Tagged salmon smolts being released


Ultrasonic tags have been implanted into the peritoneal (abdominal) cavity of Chinook salmon, steelhead trout and green sturgeon. The fish are deprived of food for 24 hours prior to surgery, and are then anesthetized. The tag is activated, its output level verified, weighed, and disinfected prior to being implanted in the fish. After anesthetization, we take a photograph of the fish, measure its length and mass, and record a description of its condition (scales, fin and eyes). Time of anesthetization, surgery, and recovery and quality of the procedure are recorded as well as the mass, serial number and ID code of each tag.

The surgeon makes a 10mm incision 3mm anterior to the pelvic girdle and beside the mid-ventral line, and the tag is inserted into the peritoneal cavity. The incision is closed using two surgeons knots with a 3-0 or 4-0 monofilament suture depending on the size of the fish. After the procedure, each fish is held in a recovery tank until it is able to maintain an upright position. It is then transported to a holding tank where it will remain until being released. Before releasing any tagged fish, we use an ultrasonic receiver to verify that the tag has turned back on and is working properly.

>>Description for Sugery video
1) the fish is placed on the surgical table after being measured and weighed;
2) an incision is made starting at the anterior end of the fish, beside the mid-ventral line;
3) the incision is completed approximately 3mm in front of the pelvic girdle;
4/5) a sterile tag is inserted through the incision into the peritoneal cavity;
6/7/8/9) the incision is then closed with two square knots; 10) the excess material is cut off leaving a clean closed incision;
11) the fish is then placed into a recovery tank where it is typical to observe an air gulping behavior;
12) the steelhead typically recover from the surgical procedure and resume normal behavior in less than 2 minutes.