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Gillnet is a popular fishing method used for catching tuna and tuna like fishes especially by small scale fisheries of coastal states of the Indian Ocean. However, gillnets are known for extremely high bycatch which includes not only commercially important fish species but also a large number of non-target endangered, threatened and protected (ETP) species. Information about gillnet bycatch is not well known from major coastal states, however, studies initiated by WWF-Pakistan provide comprehensive information about bycatch of gillnet fisheries of Pakistan. It is estimated that more than 12,000 cetaceans and 29,000 sea turtles used to be annually entangled in the gillnet fisheries of Pakistan alone. Their numbers may be equally higher in other countries of the northern Arabian Sea where a large gillnet fleet is based.
Considering high bycatch of ETP species, WWF-Pakistan introduced subsurface gillnetting in Pakistan as a mean for reducing entanglement and mortality of at least cetaceans and turtles. Placing gillnet below 2 m proved to a success, as catches of target species of gillnet fisheries including yellowfin, longtail and skipjack tunas increased substantially whereas catches of some important species such as billfish and dolphinfish substantially decreased. However, high catches of target species i.e. yellowfin, longtail and skipjack tunas compensates for the losses incurred due to decreased catches of these two species group.
There was a major reduction in entanglement and mortality of cetaceans and turtles in subsurface gillnet. Entanglement and resultant mortality of cetaceans was observed to decrease from 12,000 in 2013 to mere 186 in 2018 (reduction of 98.45 %). Increase in landings of commercially important species including yellowfin, longtail and skipjack tunas is the main incentives for the tuna fishermen to shift from surface gillnetting to subsurface operations; however, there are a number of other benefits which resulted in its immediate and large scale adoptability by the tuna fishermen. By 2017, the entire tuna fleet was converted from surface to sub-surface gillnetting in Pakistan.
The operation of subsurface gillnetting is comparatively hassle-free as compared to surface gillnetting because the chances of fouling during deployment and retrieval are reduced. The number of floats in subsurface gillnets is reduced and these float are placed in pairs attached to 2 m rope which make their chances of entanglement to much less than surface gillnetting in which floats are placed every at 4.5 m on headline where chances of getting snagged are much higher. Less entanglements of ETP species help in saving time which otherwise lost during disentanglement and process of discard. Considering these merits, the gillnet fishermen of Pakistan shifted from surface to subsurface gillnetting within a span of less than two years. This method of fishing is getting popularity in other regional countries. Crew-based observers posted by WWF-Pakistan reports that the success of subsurface gillnetting in Pakistan has induced fishermen from regional countries with whom they have regular interaction to adopt this method.
