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Comparison of some physical characteristics of salmonids under culture conditions using underwater video imaging techniques

University of British Columbia

Body dimensions and swimming speeds of Atlantic salmon (Salmo salar) and Chinook salmon (Oncorhynchus tshawytscha) were measured in order to try to explain some of the observed growth differences between the two species under similar husbandry conditions, and to find an accurate estimator of individual fish mass from body dimensions. Size distribution of individual Chinook salmon in sea cages was also examined. Data was collected using a pre-existing non-invasive underwater video imaging system (VICASS) based on the principles of stereoimagery. An existing database of physical measurements was also analyzed (consisting of 1539 Atlantic salmon ranging in size from 0.42 to 8.50 kg and 840 chinook salmon ranging in size from 0.009 to 4.91 kg). Average fish size varied significantly with position in six out of fourteen cages of chinook salmon. This result suggested the presence of a dominance hierarchy, in which the largest fish in the cage are found in the best apparent location in the cage. Swimming speeds for chinook salmon ranged from 0.37 to 1.06 m s⁻¹ or 0.72 to 2.04 body lengths s⁻¹ (bl s⁻¹). Atlantic salmon swam between 0.25 to 0.98 m s⁻¹ or 0.40 to 1.82 bl s⁻¹. The swimming speeds (in bl s⁻¹) were compared for fish between 1.0 - 3.5 kg in size, and chinook salmon were found to be swimming approximately 20% faster than Atlantic salmon on average. After testing several different models, M=BL²H was found to be the best estimator of mass. B varied from 39.58 to 73.86 in Atlantic salmon and 45.93 to 76.52 in chinook salmon. This model decreased the variability in calculating mass by between 38 and 44% as compared to the conventional fisheries model M=KL³. Chinook salmon were significantly taller and thicker than Atlantic salmon of similar mass, while Atlantic salmon were significantly longer than Chinook salmon of similar mass. The ratios of fork length to height and fork length to girth were also found to be significantly different for the two species. The drag forces acting on Chinook salmon were found to be approximately 40% higher than those for Atlantic salmon as a result of the above morphological and swimming speed differences, and the power needed to overcome these drag forces was found to be 53% higher. Due to this increased demand on the metabolic component of the energy budget of chinook salmon, their growth was decreased by 5.2 to 10.3% (depending on fish size) as compared to Atlantic salmon. This difference in growth explains over 50% of the observed difference in the FCRs of the two species. Results suggest that farmers should: a) choose chinook salmon stock that swim slower and/or have a body form that is more similar to that of Atlantic salmon, thereby decreasing the energetic demands of swimming in chinook salmon, or b) develop a higher energy feed for chinook salmon.

Thesis/Dissertation

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2009-03-11

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http://hdl.handle.net/2429/5873

Chemical and Biological Engineering

University of British Columbia

UBCV

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