Influence of decomposing Pacific salmon carcasses on macroinvertebrate growth and standing stock in southeastern Alaska streams

We compared macroinvertebrate growth rates and standing stock in the absence and presence of meat from Pacific salmon (Oncorhynchus spp.) carcasses in microcosm and natural stream rearing experiments in southeastern Alaska. In microcosm experiments, the presence of salmon meat increased growth rates and standing stock for the shredder Zapada cinctipes and the collector Psychoglypha subborealis, but not the predator Rhyacophila sp., or the scraper Cinygmula sp. In natural stream experiments, the presence of salmon meat increased the growth rate and standing stock of P subborealis, but increased only the growth rate of Z. cinctipes. Macroinvertebrate responses to inputs of salmon-derived organic material can vary by species, which may reflect their feeding ecology. Macroinvertebrate taxa belonging to the collector functional-feeding group are likely to be important in transferring the effects of spawning salmon to the rest of the food web in southeastern Alaska streams.