6.1 Fishing in the dark

The reproductive strategies and life-histories of many shallow-water species are well known, but this is not the case for the deep-sea species (Bronsdon et al. 1997). Despite the discovery of high species richness in the deep sea, knowledge of their biology is limited as a result of the difficulties and expense of sampling in this environment. Difficult areas such as steep slopes and seamounts tend to be avoided (Gordon 1996a). It is therefore considered that deepwater biological assessment and fishery development work is too complicated and expensive (Smolowitz 1996), as a result of the hostile physical conditions which inhibit deep-sea exploration (Norse 1993).

Until quite recently, most research in the deep-sea has used indirect means such as nets, grabs, bottles and instruments lowered into the depths from a surface platform. But these methods provide a very incomplete picture of the sea and its life - and - this explains why people know so little about the deep oceans (Norse 1993). Scientists have had to face the challenge of trying to imagine from fortuitously grabbed shreds of evidence what the nature of the deep sea is like. At the very best, a fragmentary catalogue of some of the slow-moving or stationary residents or structures may be obtained (Earle 1996).

The sea surface, on the other hand, is relatively easy to study using well-known techniques (Norse 1993). There is much better understanding of areas where the seabed is relatively smooth and easily sampled (Gordon 1996a), such as coastal areas or areas of the North Sea, where fishery scientists are able to sample and examine fish populations more easily.

6.2 Out of their depth

The present method of trying to regulate fisheries sustainably is an abject failure. The conventional approach to fisheries management has been to destroy fish stocks and allow fisheries to expand unhindered until sign of over exploitation have become apparent, such as declining catch rates or declining average size of fish. Fisheries management measures have usually not been taken until the need has becomes acute, and the scientific evidence for declines in stocks has become indisputable. There is always a long time lag before scientists recognise these events. This reactive approach usually results in action being taken too late (Angel 1996; Cooke 1994; Everett 1996).

Even assuming a discrete deepwater population size can be identified, the assessment of its size will be expensive or technically difficult. The assessment of potential yield is complicated by problems such as the correct identification of the catch, unrecorded discards, a high mortality of escapees from trawls, straddling stocks (stocks that extend into international waters), changes in catch per unit effort as fishermen gain experience (Gordon 1994a) and rapidly changing technology.

The European scientific body charged with providing advice on the management of fish stocks, the International Council for the Exploration of the Seas (ICES) has admitted that “very little information is currently available on the state of exploitation of deepwater species. In some cases of recently developed fisheries information is being withheld for commercial reasons. In many cases a significant proportion of the catch is being discarded at sea unrecorded. The quantities landed are probably not very well estimated due to some landings being reported to grouped categories.” (ICES 1995a).

The European Commission states that the term ‘deep-sea’ refers to areas above, or beyond the continental slope, generally of depths greater than 200 metres. ICES uses the term ‘deep-sea’ to depths greater than 400-500 metres.

The need for correct recording of species landed is of prime importance to the fishery biologist. However, many of the deepwater species are misidentified by fishermen and fisheries officers. Fishermen would be very unlikely to separate the deepwater sharks into anything other than large and small. The main market is for the Portuguese shark but it is regularly boxed with another large shark, the leafscale gulper shark. It is also unlikely that the deepwater skates will ever be sorted into individual species. The greater forkbeard and the morid are caught by both trawl and longline fisheries but are not separated very often by French fishermen landing their catches at Lochinver in Scotland (Gordon and Hunter 1994a; pers. comm. Fishery Officer Lochinver 1997).

Misidentification by fishermen, and even scientists, of species such as the sharks, rays and the many cod-like fish will undoubtedly cause major problems for stock assessment. In surveys carried out in the 1970s, even the orange roughy was incorrectly identified and was named as ‘Director’s fish’. Unrecorded discards and possible high mortalities of escapes of undersized fish will further undermine the usefulness of catch and effort data (Gordon and Hunter 1993).

Straddling fish stocks which extend beyond the 200 miles fishery limits are likely to be of common occurrence in deepwater fish species. Unreported or mis-reported catches in international waters are likely to be a major problem for any stock assessment (Gordon and Hunter 1994a).

Catch and effort data is very limited for deepwater species and also the reliability of the data is questionable (Gordon and Hunter 1993). Because the sizes of most of these fish stocks are unknown, it is impossible to estimate the productivity or recruitment for any particular fish and meaningless to even speak of a Maximum Sustainable Yield (MSY) for any deep-sea fishery (Larkin 1977; Sissenwine 1978). The supposed catch-effort relationship underlying the concept of MSY is apparently illusory (Godbout 1987). The level at which these stocks are ‘sustainable’ is not known and is unlikely to be known for many years (Gordon and Hunter 1994), if ever, because of the lack of basic information on the landings and biology of fish species.

In the absence of sufficient data, preventative or remedial action is needed to minimise the risk of detrimental effects to these vulnerable species (Vincent 1995). However, scientists are being increasingly expected to make impossibly precise conclusions from no or inadequate information (Hiscock 1997). As they have so little information on the importance of particular species and ecosystem services in each area (Norse 1993), scientific analysis cannot provide a definitive answer. If they wait for definitive data before taking a decision will come far too late. In this situation precautionary action is clearly urgently needed.