Tagging and releasing California coastal fishes

Individual fish are caught with traps or by hook and line and then brought on board the boat.

The fish is restrained on a padded surgical board with fresh seawater running over its gills, no anesthetics are used.

The acoustic tag is surgically implanted in the fish’s peritoneal cavity. (In giant sea bass the tag is placed intramuscularly.)

The incision is closed with sterile sutures.

The fish is released back into the area where it was caught.

These tags emit an acoustic signal that is picked up by the receivers in the acoustic array. All tags transmit the tag number randomly at an interval of 60 to 120 seconds; the receiver records the time that the detection was received. Some tags also have pressure sensors and can transmit the depth of the tag at the time of transmission.

From these data, researchers can then see where each fish moves among receivers, also called “stations.” They can also see if fishes move over wide ranges, from island to island, or if they stay close to a smaller area. Fish that maintain a constant presence or repeatedly return to the same location are said to have high site fidelity. One major goal of the research in the array is to learn more about what kinds of habitat are required for a certain species of fish to thrive. Or in the case of the wider-ranging species, why they come and go to specific habitats at certain times.