The impact of injury on apparent survival of whale sharks (Rhincodon typus) in South Ari Atoll Marine Protected Area, Maldives.

The whale shark (Rhincodon typus) is an endangered species with a declining global population. The South Ari Atoll Marine Protected Area (SAMPA), Maldives, is one of few locations globally where year-long residency of individuals occurs. This SAMPA aggregation appears to consist almost exclusively of immature males. Due to its year-round residency, this local aggregation is subjected to a high degree of tourism pressure. This ecotourism contributes to the high level of interest and protection offered to whale sharks by the local community. Unfortunately, if regulations are not followed or enforced, tourism can bring with it major stressors, such as accidental injuries. We used POPAN capture-mark-recapture models and lagged identification rate analysis to assess the effect of major injuries on whale shark residency within SAMPA. Injuries may be obtained outside SAMPA. We found individuals with major injuries had a higher apparent survival in the area than those without. Lagged identification rates also demonstrated that sharks with major injuries are more likely to return to the area. We suggest that major injuries result in sharks prolonging their time in the developmental habitat. These findings have implications for individual fitness and the population viability of this endangered species. We propose targeted conservation strategies be considered to protect sharks from further injury. Based on the presented spatio-temporal distributions of sharks, and current local knowledge of sighting patterns, speed limit zones and propeller-exclusion zones should be implemented and enforced. If carried out alongside tourist education, these measures will contribute to the protection of whale sharks within SAMPA and beyond. Furthermore, our results can aid research direction, alongside regulation and enforcement development, at similar sites worldwide.

Histologic Observations of Dermal Wound Healing in a Free-Ranging Blacktip Shark from the Southeastern U.S. Atlantic Coast: A Case Report.

Despite indications that sharks have an exceptional capacity to heal from traumatic injuries, no detailed microscopic observations of integumental wounds have been reported for sharks. This study details the histopathological features of such wounds in a free-ranging shark. An adult male Blacktip Shark Carcharhinus limbatus was collected in 2017 during fisheries-independent sampling efforts in the coastal southeastern U.S. Atlantic. The shark had numerous lesions on his head, torso, and left pectoral fin that were compatible with shark bites. Representative samples from two wounds on the head were examined by light microscopy. The epidermal changes included hyperplasia and hypertrophy; intracellular edema; and the absence of goblet cells, denticles, and chromatophores. In the dermis, fibrinocellular exudation, granulation tissue, and marked skeletal muscle necrosis and regeneration were observed. The above features were comparable to wound healing in bony fish, albeit minor differences were found. Although this case documents exceptionally good regeneration of skeletal muscle in the shark, we found no evidence of unique morphological healing patterns. Further studies on wound healing are needed because recent molecular and genetic findings do suggest evolutionary adaptations enhancing healing in sharks.

Presence of plastic debris and retained fishing hooks in oceanic sharks.

In a context where the problem of plastic pollution is globally increasing, more studies are needed to assess the real impact in oceanic megafauna. Here, we reported on the incidence of plastic and also retained hooks in two species of commercially exploited pelagic sharks in two ocean basins, the North Atlantic and South Pacific. In the South Pacific, 1.18% of caught blue sharks were observed with plastic debris on their body and 4.82% and with retained hooks, while 0.00% of shortfin makos had plastic debris and 1.76% were recorded with retained hooks. In the North Atlantic, 0.21% of blue sharks had plastic debris and 0.37% of blue, and 0.78% of shortfin makos were observed with retained hooks.

Mortality due to a retained circle hook in a longfin mako shark Isurus paucus (Guitart-Manday).

A female longfin mako shark Isurus paucus (Guitart-Manday, 1966) was found moribund on the Atlantic Ocean beach near Canaveral National Seashore, Florida; the shark died shortly after stranding. Macroscopic lesions included a partially healed bite mark on the left pectoral fin, a clefted snout, pericardial effusion and a pericardial mass surrounding a 12/0 circle fishing hook. The heart, pericardial mass, gills, ovary, oviduct, shell gland, epigonal organ, liver, kidney and intrarenal and interrenal glands were processed for histopathology and examined by brightfield microscopy. Microscopic examination revealed chronic proliferative and pyogranulomatous pericarditis and myocarditis with rhabdomyolysis, fibrosis and thrombosis; scant bacteria and multifocal granular deposits of iron were found intralesionally. In addition, acute, multifocal infarcts within the epigonal organ and gill filaments were found in association with emboli formed by necrocellular material. The ovary had high numbers of atretic follicles, and the liver had diffuse, severe hepatocellular degeneration, multifocal spongiosis and moderate numbers of melanomacrophage cells. This report provides evidence of direct mortality due to systemic lesions associated with retained fishing gear in a prohibited shark species. Due to the large numbers of sharks released from both recreational and commercial fisheries worldwide, impact of delayed post-release mortality on shark populations is an important consideration.