PNNL

Abstract

New methods to detect spawning of anadromous salmonids in their natural environment are needed to improve understanding of breeding behavior patterns, natural selection on reproductive traits (e.g., spawn timing), and interactions between artificially propagated and wild fish. We implanted maturing female Chinook salmon (Oncorhynchus tshawytscha) with coded electromyogram (CEMG) transmitters and continuously recorded spawning activity to develop an algorithm capable of accurately detecting spawning events from CEMG data. Marked increases in female digging frequencies that immediately follow spawning (cover digging) strongly correlated with CEMG values. The algorithm detected an average of 81% (95% C.I = 54.7% - 107.5%) of the actual spawning events (N = 16 females) when applied to all females in two separate spawning experiments. The algorithm accurately detected no spawning events for the two female salmon that did not spawn. The presence of CEMG transmitters did not affect the digging frequency, number of nests constructed, or the reproductive lifespan of implanted fish. However, the CEMG tagging procedure or the presence of tags resulted in significant increases in egg retention. DNA pedigree analyses confirmed that females implanted with CEMG transmitters exhibited significantly reduced individual reproductive success compared to non-tagged females (73% and 66% reduction in two separate experiments). However, subsequent research in adult steelhead (O. mykiss) has indicated that alternative implantation techniques hold promise for reducing the effects of the tags on reproductive success. We suggest that remote monitoring of salmonid spawning behavior is now possible using CEMG technology and should be tested in natural habitats.