An examination of a tag-shedding assumption, with application to southern bluefin tuna

Frailty models for the estimation of tag shedding rates with tagger effects

“…Numbers in parentheses are posterior standard deviations given to two significant figures. Hearn et al (1991) estimated tagger-specific shedding rates for a few prolific taggers from early SBT tagging studies. However, they pointed out that their tagger-specific parameter estimates were sensitive to recoveries after long times-at-liberty and were subject to high variance.…”

“…By contrast it was estimated that 96.1% of tags attached by tagger A during the second experiment survived type-1 shedding, but the instantaneous type-2 shedding rate of tags inserted by tagger A in this experiment was estimated to have been 0.178 per year. The purpose of the analyses in Hearn et al (1991) was to investigate the extent of bias rather than to develop a particular approach for modelling tagger-specific shedding rates (George Leigh, Department of Agriculture, Fisheries and Forestry, Brisbane, Australia, personal communication 2014).…”

“…No dependence in tag shedding rates between tags is considered. The consequences of dependencies in tag shedding rates between the two tags attached to each fish caused by using taggers with different skill levels are examined by Hearn et al (1991). They showed algebraically that standard estimators of overall shedding rates are negatively biased when fitted to recoveries pooled from two taggers with different shedding rates.…”

Tag loss in the lobster Palinurus elephas (Fabricius, 1787) and implications for population assessment with capture-mark-recapture methods

“…The following modeling assumptions were made (Hearn et al, 1991): (1) the loss of any tag is independent of the position of the tag (left or right) and of the presence of any other tag on the same specimen;…”

Fishing Mortality in North Carolina's Southern Flounder Fishery: Direct Estimates of Instantaneous Fishing Mortality from a Tag Return Experiment

“…Attaching two tags to a single animal is a well-established means for estimating tag retention rates (Beverton and Holt 1957). In using this approach, we made three assumptions about double-tagged cohorts: (1) tags attached to the same animal were a random sample from all tags; (2) the probability of tag shedding was independent among fish and among multiple tags on the same fish; (3) M, migration, catchability, and k were independent of the number of tags attached to an animal (Wetherall 1982;Hearn et al 1991). Postrelease survival may be estimated by subjecting fish to capture and handling processes and observing subsequent survival under controlled laboratory conditions or in replicate field enclosures (Pollock and Pine 2007).…”