Globally, rising temperatures have resulted in numerous examples of poleward shifts in species distribution patterns with accompanying changes in community structure and ecosystem processes. In the Gulf of Mexico, higher mean temperatures and less frequent winter freezes have led to the expansion of tropics-associated marine organisms. Our objectives were to quantify changing environmental conditions and the poleward expansion of the common snook Centropomus undecimalis into the Cedar Keys area of Florida, USA (29 deg N). The snook is an economically and recreationally important sport fish found from southern Brazil to south Florida. Cedar Key and the Lower Suwannee River are north of the snook's historically documented range, likely due to lethal water temperatures during winter. Using data from a long-term monitoring program, we report an increase in catches of snook in this area since 2007. The spatial and temporal expansion of the species began with adult fish in 2007. By 2018, snook of all sizes were found in the region, and we found strong evidence of local reproduction during 2016-2018. The locations of nursery habitat and winter thermal refuges (e.g., freshwater springs) need to be identified and have implications for land-use policy and minimum-flow regulations for rivers. The arrival of the snook in the northern Gulf of Mexico could affect food web ecology and habitat interactions among estuarine predators, and future studies should evaluate snook's food habits and competitive interactions with resident fishes in this expanded range. Our study provides an example of how species range expansions due to changing temperatures should result in new research priorities to evaluate impacts of climate change on coastal systems.

Marine fish movement plays a critical role in ecosystem functioning and is increasingly studied with acoustic telemetry. Traditionally, this research has focused on single species and small spatial scales. However, integrated tracking networks, such as the Integrated Tracking of Aquatic Animals in the Gulf of Mexico (iTAG) network, are building the capacity to monitor multiple species over larger spatial scales. We conducted a synthesis of passive acoustic monitoring data for 29 species (889 transmitters), ranging from large top predators to small consumers, monitored along the west coast of Florida, USA, over 3 yr (2016-2018). Space use was highly variable, with some groups using all monitored areas and others using only the area where they were tagged. The most extensive space use was found for Atlantic tarpon Megalops atlanticus and bull sharks Carcharhinus leucas. Individual detection patterns clustered into 4 groups, ranging from occasionally detected long-distance movers to frequently detected juvenile or adult residents. Synchronized, alongshore, long-distance movements were found for Atlantic tarpon, cobia Rachycentron canadum, and several elasmobranch species. These movements were predominantly northbound in spring and southbound in fall. Detections of top predators were highest in summer, except for nearshore Tampa Bay where the most detections occurred in fall, coinciding with large red drum Sciaenops ocellatus spawning aggregations. We discuss the future of collaborative telemetry research, including current limitations and potential solutions to maximize its impact for understanding movement ecology, conducting ecosystem monitoring, and supporting fisheries management.

Understanding the relationships between river discharge and recruitment of estuarine fishes is important because of hydrological alterations caused by anthropogenic water withdrawals. Varying river discharge alters salinity, turbidity, nutrient levels, and detrital concentrations, all of which affect estuarine biota. The lower Suwannee River, Florida, is one of the few remaining large-river systems in the United States that has no major impoundments. We assessed the relationship between seasonal river discharge and relative abundance, growth, and mortality of estuary-dependent age-0 fish of five species in the Suwannee River estuary. We analyzed 9 years of data (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) collected as part of a long-term, fishery-independent monitoring program. The results showed a positive relationship between relative abundance and river discharge for age-0 spotted seatrout Cynoscion nebulosus, sand seatrout C. arenarius, and red drum Sciaenops ocellatus. The pinfish Lagodon rhomboides was the only species for which relative abundance was negatively related to river discharge; the relative abundance of spot Leiostomus xanthurus was not significantly related to changes in discharge. Instantaneous daily growth (G) estimates were positively related to river discharge for all species except spotted seatrout, for which a negative correlation was found. Instantaneous daily mortality (Z) estimates were positively correlated with river discharge for sand seatrout, pinfish, and red drum. The G : Z ratios for pinfish and early recruiting sand seatrout were negatively related to river discharge, indicating that recruitment potential declined with higher discharge. Changes in freshwater discharge affected the abundance, growth, and survival of these juvenile fishes, stressing the importance of water allocation decisions that affect estuarine fishes and the fisheries they support.

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