Effects of Acoustic Transmitters on Swimming Performance and Predator Avoidance of Juvenile Chinook Salmon

Abstract

The objective of this study was to determine whether juvenile Chinook salmon Oncorhynchus tshawytscha are negatively influenced by the intraperitoneal implantation of acoustic transmitters. We evaluated swimming performance and predator avoidance of juvenile salmonids implanted with acoustic transmitters that weighed up to 6.7% of the fish's body weight in air. Critical swimming speeds (U crit ) of tagged, sham-tagged (surgery but no tag), and control fish were measured in a respirometer to determine tag effects on swimming performance. Swimming performance was similar among treatment groups at 1-d and 21-d postsurgery intervals. Predator avoidance of fish implanted with active tags was evaluated to determine whether tagged fish were impaired by the operation of the tags or predators were attracted to the signals emitted from the tags. Predator avoidance was evaluated by comparing the proportion of each treatment group consumed (active tag, inactive tag, sham, and control) during exposure to piscivorous adult rainbow trout O. mykiss. Surgical implantation of acoustic tags in juvenile fall Chinook salmon did not significantly affect swimming performance. Implantation of acoustic transmitters (active and inactive) did not result in greater predation susceptibility in tagged fish than in untagged fish.

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

“…However, our results showed even more damage to fish bearing external transmitters than fish bearing either gastric or surgically implanted transmitters. Previous studies as well as ours clearly show that juvenile Chinook salmon achieve neutral buoyancy by compensating for the excess mass of internally implanted transmitters by increasing the volume of gas in their swim bladder (Gallepp and Magnuson 1972;Anglea et al 2003) and…”

“…This happens in part because a transmitter increases the mass of the fish. Previous studies have shown that fish compensate (achieve neutral buoyancy) for the additional mass of a transmitter by increasing the volume of gas in their swim bladder, thereby increasing their displacement (Gallepp and Magnuson 1972;Anglea et al 2003). As the fish pass through a turbine environment, they are initially exposed to increasing pressures as they pass through the turbine intake and approach the turbine distributor.…”

“…A transmitter adds mass to the fish which the fish must compensate for by increasing its displacement to achieve neutral buoyancy. Increases in buoyancy are achieved by the fish gulping air into its swim bladder, which causes changes in the volume of the fish and thereby increases the buoyant force acting on the fish (Perry et al 2001;Anglea et al 2003;Brown et al 2005). The presence of the transmitter and increased swim bladder volume for depth-acclimated fish may create conditions that will increase, relative to untagged fish, the probability for barotrauma injury and other damage to tagged fish when they are exposed to low pressures during turbine passage.…”

Survival of seaward-migrating PIT and acoustic-tagged juvenile Chinook salmon in the Snake and Columbia Rivers: an evaluation of length-specific tagging effects

“…Research has been conducted to evaluate tag effects among many species, transmitter types and sizes, and geographic areas. Specifically, laboratory research has evaluated the survival, growth, tag expulsion, swimming performance, stress levels, and predation of tagged versus untagged fish [4][5][6][7][8][9][10][11]. In these studies, untagged or sham-tagged fish (that is, fish handled in a manner identical to treatment fish, including incisions, but not implanted with a transmitter) typically serve as a comparison to tagged fish.…”

Juvenile Salmon Acoustic Telemetry System Transmitter Downsize Assessment

“…Some biologists have suggested that this tag burden not exceed 2% (Winter 1996). However, there have been numerous laboratory based studies that indicate that a tag burden higher than this may not influence swimming performance, growth, tag retention, or survival (Brown et al 1999(Brown et al , 2006(Brown et al , 2010Anglea et al 2004;Zale et al 2005). To this day, discussion continues about the 2% rule presented by Winter (1996).…”