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AEI
Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00440

    The attraction of cod Gadus morhua to salmon farms from local coastal spawning grounds

    J. E. Skjæraasen*, Ø. Karlsen, Ø. Langangen, S. Meier, K. M. Dunlop, T. van der Meeren, N. B. Keeley, M. S. Myksvoll, G. Dahle, E. Moland, R. Nilsen, K. M. S. Elvik, R. J. Bannister, E. M. Olsen

    *Corresponding author:

    ABSTRACT: Wild fish aggregate at aquaculture netpens, but the underlying mechanisms are not fully understood. This study examines how salmon farms attract coastal Atlantic cod Gadus morhua from their inshore spawning grounds. Acoustic receivers were deployed at 5 known cod spawning grounds and at 6 salmon Salmo salar farms located at varying distances from these grounds in a mid-Norway study site. Cod were caught at each ground annually from 2017 to 2019, fitted with acoustic transmitters, and released (n = 535). A total of 289 tagged cod (54%) were detected at the salmon farms, with more cod detected at the farms closest to the focal spawning grounds and at operational farms. The latter result is likely linked to the availability of feeding opportunities at farm locations. If detected, cod spent less time at farms farther from their release locations. For the farm-associated cod, 70% were detected for <1 wk at the farms. However, 48 cod spent >1 mo close to the farms, with 1 individual staying 720 d underneath the farm. It is likely that some cod utilizing these local spawning grounds have considerable dietary input from salmon feed. A total of 135 cod visited two or more farms, with farms in proximity more connected in terms of inter-farm movement.