Thirty‐nine adult Atlantic sturgeon Acipenser oxyrinchus oxyrinchus (136–234 cm total length) were caught in gill nets fished at historical sturgeon‐fishing locations in the Combahee and Edisto rivers (South Carolina) during spring and fall 1998. All fish were tagged (with passive integrated transponders and darts), and radio and acoustic transmitters were surgically implanted in 29 fish. When possible, gonad biopsies were taken for sex and maturity‐stage determination. Locations of telemetered fish were determined several times per week from airplanes (radio) and boats (radio and acoustic). Nominal ages, based on microscopic examination of pectoral spine cross‐sections, ranged from 7 to 20 years. Of the 28 fish for which sex was definitively ascertained, 21 (aged 7–15) were male and 7 (aged 15–20) were female. All fish moved out of the rivers during the period extending from October to November. Twelve fish returned the following spring (most in March), and many took up residence at the same sites utilized the previous year. Fall and spring spawnings were documented based on histological examination of gonad biopsies and directed upriver movements of fish during both seasons. Habitats used during summer were diverse and included the lower and upper estuaries, tidal freshwater, river, and perhaps even the ocean, as some fish left the system entirely. One male was captured in two successive springs and was in spawning condition (running ripe) both years.

The Atlantic sturgeon Acipenser oxyrinchus oxyrinchus has a latitudinally broad distribution along the east coast of North America, with extant populations occurring from the Saint Lawrence River to rivers in southern Georgia. This species once supported intensive caviar-based fisheries that resulted in overharvest and sharply reduced population abundances; presently, directed commercial fishing for Atlantic sturgeon is banned in U.S. waters. We sequenced a 203base-pair section of the mitochondrial DNA (mtDNA) control region of 322 Atlantic sturgeon specimens from 11 river systems across their range to elucidate their stock structure. We found a pronounced latitudinal cline in the number of composite mtDNA haplotypes and in haplotypic diversity, which increased from north to south, from previously glaciated and subsequently recolonized systems to the portion of their range unglaciated during the Pleistocene. The observed number of haplotypes per population ranged from 1 haplotype in each of the two northernmost population samples to 17 in the sample from the Savannah River. Haplotypic diversity ranged from 0.0 to 0.90. The greater genetic diversity within and among southern populations is likely a product of the persistence of these populations through the Pleistocene and to the faster mutation rates associated with their shorter generation times. Of 39 composite mtDNA haplotypes found, 64% were unique to particular populations. Monomorphism of the two Canadian populations suggested a strong founder effect. Three haplotypes unique to northern populations were probably the result of base substitutions that occurred within the past 10,000 years. In contrast with an earlier study, we found stock structure among southern populations and evidence of at least seven genetic stocks across this subspecies' range.

No 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 bass, and benefits of deflation increased with capture depth. Deflation for vermilion snapper was also beneficial, but to a lesser extent. Comparison of control results with a previous study using identical methods suggests that ascent speed may affect survival. Deflation of black sea bass and vermilion snapper by hypodermic needle is recommended for scientists. For anglers the Sea Grant tool may be a better choice; it is commonly used to apply dart-type tags and is readily available from some natural resources agency's tagging programs. Because the results differed for the two species, further study is needed to determine whether to recommend deflation as a standard practice for all reef fishes.

No abstract

During 1978–1998, 80,558 black sea bass Centropristis striata were caught with blackfish and chevron traps off eastern Florida, Georgia, South Carolina, and North Carolina at depths ranging from 9 to 55 m. Black sea bass were found to live for at least 10 years, but most were ages 1–5. There were latitudinal differences in the size at age, significantly larger size at age occurring in the southern segment (31°20′N to 32°40′N) than in the northern segment (32°41′N to 34°00′N). Males were found in all size‐classes and age‐classes and were most frequently encountered at sizes greater than 220 mm standard length (SL) and greater than age 4 in the southern segment and at sizes greater than 240 mm SL and greater than age 5 in the northern segment. Sexual transition and maturity of females occurred at smaller sizes and younger ages in the southern segment than in the northern segment. Probit analysis indicated that between 1978–1982 and 1987–1998 the size at 50% maturity (L50) for females fell from 137 to 108 mm SL in the southern segment and from 145 to 115 mm SL in the northern segment. The L50 could not be determined for fish caught during 1983–1986 because very few immature individuals were collected. Slight increases in the mean length and catch per unit effort, as well as a decrease in fishing mortality during the 1990s, suggested that the condition of the black sea bass stock had improved, probably due to management actions.

No abstract

During 1999During -2000 juvenile (Ͻ56 cm total length) shortnose sturgeon Acipenser brevirostrum were captured in the lower Savannah River, Geor-giaϪSouth Carolina, and acoustic transmitters were implanted in or attached to 15 of them. The juveniles were located only between river kilometers (rkm; measured from the mouth of the river) 31.2 and 47.5, in salinities of 0.1‰ to (briefly at high tide) 17.6‰, and at depths of 2.1-13.4 m. The fish used two small areas very intensively. When water temperatures were above 22ЊC, the fish moved upriver; they aggregated particularly at rkm 47.5 when temperatures were greatest, and the average salinity at this location was 0.1‰. When water temperatures were below 22ЊC, the fish moved downriver into Savannah Harbor and used approximately 2km segments of the Front and Middle rivers just upriver of their confluence at rkm 31.5. Here they encountered higher salinities (mean, 5.4‰) than during warm months. During the period of lowest water temperatures, the fish aggregated just inside the mouth of the Middle River in a hole separated from the deeper Front River by a sill. Movements related to tide stage or diel phase were not observed. Fish carrying transmitters with a depth option were always located on or near the bottom (Ϯ1.5-m transmitter accuracy). No juveniles were recorded as far downriver as the nursery area identified in a study conducted about a decade earlier, perhaps due to changes in hydrographic conditions that were induced by harbor modifications. The cool-season habitat is in the portion of the harbor to be impacted by further modifications. The relative abundance of juveniles suggests that recruitment has not increased despite an apparent increase in the adult population from the stocking of hatchery-reared fish during 1985-1992.