Food competition between freshwater sculpins (genus Cottus) and juvenile coho salmon (Oncorhynchus kisutch) : an experimental and ecological study in a British Columbia coastal stream
| dc.contributor.author | Ringstad, Norman R. | en_US |
| dc.date.accessioned | 2024-08-15T17:39:47Z | |
| dc.date.available | 2024-08-15T17:39:47Z | |
| dc.date.copyright | 1974 | en_US |
| dc.date.issued | 1974 | |
| dc.degree.department | Department of Biology | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | A system of experimental troughs was designed to examine food competition between sculpins and juvenile coho. Manipulation of sculpin densities showed t hat sculp i ns at higher than s tream densities were able to crop down the benthos sufficiently to significantly reduce drift densities and thus coho growth. At close to natural stream densities sculpins did not limit coho growth. A de tailed study of the autecology of the two sculpins Cottus asper and Cottus aleuticus occurring in Carnation Creek did not alter this conclusion. Juveniles of both sculpin species are found in the estuary. This results from either estuarine spawning or upstream spawning combined with downstream movement from March to July to the estuary, and subsequent met amorphosis of larvae. Upstream migration of young cottids takes place a year later from August to December. In the lowest 1500m of the stream C. asper tends to occupy areas with good cover and low current velocity, whereas C. aleuticus is restricted to the peripheral areas of C. asper habitat and riffles. In the lowest reaches of the stream the ratio of C. aleuticus to C. csper is 4:1, Above 1500m, in the absence of C. asper, C. aleuticus occupies all available habitat. C. aleuticus is smaller per age group than C. asper and the life span of both species is up to seven years. Both species are primarily bottom foragers feeding on aquatic insect larvae. Feeding increases throughout the night with maximal activity at or just before dawn. Some sexually mature adults of both species under take a downstream spawning migration in the spring . Most C. asper spawn in the estuary while C. aleuticus may undergo only local migrations and spawns primarily in freshwater. | |
| dc.format.extent | 88 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/19456 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Food competition between freshwater sculpins (genus Cottus) and juvenile coho salmon (Oncorhynchus kisutch) : an experimental and ecological study in a British Columbia coastal stream | en_US |
| dc.type | Thesis | en_US |
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