We looked at the effects of internally tagging adult female Atlantic salmonSalmo salarand rainbow troutOncorhynchus mykissvia the urogenital tract. This method takes advantage of the fact that the oviduct in salmonids and some nonsalmonid species is not connected to the ovary; therefore, transmitters can be inserted into the body cavity of females through the urogenital opening. We found that dummy tags inserted into adult Atlantic salmon prior to egg formation did not alter survival, behavior, or general egg development. Sixty-nine percent of transmitters were retained for the entire study period (60 d). Transmitter retention (45 d) was 83% in rainbow trout tagged approximately 6 weeks before ovulation. However, proper insertion of transmitters in rainbow trout was prevented by the developing ovary, affecting egg expulsion and viability. It appears that oviduct tagging is a promising nonsurgical option in certain fish species if the transmitter is inserted prior to ovary development or after eggs have been shed.
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