Use of Muscle Growth Indices for Prioritization of Habitat Restoration

Estuarine habitat selection for rearing and outmigrating salmon is thought to affect survival, life-history diversity, ocean-entry and population resilience in the Lower Columbia River and Estuary (LCRE).  Because many physiological measures respond rapidly and are sensitive to short-term changes, spatially and temporally in the estuary, we examined the relationship between tissue accretion/degradation and habitat conditions as reflected in various food calorie levels.  Run-of-river Chinook salmon (Oncorhynchus tshawytscha) were exposed to one of four feeding regimes and sampled weekly for length, weight, several condition factors, and 3 molecular markers over 28 days.  As expected, feed groups were correlated to growth rates.  In addition, 4eBP and MuRF-1 increased within treatments accordingly to feed levels over 28 days.  MLC2 on Day 7 and 14 was not a strong indicator of treatment; however, by MLC2 was more pronounced by treatment by Day 21 and 28.  For purpose of indexing habitat benefits, tissue synthesis and degradation were ideal markers, which are not easily confounded by stressors like handling, are responsive to habitat conditions including prey accessibility and water quality, and have low statistical variability.  The management implications of this project include the evaluation of restoration effectiveness LCRE, and prioritization of new habitat restoration projects.