Mercury levels in the Smooth Hammerhead Shark Sphyrna zygaena (Carcharhiniformes: Sphyrnidae) from Northern Peru

El tiburón martillo (Sphyrna zygaena (Linnaeus, 1758)) es una de las especies de elasmobranquios más utilizada para consumo humano en el Perú. Sin embargo, se desconoce los niveles de mercurio que contiene su carne. Este trabajo tuvo como objetivo evaluar los niveles de mercurio hallados en el músculo del tiburón martillo y su posible implicancia en la salud humana. Además, determinar si existe una correlación entre el tamaño del tiburón y los niveles de mercurio. Analizamos 27 muestras de músculo de neonatos y juveniles capturados en el norte del Perú. La concentración de mercurio varió entre 0.13 – 0.85 mg kg-1 peso húmedo. Se encontró una relación negativa y significativa entre el tamaño corporal del tiburón y los niveles de mercurio. Este trabajo representa el primer estudio que evalúa los niveles de mercurio de tiburones en el Perú. Si bien los valores hallados fueron menores a lo recomendado por la Organización Mundial de la Salud (< 1 mg kg-1), se recomienda ampliar este tipo de estudios en individuos adultos de tiburón, así como en otros recursos hidrobiológicos de consumo humano.The smooth hammerhead shark Sphyrna zygaena (Linnaeus, 1758) is one of the elasmobranch species most used for human consumption in Peru. However, the level of mercury in hammerhead muscle tissue is unknown. This study assessed the level of mercury found in the muscle of hammerhead sharks and its relation with human health. Moreover, we evaluated the relationship between shark body size and mercury levels. We analyzed 27 muscle samples of neonates and juveniles captured in northern Peru. Mercury concentrations varied between 0.13 and 0.86 mg kg-1 wet weight. Moreover, we found a negative and significant relationship between shark body size and mercury levels. This study represents the first evaluation of mercury levels of sharks in Peru. Although the values found do not exceed levels recommended by the World Health Organization (< 1 mg kg-1), we recommend expanding this study to include other size classes of sharks as well as other marine resources used for human consumption

Preliminary analysis of the feeding habits of batoids from the genera Mobula and Myliobatis in northern Peru

This study provides baseline information on the feeding habits of five batoid species from the genera Mobula and Myliobatis sampled from the small-scale driftnet fishery in northern Peru. The diets of Mobula mobular, Mobula munkiana and Mobula thurstoni consisted mainly of euphausiids. Dietary niche breadth indicated a pelagic feeding behaviour of a specialist and a trophic level of a secondary predator for both M. mobular and M. munkiana. In contrast, Myliobatis chilensis and Myliobatis peruvianus consumed mostly gastropods and crustaceans. Dietary niche breadth indicated a feeding behaviour of a benthic specialist and a trophic level of a secondary predator for Myliobatis chilensis

Shark fisheries in the Southeast Pacific: A 61-year analysis from Peru [version 2; referees: 1 approved, 2 approved with reservations]

Peruvian waters exhibit high conservation value for sharks. This contrasts with a lag in initiatives for their management and a lack of studies about their biology, ecology and fishery. We investigated the dynamics of Peruvian shark fishery and its legal framework identifying information gaps for recommending actions to improve management. Further, we investigated the importance of the Peruvian shark fishery from a regional perspective. From 1950 to 2010, 372,015 tons of sharks were landed in Peru. From 1950 to 1969, we detected a significant increase in landings; but from 2000 to 2011 there was a significant decrease in landings, estimated at 3.5% per year. Six species represented 94% of landings: blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), smooth hammerhead (Sphyrna zygaena), common thresher (Alopias vulpinus), smooth-hound (Mustelus whitneyi) and angel shark (Squatina californica). Of these, the angel shark exhibits a strong and significant decrease in landings: 18.9% per year from 2000 to 2010. Peru reports the highest accumulated historical landings in the Pacific Ocean; but its contribution to annual landings has decreased since 1968. Still, Peru is among the top 12 countries exporting shark fins to the Hong Kong market. Although the government collects total weight by species, the number of specimens landed as well as population parameters (e.g. sex, size and weight) are not reported. Further, for some genera, species-level identification is deficient and so overestimates the biomass landed by species and underestimates the species diversity. Recently, regional efforts to regulate shark fishery have been implemented to support the conservation of sharks but in Peru work remains to be done

Distribution of whale shark (Rhincodon typus) off northern Peru based on habitat suitability

In the south-eastern Pacific Ocean, few studies of whale sharks (Rhincodon typus) exist. In Peru, the northern coast has been identified as the area with the highest presence of whale sharks, yet their ecology in this area is poorly defined. This study predicts the spatial distribution of whale sharks off coastal northern Peru (03°00′S–04°30′S) during La Niña and El Niño seasonal conditions, utilizing maximum entropy modelling. Between 2009 and 2018 (except for 2011), 347 whale sharks were geo-referenced in northern Peru with greatest data recordings in the austral summer and spring during La Niña events. Depth was the most important predictive variable for spatial distribution of whale sharks, followed by chlorophyll-a. Sharks were predicted in shallower coastal waters in which chlorophyll-a values are higher. Habitat suitability was higher in the northern coastal part of the study area. Spring presents the most suitable environmental conditions for whale sharks, both during La Niña and El Niño conditions. The probability of whale shark presence in the north of Peru increases at higher chlorophyll-a and sea surface temperature values. Therefore, whale sharks appear to aggregate seasonally in northern Peru, potentially exploiting rich foraging grounds. In these areas of high suitability, whale sharks are susceptible to fisheries, bycatch, ship collisions, unmanaged tourism, and pollution; thus, management actions should focus in these areas. This study represents a first step to understand the distribution and habitat suitability of whale shark in Peruvian waters. Further studies should identify suitable habitat for whale sharks in offshore areas. Also, these should focus on the connectivity of these aggregations with other localities in the south-eastern Pacific in order to contribute to regional strategies for the conservation of this iconic species in this particular region