Program on the Environment

There is a threatened population of green sturgeon in California’s rivers and coastal waters that is found in the California halibut bottom trawl fishery as bycatch. Studies show that the post-release mortality rate of these fish is 18% due to stress and injury during handling, so the aim of this study is to create mitigation techniques to avoid bycatch. I conducted an internship with NOAA Fisheries, in partnership with California Department of Fish and Wildlife, to analyze footage from cameras that are placed in the nets of bottom trawls. I recorded each species and its response to the net to better understand their interactions with it and develop solutions with engineering modifications to the net. My research looked at two possible bycatch mitigation techniques. I compared the use of light-touch bottom trawls over traditional bottom trawls with data from my video analysis. I also conducted a literature review to explore the impact that using illumination on the nets may have on fish responses. Though the use of light-touch bottom trawls does not seem to impact the target catch, there is not yet enough data to draw significance in the effects on green sturgeon. Studies from a literature review support that the illumination technique may be utilized, as sturgeon seem to have a repulsive response to red wavelengths in the visible light spectrum strobing at a low frequency. Moving forward, I suggest a crossover design study that tests the techniques to maintain the sustainability of the California halibut bottom trawl fishery.