Merten, Wessley B.
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Publication Dolphinfish horizontal and vertical movements and population structure in the Western Central Atlantic(2014) Merten, Wessley B.; Appeldoorn, Richard S.; College of Arts and Sciences - Sciences; Schizas, Nikolaos; Armstrong, Roy; Craig, Matthew; Lilyestrom, Craig; Yoshioka, Paul; Corredor, Jorge; Department of Marine Sciences; Alfaro, MónicaIn the western central Atlantic the common dolphinfish (Coryphaena hippurus) is harvested within 30 exclusive economic zones (EEZs) and local waters where it provides essential sustenance and sport fishing opportunities to commercial and recreational fisheries, respectively. Due to the shared nature of this resource and the limited information concerning movements and population structure between and among EEZs and other jurisdictional waters throughout the region, the main objectives of this study were to: (1) describe intra-regional movements along the U.S. east coast, (2) determine spatio-temporal movements and exchange routes between the Bahamas and the U.S. east coast, (3) define the diel periodicity of vertical movements of adult male dolphinfish, and (4) delineate dolphinfish population structure by comparing DNA sequences from the southeastern U.S., northeastern Caribbean Sea, eastern Caribbean Sea, and north central Atlantic. Along the U.S. east coast, movement rates of dolphinfish (n=229) were dependent upon region, latitude, and distance from shore released. Movements from Florida to the South-Atlantic Bight (SAB) and Florida to northeastern North Carolina (MAB) had the highest observed rates, while movements within the SAB were the slowest. Regional movement headings varied with latitude, with dolphinfish released from Florida Keys to Central Florida displaying the most directional variability, with 3.5% conducting southerly movements. Inter-regionally, broad scale recaptures (n=7) suggest dolphinfish migrate in a circuit around the western central Atlantic to the Bahamas from the U.S. east coast, but paths can vary widely in temporal and spatial scale. Surface drifter tracks were compared to the displacements of dolphinfish released with plastic dart tags and indicate the most probable routes into, and out of, the Bahamas were via the Northwest Providence Channel from the Straits of Florida, the Northeast Providence Channel between Great Abaco and Eleuthera, between Cat Island and Long Island, and east from north or south of Grand Turk, Turks and Caicos. Analysis of six high-rate single point pop-up satellite archival transmitters (PSATs) deployed on adult male dolphinfish (95-120 cm estimated fork length (FL)) revealed a diel activity pattern within the mixed surface layer with frequent dives below the thermocline. During the day, there appears to be a bimodal distribution of depth fixes at the surface (0-1.3 m) and within subsurface to medium-deep depths (10-59.9 m). The most extensive vertical movements (>30 m) occurred during night rather than day, with the longest surface intervals undertaken during the day indicating that dolphinfish may engage in surface and at-depth feeding strategies, have complex predator-prey interactions, and demonstrate variable fidelity with floating objects such as Sargassum spp. or flotsam. These behavioral interactions with predators, prey, and floating objects may directly influence horizontal displacements and the timing of their overall migration around the western central Atlantic. Genetic connectivity was investigated using the mitochondrial NADH dehydrogenase subunit 1 (ND1; 972 bp) gene from 324 specimens of dolphinfish sampled from 4 regions in the western central Atlantic including the southeastern U.S., northeastern and eastern Caribbean Sea, and north central Atlantic where 162 haplotypes were identified. All sampling regions were linked by conventional mark and recapture events confirming high levels of gene flow. While statistical significance of population subdivision between regions was detected, the differences were only slight indicating low overall evidence of population differentiation of dolphinfish around the western central Atlantic. However, because low levels of genetic differentiation around the western central Atlantic were detected, variability in space and time of peak abundances of dolphinfish between sampling regions (northeastern Caribbean Sea versus eastern Caribbean Sea) could be the result of a northern and southern migration circuit which would merit management based as a multi-stock fishery throughout the region.Publication Acoustically monitoring coral reef fishes to determine short-term spatial and temporal movement and habitat utilization patterns(2009-03) Merten, Wessley B.; Appeldoorn, Richard S.; College of Arts and Sciences - Sciences; Yoshioka, Paul M.; Ojeda, Edgardo; Aponte, Nilda E.; Department of Marine Sciences; Alfaro, MónicaThe spatial and temporal movement and habitat utilization patterns of coral reef fishes were quantified using acoustic telemetry on 16 coral reef fish taken from 9 species across 5 families. Fish were caught in traps and surgically implanted with coded-acoustic transmitters and released back into the water by divers. The study site in La Parguera, Puerto Rico included 12 acoustic receivers set in an array from nearshore mangrove habitats to midshelf fringing reef zones. Samples were monitored from 1 to 63 days with total detections ranging from 1 to 43,182. Only two fish, both Ocyurus chrysurus, were recorded to have moved outside of the release site to contiguous receivers. The maximum distance traveled by O. chrysurus was approximately 7 km during a 30-hr period, with the furthest displacement from the release site being 1.2 km. Temporal movement patterns were observed to vary among species. The temporal pattern of recordings suggest that some species were engaging in crepuscular and nighttime feeding while others were seeking shelter during the same period. To more accurately quantify fine-scaled spatial and temporal movement patterns future studies should focus on determining a priori receiver-transmitter detection ranges and effective receiver-receiver overlap.