You are here:
STABLE ISOTOPE STUDIES ON THE USE OF MARINE-DERIVED NUTRIENTS BY COHO SALMON JUVENILES IN AN OREGON COAST RANGE STREAM
Citation:
CHURCH, M., J. L. EBERSOLE, P. J. WIGINGTON JR, K. RENSMEYER, AND H. LAVIGNE. STABLE ISOTOPE STUDIES ON THE USE OF MARINE-DERIVED NUTRIENTS BY COHO SALMON JUVENILES IN AN OREGON COAST RANGE STREAM. Presented at American Fisheries Society, San Francisco, CA, September 02 - 06, 2007.
Description:
We are using stable isotopes (13C, 15N, 34S) to study the use of salmon carcasses, eggs and fry by over-wintering coho juveniles in two streams of the Oregon Coast Range. Our work is paired with detailed data gathering on stream habitat condition, temperature, chemistry and PIT-tagging studies to monitor movement and growth.
We have followed signatures in coho from spawner-eggs-fry-parr-smolts. Isotopic signatures decrease from equilibrium at an enriched state due to higher trophic oceanic feeding (e.g., δ15N=17) to muscle δ15N=6 per mil with in-stream diets. In one year with high winter spawner returns (thus higher numbers of carcasses, eggs and fry) smolts showed δ15N elevated above late summer values and also wide scatter in δ15N (from 4 to 8 per mil), approximating a difference within the cohort of about one trophic level. Some fish appear to consume significant amounts of MDN's while others of equivalent condition factor maintain lower signature diets.
To examine short term diet switches we have analyzed coho mucus for isotopic signatures. To our knowledge, we are the first to perform stable isotope analyses of fish mucus. Mucus signatures respond significantly faster than those of muscle and offer a significant advantage in such studies.