Effects of leaf litter on survival and growth of juvenile coho salmon

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Juvenile coho salmon (Oncorhynchus ki- sutch) were raised for a 6-week period from 2 weeks posthatching through yolk-sac absorption in oval tanks with or without a 5-cm layer of leaf litter. Each treatment was conducted in triplicate tanks; each tank initially contained 100 yolk-sac fry. The fish were fed at a reduced ration in order to discern nutritive effects (possibly from invertebrates) due to the presence of leaf litter. In each of the two consecutive years that the experiment was conducted, there was a third experimental condition- in year 1, a nylon screen was placed on top of the leaf litter to separate cover effects from nutritional effects; in year 2, a treatment group was fed full ration. Examination of total treatment mortality suggested that some factor in the leaf litter tended to improve survival, although the added leaf litter did not have any statistically significant effect on growth during the experiment. Thus, leaf litter, a component of the natural habitat of coho salmon fry, may warrant further study to determine its practical value in hatcheries for improving survival during the time when salmon undergo the transition to independent feeding. © 1990 Taylor and Francis Group, LLC.

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Progressive Fish-Culturist