Document: BRI-3-72-14

The effects of habitat limitation on consumption rates of juvenile Atlantic salmon.

KENNEDY, B.P.* ¹, K.H.NISLOW ^1,2, C.L.FOLT ¹ and J.D.BLUM ³

Dartmouth College, Hanover, NH 03755, U.S.A. ¹
University of Massachusetts, Amherst, MA, U.S.A. ²
University of Michigan, Ann Arbor, MI, U.S.A. ³

Abstract:
We used fluxes of naturally occurring cesium (Cs) to compare in situ consumption rates of stocked Atlantic salmon (Salmo salar) fry in tributaries of the Connecticut River. Foraging-based models suggest that suitable foraging habitat during the early season (3 to 6 weeks after stocking) is critical to juvenile salmon performance, however our inability to measure consumption rates in the field has previously limited our ability to test this relationship. Building upon radioisotope approaches, we parameterized a model of Cs uptake and turnover in salmon fry that allowed us to measure integrated consumption rates over time scales of weeks to seasons. Field-based estimates for assimilation efficiencies showed no differences among sites, however interspecific differences in the Cs concentration of common prey taxa emphasize the importance of quantifying fish diet composition. Significant differences in consumption rates across sites were correlated with underyearling survival. Our results compare favorably with those of a spatially-explicit individual based model and support hypothesized resource and habitat limitation during the early season. High variability in consumption rates and decoupling of growth and consumption when fish are less than 6 weeks old suggests that this a challenging time for fry when habitats are limiting and energetic demands are high.

Keywords: Atlantic salmon, consumption rates, Cs mass balance, stream habitat

This abstract is being presented at: 9:30 AM in session:
Oral Session #57: Ocean-Going Fish and Mammals.