fisheries. 1–4 structure is important to maintaining fish December 2003, Queenstown, New Zealand. In production and at least in shallower waters, press. habitat degradation by can result FAO. 2001. Report of the Ad Hoc Meeting on in fish species succession, perversely, for types Management of Deepwater Fisheries Resources that are of least commercial value. of the Southern Indian Ocean, Swakopmund, Deepwater corals are sensitive to damage from Namibia, 30 may–1 June 2001. FAO Fish. Rep. bottom trawls, e.g. in Norwegian waters it is 652. FIRM, Rome. 61pp. estimated that 30-50 percent of the Lophelia FAO. 2002. Report of the Second Ad Hoc reefs have been affected or impacted by trawling. Meeting on Management of Deepwater Fisheries Damage has also been reported from other parts Resources of the Southern Indian Ocean, of NW Atlantic, including northwest of Scotland Fremantle, Western Australa, 20–22 May 2002. and in the Porcupine sea in Irish waters and FAO Fish. Rep. 677. FIRM, Rome. 106pp. off the of Nova Scotia where active clearing of bottom corals has been reported. In FAO, 2005. Report on DEEP-SEA 2003; An Australia and New Zealand it is claimed that International Conference on Governance of fisheries using demersal trawls have cleared Deep-sea Fisheries. Queenstown, New Zealand, corals from the rocky tops of seamounts and fish 1–5 December 2003. FAO Fish. Rept. In press. that were once abundant among the corals have Garibaldi, L & Limongelli L. 2002. Trends in disappeared. oceanic captures and clustering of large marine Seamounts provide another particular fish habitat : two studies based on the FAO of concern. These seafloor features are usually capture database. FAO Fisheries Technical found in the open oceans and are the remains of Paper. No. 435. Rome, FAO. 71pp. extinct volcanoes. They range from 500 to Koslow, A.J., Boehlert, G.W., Gordon, J.D.M., 1000 m in height above the seafloor; some reach Haedrich, R.L., Lorance, P. & Parin, N. 2000. within tens of metres of the surface while others Continental slope and deep-sea fisheries: have tops more than a kilometre deep. The implications for a fragile ecosystem. ICES J. associated fauna with seamounts is poorly Mar. Sci. 57:548-557. studied and highly diverse and can include corals, soft sea pens, sponges, sea spiders and . Lehodey, P., Grandperrin, R. & Marchal, P. Many of the species are endemic to particular sea 1997. Reproductive biology and of a mounts as they form isolated habitats. Once deep-demersal fish, alfonsino Beryx splendens, damaged by fishing gear, it is believed that over the seamounts off New Caledonia. Mar. recovery may take decades, if not centuries. Biol. 128(1):17-27) Marshall, N.B. 1954. Aspects of Deep-sea REFERENCES Biology. Hutchinson Press, London. 380pp. Andriyashev, A.P. 1953. Ancient deepwater and Marshall, N.B. 1979. Developments in Deep-sea secondary deepwater fishes and their importance Biology. Blandford Press, Poole. 566pp. in a zoogeographical analysis. In “Notes on Merrett, N.R. & Haedrich, R.L. 1997. Deep- Special Problems in Icthyology. Akademiya sea Demersal Fish and Fisheries. Chapman & Nauk SSSR, Ikhtiologicheskaya Kommossiya, Hall. London. 282 pp. Moscow: 58-64. (English translation by A.R. Gosline, Bureau of Commercial Fisheries, Smith, P.J. 2000. Managing : USNM, Washington. by-catch in seamount fisheries in the New Zealand . NIWA, Annala, J. H., Sullivan, K.J., & O’Brien, C.J. Wellington, New Zealand. 30p 1999. Report from the Fishery Assessment Plenary, April 1000: stock assessments and yield estimates. Ministry of Fisheries. 430pp.