Is time running out for deepsea fish?

Fisheries carried out in waters deeper than about 400 m are generally considered to be deep-sea fisheries. In recent years fishing in deep waters has increased as traditional stocks, such as cod, have declined.

Orange roughy are one of the slowest growing of all deepwater fish and can live to be a staggering 125 years of age.

The target fish are often long-lived, late maturing, slow-breeding species such as the roundnose grenadier and the orange roughy.

Although we still have a lot to learn about these species we know that they are particularly vulnerable to overfishing because of their slow ability to reproduce. ICES has warned that several deep-sea stocks are now heavily exploited and in some cases severely depleted. This raises the question as to whether deep-sea fisheries, at their present levels, are sustainable.

The growth of deep-sea fisheries
Some deep-sea fisheries in the ICES Area are long established, and they tend to be traditional and on a small scale, using mainly static gear such as longlines. Fisheries by factory trawlers and modern longliner fleets started in the late 1960s and early 1970s and gradually expanded the deep-sea fisheries. In the 1980s and 1990s, lost fishing opportunities in shelf waters provided further stimulus for several fleets to turn to deep-sea species to make a living.

Assessing deep-sea fish stocks
As deep sea fisheries have increased, scientists have tried to estimate the size of deep-sea stocks and the level of fishing effort that they can support. The task of providing assessments of the state of deep-sea stocks in the ICES Area falls to the Working Group on the Biology and Assessment of Deep-Sea Fisheries Resources (WGDEEP).

Deep-sea stocks in decline
Analysis of several of the most important deep-sea fisheries, using catch per unit effort statistics, highlights a clear declining trend. Catch per unit effort (cpue) is the fish catch taken for a given amount of fishing effort, such as tonnes per fishing day or tonnes per 1000 hooks.

· Since the 1970s, the cpue for ling and tusk has fallen by 70% in ICES Areas north and west of the British Isles.

· There is evidence of a drop in blue ling stocks. French cpue data show a decline to a low level during the period 1985-1998.

· The most valuable but also most vulnerable deep-sea fish considered by WGDEEP is the orange roughy. In deep water areas northwest of the UK (ICES Area VI), the cpue for this species declined quite quickly after the fishery commenced in 1991, and by 1994 it was 25% of initial catch rates. In recent years cpue has increased slightly and has stabilised. The apparent stabilisation may simply reflect the discovery and subsequent fishing of previously unexploited aggregations of fish.

Roundnose grenadier

Roundnose grenadier is fished in many ICES Subareas. Assessments have only been made for areas near the Faroes and west of the British Isles (ICES Subareas Vb, VI, and VII) combined, and these suggest a strong decline in the stock size to a level below the precautionary level set by the ICES Advisory Committee on Fishery Management (ACFM).

Conclusion
These examples suggest that many deep-sea fishes stocks are in decline and can only sustain very limited fishing pressure. In light of these concerns, ICES has suggested that there should be an immediate reduction of fishing pressure on fully exploited or overexploited deep-sea stocks.

For further information please see the latest ICES advice on fish stocks.

Authors

Odd Aksel Bergstad
Institute of Marine Research
Flødevigen Marine Research Station
N-4817 His, Norway
E-mail

John D. M. Gordon
Scottish Association for Marine Science
Oban, Argyll PA34 4AD
Scotland, UK
E-mail

Philip Large
CEFAS Lowestoft Laboratory
Pakefield Road, Lowestoft
Suffolk NR33 0HT
England
E-mail

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