Rhizoprionodon Terraenovae Research Articles

Effects of Turtle Excluder Devices (TEDs) on the Bycatch of Three Small Coastal Sharks in the Gulf of Mexico Penaeid Shrimp Fishery

Abstract The stock of blacknose sharks Carcharhinus acronotus in the U.S. South Atlantic and the Gulf of Mexico is overfished, and according to the 2007 stock assessment conducted by the National Marine Fisheries Service overfishing continues to occur. Penaeid shrimp trawl bycatch rates in the Gulf of Mexico were modeled for this species as well as for the Atlantic sharpnose shark Rhizoprionodon terraenovae and bonnethead shark Sphyrna tiburo using a combination of research trawl and observer data. Research trawls have never used turtle excluder devices (TEDs), which are expected to exclude larger specimens of blacknose sharks. Most of the observer data that contain blacknose shark occurrences were collected during the pre-TED era when the two data sets tracked one another. Minimum observer data were available for the post-TED period (1990–present). As a consequence, the pre-TED (1972–1989) relationship between observer and research trawl catch per unit effort (CPUE) is driving the observer CPUE estimates...

Trophic plasticity in the Atlantic sharpnose shark (Rhizoprionodon terraenovae) from the north central Gulf of Mexico

Quantifying the trophic role of sharks in coastal ecosystems is crucial for the construction of accurate ecosystem models. This is particularly important for wide-ranging species like the Atlantic sharpnose shark (Rhizoprionodon terraenovae), ubiquitous across the northern Gulf of Mexico. We used gut content and stable isotope analyses to determine if differences in abundance of Atlantic sharpnose sharks in the waters around Mobile Bay, Alabama translated into differences in dietary sources or trophic position among sharks sampled east and west relative to the mouth of the bay. Gut content analysis suggested that Atlantic sharpnose sharks eat primarily teleost fishes (%IRI > 90% across size classes), and both stomach content and stable isotope analyses highlighted an ontogenetic shift in diet. Nitrogen stable isotope data from liver and muscle tissues indicated regional shifts in trophic position for Atlantic sharpnose sharks. The mixing model SIAR (stable isotope analysis in R) v.4.0.2 was used to suggest possible contributions from likely prey items for Atlantic sharpnose sharks sampled east and west of Mobile Bay. Portunid crabs and shrimp made higher contributions to the diet of Atlantic sharpnose sharks in the western region, compared to higher and more variable contributions from fish like croaker (Micropogonias undulatus) and hardhead catfish (Arius felis) in the eastern region. Our results suggest trophic plasticity in Atlantic sharpnose sharks, findings that emphasize the importance of examining regional variation in trophic position when constructing coastal foodweb models.

Seasonal modulation in the secondary stress response of a carcharhinid shark, Rhizoprionodon terraenovae

Some animals have the ability to modulate their stress response depending on the type and duration of the stressor. Modulations can initiate behavioral changes that increase fitness during the stressful period. The goal of this study was to determine if Atlantic sharpnose sharks, Rhizoprionodon terraenovae, exhibit seasonal modulations in their secondary stress parameters. Mature, male Atlantic sharpnose sharks were acutely stressed and serially sampled for one-hour, during spring, summer, and fall. An elevated stress response was observed for plasma glucose, lactate and osmolality during summer compared to spring and fall. Glucose also exhibited elevated initial concentrations, followed by a linear response during summer; varying from the asymptotic response during spring and fall. Hematocrit did not show differences over time or season; however, the power of the analysis was low due to the small sample size. When an additional 120 samples were included in the analysis, significantly higher initial hematocrit values were found during summer. Based on these results we suggest that summer is a demanding time for Atlantic sharpnose sharks.

Maternal meddling in neonatal sharks: implications for interpreting stable isotopes in young animals

Stable isotopes of neonatal vertebrates reflect those of their mother's diet and foraging location. Evaluating feeding strategies and habitat use of neonates is consequently complicated by the maternal isotopic signal and its subsequent elimination with growth. Thus, methods that measure the loss of the maternal signal, i.e. when the isotopic signal of a neonate reflects its own diet, are needed. Values of δ(13)C and δ(15)N were measured in liver and muscle tissues of <1 year old bull (Carcharhinus leucas) and Atlantic sharpnose (Rhizoprionodon terraenovae) sharks and related to age using, total length, date sampled and umbilical scar stage (USS). We observed a decline in δ(13)C and δ(15)N values with age that was different among species, similar among isotopes, and greater in liver than in muscle; highlighting that retention of the maternal signal is dependent on species-specific life history and tissue characteristics. USS was most effective for assessing the loss of the maternal isotopic signal in the faster growing Atlantic sharpnose shark, but was less effective for the slower growing bull shark. Total length and date sampled were overall less effective and may be more informative for slower growing species when coupled with USS, as variable size at birth and misclassification of animals >1 year old, which remain in nursery habitats, increase the variability of the isotopic values. Consideration of the maternal signal and measuring its loss are thus necessary when analyzing the stable isotopes of young animals, as there is potential to misinterpret feeding strategies, over-estimate trophic position and incorrectly assign carbon source.

A novel set of structures within the elasmobranch, ovarian follicle

Elasmobranch fishes produce some of the largest oocytes known, exceeding 10 cm in diameter. Using various microscopy techniques we investigated the structural adaptations which facilitate the production of these large egg cells in three species of shark: the Atlantic sharpnose shark, Rhizoprionodon terraenovae, dusky smoothound, Mustelus canis and the little gulper shark, Centrophorus uyato. The ovarian follicle of elasmobranchs follows the typical vertebrate pattern, with one notable exception; the zona pellucida reaches extreme widths, over 70 μm, during early oogenesis. Contact between the follicle cells and the oocyte across the zona pellucida is necessary for oogenesis. We describe here a novel set of large, tube-like structures, which we named follicle cell processes that bridge this gap. The follicle cell processes are more robust than the microvilli associated with the follicle cells and the oocyte plasma membrane and much longer. During early oogenesis the follicle increases in size relatively quickly resulting in a wide zona pellucida. At this stage the follicle cell processes appear taut, uniform and radially oriented. As oogenesis continues the zona pellucida narrows and the follicle cell processes change their orientation, appearing to wrap around the oocyte. The presence of the contractile protein actin within the follicle cell processes and their change in orientation may well be an adaptation for maintaining the integrity of these large oocytes. The follicle cell processes also contain electron dense material, identical to material found within the follicle cells, suggesting a role in the transport of metabolites to the developing oocyte.

Identification and evaluation of shark bycatch in Georgia’s commercial shrimp trawl fishery with implications for management

Abstract Many US states have recreational and commercial fisheries that occur in nursery areas occupied by subadult sharks and can potentially affect their survival. Georgia is one of few US states without a directed commercial shark fishery, but the state has a large, nearshore penaeid shrimp trawl fishery in which small sharks occur as bycatch. During our 1995–1998 investigation of bycatch in fishery-dependent sampling events, 34% of 127 trawls contained sharks. This bycatch totalled 217 individuals from six species, with Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson), the most common and finetooth shark, Carcharhinus isodon (Muller & Henle) and spinner shark, Carcharhinus brevipinna (Muller & Henle), the least common. The highest catch rates for sharks occurred during June and July and coincided with the peak months of the pupping season for many species. Trawl tow speed and tow time did not significantly influence catch rates for shark species. Gear configurations [net type, turtle excluder device (TED), bycatch reduction device] affected catch rates for shark species. Results of this study indicate gear restrictions, a delayed season opening, or reduced bar spacing on TEDs may reduce shark bycatch in this fishery.

Species delimitation in sharpnose sharks (genus Rhizoprionodon) in the western Atlantic Ocean using mitochondrial DNA

Despite Springer’s (1964) revision of the sharpnose sharks (genus Rhizoprionodon), the taxonomic definition and ranges of Rhizoprionodon in the western Atlantic Ocean remains problematic. In particular, the distinction between Rhizoprionodon terraenovae and R. porosus, and the occurrence of R. terraenovae in South American waters are unresolved issues involving common and ecologically important species in need of fishery management in Caribbean and southwest Atlantic waters. In recent years, molecular markers have been used as efficient tools for the detection of cryptic species and to address controversial taxonomic issues. In this study 415 samples of the genus Rhizoprionodon captured in the western Atlantic Ocean from Florida to southern Brazil were examined for sequences of the COI gene and the D-loop and evaluated for nucleotide differences. The results on nucleotide composition, AMOVA tests, and relationship distances using Bayesian-likelihood method and haplotypes network, corroborates Springer’s (1964) morphometric and meristic finding and provide strong evidence that supports consideration of R. terraenovae and R. porosus as distinct species.

Brevetoxins in sharks and rays (Chondrichthyes, Elasmobranchii) from Florida coastal waters

In October 2000, a mass mortality of blacktip sharks (Carcharhinus limbatus) and Atlantic sharpnose sharks (Rhizoprionodon terraenovae) in northwest Florida occurred in conjunction with a Karenia brevis red tide bloom. Before this incident, no information existed on red tide-induced shark mortalities or baseline brevetoxin levels in sharks and rays from red tide-endemic areas. We report here that brevetoxin accumulation in live and red tide-killed elasmobranchs is common during K. brevis blooms and non-bloom periods. Strong relationships were found between the frequency of red tide blooms and the average brevetoxin concentrations in elasmobranch tissues. The presence of brevetoxins in Atlantic coast sharks in the absence of documented K. brevis blooms may suggest that blooms are occurring in areas that are not well monitored. Although red tide-related shark mortalities are rarely observed, the presence of brevetoxins in shark embryos raises questions about the effects these toxins may have on the reproductive success of sharks.

Utility of mesohabitat features for determining habitat associations of subadult sharks in Georgia’s estuaries

We examined the affects of selected water quality variables on the presence of subadult sharks in six of nine Georgia estuaries. During 231 longline sets, we captured 415 individuals representing nine species. Atlantic sharpnose shark (Rhizoprionodon terranovae), bonnethead (Sphyrna tiburo), blacktip shark (Carcharhinus limbatus) and sandbar shark (C. plumbeus) comprised 96.1% of the catch. Canonical correlation analysis (CCA) was used to assess environmental influences on the assemblage of the four common species. Results of the CCA indicated Bonnethead Shark and Sandbar Shark were correlated with each other and with a subset of environmental variables. When the species occurred singly, depth was the defining environmental variable; whereas, when the two co-occurred, dissolved oxygen and salinity were the defining variables. Discriminant analyses (DA) were used to assess environmental influences on individual species. Results of the discriminant analyses supported the general CCA findings that the presence of bonnethead and sandbar shark were the only two species that correlated with environmental variables. In addition to depth and dissolved oxygen, turbidity influenced the presence of sandbar shark. The presence of bonnethead shark was influenced primarily by salinity and turbidity. Significant relationships existed for both the CCA and DA analyses; however, environmental variables accounted for <16% of the total variation in each. Compared to the environmental variables we measured, macrohabitat features (e.g., substrate type), prey availability, and susceptibility to predation may have stronger influences on the presence and distribution of subadult shark species among sites.

Plasma steroid concentrations of adult male Atlantic sharpnose sharks, Rhizoprionodon terraenovae, in the northern Gulf of Mexico, with notes on potential long term shifts in reproductive timing

In previous literature it was proposed that Atlantic sharpnose sharks, Rhizoprionodon terraenovae, from the western Atlantic Ocean (WAO) population exhibited differences in their reproductive timing when compared to the northern Gulf of Mexico (GOM) population. The objective of the current study was to examine the reproductive cycle of mature male sharpnose sharks from the northern GOM population. Plasma testosterone (T) and estradiol (E2) were measured from 76 mature male sharpnose sharks sampled from 1999 to 2001, and the gonadosomatic index (GSI) was determined for 53 additional mature males sampled from 2007-2008. Plasma T, E2, and GSI exhibited similar cycles with peak values occurring in late spring (April/May) and lowest values occurring during the summer. These results suggest that male sharpnose sharks in the northern GOM are reproductively active one to two months earlier than previously reported, which now brings them into synchrony with the WAO population. Interestingly, this shift in reproductive timing corresponds with a 3.0°C (13.4%) increase in spring sea surface temperature (SST) from the Mississippi Sound over a 29 year period, which could translate into GOM male sharpnose sharks becoming reproductively active earlier in the year thus explaining the late spring peak in GSI.

Distributions of Sharks across a Continental Shelf in the Northern Gulf of Mexico

AbstractDeclines in shark populations have sparked researchers and fishery managers to investigate more prudent approaches to the conservation of these fish. As managers strive to improve data collection for stock assessment, fisheries‐independent surveys have expanded to include data‐deficient areas such as coastal regions. To that end, a catch series from a nearshore survey off Alabama was combined with data from a concurrent offshore survey with identical methodology to examine the depth use of sharks across the continental shelf (2–366 m). The combined data set contained 22 species of sharks collected from 1995 to 2008: 21 species in the offshore data set (1995–2008) and 12 species in the nearshore data set (2006–2008). Depth was a significant factor determining species' distributions, primarily for Atlantic sharpnose Rhizoprionodon terraenovae, blacknose Carcharhinus acronotus, and blacktip C. limbatus sharks. Blacknose sharks had the highest catch per unit effort (CPUE) in the middepth stratum (10–30 m), blacktip sharks had consistently higher CPUE in the shallow depth stratum (&lt;10 m), and Atlantic sharpnose sharks showed high abundance throughout both the shallow and middepth strata. Length frequency and sex ratio analyses suggest that Atlantic sharpnose and blacknose sharks are using waters greater than 30 m deep for parturition, whereas adult blacktip sharks are probably using shallow waters for parturition. Our abundance patterns illustrate a continuum of depth use across the inner continental shelf. Surveys that do not encompass the entirety of this ecosystem fail to accurately characterize the distributions of these important predators.

Potential Sources of Survey Bias Associated with Hand‐Retrieved Longline Catches of Subadult Sharks in Georgia Estuaries

AbstractLunar phase, tide stage, and bait type were examined as potential sources of survey bias affecting catch rates of subadult sharks on hand‐retrieved longlines in Georgia estuaries. Sampling occurred during April–September from 2001 to 2003 in eight of Georgia's nine estuaries; this sampling period coincides with the pupping seasons for a variety of shark species. The effects of lunar phase and tide stage on catch rates of sharks were evaluated during 2001 and 2002. The effect of bait type (i.e., squid Loligo spp. or spot Leiostomus xanthurus) on shark catch rates was evaluated during 2003. During 2001 and 2002, 420 subadult sharks representing two families (Carcharhinidae and Sphyrnidae) and nine species were caught during 212 longline sets. Catch rates were evaluated for the four most commonly occurring shark species: the Atlantic sharpnose shark Rhizoprionodon terraenovae, bonnethead Sphyrna tiburo, blacktip shark Carcharhinus limbatus, and sandbar shark C. plumbeus. Neither lunar phase nor tide stage affected catch rates of any species other than blacktip sharks. In 2003, longline sets (n = 80) resulted in the capture of 177 subadult sharks from seven species. Overall catch rates were higher with squid bait than with spot, and bait type also affected shark species catch composition. Mean sizes of Atlantic sharpnose sharks were significantly different between the two bait types, indicating a possible ontogenetic shift in bait preference. For example, catch of neonate Atlantic sharpnose sharks was higher on hooks baited with squid than on hooks baited with spot, whereas catch of juveniles was higher on hooks baited with spot. Although timing of sampling events did not influence catch rates of subadult sharks, bait choice could bias estimates of abundance for certain life stages and affect the probability of detecting some species.

Field hearing measurements of the Atlantic sharpnose shark Rhizoprionodon terraenovae

Field measurements of hearing thresholds were obtained from the Atlantic sharpnose shark Rhizoprionodon terraenovae using the auditory evoked potential method (AEP). The fish had most sensitive hearing at 20 Hz, the lowest frequency tested, with decreasing sensitivity at higher frequencies. Hearing thresholds were lower than AEP thresholds previously measured for the nurse shark Ginglymostoma cirratum and yellow stingray Urobatis jamaicensis at frequencies <200 Hz, and similar at 200 Hz and above. Rhizoprionodon terraenovae represents the closest comparison in terms of pelagic lifestyle to the sharks which have been observed in acoustic field attraction experiments. The sound pressure levels that would be equivalent to the particle acceleration thresholds of R. terraenovae were much higher than the sound levels which attracted closely related sharks suggesting a discrepancy between the hearing threshold experiments and the field attraction experiments.

Stable‐isotope comparisons between embryos and mothers of a placentatrophic shark species

Stable nitrogen (delta(15)N) and carbon (delta(13)C) isotopes of Atlantic sharpnose shark Rhizoprionodon terraenovae embryos and mothers were analysed. Embryos were generally enriched in (15)N in all studied tissue relative to their mothers' tissue, with mean differences between mother and embryo delta(15)N (i.e. Deltadelta(15)N) being 1.4 per thousand for muscle, 1.7 per thousand for liver and 1.1 per thousand for cartilage. Embryo muscle and liver were enriched in (13)C (both Deltadelta(13)C means = 1.5 per thousand) and embryo cartilage was depleted (Deltadelta(13)C mean = -1.01 per thousand) relative to corresponding maternal tissues. While differences in delta(15)N and delta(13)C between mothers and their embryos were significant, muscle delta(15)N values indicated embryos to be within the range of values expected if they occupied a similar trophic position as their respective mothers. Positive linear relationships existed between embryo total length (L(T)) and Deltadelta(15)N for muscle and liver and embryo L(T) and Deltadelta(13)C for muscle, with those associations possibly resulting from physiological differences between smaller and larger embryos or differences associated with the known embryonic nutrition shift (yolk feeding to placental feeding) that occurs during the gestation of this placentatrophic species. Together these results suggest that at birth, the delta(15)N and delta(13)C values of R. terraenovae are likely higher than somewhat older neonates whose postpartum feeding habits have restructured their isotope profiles to reflect their postembryonic diet.

Bycatch mitigation assessment for sharks caught in coastal anchored gillnets

Fishing with modified gillnets was conducted to elucidate their potential for reducing shark bycatch. Experimental fishing focused on two commercial fisheries, Spanish mackerel ( Scomberomorus maculatus) and spot ( Leiostomus xanthurus). The modification took the form of increasing the gillnet tension using larger floats on the head-rope and increasing the lead-core lead-line weight. Gillnet mesh sizes were 7.2 cm (spot fishery) and 7.6 and 10.2 cm (Spanish mackerel fishery). Gillnet selectivity of the four most commonly encountered shark species were fitted to fork-length distribution data using the SELECT method. There was no significant difference in the catch rate of the target species between control and modified gillnets for all mesh sizes used. Catch rates of some shark species were significantly reduced in modified gillnets. Model deviance values indicated good fits to the data for blacknose ( Carcharhinus acronotus), blacktip ( Carcharhinus limbatus) and bonnethead ( Sphyrna tiburo) sharks with lowest deviance values (i.e., best fit) generally associated with the normal scale (spread proportional to mesh size) form. The selectivity results demonstrated that all life stages of Atlantic sharpnose ( Rhizoprionodon terraenovae) and blacknose sharks were available to the gillnets. The mesh selectivity of bonnethead sharks was largely uniform due to their exaggerated cepholaphoil that resulted in the majority being hammer-wrapped. Further, capture data indicated a dominance of large juveniles and adult bonnethead sharks resulting in poor model fits. The capture mortality rate for all shark species was high (78.6%) with higher mortality rates associated with heightened locomotor performance and wrapping as an entanglement mode. These results demonstrated that modified gillnets have the potential to reduce shark bycatch, particularly for those species for which wrapping was the primary entanglement mode.

Gear selectivity and sample size effects on growth curve selection in shark age and growth studies

The effects of gear selectivity and sample size on growth model selection for shark length-at-age data was investigated using simulated data sets for dusky ( Carcharhinus obscurus) and Atlantic sharpnose ( Rhizoprionodon terraenovae) sharks. Simulated data sets were generated using four different individual growth functions (von Bertalanffy, Gompertz, logistic and Schnute) with five different sample sizes and seven different sampling gear selectivity functions. Five growth models were fit to each data set and the Akaike information criterion (AIC) and AIC weights used to evaluate which fit best to the data. The accuracy of each of the fitting models was also determined and compared with estimates derived from AIC multi-model inference (MMI). The results demonstrated that no one growth model outperformed all other models in all situations, with the two-parameter von Bertalanffy model being selected most often by AIC. There were clear differences between the fitting models that were ranked the highest based on AIC selection or AIC weights and those based on models accuracy of length and growth parameter estimates. In most situations, the two-parameter von Bertalanffy model provided the least accuracy in parameter recovery, while the Schnute model was the most accurate individual model in most situations. The AIC MMI approach improved estimation accuracy over most individual models, except at very low sample sizes. These simulation results suggest that sample sizes of 200 are required to consistently achieve good accuracy for growth parameters, and that sampling gear selectivity has clear effects on which growth models fit best to the data. The use of the AIC MMI approach is recommended, as it provides the most robust estimates of growth parameters.

Use of a Fishery‐Independent Trawl Survey to Evaluate Distribution Patterns of Subadult Sharks in Georgia

AbstractWe investigated the utility of a fishery‐independent trawl survey for assessing a potential multispecies shark nursery in Georgia's nearshore and inshore waters. A total of 234 subadult sharks from six species were captured during 85 of 216 trawls. Catch rates and size distributions for subadult sharks and the ratio of neonates to juveniles were consistent among areas. The highest concentrations of subadult sharks occurred in creeks and sounds. Species composition varied among areas. The Atlantic sharpnose shark Rhizoprionodon terraenovae was the most abundant species in sound and nearshore stations, whereas the bonnethead Sphyrna tiburo was the most abundant species in creeks. The aggregate of other species occurred with higher frequency in the sounds and nearshore. Sampling characteristics of the trawl survey were compared with those from a fishery‐independent longline survey of subadult sharks to assess the similarity of the two gears. A total of 193 subadult sharks from seven species were captured during 57 of 96 longline sets, whereas 52 subadults from four species were captured during 20 of 48 trawls. Selectivity and efficiency differed between the two gears. The trawl had lower catch rates, caught smaller sharks, and encountered a different suite of species than the longline. General seasonal trends in relative abundance also differed between the two gears; the longline showed an increasing trend in abundance, whereas the trawl showed a stable trend. Although trawls were not found to be efficient for sampling subadult sharks from most species, they can be a useful source of supplemental data.

Coastal Habitat Use and Residency of Juvenile Atlantic Sharpnose Sharks (Rhizoprionodon terraenovae)

Coastal habitat use and residency of a coastal bay by juvenile Atlantic sharpnose sharks, Rhizoprionodon terraenovae, were examined by acoustic monitoring, gillnet sampling, and conventional tag–recapture. Acoustic monitoring data were used to define the residency and movement patterns of sharks within Crooked Island Sound, Florida. Over 3 years, sharks were monitored for periods of 1–37 days, with individuals regularly moving in and out of the study site. Individual sharks were continuously present within the study site for periods of 1–35 days. Patterns of movement could not be correlated with time of day. Home range sizes were typically small (average = 1.29 km2) and did not vary on a yearly basis. Gillnet sampling revealed that juvenile Atlantic sharpnose sharks were present in all habitat types found within Crooked Island Sound, and peaks in abundance varied depending on month within a year. Although telemetry data showed that most individuals remained within the study site for short periods of time before emigrating, conventional tag–recapture data indicates some individuals return to Crooked Island Sound after extended absences (maximum length = 1,352 days). Although conventional shark nursery theory suggests small sharks remain in shallow coastal waters to avoid predation, juvenile Atlantic sharpnose sharks frequently exited from protected areas and appear to move through deeper waters to adjacent coastal bays and estuaries. Given the high productivity exhibited by this species, the benefit gained through a nursery that reduces predation may be limited for this species.

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) in tissues of humans, dolphins, and sharks from the United States

Concentrations of tetrabromobisphenol A (TBBPA) and α-, β-, and γ-isomers of hexabromocyclododecanes (HBCDs) were determined by liquid chromatography–tandem mass spectrometry (LC–ESI-MS/MS) in human adipose tissue obtained in New York City, and in three marine top-level predators – bottlenose dolphin, bull shark, and Atlantic sharpnose shark – collected from coastal waters of Florida, USA. The overall mean concentrations (mean ± SD) of TBBPA and HBCDs were 0.048 ± 0.102 and 0.333 ± 0.571 ng/g lipid wt in human adipose tissue samples, 1.2 ± 3 and 7.38 ± 18 ng/g lipid wt in bottlenose dolphin blubber, 9.5 ± 12 and 77.7 ± 128 ng/g lipid wt in bull shark muscle, and 0.872 ± 0.5 and 54.5 ± 88 ng/g lipid wt in Atlantic sharpnose shark muscle. Overall mean concentrations of HBCDs were 5–10-fold higher than mean TBBPA concentrations, in all of the samples analyzed. The highest concentrations of TBBPA and HBCDs were detected in the bull shark muscle at concentrations of 35.6 and 413 ng/g, lipid wt, respectively. Concentrations of TBBPA and HBCDs, after log-transformation, were significantly correlated with each other in human adipose tissue and bottlenose dolphin blubber, but not in bull shark muscle samples. In the human adipose tissue samples, the concentrations of HBCDs were 3–4 orders of magnitude lower than the concentrations of polybrominated diphenyl ethers (PBDEs) previously reported for the same set of tissue samples. Concentrations of HBCDs in human samples from the United States were 1–5-fold lower than the concentrations reported from several European countries. HBCD concentrations in bottlenose dolphins from the United States were 1–2 orders of magnitude lower than the concentrations reported for other cetacean species from Europe. The present report is the first to determine levels of TBBPA and HBCDs in humans, bottlenose dolphins, and sharks from the United States.

Serum IgM levels against select marine bacteria in the Atlantic sharpnose shark ( Rhizoprionodon terraenovae) from three estuaries

The Atlantic sharpnose shark ( Rhizoprionodon terraenovae) is abundant and easily captured throughout the southeastern United States. Therefore this species serves as an ideal model for generating basic immunological reagents to establish baseline information regarding the immunophysiology of sharks in the wild, and for attempting to correlate shark immune responses to potential pathogens with the quality of the habitat in which they reside. Sharpnose shark serum IgM was purified over a protein-A column and used to generate mouse polyclonal anti-sera to develop indirect ELISAs for quantifying bacteria-specific IgM antibody titers against Vibrio anguillarium, Vibrio cholerae, Vibrio parahaemolyticus, Vibrio charchariae, Escherichia coli, Mycobacterium fortuitum, and Mycobacterium marinum. Serum samples from Atlantic sharpnose sharks were collected in Charleston, SC, Beaufort, SC, and New Brunswick, GA estuaries during the early summer, and again from Charleston, SC in the fall of the same year. Relative antibody titers against E. coli, V. anguillarium, and V. parahaemolyticus differed among the three sampling locations, suggesting differences in microbial abundance or immunological responses in sharks from three locations. Overall, antibody titers in Charleston, SC sharks increased between summer and fall. A combination of chronic exposure to specific bacteria and increased antibody responses due to elevated water temperatures are likely responsible for elevated specific IgM in these sharks sampled in the fall. To our knowledge, this is the first study to examine IgM responses in elasmobranchs collected directly from their habitat.