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.

Primed and cued: long-term acoustic telemetry links interannual and seasonal variations in freshwater flows to the spawning migrations of Common Snook in the Florida Everglades

“…Further, hydrological alterations affect many rivers inhabited by Snook, and these alterations may mute the environmental dependencies observed in the Shark River. Last, previous work has documented the presence of multiple contingents in Florida Snook, including riverine, coastal, and offshore marine segments of the population [ 42 , 43 ], and we acknowledge that the marked dependency of spawning on freshwater flows may only apply to riverine Snook.…”

“…The species has received considerable research attention due to their recreational and economic importance [39,41]. While some fish reside in lower estuaries and marine waters [42,43], a migratory portion of the population lives in riverine habitats for much of the year [34,38,44,45]. Freshwater prey serve as an important seasonal resource for migrant Snook, and upriver movements into freshwater habitats correspond to drying marshes when prey are concentrated in river channels in advance of the spawning season [38,[46][47][48][49].…”

Otolith microchemistry highlights the importance of extensive connectivity for conservation of an iconic migratory fish in a large tropical river basin

“…Variation was observed in patterns reflective of the extent of coastal habitat use (patterns I and II); some had natal signatures more consistent with fresher habitats (pattern III) and others appeared to remain in freshwater and brackish habitats throughout their lifetimes (pattern IV). Substantial variation in movement and habitat use has also been observed for common snook in Florida, including a broad range of freshwater habitat use (Stevens, Blewett & Poulakis, 2007; Lowerre‐Barbieri et al, 2014; Rezek et al, 2020), with some individuals remaining at offshore reef areas year‐round (Ault, Webb & Cox, 2021). Individual variation may explain some differences; Boucek et al (2019) found that the extent of riverine habitat use by individual common snook differed substantially within river systems that are managed as single stocks.…”