- It is a certainty that the deep-sea species cannot compensate for heavy fishing activity. Deep-sea fishing is also both ecologically and economically questionable. For one thing, it is very destructive, and for another the catch levels are relatively low because most deep-sea fish stocks are comparatively small due to their K-strategy. Thus, taken as a whole, the deep-sea fisheries represent only a small proportion of the worldwide catch amounts. Basically they can only be maintained because of the high subsidies, since the costs for fuel are high for the great distances ships often have to cruise out.
- 3.18 > The catches of many deep-sea fish, like the orange roughy shown here, declined rapidly within just a few years because of overfishing.
- 3.19 > Over the years, the total catches of deep-sea fisheries have remained high. However, this was only possible because new species have replaced the overfished stocks of other species. The figure shows the total amounts for different species in each year. An example of overfishing of a deep-sea species is provided by the armourhead, which had been fished by Japanese and Russian trawlers at Pacific seamounts since the 1960s. Within 10 years the stocks were so strongly reduced that the species was commercially depleted and abandoned by fisheries.
- Again and again over the years, new species that previously were not considered by fisheries have become interesting, usually to replace species that were overfished. The pursuit of various species of Sebastes is a striking example of the substitution of an overfished species by a new one. The total catch has dropped since the 1970s, but it has still remained at a comparatively high level. This has been possible because new species have been targeted. In the northeast Atlantic, starting in the 1950s, Sebastes marinus (golden redfish) was initially caught. In 1980 it still made up more than 40 per cent of the catch of Sebastes species. But then the stocks declined. In the 1990s Sebastes marinus made up less than 20 per cent of the total catch of Sebastes species in the northeast Atlantic. In lieu of Sebastes marinus, fishing of the Greenland stocks of Sebastes mentella (deepwater redfish) intensified. In this region the species is mainly demersal. As these Greenland stocks shrank, the focus shifted to the more pelagic-living Sebastes mentella stocks in the open Atlantic. Due to restraints on fishing, it has been possible for some time now for the Sebastes mentella stocks off Greenland to recover.
Destruction of unique habitatsMany species of deep-sea fish build up large stocks, especially at structures like seamounts, banks and cold-water coral reefs. Fishing for these species represents a potential threat to the environment, especially when demersal trawls are used that can destroy fragile corals. The problem is that corals grow very slowly, usually only a few millimetres each year. So it can take decades for the habitats to recover. Studies at several neighbouring seamounts off Tasmania have shown that 43 per cent of the species were previously unknown and thus could be unique. In areas where demersal trawls were used, the total number of species was diminished to 59 per cent of the original number. 95 per cent of the surface was reduced to bare, stony bedrock. It is thus highly conceivable that endemic species that only exist at a single seamount could be completely exterminated.
Is it possible to protect the deep sea?In 2008, in response to the growing knowledge that deep-sea habitats are especially threatened by fisheries, the FAO established the International Guidelines for the Management of Deep-sea Fisheries in the High Seas. These guidelines are not legally binding. They do, however, contain clear recommendations for the protection of fish species that are vulnerable to overfishing. They relate to methods by which the fishing gear comes into contact with the sea floor. These guidelines, by definition, should regulate protection in international waters outside the Exclusive Economic Zone (EEZ), where freedom of the seas and fishing is recognized.
- 3.23 > Rockall, off Ireland. At its base is a marine area considered to be one of the most species-rich and deserving of protection in the northeast Atlantic.
- The FAO refers to areas deserving protection as vulnerable marine ecosystems (VMEs). In addition to banks, seamounts and cold-water coral areas, these include large species-rich sponge communities as well as densely populated undersea hydrothermal vents and cold seeps. The following criteria are used to determine whether a marine area is given the status of a VME:
1. UNIQUENESS OR RARITY:Ecosystems that are unique or contain rare species. The loss of the ecosystem cannot be compensated for by similar ecosystems. These include: habitats with endemic species, habitats with endangered species, breeding or spawning areas.
2. FUNCTIONAL SIGNIFICANCE:Habitats that are important for the survival, reproduction or recovery of fish stocks, or are significant for rare or threatened species, or various development stages of these species.
3. FRAGILITY:An ecosystem that is highly susceptible to destruction or weakening by anthropogenic activities.
4. SIGNIFICANCE FOR SPECIES WITH SPECIAL LIFE-HISTORY TRAITS:Ecosystems that are characterized by species or assemblages with the following traits: slow growth rates, late sexual maturity, low or unpredictable reproduction, long-lived.
5. STRUCTURAL COMPLEXITY:An ecosystem that is characterized by complex structures, for example, by corals or isolated rock outcrops. Many organisms are specially adapted to these structures. Such ecosystems often have high diversity.
- The designation of an international marine area as a vulnerable marine ecosystem according to the FAO guidelines is decided, as a rule, by the Regional Fisheries Management Organizations (RFMOs). It is the task of the RFMOs to apportion the catch of fish stocks or individuals of migrating species such as tuna in their area among the member countries. In addition, they are responsible for ensuring that the protection measures and catch limits are complied with. RFMOs develop management plans and announce sanctions in cases of non-compliance. Critics claim that many fish stocks in areas managed by the RFMOs are still not fished with sufficient restraint, and that vulnerable areas are not adequately protected. A number of regional fisheries management organizations have now placed certain VMEs within their areas under special protection, particularly those at several seamounts off southwest Africa. Fishing is either completely banned there or demersal trawl fishing is prohibited. Pelagic fish that swim in the upper water layers may still be fished. Fishing for demersal species, however, which live near the bottom, is halted. There are other protected areas with VMEs northwest of Ireland, including Hatton Bank and the Rockall Bank, which is several hundred kilometres long. Here the responsible RFMO has established Marine Protected Areas (MPAs), whose primary objective is to protect overfished stocks. The relatively small vulnerable marine ecosystems are located within these much larger MPAs. Demersal trawl fishing has been banned here to protect the cold-water corals.
Species and genus A species is design-ated by a two-part name. The first part (for example, Sebastes) indicates the genus. Usually many closely related species belong to one genus. The second part indicates the species (marinus). Although species can often be very similar to one another, such as, in birds, the blue tit and great tit, they still remain clearly sepa-rated, either by a large distance (conti-nent) or because they no longer interbreed. Around 100 species belong to the genus Sebastes.
- Incidentally, one of the first protected areas in VME terms was established long before the FAO published its guidelines. In 1995, after the publication of studies on the devastating effects of demersal trawl fishing at seamounts, the Australian government established a deep-sea protected area of 370 square kilometres on the continental slope off Tasmania. There are 15 seamounts here and large stocks of orange roughy. The objective was to protect slow-reproducing fish species as well as their vulnerable habitats on the sea floor. The Australian officials only allow fishing down to a depth of 500 metres. This should prevent the overfishing of deep-sea fish and the fragile bottom from net contact. With this decision the Australian officials were more than 10 years ahead of their time and the FAO guidelines. On the other hand, in the region south of Tasmania there are a total of 70 seamounts and only 15 are protected. The question of whether the protected area is large and representative enough to preserve all of the species indigenous to the Tasmanian seamount region is still being discussed today. The FAO guidelines for deep-sea fishing on the high seas were developed to protect vulnerable habitats in international waters. Of course, they also apply to equivalent deep-sea areas inside national waters that fulfil the criteria for a VME. In this respect, the guidelines are also an important orientation point for the countries themselves. Many nation-states have now designated valuable areas as VMEs and placed them under special protection. Norway, for example, protects parts of its cold-water coral regions in this way. Critics claim, however, that the extent of these areas is far from sufficient to preserve the full diversity of the cold-water coral systems.