Rhizoprionodon Porosus Research Articles

Can the Caribbean sharpnose shark Rhizoprionodon porosus Poey, 1861 be used as a ‘flagship umbrella species’ in an artificial reef complex to facilitate management actions and sustainability?

ABSTRACT Conservation of flagship and umbrella species has popular support and benefits coexistent species. We investigated whether the Caribbean sharpnose shark Rhizoprionodon porosus gathers necessary attributes of a ‘flagship umbrella’ species in the region of the Artificial Reef Complex of Guaxindiba (ARCG), southeastern Brazil. To do so, we compared fish community in areas and periods with and without this species, including areas with artificial reefs (ARs) and control areas (CAs); we combined these data with interviews with fishers. Ichthyofauna richness and abundance were higher in co-occurrence with the Caribbean sharpnose shark mainly in ARs. Thus, from an ecological standpoint, this shark can be considered an umbrella species. Moreover, this species raised awareness among fishers for conservation, mainly because of its commercial value and risk of losing their income, characterizing it as a flagship species. Therefore, it is recommended that sharks become symbols in conservation actions aiming the sustainability of the ARCG.

Fifteen years of elasmobranchs trade unveiled by DNA tools: Lessons for enhanced monitoring and conservation actions

The trade of elasmobranchs (sharks and rays) in Brazil threatens the country's rich endemic biodiversity. The present study explored the use of DNA-based tools to monitor the Brazilian elasmobranch trade, focusing on their role in identifying processed products and supporting conservation efforts. A systematic search of literature was conducted and included 35 peer-reviewed papers published between 2008 and 2023. A shift from the development of DNA-based tools to direct trade applications has been observed since 2015. Molecular identification challenges, including costly sequencing and limited resources in national databases, were identified along with proposed solutions, such as protocol optimization and exploration of cost-effective alternatives. Biases in trade analysis papers, particularly the lack of research in the Northeast Region of Brazil, and issues with sample sizes were evident. Species identified using DNA-based tools included the critically endangered Scalloped Hammerhead Shark (Sphyrna lewini), which appeared in 46 % of the evaluated papers, followed by the Blue Shark (Prionace glauca), and several others threatened species, such as the critically endangered and endemic Brazilian Guitarfish (Pseudobatos horkelii) and the recently categorized as vulnerable Sharpnose Shark (Rhizoprionodon porosus). Other species were reassessed by IUCN, including previously non-threatened species that are now at risk, emphasizing the need for fisheries management, trade monitoring and conservation measures. Our findings highlight the importance of continued genetic monitoring to analyze market trends and adjust legislation, encouraging compliance with frequent inspections to enhance wildlife conservation. We also identified gaps in research and recommended strategies for accurate species identification, broader investigation, and effective management.

BASELINE DATA ON RUBIDIUM (Rb) CONTAMINATION IN JUVENILE CARIBBEAN SHARPNOSE SHARK Rhizoprionodon porosus FROM SOUTHEASTERN BRAZI

Although pollution has been recently identified as a priority for elasmobranch conservation, metal contamination assessments in sharks and rays are still scarce, especially in southeastern Brazil. In this regard, rubidium (Rb) is a biomagnifying non-essential element determined in only two elasmobranch assessments to date. Therefore, the aim of this study was to obtain baseline Rb data and discuss the implications of Rb concentrations in the muscle and liver of the vulnerable Caribbean Sharpnose shark Rhizoprionodon porosus from Southeastern Brazil. Samples from 18 juvenile specimens were analyzed by inductively coupled plasma mass spectrometry following acid decomposition. When grouping males and females, muscle concentrations (1.117 ± 0.269 mg kg-1 w.w.) were significantly higher than liver (0.677 ± 0.146 mg kg-1 w.w.), indicating probable Rb bioaccumulation. Significant differences were observed between male and female liver and muscle Rb concentrations, both higher in muscle. Females also presented significantly higher liver concentrations. A negative correlation was observed between total length and liver Rb when grouping males and females, which may indicate the contaminant dilution effect, while a positive correlation was noted between total length and muscle Rb for males, indicating bioaccumulation processes. Significant ecological concerns regarding Rb contamination for this group are, therefore, noted, requiring further investigations.Keywords: Chondrichthyes, toxic elements, bioaccumulation, environmental pollution, Elasmobranchii.

Vulnerability of marine resources affected by a small-scale tropical shrimp fishery in Northeast Brazil

Abstract Tropical fisheries tend to be multispecies and require management approaches adapted to high diversity but scarce and poorly informative data. Productivity and Susceptibility Analysis-PSA is particularly useful where catch or biological data are incomplete, aggregated across species or insufficient for quantitative stock assessment. We applied PSA to estimate vulnerability and potential risk to target and non-target species caught by the small-scale shrimp fishery in northeast Brazil, adapting the method to regional conditions and incorporating an assessment of uncertainties caused by its subjective choices. Our findings suggest that non-target species can be more vulnerable than target ones. Bagre marinus, Pseudobatos percellens, Micropogonias furnieri, Hypanus guttatus, Macrodon ancylodon, Polydactylus virginicus, Rhizoprionodon porosus, Cynoscion virescens, Larimus breviceps, and Menticirrhus americanus, were the top 10 species potentially at risk due to their low productivity (long lifespans, low spawning), high capture rates of juveniles and overlap of feeding and breeding grounds with fishing areas. Most species (76%) maintained the same risk category (low, moderate, or high) regardless of the score weighting or productivity and susceptibility attribute boundaries applied. Overall, the target species are not currently the main ones threatened, but bycatch such as elasmobranchs, catfishes and Scianidae should be prioritized for assessment and data collection.

Mercury concentrations in coastal Elasmobranchs (Hypanus guttatus and Rhizoprionodon porosus) and human exposure in Pernambuco, Northeastern Brazil.

Elasmobranchs are long-lived predatory fish that show high Hg concentrations generally reflecting environmental levels, notwithstanding they are widely consumed in Brazil increasing Hg exposure to humans. This study reports on Hg concentrations in largely consumed sharks (Rhizoprionodon porosus) and rays (Hypanus guttatus) from the Pernambuco coast, NE Brazil and the risk associated with their consumption. Muscle tissue concentrations of Hg in H. guttatus and R. porosus varied from 40 to 1,020 ng.g-1 w.w. (median = 125; mean = 124 ± 48 ng.g-1 w.w.) in sharks and from 129 to 2,130 ng.g-1 w.w. (median = 976; mean = 919 ± 139 ng.g-1 w.w.) in rays. Concentrations of Hg positively correlated with size in sharks, but not in rays. Concentrations reflect the local environmental contamination of a large urban center and industrial park concentrated in a short extension of mangrove-dominated coastline (50 km) and are higher compared to other Brazilian sites where Hg concentrations in these species have been reported. Sharks had a risk coefficient (HQ) range of 0.04 to 1.1, not surpassing the reference level of exposure. On the other hand, rays' HQ ranged from 0.14 to 2.3, and exceeds the reference level of exposure and suggests adverse effects to consumers.

Espécies de peixes do estuário do Rio Paraíba, nordeste do Brasil

The Paraiba River estuary is the largest and most important estuary of Paraiba state, northeastern Brazil. It is under intense environmental degradation by the surrounding human population, and possibly several fish species are at risk in this habitat. Scientific sampling of the ichthyofauna started in the late 1970’s and proceeded until recently. We present a list of fish species captured in this estuary, based on voucher specimens housed at the Federal University of Paraiba collection. Four orders of Chondrichthyes and 26 orders of Osteichthyes were identified. A total of 187 fish species, including eight species of Chondrichthyes and 179 Osteichthyes, with 123 genera and 57 families were identified. Perciformes dominated in terms of richness (32 species), followed by Acanthuriformes and Clupeiformes. Comparing estuaries along the Brazilian northeastern coast and considering our large time sampling span, a higher richness would be expected. According to the IUCN Red List, Urotrygon microphthalmum is considered Critically Endangered and more seven species are classified as Vulnerable: Rhizoprionodon porosus, Rhinoptera bonasus, Megalops atlanticus, Epinephelus itajara, Hyporthodus niveatus, Lutjanus cyanopterus, and Cynoscion acoupa. Three of these species also appear in the same category in the threatened Brazilian list, all of which have declining population trends. Concerning the Elasmobranchii, Carcharhinus porosus is listed as Critically Endangered in our country and globally. This inventory organizes and broadens knowledge on the fish community that occurs in this important ecosystem, with inferences about life habits, ecological guilds and conservation status of the fish species.

Arsenic contamination in widely consumed Caribbean sharpnose sharks in southeastern Brazil: Baseline data and concerns regarding fisheries resources

Although shark meat is consumed worldwide, elevated arsenic (As) concentrations have been increasingly reported. The Caribbean sharpnose shark (Rhizoprionodon porosus) is a widely consumed fishing resource in Brazil, with scarce information on As burdens to date. Herein, commercial-sized juvenile Caribbean sharpnose sharks from Rio de Janeiro (Brazil) were assessed in this regard, presenting significantly higher hepatic As concentrations in males (8.24 ± 1.20 mg kg-1 wet weight; n = 12) compared to females (6.59 ± 1.87 mg kg-1 w.w.; n = 8), and a positive correlation (r = 0.74) was noted between female muscle and liver As concentrations, indicating systemic inter-tissue transport not evidenced in males. Arsenic concentrations were over the maximum permissible As limit established in Brazilian legislation for seafood and calculated Target Hazard Quotients suggest consumption risks, although cancer risks were not evidenced. Therefore, Public Health concerns with regard to Caribbean sharpnose shark As burdens deserve careful attention.

Isotopic enrichment in Rhizoprionodon porosus (Poey, 1861) and Carcharhinus porosus (Ranzani, 1840) embryos.

Isotopic values of two Caribbean sharpnose shark Rhizoprionodon porosus litters (Poey, 1861) with two and three embryos and one litter of 11 smalltail shark Carcharhinus porosus embryos showed enriched 15 N and 13 C compared to their mothers. In R. porosus, embryonic isotope values were 3.06 ± 0.07‰ and 0.69 ± 0.15‰ greater than their mothers' for δ15 N and δ13 C, respectively, whereas in C. porosus, δ15 N and δ13 C were 1.79 ± 0.09‰ and 1.31 ± 0.17‰ greater in embryos than their mothers.

Record of morphological abnormality in embryos of Caribbean sharpnose shark, Rhizoprionodon porosus (Elasmobranchii, Carcharhinidae), from the south coast of São Paulo State, Brazil

Record of morphological abnormality in embryos of Caribbean sharpnose shark, Rhizoprionodon porosus (Elasmobranchii, Carcharhinidae), from the south coast of São Paulo State, Brazil

Genetic structure and congeneric range overlap among sharpnose sharks (genusRhizoprionodon) in the Northwest Atlantic Ocean

Sharpnose sharks (genus Rhizoprionodon) experience extensive fishing pressure throughout their ranges in the Atlantic Ocean. As such, it is important to understand the degree to which intraspecific populations interact across a spatial gradient. The Atlantic sharpnose shark (Rhizoprionodon terraenovae) and Caribbean sharpnose shark (Rhizoprionodon porosus) share a similar appearance and spatial presence within the Gulf of Mexico, though until recently only R. terraenovae was observed north of the Bahamas. We assessed the population structure of R. terraenovae using the mitochondrial control region (650 bp). Our results indicate significant genetic structure (FST= 0.049, P < 0.001; ΦST= 0.017, P = 0.008) between the Gulf of Mexico and the rest of the Atlantic. In addition, we observed R. porosus outside their known range, in South Carolina, Virginia, and northern Florida. Given the overlapping range with R. terraenovae, we assessed the potential for congeneric hybridization with the addition of the nuclear ribosomal internal transcribed spacer 2 gene (1260 bp). Results designate these specimens to be true R. porosus specimens, indicating the need for reevaluation of this species’ range.

SHAPE AND CLUSTER ANALYSES FOR DISCRIMINATING POPULATIONS OF RHIZOPRIONODON POROSUS OF NORTHEAST COAST OF BRAZIL THROUGH CHONDROCRANIUM MORPHOMETRY

The genus Rhizoprionodon comprises seven species of sharks occurring in the Atlantic, Pacific and Indian Oceans. The sharks are small sized attaining about 150 cm, inhabiting coastal waters, estuaries and brackish waters. In Brazil, the two species found are Rhizoprionodon porosus and R. lalandii. The use of morphometric approaches has limitations for this group due to lack of anatomical landmarks, since they have a continuous form without angles. This study will analyze the chondrocranium, a structure that has species-specific shape, aiming at verifying the hypotheses suggested in the literature of two populations of R. porosus off northeastern Brazil. One population corresponds to the northern coast of the Northeast (RN) and, the other to the eastern coast of this region (PE). We performed a comparative morphometric study of the chondrocranium of R. porosus between areas using shape and cluster analyses. The results showed that there were differences for both adult and juvenile phases by areas of capture. In conclusion, there is indeed differences between chondrocrania from Pernambuco and Rio Grande do Norte.

CARACTERIZAÇÃO DE UMA PESCARIA DE PEQUENA ESCALA EM UM BAIRRO URBANO DE SALVADOR, BAHIA

O presente estudo teve como objetivo identificar áreas e esforço de pesca e recursos pesqueiros capturados pela frota linheira artesanal alocada no bairro da Pituba Salvador, Bahia - Brasil. Os dados foram coletados durante o ano de 2009 sendo monitorados 560 desembarques pesqueiros. Foram registradas no total 96 espécies sendo as de maior frequência de ocorrência (> 15%) a bicuda (Sphyraena guachancho), ariacó (Lutjanus synagris), cavala (Scomberomorus cavalla), albacora (Thunnus atlanticus), bonito (Euthynus alleteratus), caçonete (Rhizoprionodon porosus) e dourado (Coryphaena hippurus). A dinâmica de pesca é sazonal marcada por entre safras do período chuvoso (março a agosto) e seco (setembro a março). Importante destacar que a área de pesca utilizada pela comunidade pesqueira é a mesma há mais de um século, sendo quantificada a utilização de 42 subáreas, se destacando a Lama (35,2%) dentre as mais visitadas principalmente no período chuvoso.

Gross chemical profile and calculation of nitrogen-to-protein conversion factors for nine species of fishes from coastal waters of Brazil

The amino acid composition and contents of nitrogen, phosphorus, lipid, carbohydrate and protein were determined in muscles of Dactylopterus volitans, Genypterus brasiliensis, Mullus argentinae, Paralichthys patagonicus, Percophis brasiliensis, Pinguipes brasilianus, Rhizoprionodon lalandii, Rhizoprionodon porosus, and Urophycis cirrata. The samples showed low carbohydrate content (<3.5% dry weight in all species) and were rich in protein (>66% dry weight in all species). The percentage of total lipid varied widely among species, and M. argentinae showed the highest concentrations (16%). The percentage of nitrogen and phosphorus was high and similar among species, with overall average values of 13.3% and 1.2%, respectively. The amino acids composition was similar among the animals, with glutamic acid and lisine as the most abundant amino acid and histidine in low concentrations. Among species, the content of proteinaceous nitrogen was high, with an average of 96.8% of the total nitrogen. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-toprotein conversion factors ranged from 5.39 to 5.98, with an overall average of 5.71. These findings showed that the traditional conversion factor of 6.25 overestimates the actual protein content and should be avoided.

EVALUACIÓN DE AMPLIFICACIÓN CRUZADA DE MICROSATÉLITES PARA ESTUDIOS DE GENÉTICA POBLACIONAL DEL CAZÓN ANTILLANO RHIZOPRIONODON POROSUS (CARCHARHINIDAE) EN EL CARIBE COLOMBIANO

The Caribbean sharpnose shark, Rhizoprionodon porosus is an important resource for artisanal small-scale fisheries. It is one of the most abundant coastal sharks within its distribution range, and plays an important role as a predator in coastal marine ecosystems. For its coastal habits, it is susceptible to intensive extraction, especially the juveniles. To accomplish proper management and conservation of exploited Rhizoprionodon populations, knowledge about its genetic diversity and its population structure within their distribution range is needed. The ability of heterologous primers developed for other requiem sharks to amplify microsatellite molecular markers in R. porosus was tested in this study (cross amplification). The change in allele frequency of four microsatellite loci served to assess the genetic structure of R. porosus in the Colombian Caribbean. Analysis of molecular variance Amova and population structure analysis using the Фst statistical of genotype frequencies indicate low but significant genetic differentiation among R. porosus from the departments analyzed (Фst (3,165) = 0.002; p = 0.000). Besides, the analysis of pairs of departments indicates that there is significant genetic differentiation among La Guajira and the other samples analyzed of the Antillean sharpnose shark (all p values = 0.000). The information obtained helps to understand the dynamics of natural populations of the Caribbean sharpnose shark, serving as a baseline for the formulation, development of conservation strategies and management of this fishery resource; however, due the low number of heterologous loci useful for population genetics studies, research efforts on the development of specific markers for the species should be done for further population genetic studies of this species.

Sexual dimorphism of sharks from the amazonian equatorial coast

Sexual dimorphism is a widespread feature in several groups of vertebrates. Chondrichthyans differ sexually due to the presence of the clasper, a structure for internal fertilization, and other sexual differences in secondary characteristics. Nevertheless, studies assessing these variations are fairly rare. The main goal of this study is to identify differences in sexual dimorphism in three species of sharks from the Carcharhinidae family (<em>Rhizoprionodon porosus</em>, <em>Carcharhinus porosus</em> and <em>Isogomphodon oxyrhynchus</em>) using morphometric tools. A total of 213 specimens were captured in the Amazonian Equatorial Coast and analyzed using 65 morphometric characters. Discriminant analysis and The Student's t-test were used to demonstrate the morphological differences among sexes. Sexual dimorphism was reported at different levels for the three species. This study suggests that the most likely explanation for the presence of these variations is related to their reproductive characteristics and mating behavior.

Influence of the artificial reef size configuration on transient ichthyofauna – Southeastern Brazil

To investigate how variations in the volume of artificial reefs affect the structure and composition of the transient ichthyofauna, reefball-type concrete modules were arranged at 9 m of depth along the northern coast of the state of Rio de Janeiro. The modules were arranged in three configurations, each in triplicate: (1) solitary modules (1 m3), (2) side-by-side modules (2 m3) and (3) modules forming a triangle (3 m3). The surrounding ichthyofauna were sampled in two periods of the year (dry: September 2009 and October 2010; rainy: April 2010 and April 2011) with gillnets to record the richness, species diversity, number of individuals and biomass per volume unit. The total mean values of richness, diversity, number of individuals and biomass did not differ significantly among the reef volumes. However, when these variables were analyzed per standardized volume unit, there was an increase in these variables with the increase in reef volume, considering all the transient ichthyofauna as well as the most representative families, Ariidae and Sciaenidae. A non-metric multidimensional scaling ordination analysis revealed differences in the composition of the ichthyofauna between the sampling periods, dominated by Sciaenidae (Stellifer rastrifer, Paralonchurus brasiliensis, Larimus breviceps and Cynoscion virescens) in the dry period and by Ariidae (Aspistor luniscutis) and Carcharinidae (Rhizoprionodon porosus) in the rainy period. The results suggest that the increase in module size from 1 to 3 m3 may result in slight alterations in the community descriptors, with a decrease in the relative values of richness, diversity and density per standardized volume unit. Furthermore, the effects of the seasonal flow of the Paraíba do Sul River may overlap the effects of reef configuration, mainly in the rainy period with higher flow. The implementation of several dispersed 1 m3 modules seems to be the most favorable configuration to attract transient ichthyofauna, especially Ariidae and Sciaenidae, on the northern coast of the state of Rio de Janeiro.

Abnormal embryos of sharpnose sharks, Rhizoprionodon porosus and Rhizoprionodon lalandii (Elasmobranchii: Carcharhinidae), from Brazilian coast, western South Atlantic

This study presents the second worldwide report on abnormal embryos of the sharpnose sharks, Rhizoprionodon, based on the two species (Rhizoprionodon porosus and Rhizoprionodon lalandii) occurring on the Brazilian coast. For R. porosus two conjoined twin embryos showing complete duplication of the vertebral column, viscera and several external structures (head, first and second dorsal fins, pectoral fins), and scoliosis in both axis at the pelvic fin level are reported. The three embryos of R. lalandii exhibited numerous lordosis and kyphosis along the entire vertebral column. The possible relationship between anomalies and the human major threats to sharks is discussed based on previous reproductive, genetic and ecotoxicological studies on R. lalandii for southern Brazil.

Multiple substitutions and reduced genetic variability in sharks

Abstract The present study analyzed the genetic variability of the populations of four shark species (Carcharhinus limbatus, Carcharhinus porosus, Rhizoprionodon porosus, and Sphyrna tudes) from the Atlantic coast of the Amazon region. The analyses were based on the sequencing of the mitochondrial Control Region and Cytochrome b gene. S. tudes presented reduced diversity for both markers, which may be related to overexploitation by local fisheries. Most of the genetic variation in the four species was found in the 5′ portion of the Control Region, corresponding to a region of 210 bps, characterized by multiple substitutions (mutational hotspots) at the same sites. These mutations clearly biased the genetic diversity and affected the reliable of the analyses based exclusively on the Control Region. As Cytochrome b was not affected by these mutational events, this marker provided more reliable parameters for the evaluation of patterns of demographic expansion only for R. porosus. The present study indicated that the analysis of both markers is essential to guarantee the reliability of estimates of genetic variability, given that estimates based on the Control Region may be biased, and thus reduce the effectiveness of conservation and management measures designed to guarantee the long-term protection of stocks.

Phylogeography and genetic population structure of Caribbean sharpnose shark Rhizoprionodon porosus

Sharks of the genus Rhizoprionodon are among the most important predators along the coastal marine ecosystems, and they represent an important economic resource for the small-scale fisheries. To properly manage and conserve exploited shark spe- cies, detailed analyses of their population structure are needed. To evaluate the gene flow and levels of the genetic diversity among populations of the Caribbean sharpnose shark R. porosus, we identified the nucle- otide sequence based on collections (n = 321 speci- mens) from 10 different areas, including the Caribbean Sea and several locations along the entire Brazilian coast. The analysis of 802 nucleotides from the mitochondrial DNA control region revealed 53 distinct haplotypes. The majority of these haplotypes were restricted to their collection locales with a significant genetic structure detected among the overall popula- tions (UST = 0.237, P \ 0.0001). The data suggest a population division with two distinct management units in the western Atlantic. These management units are likely separated by the Equatorial Current. The strong population structure in R. porosus indicates that regional populations, if depleted, will not recover swiftly through immigration.

Genetic identification of the sharks Rhizoprionodon porosus and R. lalandii by PCR-RFLP and nucleotide sequence analyses of 5S rDNA

A molecular approach based on nuclear 5S rDNA sequence variability was applied successfully to correctly identify samples from the two Rhizoprionodon species collected in the wild or sold in markets. The sequence of the non-transcribed spacer (NTS) of the 5S rDNA showed high interspecific variability and no intraspecific polymorphism, making it a useful marker for sharpnose shark identification. Polymorphisms in the NTS sequences of Rhizoprionodon sharks also created unique restriction patterns for each species after PCR-RFLP analysis. The 5S rDNA polymorphism represents a fast and non expensive tool to access species identification when rapid and unequivocal identification of shark products is needed, particularly for future management and other investigations.