2.1 Purpose and scope of guidelines
2.3 Characterization of sharks and other chondrichthyans and their fisheries
These guidelines have been produced to support implementation of the International Plan of Action for the Conservation and Management of Sharks. The guidelines are aimed at government, fisheries agencies at sub-national, national, regional and international level, and non-government organizations. They are designed to raise awareness of the conservation and management needs of sharks and other chondrichthyans and should be interest to fishing companies and other parties involved in the harvest of these resources.
The guidelines provide general advice and a framework for development and implementation of national Shark Plans for conservation and management of sharks consistent with the IPOA-Sharks. The guidelines are also intended to provide information to assist with the preparation of shark assessment reports. The guidelines also provide nations and RFMOs with general advice on requirements and a framework for development and implementation of Shark Plans for conservation and management of transboundary species of shark.
These guidelines are not intended to be a manual on methods of management, monitoring and research for shark fisheries. The guidelines have no formal legal status.
Batoids: Skates and rays, which include guitar fishes, sawfishes and electric rays, are dorsoventrally flattened and generally suited for life on the bottom. They have enlarged wing-like pectoral fins and 5-6 ventrally located gill openings. There are about 600 species worldwide.
Chimaera: Chondrichthyans are taxonomically separate from Elasmobranchs (sharks, skates and rays). There are about 35 species world-wide and all are marine. They have large heads, smooth skin without scales and often have whip-like tails. There is a long sharp spine on the leading edge of the first dorsal fin.
Gill-slits: Narrow gill openings behind the head.
Pectoral fins: Paired fins just behind or below the gill-slits; united to form disc in most rays.
Pelvic fin: Paired fins (rarely joined) positioned on the underside between the head and vent.
Sharks: True sharks are mainly fusiform in shape although a few species are ray shaped with 5-7 gill openings. There are about 400 species world-wide.
Special protection or special management: A term adopted for species requiring special protection or management because of its poor conservation status or rarity. This term is adopted to replace terms such as endangered, threatened, vulnerable or depleted species or in danger of extinction. Some countries have adopted definitions for some of these terms, which have legal standing in their jurisdictions, and some international organizations have published classification criteria for the conservation status of species, but, as yet, there is no single set of criteria accepted by all nations.
State: Country, nation, fishing entity or any entity, or organization, to which countries have transferred their right to set policies and manage fisheries.
Wild fisheries: Fisheries based on the harvest of natural populations and recruitment.
Sharks, skates, rays and chimaeras are often characterized as long-lived, slow-growing and producing few offspring. These characteristics are associated with low productivity, close stock-recruitment relationships and slow stock recovery in the event of overfishing.
The number of species is small compared with the number of species of teleost and various phyla of invertebrates. About 1000 chondrichthyan species have been described from a variety of habitats from near shore to the ocean abyss. They are most numerous at depths less than 2000 m in tropical and warm temperate marine habitats, but a few occur in freshwater and hypersaline habitats.
The use of shark and other chondrichthyan products pre-dates recorded history, and every part of these animals has been used for some purpose. Shark meat is important food consumed fresh, dried, salted or smoked in many communities. The demand for fins of sharks is growing such that they are among the worlds most expensive fishery products, and recently demand has been increasing for shark cartilage and other products for medicinal purposes. In some fisheries only the meat is retained, while the rest of the animal is discarded. In other fisheries, only the fins, or liver or skin are retained; few fisheries utilize all parts of the animals. Given the growing demand for shark products while many stocks are in decline, there is an urgent need to rationalize current patterns of usage.
Fisheries taking sharks and other chondrichthyans are common throughout the world and, although the overall number of species harvested is relatively small, they are taken with a variety of types of fishing gear and vessels. Sharks are taken mainly by gillnet, hook or trawl in industrial and artisanal fisheries. Small amounts are taken in traditional and recreational fisheries (including game fishers and divers) and in beach gillnet and drumline fishing bather protection programmes. There are several fisheries directed at one or a small number of species of shark, but most sharks are taken in multispecies fisheries where the fishers tend to target more highly valued teleosts. In some fisheries part or the entire shark catch is discarded.
Shark fisheries cannot be simply classified to avoid overlap of the species caught, but for the purpose of these Guidelines they are classified as coastal hook and gillnet fisheries, demersal trawl bycatch fisheries, deepwater bycatch fisheries, pelagic bycatch fisheries (primarily bycatch in tuna longline and purse seine fisheries) and freshwater shark fisheries (see Appendix 2).
The lack of public awareness of the conservation needs, which stems from the low productivity of sharks, and the historically low value of shark products are the main reasons why few countries currently manage their shark fisheries. Furthermore, until very recently, none of the RFMOs actively addressed the capture of sharks. However, there are indications that an international consensus is beginning to emerge on the need for improved control of fishing for shark and other chondrichthyan species. The prevailing view is that it is necessary to control shark directed fisheries and implement bycatch reduction devices (BRD) for fisheries in which sharks constitute a significant discarded bycatch.
Managers need to approach the management of fisheries for sharks somewhat differently from the approach they normally use in the management of marine capture fisheries. This is because sharks often have a close stock-recruitment relationship, long recovery periods in response to overfishing and complex spatial structures (size/sex segregation). In addition, they are generally difficult to identify down to the species level.
A major difficulty in assessing shark fishery stocks is that the number of species targeted is small and therefore they have not been intensively studied as a group. Furthermore, most of the shark catch is taken by fishers targeting teleost species which results in most of the catch reported as unidentified shark or mixed fish or not reported at all. This lack of species identification for catches and lack of information on fishing effort means basic data for fishery stock assessment are currently available for only a few species.
Furthermore the state of knowledge of sharks and the practices employed in shark fisheries cause problems in the conservation and management of sharks. Some areas require urgent attention.
Most species of shark are captured in multi-species fisheries directed at more productive and more highly valued teleost species. Harvest strategies designed to maximize economic and social benefits from these multi-species fisheries will inevitably deplete the less productive shark and other chondrichthyan species unless methods for reducing the catch of the less productive species can be developed and implemented. As fishing effort increases characteristic and predictable changes occur in the fish assemblages which have major implications for sustainability and management. In general as effort increases larger individuals and species disappear from the assemblage to be replaced by smaller counterparts. This results in a gradual drift towards shorter-lived, faster-growing species. This is accompanied by an initial increase and later a decrease in the number of species in the exploitable population although the number of fish actually appearing in the catch can increase until a maximum level is passed.