Harpacticoid copepods:potential link between inbound adult salmon and outbound juvenile salmon

Abstract

Stable isotope ratios (615N and 613C) of estuanne organisms were measured monthly within 2 field seasons in Seldovia Bay, Alaska, USA, to assess the impact of salmon carcass decompositlon on estuarine productivity. A hypothesized indirect link between adult and juvenile salmon, with estuarine harpact~coid copepods a c t ~ n g as an intermediary, was supported by the data. Data show an Influence of nutr~ents derived from salmon carcasses on estuanne macroalgal primary production, as nitrogen stable isotope ratio values of Ulva sp. , an estuarine macroalga, were elevated In late summer following the salmon run. The isotope data also indicate that harpacticoids depend on Ulva sp. and possibly its epiphytes. Stomach content data for chum salmon fry (Oncorhynchus keta) show that they depend primarily on harpacticoids. Therefore, there is a nutrient link between adult and juvenile chum salmon in Seldovia Bay. Because harpacticoid production in an estuary is thought to control survival of chum fry, the nutrient link may functlon as a positive feedback mechanism influencing population fluctuatlons. K E Y WORDS: Harpacticoid copepod . Salmon. Seagrass . Ulva . Estuary Food web . Nutrients. Stable isotope