The influence of stocking density and acoustic conditioning on the behavior and growth of Atlantic cod, Gadus morhua

• Main Author: Ward, Daniel
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2010
• Subjects: Biology; Zoology; Agriculture; Fisheries and Aquaculture; atlantic cod; Gadus morhua
• Online Access: https://scholars.unh.edu/thesis/617; https://scholars.unh.edu/context/thesis/article/1616/viewcontent/1489970.pdf

The goal of experiment one (Chapter One) was to determine if stocking density had an influence of the swimming behavior and spatial distribution of adult cod that were being raised in an aquaculture cage at the University of New Hampshire's Coastal Marine Laboratory. Acoustic telemetry and underwater video were used to quantify the behavior and distribution of cod that were stocked at four densities (5, 10, 25 and 45 kg/m³). At the lowest density (5 kg/m³) cod remained deep in the cage and spent 64.3 +/- 0.8% of their time below 1.80m (of a 2.70m cage). This contrasts to the middle density (10 kg/m³) and the high density (25 kg/m³) treatments, during which fish spent 48.7 +/- 1.2% and 46.8 +/- 0.8% of the time below 1.80m, respectively. One of the objectives was to determine if adult cod will school if raised at a high density, therefore reducing milling activity. At no time did the cod school in the experimental cage, regardless of raising the density to 45 kg/m³. The objective of experiment two (Chapter Two) was to determine if conditioning cod with an acoustic stimulus presented during feeding would increase their growth rate. Conditioned fish became active as soon as the sound stimulus was presented and spent less time milling at the surface prior to feeding, as compared to the group which was fed at the same time twice daily, but without a conditioning sound stimulus. Length and weight measurements for each group were not statistically different at the end of the experiment, though the acoustically conditioned group had the lowest food conversion ratio (FCR, 4.17), and a higher daily growth rate (0.11 g/d) than the group with the randomly changing daily feeding times. The results from these two studies further develop our knowledge of cod behavior in an aquaculture setting. Understanding how acoustic conditioning can reduce wasted feed, will allow farmers to reduce waste and increase growth rates. By better understanding how density impacts cod behavior, cages can be better designed for cod in particular, ...