Systematic review and meta-analysis of PIT tagging effects on mortality and growth of juvenile salmonids

Vollset, Knut Wiik; Lennox, Robert J.; Thorstad, Eva B.; Auer, Samuel; Bär, Kerstin; Larsen, Mette Voldby; Mahlum, Shad Kenneth; Näslund, Joacim; Stryhn, Henrik; Dohoo, Ian R.

doi:10.1007/s11160-020-09611-1

Cited by 50 publications

(40 citation statements)

References 55 publications

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“…However, the selection of fish for tagging, handling and tag effects can alter migration and survival of smolts, and thus biasing the dataset used for estimating the time of migration. This is supported by recent findings suggesting that tagged fish consistently migrate earlier than fish monitored using other methods, such as video surveillance and traps (Vollset et al, 2021).…”

Section: Introductionsupporting

confidence: 75%

“…Although the overlap was substantial, it was not evidenced that the length distribution was identical at the time of tagging due to compensatory growth. Growth rates in tagged smolts can be slower than in untagged smolts for ~1–3 months after tagging (Vollset et al, 2021), which could have shifted the length distribution between the time points. Handling stress, tag burden and auxiliary factors associated with telemetry tagging may affect growth of treated fish (Wargo Rub et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

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Validating timing of salmon smolt runs obtained by telemetry studies

Hulbak

Hanssen

Lennox

et al. 2021

Fisheries Management Eco

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Telemetry tags are increasingly used in management to monitor the migration timing of Atlantic salmon smolts (Salmo salar L.). It has been postulated that (1) effects from tagging and handling may alter migration behaviour, and (2) that the selection of fish during sampling is not representative of all migrating smolts, yielding bias in migration timing estimates. In the River Dale (Vestland, Norway), five groups of wild Atlantic salmon smolts (N = 385) were tagged in April–May and recaptured in a wolf trap. Migration timing was then compared to the untagged population. Migration timing differed between tagged (12 mm PIT) and untagged fish for 4/5 groups. Only fish tagged at the first time point did not have significantly different timing of migration from untagged counterparts. The relationship between length and the timing of migration was different for initial length and length at recapture; initial length suggested earlier migration of longer fish, but the extra time spent in the river prior to migrating for smolts that were initially smaller compensated for the size difference. The tagging protocol is crucial to obtaining representative migration timing results. Smolts should be tagged as early as possible and include the entire size distribution.

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Section: Introductionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Validating timing of salmon smolt runs obtained by telemetry studies

Hulbak

Hanssen

Lennox

et al. 2021

Fisheries Management Eco

Self Cite

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“…However, their application to study behaviour is increasing. As PIT tags are quick to insert, do not require sutures and are generally small (24 mm max), negative physical effects of PIT tags are assumed to be less common than for larger electronic tags; however, dependent on fish and PIT tag size PIT tags can still have adverse outcomes for fish welfare (Vollset et al 2020). Although PIT tags cannot provide information such as heart rate or muscular activity, using these lightweight tags in more creative ways can yield insight to individual fish behaviour.…”

Section: Tag Typesmentioning

confidence: 99%

“…For example, counting registrations of individuals at PIT antennae has shed light on feeding habits and coping styles of halibut (Kristiansen & Fern€ o 2007), the learning ability of salmon to refill their swim bladder at underwater air domes (Macaulay et al 2020a), and the spatial learning skills of mulloway (Argyrosomus japonicus) (Raoult et al 2017). However, PIT tag use is limited by the short detection range (only a few cm), one tag occupying the detection range can block other tags from being detected, and that when tags approach antennae diagonally, identification of the tag's unique code may fail to be registered (Br€ ann€ as & Alan€ ar€ a 1993; Baras & Lagard ere 1995) and their use in small fish can lead to increased mortality and tag loss (Vollset et al 2020).…”

Section: Tag Typesmentioning

confidence: 99%

Tag use to monitor fish behaviour in aquaculture: a review of benefits, problems and solutions

Macaulay

Warren‐Myers

Barrett

et al. 2021

Reviews in Aquaculture

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A variety of tagging techniques are now available to monitor fish behaviour, physiology and their environmental experience. Tagging is frequently used in aquaculture research to monitor free-swimming individuals within farmed populations. However, for information gathered from tagged fish to be representative of farmed populations, tagging must not fundamentally affect fish behaviour, physiology or survival. Here, we systematically review studies that used tags to monitor farmed fish behaviour and test factors that affect tag retrieval and tag-related mortality. Most studies using tags assessed movement and swimming behaviour in salmonids, predominantly in Europe and North America. Mortality of tagged fish was 10 times higher in sea-cages (mean = 25%, range = 0-61.5%, n = 22 studies) than in tanks (mean = 2.5%, range = 0-17%, n = 23 studies), while mortality of tagged fish in sea-cages was markedly higher in longer trials (from 4% in single day trials to 36% after 100 days). Higher-than-usual mortality rates among tagged fish, together with largely unknown sublethal effects on behaviour, should caution against using tagging studies to make decisions related to farm management. Moreover, key metrics such as mortality rates of tagged and untagged fish or evidence of sublethal effects are often unreported. We make several recommendations to improve future tagging studies and increase transparency in reporting. A greater insight into the causes of tagged fish mortality in sea-cages is required to secure animal welfare and data validity in studies that use tags to assess fish behaviour in aquaculture.

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“…A contentious point of using telemetry has always been to estimate the direct effect of tagging on smolt fate, which has been mostly tested experimentally or using models, but rarely in the wild (Hueter et al 2006, Newton et al 2016, Klinard and Matley 2020, Vollset et al 2020). This study suggests some tagging-induced mortality, but it was unrelated to tag burden.…”

Section: Discussionmentioning

confidence: 99%

The benefits of merging passive and active tracking approaches: new insights into riverine migration by salmonid smolts

Chavarie

Honkanen

Newton

et al. 2021

Preprint

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The process of smolting is a critical phase in the life-cycle of anadromous salmonids and it has been associated with substantial rates of mortality. Survival during freshwater and marine migration is known to have population level effects, thus an understanding of the patterns of mortality has the potential to yield important insights into population bottlenecks. Despite important advancements in tracking techniques, the specifics of mortality events in anadromous salmonids during their initial migration to sea remains somewhat elusive. Here, we develop a framework combining spatial and temporal detections of smolt riverine migration from two tracking techniques, which enable inferences to be made about mortality locations, causes, and rates. We embed this framework into a fine-scale behaviour study of migration and social structure. In this study, we demonstrate that during their initial riverine transitional phase, smolts were particularly vulnerable to predators. Specifically, avian predation appeared to be the main cause of mortality (42%), although piscine predation events were not trivial (14%). Our results suggested some direct and indirect tagging-induced mortality (e.g., through increased predation vulnerability), which highlights the importance of determining tagging mortality in a telemetry study to ensure adequate interpretation of migration success. There is evidence that predation induced selection on smolt morphology. Unsuccessful river salmon migrants with a phenotype comprising a shorter head and jaw and smaller eye had a higher probability of mortality in the later parts of riverine migration where avian and aquatic predation mortality dominated. In contrast, mortality earlier in river migration was independent of phenotype, most likely a result of tagging effects. Successfully river migrants were found to be interacting with each other, often in a pair or as a trio, indicating that a few individuals of Atlantic salmon and sea trout formed notable intra- and interspecific social associations. However, the heterogeneity of the social associations of successful migrants did not support the assumption that social network features attributed any clear specific benefits of reduced predation risk. Overall, by estimating migration loss and its variability, our study framework should help to guide management actions to mitigate the widespread population declines these species are currently facing.

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Systematic review and meta-analysis of PIT tagging effects on mortality and growth of juvenile salmonids

Cited by 50 publications

References 55 publications

Validating timing of salmon smolt runs obtained by telemetry studies

Validating timing of salmon smolt runs obtained by telemetry studies

Tag use to monitor fish behaviour in aquaculture: a review of benefits, problems and solutions

The benefits of merging passive and active tracking approaches: new insights into riverine migration by salmonid smolts

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