Effects of Surgically and Gastrically Implanted Radio Transmitters on Growth and Feeding Behavior of Juvenile Chinook Salmon

Abstract

We examined the effects of surgically and gastrically implanted radio transmitters (representing 2.3–5.5% of body weight) on the growth and feeding behavior of 192 juvenile chinook salmon Oncorhynchus tshawytscha (114–159 mm in fork length). Throughout the 54‐d study, the 48 fish with transmitters in their stomachs (gastric fish) consistently grew more slowly than fish with surgically implanted transmitters (surgery fish), fish with surgery but no implanted transmitter (sham‐surgery fish), or fish exposed only to handling (control fish). Growth rates of surgery fish were also slightly impaired at day 21, but by day 54 they were growing at rates comparable with those of control fish. Despite differences in growth, overall health was similar among all test fish. However, movement of the transmitter antenna caused abrasions at the corner of the mouth in all gastric fish, whereas only 22% of the surgery fish had inflammation around the antenna exit wound. Feeding activity was similar among groups, but gastric fish exhibited a coughing behavior and appeared to have difficulty retaining swallowed food. Because growth and feeding behavior were less affected by the presence of surgically implanted transmitters than by gastric implants, we recommend surgically implanting transmitters for biotelemetry studies of juvenile chinook salmon between 114 and 159 mm fork length.

Comparative Performance of Acoustic-tagged and PIT-tagged Juvenile Salmonids

“…Similarly, Adams et al (1998a) found that most juvenile Chinook salmon they studied (surgery incisions from sham surgeries or transmitter implantation) were well 64 healed by day 21, but incisions on 29% of the fish were slightly inflamed, reddened, or incompletely healed 21 d after surgery. They noted that by 54 d after surgery, only 21% of fish had similar incisions.…”

“…Similarly, Adams et al (1998a) found that surgically implanted juvenile Chinook salmon had lower growth 21 d after implantation than control fish, but that there was no difference between the two groups 54 d after implantation.…”

“…Martinelli et al (1998) saw no transmitter expulsion over the 21 d in surgically implanted Chinook salmon (see Table 14 for fish and transmitter details). Adams et al (1998a) also did not find any radio transmitters expelled during their 54-d study of juvenile Chinook salmon. Robertson et al (2003), however, did find transmitters expelled from juvenile Atlantic salmon 20-29 d after implantation.…”

“…Less than 2% of the acoustic tagged fish in our study had a tag burden greater than 5%. Adams et al (1998a) demonstrated that the growth, feeding behavior, and survival of juvenile Chinook salmon were unaffected by surgically implanted radio transmitters that weighed from 2.3 to 5.5% of the fish's weight 54 d after tagging. Although our transmitters are very small, battery technology, tag-life requirements, and transmission capability may limit the manufacture of even smaller transmitters.…”

Assessment of Barotrauma Resulting from Rapid Decompression of Depth Acclimated Juvenile Chinook Salmon Bearing Radio Telemetry Transmitters

“…Transmitter treatment factors were 1) gastrically implanted radio transmitter, 2) surgically implanted radio transmitter, and 3) fish not implanted with a radio transmitter. Transmitters were implanted by U.S. Geological Survey (USGS) staff at McNary Dam using the methods of Adams et al (1998). Following implantation, Battelle staff freeze branded each fish with a unique external mark to provide a means to visually identify each individual fish during observation through acclimation, exposure, and post-exposure holding periods.…”