UBC Theses and Dissertations

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UBC Theses and Dissertations

Effects of crowding and water borne stressors on five fishes with different social and ecological habits Furnell, Donald J.


The responses of five ethologically distinct fishes to crowding and water born stressors were examined. Initial experiments using one stocking density indicated activated carbon removed a water born stressor inhibiting growth in Corynopoma riisei but not Rivulus harti. Later experiments using Brachydanio rerio, Astronotus ocellatus, and Betta splendens confirmed the removal of a water born stressor by activated carbon for all but Betta splendens. The stressor's effect appeared to depend on a species' natural habitat. When cultured, fishes adapted to small transient water bodies tolerated or did not secrete stressors; those from permanent, rapidly diluting environments were inhibited in growth or survival. Response to crowding or social interaction was examined in Brachydanio rerio, Astronotus ocellatus and Betta splendens. Reduction of growth or survival was directly related to stocking density in Brachydanio rerio and Astronotus ocellatus, but the effect was less than half that of water born stressors. In Astronotus ocellatus crowding stress reached a threshold beyond which increased density had no effect. Social interaction in Betta splendens did not inhibit growth, but caused an increase in energy consumption. No relationship between a species' social habits and response to crowding could be discerned. In Brachydanio rerio and Astronotus ocellatus, the combined effects were compensatory or additive, respectively, when crowding and water born stressors were simultaneously examined.

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