Trawler Bycatch at Malvan
By Trisha Gupta
We’ve been monitoring sea snake assemblages in fishing nets at Malvan, Maharashtra, for a couple of years now and have been studying the impact of fishing on sea snake ecology. This year we’ve added some new components to this project, one of which involves the monitoring of low-value bycatch from trawl fisheries.
Low-value bycatch, or ‘trash fish’, is a non-targeted portion of the catch that has little or no commercial value. Fishermen bring this back to the shore and sell it to industries to serve as raw material for the preparation of fish meal, which is primarily used to feed poultry and cultured fish.
Trash fish is sometimes generated in massive quantities, with up to 1,000 kg from a single boat, but little is known about what’s in it. We spent five months collecting samples of (often-rotting) fish and pouring over numerous guidebooks to identify the species caught. This was a happy time for Malvan’s cats as they feasted on my sampled fish. We also started monitoring bycatch of sharks and rays from trawlers.
We were also interested in learning where the trawlers obtained the most bycatch and what fishing gear they used. This information is best obtained on board the fishing vessel while out at sea. However, getting on board a trawler is not easy for outsiders, and is especially difficult for women. The trawlers at Malvan are relatively small and lack toilets; the fishermen use the sea for all their needs. This “number 1–number 2” problem, as one fisherman put it, made them very uncomfortable with the idea of a woman on board.
With lots of trust building (and some begging), I managed to get on board a trawler going on a single-day fishing trip on two occasions. During the trips, I was discretely told to sit inside the cabin any time a fisherman needed to do his business, which was a strange experience! I also managed to burn myself during the first trip; the trawler was rocking with the wind and to balance myself I held on to the closest available thing, which happened to be part of the engine. I received some lovely burns and blisters on my hand and a lesson on what not to do on a trawler. Aside from these incidents, however, we did collect some good data on the catch and fishing efforts.
After five months of data collection, we found that nearly a quarter of a trawler landed catch is trash fish, made up of 115 different species of fish and other marine life. Thanks to hours of tedious length measurements, we determined that a bulk of the trash is made up of juvenile fish. The composition and amount of trash fish varied greatly depending on the type of trawler (bottom or mid-water), and this is something we’re looking further into.
We’ve also recorded 15 species of sharks and rays caught as bycatch in trawlers, including endangered species like the scalloped hammerhead shark and the longhead eagle ray. The breeding season for many of these species overlaps with the fishing season, and we sadly found gravid (pregnant) females in the catch on multiple occasions.
Our next field season starts in October, where I plan to continue this work – minus trawler burns and other disasters hopefully!