Catsharks (family Scyliorhinidae) and the recently reclassified deepwater catsharks (family Pentanchidae) are two of the largest families of elasmobranchs and include species that function as important mesopredators in almost all marine ecosystems. This study focuses on four species endemic to the coast of southern Africa: the puffadder shyshark Haploblepharus edwardsii, dark shyshark H. pictus, leopard catshark Poroderma pantherinum and pyjama catshark P. africanum. Similar to most catsharks, these four species are underrepresented in chondrichthyan research. Our investigation aimed to gain insight into the distribution and site fidelity of the focal species through mark-recapture efforts in Walker Bay on the southwest coast. The use of 95% minimum convex polygons indicated large overlaps in distribution among the species as well as between sexes, except for H. edwardsii. Site fidelity was universally low (0.005) at three key sample sites, although travel distances between sites averaged 3-5.5 km across all species. The results suggest that sexual segregation is not present for the studied catshark species, with the possible exception of H. edwardsii, which had a low capture rate. The low levels of site fidelity and movement also indicated significant levels of site interconnectivity between the three commonly sampled sites as they fell within the same 5-km2 region of the bay. From the present findings, Walker Bay could be considered an area of interest for conservation with respect to the four species, allowing for further study of their population dynamics and the influence of the local marine protected area.

The spotted gully shark Triakis megalopterus (Triakidae) is a mesopredatory species endemic to southern Africa. It is currently listed as Least Concern on the IUCN Red List in accordance with an estimated increase in population size, general release by recreational linefishers and incidental catches in the commercial linefisheries. Previous research suggests this species to be resident, and as such it is likely to receive protection in coastal marine protected areas (MPAs). However, its ecology and movement behaviour remain poorly studied. This study employed acoustic telemetry to provide information on the species' movements along the coast of the Western Cape Province, South Africa. We used network analyses to investigate movement randomness, associations between individuals, sexual segregation, and the effectiveness of MPAs. Our findings reveal nonrandom movements as well as patterns of co-occurrence between individuals. Spatial network analysis suggested sexual segregation, because areas of high use (Walker Bay and De Hoop) differed between males and females. Co-occurrences were observed exclusively in Walker Bay, chiefly between males, with no co-occurrence found between females. The tagged spotted gully sharks were not detected extensively within existing MPA boundaries, though there was no significant difference between their movements inside and outside protected areas for both sexes.

We report a sighting of a Spotted Gully Shark Triakis megalopterus at Robben Island, 7 km from the nearest mainland, in Table Bay, South Africa. The sighting was made on 18 February 2023 within an hour of high tide.

The pyjama shark (Poroderma africanum) is a Scyliorhinid species endemic to South Africa. Even though it is kept in captivity in many aquaria, there is a lack of research on its growth and development. In this study, we investigated the fertilization rate of eggs and the age at female sexual maturation in captive sharks and compared their growth to that of wild individuals. This is the first study to compare the growth of captive and wild catsharks as well as the first study to compare growth in male and female pyjama sharks and benefits from a much larger sample size than has previously been collected. The mean incubation rate (& PLUSMN;standard error of the mean [SE]) was 239.46 & PLUSMN; 4.97 days, the mean Lt of hatchlings (& PLUSMN;SE) was 14.65 & PLUSMN; 0.24 cm, and the mean Wt (& PLUSMN;SE) was 17.19 & PLUSMN; 0.75 g. The observed ratio of male to female offspring (1:3.5) was also significantly different from 1:1. One female laid fertilized eggs 6.6 years after hatching and was considered sexually mature. Both in captivity and in the wild, males showed negative allometric growth and females showed isometric growth. The growth performance (f') was also greater in captive sharks compared to wild sharks regardless of sex. However, there was significant variation in growth between individuals of the same sex. The similar growth patterns (i.e., allometry and isometry) found in wild and captive populations are a very useful tool for informing future conservation management if the population of this shark species were to decline in the future and also prove that captive studies for this species are transferable to wild populations with regard to sexual differences. This study also provides a benchmark for further captive studies in other lesser-studied catshark species and raises interesting questions concerning sexual differences in growth for other shark species.

Abstract The pyjama shark (Poroderma africanum) is a Scyliorhinid species endemic to South Africa. Even though it is kept in captivity in many aquariums, there is a lack of research on its growth and development. In this study, we investigated the fertilization rate of eggs, growth, and age at female sexual maturation in captive pyjama sharks, and compared their growth to that of wild individuals. The fertilization rate of 319 eggs was 18.8%, and total length (Lt) and body weight (Wt) at hatching were 14.65 ± 0.26 cm and 16.6 ± 0.8 g, respectively. Both in captivity and in the wild, males showed negative allometric growth and females showed isometric growth. The growth performance (Φ') was also greater in captive sharks compared to wild sharks regardless of sex. One female laid fertilized eggs (85.2 cm Lt and 3300 g Wt at laying) 2419 days (6.6 years) after hatching and was considered sexually mature. It was suggested that the difference in growth was due to the difference in habitat depth preference between males and females. This is the first study to compare the growth of captive and wild catsharks as well as the first study to compare growth in male and female pyjama sharks. Therefore, this study provides a greater insight into the effects of captivity on different elasmobranch families, as well as aiming to inform differential husbandry techniques depending on sex.

Understanding diet flexibility is important for resource management as climate change alters ecological communities. However, food web complexity often limits our ability to predict how changes in prey communities may alter predator diets. Stomach content and stable isotope analyses are traditionally used to evaluate trophic interactions, but costs and logistical constraints can limit their efficacy. Using boosted regression tree (BRT) models, we predicted how juvenile bull shark Carcharhinus leucas diets respond to shifts in potential prey communities using patterns of shark and prey distributions, and size-based differences in shark gape widths. BRT models were based on bull shark diets from published literature and long-term monitoring of sharks and prey in a coastal estuary in the western Gulf of Mexico. In situ diet data were used to test model accuracy, which revealed that BRT models effectively predicted the most abundant prey families in the diets of bull sharks (Sciaenidae: ~37%; Ariidae: ~34%), with Pearson’s correlation rates as high as 0.778 for predictions and in situ diet data. Inaccuracies were evident for rarer prey families (e.g. Mugilidae), which was attributed to monitoring limitations, elucidating how BRT models can be improved before future application. High model accuracy suggests BRTs may serve as an appropriate complement to stomach content and stable isotope analyses when monitoring data of predators and potential prey are available. Such results are promising for reducing stressful or harmful sampling and broadening the applications of current monitoring programs used to assess changes in species densities and distributions, particularly for resource-limited management agencies.