Rare seahorses have big implications for small fishes in bycatch

The incidental capture of marine organisms is a critical area of concern in fisheries management, and despite the dominance of small fishes in bycatch biomass around the globe, we know little about the impacts of bycatch on these small fishes. Here, I focus on one such small fish taxon, the seahorses (Hippocampus spp.). Seahorse populations are typically patchy, and they have a specialized life history that makes them more likely to be vulnerable to overfishing.

I assessed the impacts of nonselective gear on seahorses in one country by examining potential impacts for three species in peninsular Malaysia. I also assessed the impacts of seahorse bycatch globally, by synthesizing a global array of studies. For my national analysis, I used data-poor assessment methods to estimate life history parameters for three species of seahorse in peninsular Malaysia (Chapter 2). For my global analysis, I extracted data found in a published and unpublished reports to generate a synthesis of global seahorse bycatch (Chapter 3).

Nationally, my findings indicate the potential for overfishing for one species found in the southwest region of the peninsular Malaysia. Globally, my synthesis revealed that all fishing gears obtained seahorses in bycatch, but at very low rates of capture per vessel per day. Across all countries, fishers characterized seahorses as relatively rare in their bycatch and declining in catches. One key finding was that low CPUE scaled up to tens of millions of seahorses obtained globally as bycatch each year. My results address the impacts of bycatch on seahorses and discuss the implications for other small bycaught fish species, especially those that are demersal or rare.

Lawson, J.M. (2014). Rare seahorses have big implications for small fishes in bycatch. Master of Science dissertation, University of British Columbia, Canada.