Drift, Gill and Set Nets

Basking Shark © Jonas Andersson.
Drift-netting for shark and associated species is a passive fishing method. This technique involves a combination of gears carried out mainly by small scale and advanced artisanal fisheries in tropical or sub-tropical countries targeting both sharks and tuna. Many of the sharks taken by driftnets are within directed fisheries or as incidental bycatch. Pelagic sharks are a major component caught in this fishing method, such as Shortfin Mako (Isurus oxyrinchus), hammerheads (Sphyrnidae), Big-eye Thresher (Alopias superciliosus) and Blue (Prionace glauca).

The fishing gear usually consists of a number of panels joined together to form a wall of netting suspended vertically in the water. Each panel is 1000 meshes long and 120 meshes deep. In the case of the 150mm mesh stretched meshes, the most popular in Sri Lanka, panel’s measure 83m in length and 12.6m in depth. The vessels can be as small as 6m in length fishing for sharks all over the world; in the vast majority they are non-mechanised fishing units relying on man-power to haul their fishing gears. In western waters boats tend to be larger, ranging from 10-30m, these vessels are well equipped with technologies such as electronic fish finding devices. Boats fish in both coastal and offshore regions, with offshore vessels catching more shark species. In Benin, West Africa, target species consist of Dusky (Carcharhinus obscurus), Bull (Charcharinus leucas), requiem sharks (Carcharhinidae), Blacktip (Carcharinus limbatus) and Blue (Prionace glauca) as well as Yellow (Thunnus albacares) and Skipjack Tuna (Euthynnus pelamis).

Fishing is usually carried out at night with a round trip taking 16-20 hours. In Europe, during summer months, Blue Sharks move north to cooler waters, as far as the south coast of England and southern and western coasts of Ireland, where a directed fishery using longlines and gillnets commenced in 1991. In the Azores, the Kitefin Shark (Oxynotus paradoxus) has been targeted for over 20 years by both gillnets and hand-lines which tend to catch more males and females respectively. In Australia, with the introduction of power hauled gillnets, longlines began to decrease in popularity, by the 1980s few long-liners remained leading to a shark fishery dominated by gillnets by the 1990s. The net size grew with popularity, extending from 8-16km in just under a decade, with some nets reaching 20m in length. A similar trend of increasing popularity and development of gillnet fisheries is witnessed in Sri Lanka. Multi-day boats are operated, most of which are 36-45 feet in length, as a result their annual catch has risen continuously to a present 55,000 tons, composed of skipjack tuna, shark and billfish.

Sharks can be caught all year round within these fisheries, with overexploitation being an obvious concern. In the Gulf of Benin, West Africa the abundance of shark resources is still unknown. In addition there is increasing ambiguity in the difference between bycatch and target species due to the increase in value of fins.    

Within the Maldives, the use of purse seines and trawls of any sort, and pelagic driftnets are prohibited. In August 1998, the Seychelles put forth a ban of fishing sharks with nets; however there are no regulations for any other type of fishing method.