Diversification and depletion in Vietnamese seahorse fisheries

The development of effective evidence-based management is limited by a lack of long-term records for many vulnerable marine species that are caught in small-scale fisheries. To address this data gap, I studied a small-scale fishery in southern Vietnam with a focus on seahorses (Hippocampus spp.), globally traded, cryptic fishes that are notably vulnerable to overexploitation. Using a combination of fisher interviews and catch landings surveys, I documented five fishing gears that regularly caught seahorses intentionally and/or incidentally: otter trawls, beam trawls, pair trawls, crab nets, and compressor diving.

About 20% of fishers I studied specifically targeted seahorses and made the majority of their income from selling these fish; a novel finding. The seahorse catch consisted of three species – Hippocampus spinosissimus, H. kuda and H. trimaculatus – with catch composition varying by gear and fishing ground. Bottom trawl boats and compressor divers that targeted seahorses caught them at mean rates of 23 and 32 seahorses per day respectively, while those that caught seahorses incidentally caught 1 and 3 per day respectively.

The total catch from the island from these two fishing methods was approximately 162,000–234,000 seahorses per year. This catch is up to four times higher than in other studied regions of Vietnam and throughout Southeast Asia. Fishers reported that seahorse catch rates had decreased by 86-95% from 2004 to 2014. Meanwhile, the landed value of seahorses had increased by 534% during the same time period, encouraging fishers to continue capturing and selling seahorses.

These signs point toward a high-pressure fishery that is likely unsustainable. Fisheries management efforts in the area should be strengthened by enforcing marine protected areas and improving fishers’ compliance to regulation. My findings emphasize the transitions that can occur in a high-pressure small-scale fishery and highlight the need for effective management to ensure sustainable seahorse populations.

Stocks, A. 2016. Diversification and depletion in Vietnamese seahorse fisheries. Master of Science dissertation, University of British Columbia, Canada. http://hdl.handle.net/2429/56251