Testing assumptions of mark–recapture theory in the coral reef fish Lutjanus apodus
This study tested assumptions of the Cormack–Jolly–Seber capture–mark–recapture (CMR) model in a population of the tropical snapper Lutjanus apodus in the central Bahamas using a combination of laboratory and field studies. The suitability of three different tag types [passive integrated transponder (PIT) tag, T-anchor tag and fluorescent dye jet-injected into the fins] was assessed. PIT tags were retained well, whereas T-anchor tags and jet-injected dye were not. PIT tags had no detectable effect on the rates of growth or survival of individuals. The capture method (fish trapping) was found to provide a representative sample of the population; however, a positive trap response was identified and therefore the assumption of equal capture probability was violated. This study illustrates an approach that can be used to test some of the critical assumptions of the CMR theory and it demonstrates that CMR methods can provide unbiased estimates of growth and mortality of L. apodus provided that trap response is explicitly modelled when estimating survival probability.
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