Reproductive behavior affects spatial population structure and our ability to manage for sustainability in marine and diadromous fishes. In this study, we used fishery independent capture-based sampling to evaluate where Common Snook occurred in Tampa Bay and if it changed with spawning season, and passive acoustic telemetry to assess fine scale behavior at an inlet spawning site (2007–2009). Snook concentrated in three areas during the spawning season only one of which fell within the expected spawning habitat. Although in lower numbers, they remained in these areas throughout the winter months. Acoustically-tagged snook (n = 31) showed two seasonal patterns at the spawning site: Most fish occurred during the spawning season but several fish displayed more extended residency, supporting the capture-based findings that Common Snook exhibit facultative catadromy. Spawning site selection for iteroparous, multiple-batch spawning fishes occurs at the lifetime, annual, or intra-annual temporal scales. In this study we show colonization of a new spawning site, indicating that lifetime spawning site fidelity of Common Snook is not fixed at this fine spatial scale. However, individuals did exhibit annual and intra-seasonal spawning site fidelity to this new site over the three years studied. The number of fish at the spawning site increased in June and July (peak spawning months) and on new and full lunar phases indicating within population variability in spawning and movement patterns. Intra-seasonal patterns of detection also differed significantly with sex. Common Snook exhibited divergent migration tactics and habitat use at the annual and estuarine scales, with contingents using different overwintering habitat. Migration tactics also varied at the spawning site at the intra-seasonal scale and with sex. These results have important implications for understanding how reproductive behavior affects spatio-temporal patterns of fish abundance and their resilience to disturbance events and fishing pressure.
Common snook Centropomus undecimalis support a recreational fishery that contributes greatly to Florida's economy and have been the subject of many diverse studies in which aspects of their life history, reproductive biology, and fishery dynamics have been defined. The current stock assessment contains assumptions based on historical reproductive schedules measured at the population level during the early 1990s. Recent research, however, suggests our understanding of habitat residency and spawning schedules may be overly generalized. We used acoustic telemetry to study the movements and migrations of common snook from the tidal reaches of the Caloosahatchee River, a major tributary of Charlotte Harbor, for 3 years (2005–2007). During this period, 60% of the tagged snook left the study area during at least one spawning season, presumably to enter higher salinity waters where they spawn. The onset and duration of these annual migrations are similar to those reported in previous reproductive studies of snook, but individual dynamics varied. Unexpectedly, 40% of tagged snook remained within the monitored portion of the river for up to three spawning seasons, providing initial evidence for skipped spawning. These detailed data indicate differential individual contributions to total spawning biomass. If further investigation confirms skipped spawning in common snook and shows similar rates of skipped reproduction throughout the snook population, this information should be incorporated into future stock assessments.
Increasing human populations and urban development have led to losses of estuarine habitats for fish and wildlife. Where resource managers are restoring coastal wetlands, in addition to meeting goals related to hydrologic connectivity, biodiversity, and recreational opportunities, efforts are being made to provide habitat that is suitable for juvenile sportfish. An 18-month study was conducted to compare juvenile sportfish use of natural, restored, and impacted sites along Tampa Bay, Florida, shorelines. Juvenile sportfish densities at restored sites were broadly comparable to natural sites and greater than at impacted sites. However, site-specific differences in sportfish use did occur within site types. For example, one restored site had significantly higher densities of red drum Sciaenops ocellatus than any other site, while black drum Pogonias cromis were found exclusively at another restored site. To evaluate whether the restored sites are providing suitable habitat for juvenile fish, we assessed growth (estimated from counts of daily rings on otoliths) and condition (determined by lipid analyses) of juvenile common snook Centropomus undecimalis, an archetypal coastal wetland-dependent species. Growth (0.43-0.56 mm SL/day) and condition (4.6-6.1% lipid of dry weight) exhibited only site-specific differences and did not vary among natural, restored, and impacted site types. Although mortality rates of juvenile sportfish were not determined, use of a 40-m seine found that densities of potential piscine predators in these coastal wetlands were relatively low compared to published studies of open estuarine shorelines. The restoration and creation of coastal wetlands in Tampa Bay provides improved habitat for juvenile sportfish.
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