Effects of 3D seismic surveying on the snow crab fishery (PDF)

Morris, C.J., D. Cote, S.B. Martin, and D. Mullowney

Fisheries Research 232: 105719 (2020)

DOI: 10.1016/j.fishres.2020.105719

• This study was conducted approximately 350 km offshore along the Canadian continental slope, to examine effects of seismic surveying noise on commercial snow catch rates.

• A realistic field experiment incorporated industry-based 3D seismic oil and gas exploration surveying and commercial snow crab fishing, into a replicated before-after-control-impact study design.

Commercial Snow Crab (Chionoecetes opilio) harvesters believe marine noise from seismic surveys reduces commercial Snow Crab catch rates. Depending on the type of seismic survey used, animals living in a particular area could be exposed to loud noise (e.g. daily Sound Exposure Level (SEL) >165 dB re 1 μPa^2·s) for periods ranging from hours (typical 2D survey) to months (detailed 3D survey). This field experiment applied a series of comparisons conducted within a Before-After-Control-Impact study design to investigate the effect of prolonged industrial 3D seismic exposure on the catch rates of Snow Crab over nine weeks in 2017 and five weeks in 2018. Changes in catch rates at 3D seismic surveying sites were inconsistent across years, with reduced catches in 2017 and increased catches in 2018. Catch rates were similar at experimental and control sites within two weeks after exposure, and the potential effect of seismic surveying was not measured at a distance of 30 km. The large variation in catch rates across small temporal and spatial scales coupled with the absence of notable mechanistic responses of Snow Crab in past studies to seismic in associated snow crab movement behavior, gene expression and physiology, we conclude that the observed differences owing to seismic surveying in our study design are likely a result of stochastic processes external to our manipulation.