By Pradip Namdev Chogle and Harshada Sable
Fish is a rich source of vitamins, minerals, fatty acids, and high-quality proteins. Around one billion people, or about 20% of the world's population, eat fish as their main source of animal protein. Because of this huge demand for fish, about 41 million people in 144 countries are employed in marine fisheries full-time or part-time, while 123 million others depend on it indirectly. Employment opportunities in marine fisheries across the world are abundant. Compared to developed countries, developing countries, mainly Asian countries, have far more of them and offer over 86% of the total employment in marine fisheries worldwide. Almost 70% of the world's small and large-engine fishing boats are located in Asian countries.
The day’s catch at a local fish market. Credit: Opensource/Canva
Be it in terms of food or fishing, by now, you must have realized how gigantic this trade is. Along with so many positive sides, there is also one aspect of fishing that is causing concern among the scientific community. It is called Fishing Bycatch or simply bycatch. The species that are actually of no use to fishermen but are caught in the fishing nets are called bycatch. These include seabirds (shearwater, booby etc.), sea mammals (dolphins, whales), sea turtles (green sea turtles, olive-ridley, etc.), invertebrates (marine corals, sea snails, etc.), and other fish. Around 8-40% of the marine life landing on coasts and harbours for sale across the world has been recorded as bycatch.
Long lifespan, delayed reproduction, a limited number of offspring, and greater risk from natural hazards mean large marine species like sea turtles and dolphins suffer a far greater loss due to bycatch. All these species play a vital role in maintaining a healthy oceanic environment and fish production. Sea turtles, such as the olive ridley, help maintain a healthy habitat by eating more than 30 problematic sea species. At the same time, the green sea turtle, during a certain period of its initial phase of life, is largely dependent on sea grasses and then subsists on faunal components, mainly jellyfish and other plankton. This makes the marine habitats more fertile and keeps the number of organisms in the marine habitat under control. Blue whales and other marine mammals make long annual migrations that help distribute nutrients far and wide in marine habitats. It is reported that over 85,000 sea turtles were entangled in fishing nets across the world from 1990 to 2008.
The Food and Agriculture Organization of the United Nations (FAO) has classified the different types of fishing and fishing nets used around the world into international standard fishing gear. Out of these, about 18 types of fishing nets have been recognized as mainly responsible for bycatch. Fishing with trawl, gillnet, trap net, long-line, purse-seine, and its subtypes are responsible for bycatch globally. Another interesting but serious aspect of this is what quantity (Fish Catch) of fish was caught with how much effort (fishing effort) is usually recorded where a large number of mechanized boats are engaged in commercial fishing. However, in most developing countries, fishing is done more or less for subsistence using moderate mechanization. Large-scale commercialization is not involved here. It is called traditional or artisanal/small-scale fishing. The proportion of bycatch in this type of traditional fishing is often not recorded properly.
Accidental bycatch on a fishing boat. Credit: Opensource/Canva
The amount of bycatch around the world varies more or less based on the specific geographical location, fishing season, and method. In the case of India, it is estimated that 56.3% of the total marine capture is bycatch. Bycatch rates are significantly higher in India, where fishing is done mainly by trawling and with shrimp as the target species. There is plenty of scope for improvement in the above-mentioned information because, even today, there is no efficient modern system available for collecting reliable information about fishing in India. There are 132 known marine mammal species in the world, of which about 27 species have been recorded in India.
A total of 1356 marine mammals, such as dolphins, different types of whales, sea cows, and finless porpoises, have been reported killed in fishing nets in about 240 different incidents across the Indian Ocean in 269 years from 1748 to 2017. Since 1960, fishing by mechanized trawlers has been greatly encouraged in our country. But today, the amount of bycatch in the total fish production has increased significantly. The worst thing about this is that the species that were previously neglected as bycatch are now gaining commercial importance, and bycatch is used to maintain profitability in the fishery. Very limited research information is available about bycatch in the coastal areas of Maharashtra. According to a research paper published in 2011, around 101 different species were recorded as bycatch. These include economically important 29 species of marine fish fry, 22 species of shrimp-like crustaceans, 31 different types of shellfish, 11 species of mussels, and some other species. Researching marine mammals and bycatch is costly and time-consuming.
Turtle caught in a fishing net. Credit: Opensource/Canva
Various measures like turtle excluder devices, tori lines, and pingers are planned to reduce bycatch worldwide. Marine organisms caught as bycatch, such as marine mammals, seabirds, and sea turtles, migrate long distances almost every year in their lives for breeding, feeding, and suitable habitat. Widespread marine habitats transcend national and state boundaries, so we need international cooperation to design conservation strategies for such species.
Bangalore-based Wildlife Conservation Society-India is also working towards reducing bycatch and marine conservation in India. The 'Marine Team' in the said organization is actively working on this issue. We can certainly reduce the bycatch problem through the mutual cooperation of fishing communities, researchers, and informed citizens like us.
This article was originally written in Marathi. Read the original article here.