PROACTIVE MANAGEMENT FOR SUSTAINABLE RANGELAND PRODUCTION
Location: Range and Livestock Research
Title: Salmon returns and consumer fitness: growth and energy storage in stream-dwelling salmonids increases with spawning salmon abundance
Submitted to: Canadian Journal of Fisheries and Aquatic Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 2011
Publication Date: March 26, 2012
Citation: Rinella, D.J., Wipfli, M.S., Sticker, G.A., Heintz, R.A., Rinella, M.J. 2012. Salmon returns and consumer fitness: growth and energy storage in stream-dwelling salmonids increases with spawning salmon abundance. Canadian Journal of Fisheries and Aquatic Sciences 69:73-84.
Interpretive Summary: We examined the effect of eggs and remains of adult Pacific salmon that had spawned and died on the nutritional status of stream-dwelling fishes. We sampled juvenile coho salmon and Dolly Varden during spring and fall from 11 streams on the Kenai Peninsula, south-central Alaska that varied widely in salmon remains. For juvenile fish sampled in the spring (both species combined), there was a positive relationship between adult salmon weight and juvenile fish growth rate. This indicates marine-derived nutrient effects can carry over through the winter months. For fish sampled in the fall, there was not a conclusive relationship between salmon weight and juvenile fish growth rate, but other measures of juvenile fish fitness were positively related to salmon weight.
We examined how biomass of marine-derived nutrients (MDN), in the form of spawning Pacific salmon, influenced the nutritional status and nitrogen stable isotope ratios (d15N) of stream-dwelling fishes. We sampled coho salmon (Oncorhynchus kisutch) parr and juvenile Dolly Varden (Salvelinus malma) during spring and fall from 11 south-central Alaskan streams that varied widely in spawning salmon biomass (0.1 to 4.7 kg m-2). Growth rate (as indexed by RNA-DNA ratios), energy density, and d15N enrichment in spring-sampled fishes increased with spawner biomass, indicating the persistence of spawner effects >6 months after salmon spawning. Point estimates suggest that spawner effects on nutrition were substantially greater for coho salmon than Dolly Varden (268% and 175% greater for growth and energy, respectively). Although the data were less conclusive for fall- than spring-sampled fish, they do suggest spawner effects were also generally positive during fall, soon after salmon spawned. In a follow-up analysis where growth rate and energy density were modeled as a function of d15N enrichment, results suggested that both increased with MDN assimilation, especially for coho salmon. Despite the variation in geomorphic features, ambient nutrient levels, and species composition of spawning salmon at our sites, spawner biomass appears to be an important factor in determining growth and energy among stream-dwelling fishes. Our results highlight the importance of maintaining large salmon runs in systems where the maintenance or recovery of stream-dwelling salmonid populations is a priority.