Assessing bottom trawling
Project Seahorse is enhancing our knowledge of bottom trawling, for greater scientific and public engagement and to drive significant policy change.
Bottom trawling is wreaking havoc around the world with little understanding of its impacts and few attempts to ensure its sustainability.
The relatively few studies to date are anchored in a few developed countries, although even there the analyses are very patchy and problematic. We urgently need research on the effects of bottom trawling in developing countries where trawling is most egregious, especially in Asia.
We have examined bottom trawl fisheries since 1994, sometimes through port surveys and sometimes through intense sampling at sea. This work has taken us to more than twenty countries on six continents, and revealed the terrible toll that bottom trawling takes on incidentally caught species and their habitats.
Bottom trawls catch seahorses
Project Seahorse has probed the role of bottom trawls in capturing seahorses for nearly thirty years, documenting the cumulative tally of their catch. Some investigations were port surveys, as in Malaysia and Viet Nam. Some investigations involved getting on fishing boats, such as our survey of seahorse bycatch in Florida, USA. Some involved detailed analyses as in India and Thailand. In India, we learned that bans on capture and trade of threatened species are futile if they are obtained as bycatch in poor regulated (indeed, often illegal) bottom trawl nets. In Thailand, we learned that annual catches were more than threefold larger than previously documented, and confirmed the seahorse species most susceptible to overfishing.
Monitoring bottom trawl fisheries
We have also conducted intensive monitoring of bottom trawl fisheries, exploring issues beyond seahorses. One of our team spent six months living aboard industrial shrimp trawlers in the Gulf of California, Mexico to monitor catch in detail. We then developed effective ways of using the life histories of small fish species to predict the effects of trawling on their populations. We also learned that supposedly effective management options, such as turtle excluder devices, were pointless if they were not embraced by the crew. Our comprehensive review of China’s approach to bottom trawl fisheries over seven decades highlighted the problems in managing China’s bottom trawl fisheries, and challenges and suggestions in policy implementation.
Ecological, social and regional analyses
We are now adding broad ecological, social and regional analyses of bottom trawling, as just these examples show:
- We are developing the first tally of how many species are obtained in bottom trawls and a synthesis of the ecological impacts of this dangerous form of fishing.
- We are probing the backgrounds of trawl fishers, asking why and how they entered the industry, so that we can infer the consequences of constraining trawling.
- Our ongoing analyses of China’s bottom trawling explore how their high levels of pressure emerged, how they are regulated, and their impacts at home and around the world.