Abstract Title

Session S-09D: Salmon Recovery: Implementation and Progress II

Keywords

Species and Food Webs

Location

Room 611-612

Start Date

2-5-2014 10:30 AM

End Date

2-5-2014 12:00 PM

Description

We used bioenergetics modeling to investigate how environmental factors affected early growth and survival in steelhead, Oncorhynchus mykiss, under different environmental constraints in tributaries to the Skagit River, Washington. Differences in early growth between the average juvenile and juveniles that survived to later stages were due to differences in feeding rates and environmental factors associated with each tributary. In Bacon Creek, feeding rates between the average juvenile and juveniles that survived to later stages were not substantially different, but low summertime prey energy density and water temperatures decreased the scope for growth in the average juvenile and juveniles that survived to later stages. In Illabot Creek, low mean annual feeding rate in the average age 1–2 juvenile decreased the summer scope for growth, and low water temperatures during fall and winter combined with low winter prey energy density caused prolonged weight loss. The average age 2–3 juvenile fed at the same rate as age 2–3 juveniles that survived to later stages in Illabot Creek, but because of lower feeding and growth during age 1–2, the average juvenile was unable to reach the size attained at age-2 and -3 by juveniles that survived to later stages. In Finney Creek, the water temperature regime was relatively extreme, but elevated annual feeding rates and summertime prey energy densities greatly increased the scope for growth in the average juvenile that survived to the adult stage, indicating that feeding rate and summertime food quality may be critical to survival in these steelhead. Early growth of steelhead in the Skagit River influences survival to smolt and adult stages, and recovery of this threatened species could be enhanced by gaining a better understanding of general factors that limit growth in the mosaic of riverine habitats that support wild steelhead.

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May 2nd, 10:30 AM May 2nd, 12:00 PM

Size-selective mortality and bioenergetic limitations of juvenile steelhead under different freshwater environmental constraints in the Skagit River, Washington

Room 611-612

We used bioenergetics modeling to investigate how environmental factors affected early growth and survival in steelhead, Oncorhynchus mykiss, under different environmental constraints in tributaries to the Skagit River, Washington. Differences in early growth between the average juvenile and juveniles that survived to later stages were due to differences in feeding rates and environmental factors associated with each tributary. In Bacon Creek, feeding rates between the average juvenile and juveniles that survived to later stages were not substantially different, but low summertime prey energy density and water temperatures decreased the scope for growth in the average juvenile and juveniles that survived to later stages. In Illabot Creek, low mean annual feeding rate in the average age 1–2 juvenile decreased the summer scope for growth, and low water temperatures during fall and winter combined with low winter prey energy density caused prolonged weight loss. The average age 2–3 juvenile fed at the same rate as age 2–3 juveniles that survived to later stages in Illabot Creek, but because of lower feeding and growth during age 1–2, the average juvenile was unable to reach the size attained at age-2 and -3 by juveniles that survived to later stages. In Finney Creek, the water temperature regime was relatively extreme, but elevated annual feeding rates and summertime prey energy densities greatly increased the scope for growth in the average juvenile that survived to the adult stage, indicating that feeding rate and summertime food quality may be critical to survival in these steelhead. Early growth of steelhead in the Skagit River influences survival to smolt and adult stages, and recovery of this threatened species could be enhanced by gaining a better understanding of general factors that limit growth in the mosaic of riverine habitats that support wild steelhead.