Exploring movement patterns of an exploited coral reef fish when tagging data are limited

Movement is one of the most fundamental demographic variables affecting the distribution and abundance of populations, but movement patterns for exploited populations of coral reef fish have not been studied extensively. Obtaining movement data for many species by means of traditional tagging methods can be difficult because of high tagging-induced mortality and low recapture rates. We used an age-structured population dynamics model parameterised using data from different regions to explore potential movement patterns for the red throat emperor Lethrinus miniatus, an exploited coral reef fish species for which traditional tagging studies have been unsuccessful. The model used a Gaussian function to describe the proportion of fish of a given age moving to or from 1 of 3 regions (Townsville, Mackay and Storm Cay) of the Great Barrier Reef. The model was fitted with and without movement to empirical age frequency data from each region over a 5 yr period (1995 to 1999). Including movement in the model led to significantly better fits to the data and revealed discrete movement patterns within each region. The model predicted net immigration to the Townsville region and net emigration from the Mackay and Storm Cay regions. We present alternative hypotheses about migration patterns of L. miniatus and highlight the importance of determining the scales at which movement in larger, exploited coral reef fishes occurs.