Swimming Performance and Growth Rates of Juvenile Atlantic Cod Intraperitoneally Implanted with Dummy Acoustic Transmitters

Short‐term and long‐term effects of intraperitoneal implantation of dummy acoustic transmitters (1.9–4.6% of the fishes' body weight) in wild juvenile Atlantic cod Gadus morhua were investigated. Short‐term effects were examined by comparing critical swimming speeds 24 h after surgery for implanted, sham‐implanted, and control groups using a Blazka‐style swim tube. Additionally, comparative growth rates, mortality, and tag expulsion by cod in the same three groups were determined during a 220‐d period. Critical swimming speed performance between treatments was found to be nonsignificant between groups, suggesting that tagged juvenile cod are capable of similar physical performance to that of untagged cod when released 24 h after surgery. During the long‐term study, no significant difference in growth between groups, no increase in mortality associated with the tagging procedure, and no incidents of transmitter expulsion occurred. This study suggests that intraperitoneal implantation of acoustic transmitters can be a valid tagging technique to examine the behavior of juvenile Atlantic cod in both short‐term and long‐term studies.