Comparing catch rate, conventional tagging, and acoustic telemetry data for understanding the migration patterns of coastal fishes

While acoustic telemetry (AT) has become the dominant technique for understanding patterns of fish migration, catch rate (CR) and conventional tagging (CT) techniques still play a major role, particularly in developing countries. Understanding the potential biases of each technique is important for fish migration research. We compared these techniques for understanding the migration patterns of two coastal fishery species (Argyrosomus coronus and Lichia amia) in southern Angola. Seasonal fluctuations in the catchability of A. coronus led to incorrect conclusions about migration patterns using CR and CT and we recognised “cryptic residency” during the austral summer. This was attributed to a fine-scale offshore movement that was detected using AT. The AT data provided evidence for partial migration in L. amia, and while supported by the CR and CT data, these did not provide direct evidence for this intraspecific behavioural diversity. Range test results indicated that the optimal placement of nearshore AT receivers is essential, especially when migratory routes proceed along noisy, nearshore pathways. These limitations should be addressed during the design phase of fish migration experiments.