Gillnets are one of the biggest causes of Bycatch in the oceans today as they have been a major source of mortality for many species including dolphins. It really should not be a secret that there is the potential for bycatch with any marine animal when throwing nets into the sea, but tuna fishing, which often uses gillnets, is one of the leaders in total bycatch due to the nets.
Researchers are learning more on how gillnet fishing impacts dolphins and in a new study, it is estimated that four million dolphins have being killed and caught as a result of tuna gillnet fishing in the Indian Ocean since 1950.
The staggering number is result of combining 10 bycatch sampling programs that occurred in Australia, Sri Lanka, India and Pakistan to estimate bycatch rates for cetaceans across all Indian Ocean tuna gillnet fisheries. The results of the study have shown that dolphin bycatch peaked at almost 100,000 individual animals per year during the years of 2004-2006, but that number has declined by over 15% since then even though tuna gillnet fishing has increased.
According to lead author of the study Charles Anderson, a Maldives-based marine biologist and lead author of the study, the issue has been largely ignored for the most part.
“This level of by-catch is unsustainable,” he says. The number of dolphins being caught “is directly comparable to the number of whales taken by all commercial whaling during the entire 20th century.”
The study highlighted that Indian Ocean gillnet fishing is poorly regulated, allowing for the issue to fly under the radar and not be brought to the forefront of the publics attention. With the total amount of bycatch having decreased since 2006 while fishing has increased, researchers are concerned that dolphin populations are in deep trouble as populations are seeing a drastic decline in numbers.
The countries that had the largest current gillnet catches of tuna and therefore, the highest amount of bycatch are listed from highest to lowest: Iran, Indonesia, India, Sri Lanka, Pakistan, Oman, Yemen, UAE, and Tanzania. The nine countries together accounted for roughly 96% of all cetacean bycatch from tuna gillnet fisheries in the Indian Ocean.
The researchers recommend multiple efforts to slow the amount of bycatch and ensure these populations of dolphins have a future. To start, most of the countries mentioned above lack basic information on population sizes and distributions for dolphins so that first and foremost needs to be tackled. By identified these specifics, researchers and conservationists have the opportunity to push governments to protect certain areas to help the animals avoid being caught.
Outside of teaching fisherman responsible fishing practices and modify fishing gear with low-cost tech that help reduce bycatch, ecotourism can also play a pivotal role as it can provide an opportunity for locals to earn a living outside of fishing and promote conservation.