In the present study, quantitative data were collected to clarify the relationship between calling, call structure and eggs produced in a captive population of red drum Sciaenops ocellatus. Sciaenops ocellatus were held in four tanks equipped with long-term acoustic loggers to record underwater sound throughout a simulated reproductive season. Maximal sound production of captive S. ocellatus occurred when the photoperiod shifted from 13·0 to 12·5 h of light, and the water temperature decreased to c. 25° C. These captive settings are similar to the amount of daylight and water temperatures observed during the autumn, which is the primary spawning period for S. ocellatus. Sciaenops ocellatus exhibited daily patterns of calling with peak sound production occurring in the evenings between 0·50 h before dark and 1·08 h after dark. Spawning occurred only on evenings in which S. ocellatus were calling, and spawning was more productive when S. ocellatus produced more calls with longer durations and more pulses. This study provides ample evidence that sound production equates to spawning in captive S. ocellatus when calls are longer than 0·8 s and contain more than seven pulses. The fact that more calling, longer calls and higher sound pressure levels are associated with spawns that are more productive indicates that acoustic metrics can provide quantitative information on spawning in the wild.

In this study, we investigated the metabolic effects of four different commercial soy-based protein products on red drum fish (Sciaenops ocellatus) using Nuclear Magnetic Resonance (NMR) spectroscopy-based metabolomics along with unsupervised principal component analysis (PCA) to evaluate metabolic profiles in liver, muscle and plasma tissues. Specifically, during a 12-week feeding trial, juvenile red drum maintained in an indoor recirculating aquaculture system were fed four different commercially available soy formulations, containing the same amount of crude protein, and two reference diets as performance controls: a 60 % soybean meal diet that had been used in a previous trial in our lab and a natural diet. Red drum liver, muscle, and plasma tissues were sampled at multiple time points to provide a more accurate snapshot of specific metabolic states during the grow-out. PCA score plots derived from NMR spectroscopy data sets showed significant differences between fish fed the natural diet and the soy-based diets, both in liver and muscle tissues. While red drum tolerated the inclusion of soy with good feed conversion ratios, a comparison to fish fed the natural diet revealed that the soy-fed fish in this study displayed a distinct metabolic signature characterized by increased protein and lipid catabolism, suggesting an energetic imbalance. Furthermore, among the soy-based formulations, one diet showed a more pronounced catabolic signature.

BackgroundFish sound production is widespread throughout many families. Territorial displays and courtship are the most common reasons for fish sound production. Yet, there is still some questions on how acoustic signaling and reproduction are correlated in many sound-producing species. In the present study, our aim was to determine if a quantitative relationship exists between calling and egg deposition in captive spotted seatrout (Cynoscion nebulosus). This type of data is essential if passive acoustics is to be used to identify spawning aggregations over large spatial scales and monitor reproductive activity over annual and decadal timeframes.MethodsAcoustic recorders (i.e., DSG-Oceans) were placed in three laboratory tanks to record underwater sound over an entire, simulated reproductive season. We enumerated the number of calls, calculated the received sound pressure level, and counted the number of eggs every morning in each tank.ResultsSpotted seatrout produced three distinct call types characterized as “drums,” “grunts,” and “staccatos.” Spotted seatrout calling increased as the light cycle shifted from 13.5 to 14.5 h of light, and the temperature increased to 27.7 °C. Calling decreased once the temperature fell below 27.7 °C, and the light cycle shifted to 12 h of light. These temperature and light patterns followed the natural reproductive season observed in wild spotted seatrout in the Southeast United States. Spotted seatrout exhibited daily rhythms in calling. Acoustic signaling began once the lights turned off, and calling reached maximum activity approximately 3 h later. Eggs were released only on evenings in which spotted seatrout were calling. In all tanks, spotted seatrout were more likely to spawn when male fish called more frequently. A positive relationship between SPL and the number of eggs collected was found in Tanks 1 and 3.DiscussionOur findings indicate that acoustic metrics can predict spawning potential. These findings are important because plankton tows may not accurately reflect spawning locations since egg capture is likely affected by predator activity and water currents. Instead, passive acoustics could be used to monitor spotted seatrout reproduction. Future studies can use this captive study as a model to record the estuarine soundscape precisely over long time periods to better understand how human-made stressors (e.g., climate change, noise pollution, and chemical pollutants) may affect spawning patterns.

Abstract-Cobia (Rachycentron canadum) is a pelagic, migratory species with a transoceanic distribution in tropical and subtropical waters. Recreational fishing pressure on Cobia in the United States has increased substantially during the last decade, especially in areas of its annual inshore aggregations, making this species potentially susceptible to overfishing. Although Cobia along the Atlantic and Gulf coasts of the southeastern United States are currently managed as a single fishery, the genetic composition of Cobias in these areas is unclear. On the basis of a robust microsatellite data set from collections along the U.S. Atlantic coast , offshore groups were genetically homogenous. However, the 2 sampled inshore aggregations (South Carolina and Virginia) were genetically distinct from each other, as well as from the offshore group. The recapture of stocked fish within their release estuary 2 years after release indicates that some degree of estuarine fidelity occurs within these inshore aggregations and supports the detection of their unique genetic structure at the population level. These results complement the observed high site fidelity of Cobias in South Carolina and support a recent study that confirms that Cobia spawn in the inshore aggregations. Our increased understanding of Cobia life history will be beneficial for determining the appropriate scale of fishery management for Cobia.Cobia (Rachycentron canadum), belonging to the monotypic family Rachycentridae (Actinopterygii: Perciformes), is a large, pelagic, migratory species distributed throughout tropical and subtropical waters of the Atlantic, Indian, and western Pacifi c oceans (Shaffer and Nakamura, 1989). The species is highly prized by both recreational fi sheries and aquaculture producers as excellent table fare. Within the United States, this recreationally and commercially important fi sh species occurs along the southeastern Atlantic and Gulf of Mexico coasts. Cobia has historically been managed by the South Atlantic Fishery Management Council and Gulf of Mexico Fishery Management Council as a single reproductive stock on the basis of minimal data from tag and recapture research and mitochondrial fragment analysis (Hrincevich, 1993). Most early life history information on Cobia comes from aquaculture research, and little is known about its natural life history.In the spring and early summer months, Cobias in the western North Atlantic are thought to migrate with warming waters from Florida to the Chesapeake Bay (Shaffer and Nakamura, 1989). During this putative northward migration, Cobias enter high salinity bays and estuaries, including Port Royal Sound and St. Helena Sound in South Carolina (SC), Pamlico Sound in North Carolina (NC; Smith, 1995), and the Chesapeake Bay (Shaffer and Nakamura, 1989). Cobias have been reported to spawn from April to September (Smith, 1995;Lotz et al., 1996;Burns et al.; 1 Brown-Peterson et al., 2001). Regional peaks in spawning correlate with their proposed annual migration from Florida to Massachusett...

No abstract