| Title: |
Growth performance of Rainbow Trout in reservoir tributaries and implications for steelhead growth potential above Skagit River dams. |
| Authors: |
Jensen, B. L.1 (AUTHOR) bljensen@usgs.gov; Johnson, R. C.1 (AUTHOR); Duda, J. J.1 (AUTHOR); Ostberg, C. O.1 (AUTHOR); Code, T. J.1 (AUTHOR); Mclean, J. H.1 (AUTHOR); Stenberg, K. D.1 (AUTHOR); Larsen, K. A.1 (AUTHOR); Hoy, M. S.1 (AUTHOR); Beauchamp, D. A.1 (AUTHOR) |
| Source: |
North American Journal of Fisheries Management. Oct2023, Vol. 43 Issue 5, p1427-1446. 20p. |
| Subject Terms: |
Rainbow trout; Steelhead trout; Hydroelectric power plants; Dams; Pacific salmon; Fish growth |
| Abstract: |
Objective: In the Pacific Northwest (USA), Pacific salmon Oncorhynchus spp. populations have been declining significantly for decades, prompting stakeholders to respond with a variety of conservation and restoration measures. One such measure being considered in the Skagit River basin (Washington, USA) is the introduction of steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) above the impassable Gorge, Diablo, and Ross dams to bolster their populations. Because freshwater growth is key to survival at subsequent life stages, we evaluated current trends in size and growth of Rainbow Trout among key tributaries to Gorge, Diablo, and Ross reservoirs using empirical data collection and bioenergetics modeling. Methods: For nine candidate streams, a bioenergetics model was used to assess how temperature and prey consumption affected growth performance of Rainbow Trout between annuli 1 and 2, and 2 and 3. Thermal scenarios were created to evaluate how fish growth responded to temperature variability while total annual consumption was constrained within empirical growth estimates. We then compared these results to back‐calculated size thresholds established by size‐at‐age observed in wild steelhead adults that returned to the Skagit River below the dams. Result: Of the streams proposed for introductions, there was one instance (McMillan Creek) in the nominal simulations where growth met or exceeded the size at annulus 2 or 3 of a returning adult steelhead (24.9 g at annulus 2 and 50.3 g at annulus 3). Modeled growth under different thermal scenarios showed that colder temperatures (0.1–10.7°C, Canyon Creek) produced higher growth than under the nominal or warm scenarios (2.0–15.3°C, Canyon Creek), as well as one additional tributary where size at annulus 2 or 3 (±2 SE) was comparable to the threshold established by adult steelhead below the dams (Big Beaver Creek, annulus 3). Conclusion: These results suggest Rainbow Trout growth is most limited by prey availability in the examined upper Skagit tributaries. Impact statementUsing empirical data and bioenergetics modeling, we evaluated differences in freshwater growth rate—a primary indicator of marine survival—between juvenile Rainbow Trout in tributaries above the Skagit River dams and returning adult steelhead below the dams, providing useful data for managers to evaluate anadromous introduction feasibility. [ABSTRACT FROM AUTHOR] |
| Database: |
Supplemental Index |