Size estimation of circular home range from fish mark-release-(single)-recapture data: case study of a small labrid targeted by recreational fishing

Contrary to common belief, empirical evidence shows that a number of marine littoral fish species tend to remain in a small geographic area. Despite the growing awareness about the consequences of reduced mobility (e.g. design of marine protected areas), an accurate description of fish movement is technically difficult; thus, it is usually not considered. Mark-release-(single)-recapture (MRsR) data obtained from externally tagged fish that are returned by fishermen or recreational fishers are potentially useful for describing fish movement. The present study is a methodological contribution aimed at demonstrating a simple analytic strategy for estimating the size of the circular home range (i.e. the area where a fish spends most of the time) from MRsR data. This analytic strategy is not adequate for pelagic or large predators moving at the oceanic scale but could be suitable for some reef or littoral fish. The estimates obtained by this method are robust even if (1) the number of recaptured fish is small, (2) fishing effort or habitat suitability displays some spatial variability and (3) fish display some intra-specific variability. Based on only 32 recaptures, our data demonstrate that Coris julis (a small labrid targeted by recreational fishers) is more sedentary than previously assumed; this fish spends 95% of its time within an area 227 m in radius (Bayesian 95% credibility interval: 192 to 275 m).