Visual modeling approach to assess fishing gear efficiency and visual capacity of snow crab (Chionoecetes opilio): a case study on luminescent-netting pots in commercial fisheries

Frank, Colin (2023) Visual modeling approach to assess fishing gear efficiency and visual capacity of snow crab (Chionoecetes opilio): a case study on luminescent-netting pots in commercial fisheries. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis explored the visual capabilities of snow crab (Chionoecetes opilio) and their interactions with luminescent-netting pots to better understand the role of light intensity during capture. I compared three experimental luminescent-netting pots with increasing brightness to the traditional non-luminescent pots used in the Newfoundland and Labrador snow crab fishery. First, I developed a visual model for snow crab by characterizing their visual parameters, the emitted pot light, and environmental factors. I found that the distance that snow crab can see the light from the pots at 200 meter depth (fishing grounds) depends primarily on the solar angle (height of the sun) and the time elapsed after deployment. I then performed field trials, comparing the catch per unit effort (CPUE; number of crab per pot) and size-selectivity (size-based capture) between each pot treatment. Results showed that the lowest light level pot performed better in comparison to other treatments when considering a balance between commercial, management, and environmental concerns, catching more large crab and fewer small crab. In conclusion, this thesis describes how snow crab vision and pot light intensity effect luminescent-netting pot effectiveness and that increasing the light in luminescent-netting pots does not lead to an improved approach.

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