No abstract

The Gray Triggerfish Balistes capriscus supports fisheries on both sides of the Atlantic Ocean. We utilized fishery-independent samples to assess the age structure, growth, sex ratio, size and age at maturity, spawning season, and spawning frequency of the Gray Triggerfish population off the southeastern U.S. Atlantic coast. From 1991 to 2012, 7,685 samples were collected, ranging in FL from 82 to 578 mm and ranging in age from 0 to 13 years. Our study provides key life history information for an exploited population and is the first to comprehensively describe age, growth, and reproduction for a Balistes species. We documented that the Gray Triggerfish is sexually dimorphic, with adult males attaining larger sizes at age and a larger maximum size than females. Sex-specific growth curves were fitted, yielding the following von Bertalanffy equations: FL t = 419[1 -e -0.54(t + 0.61) ] for males and FL t = 352[1 -e -0.94(t + 0.22) ] for females. This species is characterized by a medium size at maturity (the smallest mature female was 179 mm FL; the smallest mature male was 183 mm FL) and relatively early age at maturity (the youngest mature female and male were age 0). Some shifts in population attributes coincided with a period of increased fishing pressure. Due to tighter regulations on snapper and grouper fisheries, the Gray Triggerfish has become a more targeted species. Fisheries biologists and managers should continue to evaluate potential impacts and establish management regulations that consider the region-specific reproductive season, size and age at maturity, and sex-specific differences in growth documented in this study.

The sagittal otoliths of 300 lane snapper Lutjanus synagris (Linnaeus) with a size range of 18 to 37 cm fork length were analyzed to estimate age. Transverse sections of embedded sagittae were prepared for microstructural analysis. All specimens presented clear annular increments that were readily counted by 3 independent readers. Marginal increment analysis and OTC (oxytetracycline)-injected specimens held in captivity validated that 1 increment was formed annually. The results enabled us to estimate von Bertalanffy growth parameters (growth coefficient, K = 0.395, asymptotic length, L ∞ = 33.09, t 0 = -1.95). Ninety percent of L ∞ is reached in 4 yr and first sexual maturity is attained in the 1+ yr class. There was no significant difference in the growth-parameter estimates between males and females. The high correlation between otolith weight (OW) and age permits the use of OW as a proxy for age in future stock assessments. The maximum age of 19 yr determined in this study is the oldest age recorded for this species in the western Atlantic Ocean.

We developed an index of biotic integrity (IBI) and a biotic index based on fish species richness (FSBI) to assess the ecological health of streams on the Savannah River Site, a 780‐km2 U.S. Department of Energy facility located in the Sand Hills ecoregion on the upper coastal plain of South Carolina. To maintain the responsiveness of the IBI to a variety of impacts yet incorporate sufficient ecoregion specificity to achieve acceptable accuracy, we included metrics from each of six metric categories proven useful in other ecoregions (species number, species composition, trophic composition, local indicator species, fish abundance, and fish condition) but selected specific metrics within each category based on their ability to discriminate between disturbed and undisturbed sites in the Sand Hills ecoregion. We also developed a procedure based on species–area curves to remove the potentially confounding effects of site‐specific differences in sample unit size and sampling effort from species number metrics. With these changes, the modified IBI was minimally affected by sample unit size and sampling effort and accurately discriminated undisturbed sites from sites affected by physical habitat alterations, thermal effluents, and chemical pollution. The FSBI, based on four species richness metrics (adjusted for the effects of sample unit size and sampling effort), discriminated between disturbed and undisturbed streams approximately as well as the modified IBI. The precision of both indices was affected by sample reach length, with samples from 50‐m reaches exhibiting relatively low precision and samples from 150‐m reaches high precision.

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.