Offshore behavioral contingent of an estuarine fish population, common snook Centropomus undecimalis

Abstract

Research that identifies behavioral contingents, portions of a population that exhibit alternate life history strategies or habitat preferences, can provide a better understanding of a species’ resilience to disturbances, changes in environmental factors, and harvest. Sightings of the estuarine-dependent common snook Centropomus undecimalis at offshore reef areas throughout the year in southeast Florida prompted an investigation to determine whether a contingent of the snook population remains offshore year-round and if they can contribute to the inshore population. This study employed underwater visual observations, specimen collections, and acoustic telemetry over 7 yr to document and describe the snook that utilize offshore habitat. Fish were observed in groups of up to 225 individuals, 20.4 km from an inlet, and in waters up to 36.6 m deep. Snook were present in 79.4% of dive surveys conducted on artificial reefs but only in 18.4% of surveys on natural reefs. Acoustic telemetry showed that many fish remained offshore for multiple years. Most sampled fish (89.1%) were spawning capable, with some classified as actively spawning (15.8%). Reports of snook using offshore reefs occur elsewhere, including southwest Florida and the Florida Keys, indicating that this contingent behavior may not be unique to southeast Florida. Evaluating these occurrences and identifying potential triggers that prompt snook to leave the estuary for an offshore environment can aid in determining how the offshore contingent affects the overall population.