The requirement by many species for multiple habitats reinforces the need to understand connectivity to better protect key habitats at appropriate time scales. The objectives of the study were to 1) create a representative model for how common snook use riverine, estuarine, and marine habitats and 2) examine the effects of individual behavior, time, and region on habitat use. Using network analysis techniques, where nodes represent physical locations of receivers and edges are movements between locations, we explored the connectivity of habitats during the spawning and overwintering seasons among 280 common snook, Centropomus undecimalis, surgically implanted with acoustic transmitters with four year battery life along the east coast of Florida. Raw detection data from receivers deployed in all habitats along 300km of coastline were validated and transformed into matrix format. Network visualization and analyses were conducted using Netdraw and Ucinet software.
Results/Conclusions
Comparisons of the number of movements between nodes, centrality, and gateways over 5 years revealed differences in habitat use and connectivity between seasons. Low network centralization (<2%) and high node size and edge weight suggest common snook utilize a greater area during the spawning season but movements were not focused. Number and direction of ties suggest common snook approach spawning sites through the estuary from the north. During the overwintering season, tagged fish were detected on significantly fewer receivers; combined with a marginally higher network centrality (<3%) and lower node size and edge weight this suggests that movements are smaller and more localized during this time period. Segregation of the population between inshore and offshore sub-populations was most evident during the overwintering season with moderate exchange occurring during the spawning season through nearshore habitat. . Larger fish site exhibited greater movements (e.g. degree = 0.32) compared to the population (mean degree = 0.08), suggesting spatial sub-structuring by size. Overall, spatial utilization of the population changed dramatically between seasons, this result emphasizes the importance of understanding temporal shifts in habitat prioritization for spatial management of catadromous species.