Mortality and tag loss in dart and loop‐tagged captive snapper, Pagrus auratus (Sparidae), with comparisons to relative recapture rates from a field study

Abstract

Tag shedding rates of Hallprint dart and loop tags, and tag‐related mortality in the snapper Pagrus auratus were experimentally determined on fish held in captivity for periods up to 18 months. An artefact of the experimental process appeared to exacerbate dart tag shedding in one treatment. However, for other treatments, the instantaneous shedding rates for the first 7 months was 0.0006 day−1. Shedding rates were not linear for periods beyond 7 months and were described by a logistic function. The instantaneous shedding rate for the loop tags was much lower at 0.00016 day−1. Overall mortality during the experiment was only 1.9% and the causes of death could not be related to tagging. The relative return rates of the two different tag‐types from a field tagging programme were compared after analysis of fish size, spatial, temporal, and tagger‐type distribution. In all direct comparisons within each stratum, loop tag return rates were higher. It was concluded that the retention capabilities are better for loop tags than for dart tags in P. auratus.