Effects of Surgically Implanted Transmitter Weights on Growth and Swimming Stamina of Small Adult Westslope Cutthroat Trout

Abstract

The generally accepted 2% ratio of transmitter weight to body weight constrains or precludes telemetry studies examining the timing and location of spawning of small adult westslope cutthroat trout Oncorhynchus clarkii lewisi in headwater streams. We empirically determined effects of surgically implanted dummy transmitters ranging in weight from 1 to 5 g on the swimming stamina and growth of small (81.3–206.9 g) adult westslope cutthroat trout in the laboratory to establish acceptable transmitter weights for field studies on this species. Mean growth rates and swimming stamina were not significantly different among treatments, including controls. No precipitous decline or threshold beyond which performance deteriorated markedly was observed. Data collected using telemetered westslope cutthroat trout implanted with transmitters less than about 4% of body weight should therefore approximate information about untelemetered individuals without significant bias. However, we also detected subtle effects on growth within this transmitter weight range related to individual transmitter–body weight ratios (0.5–5.3% initially), and there were indications that swimming stamina was affected similarly. Each 1% increase in transmitter– body weight ratio elicited an 11.6% decrease in growth and a possible 5.6% decrease in swimming stamina at 6 weeks postimplantation. Therefore, transmitter selection should weigh the costs of increased transmitter weight on fish performance against the benefits of longer transmission durations. In the case in which transmitter weights approaching 4% of body weight are necessary to complete a study and slight decreases in performance are not expected to affect findings materially, such weights may be acceptable. In other cases, researchers should choose the lightest possible transmitters that allow study goals to be achieved and not automatically select transmitters weighing 4% of body weight.

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

“…Another study found no correlation between fish size and cortisol level 24 h or 7 d after implantation of radio tags in juvenile Chinook salmon (length range: 140 mm to 260 mm; tag burden range: 1.3% to 3.5%) [5]. Among other species, it has been recommended that only steelhead O. mykiss parr greater than 74 mm should be implanted with PIT tags [32], and Zale et al [22] did not find a negative influence on mean growth rate or swimming performance of cutthroat trout with tag burdens varying between 0.8% and 5.3%. Thus, our study corroborates the literature from laboratory research in that relative to control fish, the size-specific survival of yearling Chinook salmon with tag burdens up to 5.7 (that is the largest median tag burden per size class encountered in this study) was not affected by the implantation or presence of an acoustic transmitter.…”

“…Laboratory studies have attempted to set recommendations and further studies are challenging these recommendations by examining tag effects on salmonids along a range of sizes. Zale et al [22] examined the minimum size at which fish could be tagged without influencing the growth and swimming performance of small cutthroat trout O. clarkii (tag burden range: 0.5% to 5.3%) implanted with dummy radio transmitters. There was no relationship between tag burden and swimming performance, but there were subtle decreases in growth as tag burden increased.…”

Spatio‐temporal temperature variation influences juvenile steelhead (Oncorhynchus mykiss) use of thermal refuges

“…Fish were caught (n ; 20-40 per site) within 50 m of the tributary confluence (in either the tributary, thermal mixing zone, or mainstem) using a combination of angling and electro-fishing, and held in the tributary for a maximum of 12 hours before tagging. We measured fish weight and fork length, and surgically implanted the tags (Lotek's MST-720T temperature-sensor transmitter tags; 1.3 g dry weight; 60.88C) following a tagging protocol similar to Adams et al (1998); tag weight never exceeded 4% of fish body weight (Zale et al 2005). After surgery, fish were held in net-pens within tributaries for recovery for 1 hour prior to release near the area where they were caught.…”

Surgically Implanted JSATS Micro-Acoustic Transmitters Effects on Juvenile Chinook Salmon and Steelhead Tag Expulsion and Survival, 2010

“…A fundamental assumption of telemetry is that the 1.2 behavior, migration, and physiological state of the fish are not affected by the transmitter presence or tagging process (Skalski et al 2001;Deriso et al 2007). In addition, the transmitter presence or tagging process should not affect fish growth or survival (herein referred to as "tag effects"; Jepsen et al 2002;Zale et al 2005). Tag effect and/or the effect of tagging responses have been a staple of the telemetry literature since 1933 (Markus 1933) and have remained a concern as newer approaches and transmitter technologies have been developed (Moore et al 1990;Jepsen et al 2002;Welch et al 2007).…”