George R. Sedberry

Stock Identification of Gag, Mycteroperca microlepis, Along the Southeast Coast of the United States

Abstract: The gag grouper Mycteroperca microlepis is an important component of commercial and recreational fisheries along the South Atlantic coast of the United States and in the Gulf of Mexico. Over the past two decades, this species has experienced significant declines in abundance and an increasing skew in sex ratios. Analysis of microsatellite DNA variation in this species shows mosaic patterns of population subdivision and significant departures from Hardy-Weinberg equilibrium in all sampling locations. Given the length of the pelagic stage (egg and larvae), the prevailing current patterns, and the migratory capabilities of the adults, it is unlikely that these observations are the result of restricted gene flow among genetically differentiated populations. The apparent structure of gag populations most likely reflects inbreeding in size-limited populations. Population declines, skewed sex ratios, and perhaps variance in female fecundity appear to have acted in concert to limited the number of individuals that contribute to a given year class. These data are reinforced by studies of other fish stocks that have experienced precipitous declines over the past two decades.

An Overview of Marine Biodiversity in United States Waters

Marine biodiversity of the United States (U.S.) is extensively documented, but data assembled by the United States National Committee for the Census of Marine Life demonstrate that even the most complete taxonomic inventories are based on records scattered in space and time. The best-known taxa are those of commercial importance. Body size is directly correlated with knowledge of a species, and knowledge also diminishes with distance from shore and depth. Measures of biodiversity other than species diversity, such as ecosystem and genetic diversity, are poorly documented. Threats to marine biodiversity in the U.S. are the same as those for most of the world: overexploitation of living resources; reduced water quality; coastal development; shipping; invasive species; rising temperature and concentrations of carbon dioxide in the surface ocean, and other changes that may be consequences of global change, including shifting currents; increased number and size of hypoxic or anoxic areas; and increased number and duration of harmful algal blooms. More information must be obtained through field and laboratory research and monitoring that involve innovative sampling techniques (such as genetics and acoustics), but data that already exist must be made accessible. And all data must have a temporal component so trends can be identified. As data are compiled, techniques must be developed to make certain that scales are compatible, to combine and reconcile data collected for various purposes with disparate gear, and to automate taxonomic changes. Information on biotic and abiotic elements of the environment must be interactively linked. Impediments to assembling existing data and collecting new data on marine biodiversity include logistical problems as well as shortages in finances and taxonomic expertise.

Swim Bladder Deflation in Black Sea Bass and Vermilion Snapper: Potential for Increasing Postrelease Survival

Abstract Although some anglers regularly deflate swim bladders of demersal fishes being released, it is not known whether this practice actually increases postrelease survival of reef fishes. Benefits of deflating the swim bladder of black sea bass Centropristis striata and vermilion snapper Rhomboplites aurorubens before release were evaluated; survival of fishes deflated with one of two tools was compared to survival of nondeflated controls. Capture depths were 20–22 m, 29–35 m, and 43–55 m. Fishes were deflated with a 16-gauge hypodermic needle (99 black sea bass, 64 vermilion snapper) or with a Sea Grant tool consisting of a sharpened stainless steel canula (119 black sea bass, 64 vermilion snapper). Deflated fish were held in cages and observed in situ for 24 h. Controls (108 black sea bass, 89 vermilion snapper) were first segregated in a live well and then held in situ for 24 h in cages. Deflation, especially with the hypodermic needle, provided very significant reductions in mortality of black sea...

Iceberg scours along the southern U.S. Atlantic margin

Rapid climate fluctuations associated with ice-sheet oscillations have resulted in pulses of iceberg discharge that are recorded by iceberg scour marks along continental shelves and ice-rafted debris deposits across the North Atlantic. Iceberg transport is largely controlled by ocean surface currents; therefore, iceberg trajectories can serve as a proxy for paleo-circulation studies. Records of iceberg transport from ice-rafted debris (i.e., Heinrich layers) in the North Atlantic suggest that most icebergs released during Quaternary glaciations were entrained in a cyclonic subpolar gyre restricted to polar and mid-latitudes; however, new data suggest that there may have been an additional southerly component of transport along the western Atlantic margin. Here, we present evidence of extensive iceberg scouring across the upper slope offshore of South Carolina, ~1000 km south of the proximal ice margin during Quaternary glacial maximums. The location and orientation of the keel marks suggest that icebergs were entrained in a southwestward-flowing coastal current. At present, warm waters of the rapid, northeastward-flowing Gulf Stream bathe the upper slope off the southeastern United States. An offshore shift in the Gulf Stream axis during sea-level lowstand may have allowed glacially fed coastal currents to penetrate farther south. This may be the first evidence of iceberg rafting to subtropical latitudes in the North Atlantic.

Vertical Movements of a Shortfin Mako in the Western North Atlantic as Determined by Pop-up Satellite Tagging

Abstract A self-releasing satellite “pop-up” tag was attached to an adult male shortfin mako captured off of the southeastern United States. The tag was deployed in the spring of 2002 and detached after 60 days in an area approximately 72 km from the tagging location. Archived tag data indicated a depth range of 0 to 556 m in ambient temperatures between 10.4 and 28.6 °C. The shortfin mako demonstrated a diel pattern of vertical movement defined by greater mean depths and larger depth ranges during daylight hours. Depth and temperature data suggested a seasonal behavioral change in vertical movements associated with an increase in sea-surface temperatures during the study period.

Status of Vermilion Snapper and Red Porgy Stocks off South Carolina

Abstract Standardized trap and hook-and-line collections were made annually at four areas of reef habitat off South Carolina during 1983–1987 for red porgy Pagrus pagrus and vermilion snapper Rhomboplites aurorubens. We calculated mean annual values for catch per unit effort, estimated mean individual weights, and derived percentages of fish that were smaller than previously recommended yield-per-recruit critical lengths based on data from the two gear types. Although the two gear types did not generate identical results, there are indications that stocks of these reef fishes are overfished. The ratio of vermilion snapper to red porgy in hook-and-line samples increased during the study and in comparison to historical data, suggesting that abundance of red porgy declined more rapidly than that of vermilion snapper.

Reef Morphology and Invertebrate Distribution at Continental Shelf Edge Reefs in the South Atlantic Bight

Abstract Video footage recorded from 14 submersible dives on the continental shelf edge was used to describe and categorize reef morphology and quantify density and number of morphotypes of large sponges and corals. Significant variation in number of morphotypes and density of three dominant species among temperature classes, depth classes, and reef morphology categories was tested using a multiple response permutation procedure. The greatest densities of Ircinia campana, Stichopathes sp., and Muricea pendula, and the largest numbers of morphotypes were found between 18.1 and 21.0 °C and at depths between 51.0 and 60.9 m. Among reef morphology types, those that contained unconsolidated sediments such as “sand” and “large boulders with sand” exhibited the lowest densities and richness of morphotypes, while “block-shaped boulders,” “buried block-shaped boulders,” and “low-relief bioeroded” reefs had the greatest densities and largest numbers of coral and sponge morphotypes. Rocky reefs along the shelf edge with rough texture, complexity, and relief provide favorable conditions for epibenthic invertebrates. The warming and stabilizing effect of the Gulf Stream along the continental shelf edge allows some sessile macrofauna to inhabit deeper waters and more northern latitudes.

Timing and locations of reef fish spawning off the southeastern United States

Managed reef fish in the Atlantic Ocean of the southeastern United States (SEUS) support a multi-billion dollar industry. There is a broad interest in locating and protecting spawning fish from harvest, to enhance productivity and reduce the potential for overfishing. We assessed spatiotemporal cues for spawning for six species from four reef fish families, using data on individual spawning condition collected by over three decades of regional fishery-independent reef fish surveys, combined with a series of predictors derived from bathymetric features. We quantified the size of spawning areas used by reef fish across many years and identified several multispecies spawning locations. We quantitatively identified cues for peak spawning and generated predictive maps for Gray Triggerfish (Balistes capriscus), White Grunt (Haemulon plumierii), Red Snapper (Lutjanus campechanus), Vermilion Snapper (Rhomboplites aurorubens), Black Sea Bass (Centropristis striata), and Scamp (Mycteroperca phenax). For example, Red Snapper peak spawning was predicted in 24.7–29.0°C water prior to the new moon at locations with high curvature in the 24–30 m depth range off northeast Florida during June and July. External validation using scientific and fishery-dependent data collections strongly supported the predictive utility of our models. We identified locations where reconfiguration or expansion of existing marine protected areas would protect spawning reef fish. We recommend increased sampling off southern Florida (south of 27° N), during winter months, and in high-relief, high current habitats to improve our understanding of timing and location of reef fish spawning off the southeastern United States.