Juvenile steelhead are known to associate with shiner groups, though they also compete for food. Steelhead form dominance hierarchies within cohorts and aggressively defend feeding territories against all other fish. This study focused on the differential effect of shiner competition on steelhead of different social standing.
Survival of subordinate juvenile steelhead was significantly enhanced by the presence of redside shiner under laboratory conditions. A factorial experiment in 80 L tanks examined the relative effects of 0, 3, and 9 shiner at 15�� and 20��C on the growth and survival of 3 juvenile steelhead per tank. No temperature effect was detected and there was no significant difference in steelhead growth though statistical power was low (n=5). The largest steelhead did not die in any treatment and no steelhead died in the presence of 9 shiner. In treatments where no shiner were present mortality in the smallest steelhead was 80% (p-value<0.01). Aggressive interactions between steelhead allowed pathogens to colonize breaks in the skin of stressed fish resulting in death.
In 6800 L recirculating stream channels with natural substrate, 10 steelhead were held either alone or with 20 shiner at 15��C. No steelhead died and their growth was not significantly different between treatments, but, in the absence of shiner fin damage was 16 times greater (p-value<0.01) in the smallest three steelhead. If a shiner group was present the smallest steelhead appeared to shoal with shiner to avoid attack by dominant steelhead. / Graduation date: 1999
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33598 |
| Date | 02 March 1999 |
| Creators | Tinus, Craig A. |
| Contributors | Reeves, Gordon H. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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