Distribution, occurrence, diet and growth of juvenile blacktip sharks, Carcharhinus limbatus, were examined based on specimens caught between 1995 and 2002 by the artisanal shark fishery from Los Roques Archipelago. Fishery monitoring revealed that C. limbatus was the species most frequently caught, accounting for 48.5% of the shark catch. Capture of neonate and juvenile sharks was concentrated in the central lagoon of the archipelago, indicating that this area corresponds to a nursery area for the species. Birth season was approximately from mid June to the end of August. Average length at birth was 63.5 cm TL, based on neonates with an open umbilical scar. The smallest mature male and female sharks measured 152 and 161 cm TL, respectively. Diet was composed of teleost fishes, with the most important prey being Eucinostomus argenteus (13.3 %IRI), Opisthonema oglinum (6.9 %IRI) and Gerres cinereus (5.5 %IRI). Monthly length frequencies revealed that juveniles remain within the nursery area for 14–16 months after birth, reaching a length of about 130 cm TL during this period. The growth of the juvenile population is characterized by a linear function, with sharks almost doubling their birth length during the first year of life. This growth was more rapid than the estimated rates reported from the Gulf of Mexico, western Florida and South Africa. The results suggest that growth rate is negatively correlated with latitude or positively correlated with temperature. The rapid growth shown by these juveniles will have positive implications for the recovery of the adult populations of this species.

Nursery area and size structure of the lemon shark population, Negaprion brevirostris (Poey, 1868), in Los Roques Archipelago National Park, Venezuela

Defining demographically independent units and understanding patterns of gene flow between them is essential for managing and conserving exploited populations. The critically endangered scalloped hammerhead shark, Sphyrna lewini, is a coastal semi-oceanic species found worldwide in tropical and subtropical waters. Pregnant females give birth in shallow coastal estuarine habitats that serve as nursery grounds for neonates and small juveniles, whereas adults move offshore and become highly migratory. We evaluated the population structure and connectivity of S. lewini in coastal areas and one oceanic island (Cocos Island) across the Eastern Tropical Pacific (ETP) using both sequences of the mitochondrial DNA control region (mtCR) and 9 nuclear-encoded microsatellite loci. The mtCR defined two genetically discrete groups: one in the Mexican Pacific and another one in the central-southern Eastern Tropical Pacific (Guatemala, Costa Rica, Panama, and Colombia). Overall, the mtCR data showed low levels of haplotype diversity ranging from 0.000 to 0.608, while nucleotide diversity ranged from 0.000 to 0.0015. More fine-grade population structure was detected using microsatellite loci where Guatemala, Costa Rica, and Panama differed significantly. Relatedness analysis revealed that individuals within nursery areas were more closely related than expected by chance, suggesting that S. lewini may exhibit reproductive philopatric behaviour within the ETP. Findings of at least two different management units, and evidence of philopatric behaviour call for intensive conservation actions for this highly threatened species in the ETP.

The relative abundance and distribution of sharks caught by the artisanal fishery was determined for the most important offshore islands of Venezuela (Los Roques, Las Aves and La Blanquilla). Data were collected from January 1997 to October 1998, corresponding to 123 fishing days targeting sharks using bottom longline. We also present the results of 10 days of fishing activities targeting tunas and marlins by the same fleet using pelagic longline, in order to determine the importance of the shark bycatch in these fisheries around the offshore islands. A total of 15 shark species representing five families were captured during the study period. The catch composition and CPUE values expressed in weight and number showed that the most abundant species were Carcharhinus perezi and C. falciformis for Los Roques Archipelago and La Blanquilla Island, while C. perezi and Ginglymostoma cirratum were more common in Las Aves Archipelago. In Los Roques Archipelago, C. perezi and C. falciformis were most common during the second half of the year; a similar trend was observed for the rest of the shark species caught by the fishery. A positive relationship was observed between CPUE and fishing depth in the case of C. perezi and C. falciformis off Los Roques Archipelago: CPUE by weight increases with depth, while CPUE by number decreases with depth. The main factors that could be determining shark abundance and their spatial-temporal distribution are the characteristics of the ecosystem, depth, and biological characteristics such as birth, mating season and migratory patterns of the species.

Basic population parameters such as age, size, and distribution have been poorly evaluated for the Shortfin Mako Isurus oxyrinchus in the Mexican Pacific Ocean. According to data collected by scientific observers on board medium‐size fishing vessels during the period of 2006–2013, size as TL was obtained for 5,740 individual sharks. The range of TL was 70–362 cm for females and 71–296 cm for males. Weight (W), measured randomly from 1,409 individuals, ranged from 2 to 90 kg for females and from 2 to 80 kg for males. The weight‐to‐TL ratio was best fitted by the equation W = 4 × 10⁻⁵(TL)^2.59 (r² = 0.6532). No sex‐specific difference was found in the weight‐to‐TL relationship between males and females, nor in W or TL separately. By using the inverse von Bertalanffy equation and parameters described by other authors for the same study area, we determined the age range for individuals captured on the basis of their TL. The age ranged from 0 to 39 years in females and from 0 to 21 years in males. Using a logistic model, the mean length at sexual maturity was obtained for 2,532 males (TL = 190 cm). The quarterly distribution of young of the year and 1‐year‐old juveniles showed that there is a tendency for these sharks to move northward as sea surface temperature increases. Our findings shed new light on how Shortfin Mako juveniles use a habitat that has been proposed by other authors as a nursery area for this species, information that is valuable for the sustainability of the Mexican Pacific fisheries.