The annual energy budget was determined for the rainbow trout and kokanee populations of a small (13.3 ha) British Columbia lake. Population size of the rainbow trout aged 1⁺ and older was 4000 based on a 55 catch-day Schnabel estimate. Number of kokanee present in the lake (9000) was based on the ratio of occurrence of kokanee to rainbow trout (2.25:1) in catch. Monthly instantaneous growth and mortality rates were applied to each age group. Seasonal change in gonad weight as a percentage of body weight was similar in both species (ovaries 0.5%-13%, testes 0.5%-4%). Sex ratios were generally even in kokanee but there was a higher percentage of females (57.7%) in the rainbow trout. The relationship between egg number per female (F) and fork length (L) was calculated (rainbow trout, F = 18.7 L•⁹⁵⁹; kokanee, , F = 2.84 L¹•⁴¹⁴).
The percent volume of each major food item was determined by stomach analysis. In only one month (May) was the food item of highest % volume the same in both species. Seasonal change in energy content of the food was estimated. Calculation of daily ration (as a percentage of body weight) was based on turnover rates (y) of food consumed at different temperatures (y = .545 e•º⁹¹x, where x is in °C). Feeding experiments using natural foods indicated assimilation efficiencies of 85.5%.
Continuous (20 hr) measurement of routine metabolism of individual fish was made with a respirometer situated in Marion Lake, between, August 1967 and October 1968. Rate of oxygen uptake (Q) in ml/hr, at 15 °C was plotted against weight (W) in kg (Q = 62.6 W•⁷⁶).
To determine the amount of energy trapped within the two populations, sample fish were dried (gonads separately) and burned in a calorimeter. The percent moisture of the fish was 74-78% during the year with marked increases at spawning time (rainbow 82%, kokanee 88%). The seasonal changes in energy content of immature fish were small (rainbow trout 6050-6200 cal/ash-free g; kokanee 6150-6300 cal/ash-free g). However mature fish underwent sharp reductions in energy content prior to spawning (rainbow trout 6100 to 5500 cal/ash-free g; kokanee 6100 to 5^00 cal/ash-free g). The pattern of seasonal change in energy content of the gonads was similar to that of the body.
Average biomass present in the lake was 1.53 x 10⁴ Kcal/ha (12.3 kg/ha) for the rainbow trout, and 2.23 x 10⁴ Kcal/ha (16.6 kg/ha) for the kokanee. Annual production for the two populations was 2.81 x 10⁴ Kcal/ha. The ratio of production to biomass for rainbow trout was 0.80, and for kokanee was 0.71. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/34824 |
| Date | January 1969 |
| Creators | Sandercock, Frederick Keith |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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