Taking the Bait: In Situ Voluntary Ingestion of Acoustic Transmitters by Atlantic Cod (Gadus Morhua)
Due to ethical concerns with tagging on animals, the scientific community has been challenged to adopt ethically acceptable tagging techniques. This is in part to the development of electronic tracking devices used to monitor movements of marine animals, such as Atlantic Cod (Gadus Morhua). Many techniques are available; however, the least invasive tagging technique available is in situ voluntary ingestion. This study utilizes in situ voluntary ingestion of baited acoustic transmitters by Atlantic Cod under field conditions in the shallow inshore waters off Newfoundland.
The study uses a surface-controlled tagging frame to suspend and monitor baited transmitters near the seafloor at depths ranging from 12.5 to 39.0m. An underwater video camera was erected to quantify the cods behaviour. Eight successful taggings were completed with cod ranging in various sizes from 34 to 92cm. Each transmitter yielded different results as the ones in the morning were consumed faster than the transmitters deployed in the afternoon. Tracking revealed that cod were active immediately following tagging, thus suggesting no effect of the tagging procedure. Also, individual fish were tracked with none of the fish regurgitating transmitters during the period for which they were tracked, resulting in a favored tagging technique.