David William Kerstetter

Muchos peces marinos tropicales utilizan el ecosistema de manglares para alimentarse, protegerse, desovar y como hábitat de cría. Para comprender mejor el flujo de energía entre los ecosistemas costeros de manglares y los arrecifes de coral cercanos a la costa, se examinó la conectividad trófica de los peces de arrecife mediante el análisis de isótopos estables. Se recogieron tanto juveniles y adultos de pargo mulato (Lutjanus griseus), pargo biajaiba (Lutjanus synagris), ronco carite (Haemulon sciurus), ronco condenado (Haemulon flavolineatum), boquilla (Haemulon parra), mojarra trompetera (Gerres cinereus) y barracuda (Sphyraena barracuda) tanto en manglares como en arrecifes de coral en el condado de Broward, Florida, E. U. A. Se analizaron los valores de δ13C y δ15N en los tejidos musculares y de δ18O y δ13C en los otolitos de todas las especies para evaluar los movimientos ontogenéticos, la alimentación y la ocupación del hábitat tanto en los manglares como en los arrecifes. Los valores de δ13C y δ15N en el tejido muscular fueron menores en los peces juveniles de los manglares que en los adultos capturados en el arrecife adyacente. Los valores de δ18O en los otolitos no mostraron diferencias significativas entre especies ni estados de madurez; sin embargo, los valores de δ13C fueron significativamente más bajos en los peces juveniles capturados en los manglares. Se observó una tendencia general de aumento de δ13C en los otolitos a medida que aumentaba la longitud de los peces, lo que corrobora los movimientos ontogenéticos desde los manglares hacia los arrecifes costeros. En resumen, este estudio caracteriza con mayor detalle la conectividad ecológica entre los arrecifes de coral y los manglares del Atlántico tropical occidental.

The lemon shark (Negaprion brevirostris), currently listed as Vulnerable by the IUCN Red List of Threatened Species, is a large sub-tropical elasmobranch found in the western Atlantic Ocean from Virginia, U. S. A. to Brazil, including The Bahamas and the Caribbean Sea. Habitat use by juveniles in Florida, U. S. A. and in The Bahamas has been previously well described, but little is known about horizontal and vertical movements of adults. Pop-up satellite archival tags (PSATs) and acoustic tags were deployed on lemon sharks off Jupiter, Florida, U. S. A. (n = 6; two females, four males) and at Tiger Beach, The Bahamas (n = 1; one female) for programmed deployment periods ranging from 10 to 120 days. All sharks demonstrated similar day and night patterns across the tracked period regardless of location or sex. A male tagged in Jupiter crossed the Gulf Stream, and the tag detached near Tiger Beach, while the female tagged at Tiger Beach in 2008 was recorded on the acoustic array in Florida in 2013–which are the third and fourth documented cases of a lemon shark crossing the Gulf Stream. The same sharks that crossed the Gulf Stream also periodically went to depths below 100 m, with a maximum recorded depth of 176 m. Finally, all tagged sharks were present around Jupiter in the winter months from December to May and absent from June to November. This study provides new information on vertical habitat use in lemon sharks as well as data relevant to the species' U. S. Federal Essential Fish Habitat (EFH) designations.

Climate change will continue to alter key physical and biological oceanographic processes throughout the global ocean, modifying environmental conditions for U.S. highly migratory fish species found in the Atlantic Ocean. The Atlantic Highly Migratory Species Climate Vulnerability Assessment evaluated the vulnerability of 58 species and stocks to projected ocean conditions, using a combined qualitative and quantitative analysis of species sensitivity (physiological, ecological, and behavioral attributes) and estimated exposure to possible future ocean stressors. Key modeled environmental variables included bottom and sea surface temperature, sea surface oxygen, and ocean acidification (pH), whereas the most influential biological attributes considered were population growth rate, stock size, and stock status. We produced vulnerability rankings (i.e., low, moderate, high, and very high) based on biological attribute sensitivity and exposure to the environmental variables, and separate analyses including estimated ability of distributional shifts, predicted directional effects of climate change, certainty, and data quality scores for the species and stocks assessed, with exceptions for species with undetermined geographic distributions. Of the 58 species and stocks assessed, 4 had very high vulnerability to climate change, 14 had high vulnerability, 22 had moderate vulnerability, 6 had low vulnerability, and 12 could not be assigned a rank. The majority (n = 45) of species and stocks had high ability for distributional shifts in response to projected changes in climate. Further, directional effect results suggest that climate change impacts on the majority of species and stocks will be neutral, implying that these species have life history or behavioral traits that impart some level of resilience and adaptability to the impacts of climate change. These results provide information for use in ecosystem-based fisheries management, particularly for prioritization of vulnerable species and stocks in conservation activities and research endeavors.

Elasmobranchs are an understudied taxon of cartilaginous fishes. DNA repair studies have been performed in very few elasmobranchs. Because DNA repair maintains the integrity of the genetic code, it is important for the survival of elasmobranchs in increasingly polluted oceans. Oil spills, for example, have been shown to cause DNA adducts in marine animals. We hypothesized that four elasmobranch species would show differential DNA repair expression. Dermal tissue was harvested from nurse sharks ( Ginglymostoma cirratum ), spiny dogfish (also considered to be sharks) ( Squalus acanthias ), yellow stingrays ( Urobatis jamaicensis ), little skates ( Leucoraja erinacea ), and RNA was isolated. RNA sequencing was performed using the holocephalan Australian ghostshark ( Callorhincus milii ) reference genome. ANOVA KEGG pathway analysis revealed that RNA from the sharks manifested significantly higher expression than those of rays/skates in 4/5 major DNA repair pathways (Base Excision, Nucleotide Excision, Mismatch Repair, and Homologous Recombination). Each of the four pathways of DNA repair manifested differential expression of pathway-specific genes ( mpg, polL, parp4, polD2, xpa, gtf2h3, gtf2h5, ercc8, ercc4, cul4b, rad51D, rad51C, blm, ssbp1, top3a, rad51, xrcc3, mre11a, brip1, rad54b , etc.). One gene, polD2 , was consistently elevated in the sharks vs. rays/skates in all four pathways. A subunit of polD , has been proposed to contribute to the spreading and amplification of hypermutations in sharks by generating higher diversity of the T cell receptor repertoire. With increased expression of four major DNA repair pathways, sharks may be more successful than rays/skates in remediating DNA damage and surviving the genotoxic effects of increasingly polluted oceans and possibly eluding cancer.

Microplastics threaten the health of numerous marine organisms at all trophic levels. Currently, the topic is well studied among large predators. However, knowledge of microplastics present in organisms at lower trophic levels is poorly understood. The aim of this study was to assess the presence of microplastics within lower trophic level forage fishes. Four locations were sampled, classified into two categories based on human population: urban and non-urban. Five species were sampled: Striped Mullet (Mugil cephalus), Scaled Sardine (Harengula jaguana), Redfin Needlefish (Strongylura notata), Pinfish (Lagodon rhomboides), and Irish Pompano (Diapterus auratus). Of the 248 fish sampled, 99.6% contained microplastics, with a total of 2,126 pieces found in gastrointestinal tracts and livers. No significant difference in microplastics concentration among forage fish species was found. However, location had a significant effect on the frequency of microplastics found within the fishes, with the urban location near Miami, Florida having a higher frequency of occurrence compared with the other three sampled locations. This was the first study to assess microplastics within the forage fishes of southeastern Florida and provides further evidence that microplastics are pervasive throughout multiple trophic levels.

Predatory fishes often have strong top-down effects on coastal marine ecosystems and are considered a priority for conservation and management. Predator activity can influence prey distribution, abundance, and foraging behaviors, and is likely to influence habitat by impacting ecological and environmental characteristics as well as presence of competitor species. There are knowledge gaps of the effects of functional diversity, non-consumptive predator association, and environmental effects on fish assemblages, particularly within the Greater Caribbean region. In this study, effects of apex marine predatory fishes on diversity and abundance of prey ichthyofaunal communities were examined in putative predation low-risk (north side = lagoon) and high-risk (south side = flat) areas around South Bimini Island, The Bahamas. Baited remote underwater video surveys (BRUVs, n = 100 sites) deployed in the two nearshore habitat types captured abundance and potential predator-prey interactions, which were compared to assess potential risk effects within low-risk and high-risk habitats. Results showed a difference in ichthyofaunal communities between the two habitats, with teleost abundance highest on the south side. Depth, temperature, salinity, and dissolved oxygen were significantly linked to biotic assemblages. There were no differences in flight (escape) behavior of prey from predator (sharks versus great barracuda), suggesting that predator avoidance was a minimal factor in ichthyofaunal community structures. In the rapidly developing Greater Caribbean region, knowledge of ichthyofaunal communities and predator-prey interactions in different coastal habitats can better inform management regarding ecological changes over time and between island locations.