A field evaluation of the growth and survival of age-0 Oncorhynchus mykiss tagged with 8-mm passive integrated transponder (PIT) tags

Abstract

Background: In fish tagging studies, tag size limits the size of fish that can be tagged, the fraction of a population that can be represented, and ultimately inferences that can be made about the study population, particularly when juvenile fish are the subject of interest. Introduction of an 8-mm passive integrated transponder (PIT) reduced the minimum taggable size of fish, but it has not been evaluated in field trials. We evaluated the growth and survival of age-0 Oncorhynchus mykiss tagged with 8-mm PIT tags in four streams in southwest Washington, USA. Results: A total of 351 PIT tagged fish and 340 control fish (marked with pelvic fin clips) were released, but recapture rates were low, particularly for control fish. Growth in length and mass did not differ between small (42-54 mm) and large (55-64 mm) PIT tagged fish. There was a slightly positive, but weak, relation between tag burden and growth in mass; however, there was considerable variability in this relation (R 2 = 0.115). Summer to autumn joint probability of fish surviving and remaining in the study area estimated with a Bayesian mark-recapture model ranged from 0.228 to 0.478 in study streams. We found no significant relation between tag burden and survival, suggesting neither tag burden nor fish size at tagging affected survival. Conclusions: Although this study was limited in scope, it provided insight into how age-0 O. mykiss tagged with 8-mm PIT tags grew and survived under natural conditions. We showed that fish as small as 42 mm could be tagged without detrimental effects, which should allow researchers to represent a larger portion of study populations through PIT tagging.

Performance of Subyearling Fall Chinook Salmon Tagged with 8‐, 9‐, and 12‐mm Passive Integrated Transponder Tags in the Snake River

“…All things being equal, it is reasonable that a smaller tag should result in fewer negative impacts than larger tags. Although past field and laboratory studies have tagged juvenile salmonids smaller than 45 mm with no ill effects (Tiffan et al 2015(Tiffan et al , 2019O'Donnell and Letcher 2017), a minimum tagging size of 45 mm in field studies will ensure better outcomes given the demands of the natural environment.…”

“…Furthermore, Cary et al (2017) found that six different species of small (≥39 mm TL), nongame fish tagged with 8-mm tags had high (≥93%) survival in stream enclosures and open stream reaches. More recently, Tiffan et al (2019) studied age-0 steelhead Oncorhynchus mykiss in four small Washington streams. They found that fish as small as 42 mm FL tagged with 8-mm tags had growth and survival similar to those of untagged fish.…”