Gadoid habitat observations using stereo cameras

What is it about?

The protection of species requires an understanding of their habitat requirements and how habitat characteristics affect their distribution, survival and growth. This need is especially important in areas where human pressures can not only have a significant direct impact on the survival of the species but also damage their habitat. The Firth of Clyde in southwestern Scotland was an important commercial fishing area for a variety of ground fish species up until 1973. However, stocks rapidly declined thereafter and the catch of targeted species ceased in 2005, despite fisheries measures put in place to aid recovery. Changes in the availability and quality of fish habitat are possible explanations for this lack of recovery. Here, we report on stereo baited remote underwater video surveys in the Firth of Clyde between June and September in 2013 and 2014 to determine the habitat of juvenile Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus and whiting Merlangius merlangus. Habitat predictor variables explored included seabed type, depth, wave fetch, and fauna diversity. G. morhua were most abundant in shallow, sheltered areas composed of gravel−pebble containing maerl. M. aeglefinus and M. merlangus predominated over deeper sand and mud. Shifts in habitat occupance was observed in all 3 species. Relative abundances of G. morhua and M. merlangus were positively related to the diversity of fauna. Our results indicate that spatial conservation measures to benefit ground fish should be advised by patterns fauna diversity as well as physical seabed types.

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Why is it important?

This paper has links to conservation, fish management and policy related measures as it links seabed type and diversity to commercial fish abundance and growth.