Detection and effects on mortality estimates of changes in tag loss

Abstract

When estimates of mortality are obtained from tagging experiments the rate of tag loss is usually assumed to be constant, but if the rate of tag loss increased over the time after tagging and is measured over a short period, it will be seriously underestimated when extrapolated to a longer period, with a corresponding overestimate of mortality. The authors describe a method for testing the assumption of constant tag loss on single-tagged animals, using a multiple release of tagged animals combined with recaptures or "searches' at a number of later times. An experiment using polyethylene shellfish tags attached with superglue to the limpet Cellana tramoserica suggested that the rate of tag lo..