A feeding experiment was designed to examine how fish growth rates are affected by the size abundance of pelagic zooplankton. Juvenile chinook salmon, Oncorhynchus tshawytscha , were raised in 90 m³ mesh enclosures in Saanich Inlet, B.C. The enclosures permitted ample water and zooplankton circulation while retaining 5-6 gram juvenile salmon. The enclosed fish grew at an average rate of 1.8% wet body weight/day for a six week experimental period. Weekly growth rates ranged from 3.9%/day while food was abundant, to -0.5%/day when food was scarce.
Several analytical methods were used to establish a relationship between fish gr.owth and the size and abundance of zooplankton in the enclosures. There is a strong relationship between the fish growth rates and the abundance of 1.4-4.5mm prey. Rates of successful search vary directly with the size and inherent contrast of a prey item. A minimum rate of successful search of 2.0m³/hour was estimated from a functional response curve for salmon feeding on 1.4-4.5mm zooplankton. This value is discussed in relation to a salmonids physical capabilities and results from previous field studies and tank experiments.
Daily growth increments on the otoliths of the enclosed fish were examined with respect to daily variations in water temperature and zooplankton abundance. Extremes in food abundance appear to have a significant and consistent effect on the spacing of the growth rings. However, water temperatures would have to be kept constant in order to establish any closer
relationship between food abundance and otolith growth rings. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/23128 |
| Date | January 1981 |
| Creators | English, Karl K. |
| 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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