A spatially explicit estimate of the prewhaling abundance of the endangered North Atlantic right whale.

The North Atlantic right whale (NARW) (Eubalaena glacialis) is one of the world's most threatened whales. It came close to extinction after nearly a millennium of exploitation and currently persists as a population of only approximately 500 individuals. Setting appropriate conservation targets for this species requires an understanding of its historical population size, as a baseline for measuring levels of depletion and progress toward recovery. This is made difficult by the scarcity of records over this species' long whaling history. We sought to estimate the preexploitation population size of the North Atlantic right whale and understand how this species was distributed across its range. We used a spatially explicit data set on historical catches of North Pacific right whales (NPRWs) (Eubalaena japonica) to model the relationship between right whale relative density and the environment during the summer feeding season. Assuming the 2 right whale species select similar environments, we projected this model to the North Atlantic to predict how the relative abundance of NARWs varied across their range. We calibrated these relative abundances with estimates of the NPRW total prewhaling population size to obtain high and low estimates for the overall NARW population size prior to exploitation. The model predicted 9,075-21,328 right whales in the North Atlantic. The current NARW population is thus <6% of the historical North Atlantic carrying capacity and has enormous potential for recovery. According to the model, in June-September NARWs concentrated in 2 main feeding areas: east of the Grand Banks of Newfoundland and in the Norwegian Sea. These 2 areas may become important in the future as feeding grounds and may already be used more regularly by this endangered species than is thought.

Captura por unidad de esfuerzo y estructura poblacional de la tortuga verde de Pacífico ( Chelonia mydas ) en el Golfo Dulce, Costa Rica / Catch per unit effort and population structure of the Pacific green turtle (Chelonia mydas) in the Golfo Dulce, Costa Rica

Resumen El Golfo Dulce es uno de los pocos fiordos tropicales del mundo, y recientemente ha sido declarado como un Área Marina de Pesca Responsable (AMPR), albergando ecosistemas de manglar, corales y pastos marinos que son áreas de alimentación importantes para la tortuga verde (Chelonia mydas). En este estudio estimamos la captura por unidad de esfuerzo (CPUE) y la estructura de la población, en un sitio del sector oeste del Golfo Dulce. Entre agosto de 2010 y marzo de 2013, se capturaron un total de 253 tortugas verdes (incluyendo 20 recapturas) utilizando redes de enmalle. La CPUE anual (CPUE, 1 unidad: 100m de red por 7h) durante el estudio osciló entre 0.19 y 0.45, reduciéndose progresivamente a través de los años, posiblemente propiciado por una mortalidad masiva ocurrida en enero de 2013. Se encontró que la estacionalidad y la temporalidad influyen en la CPUE de acuerdo al modelo de mejor ajuste. Cerca del 78.17% de las tortugas capturadas fueron consideradas como adultas, con un promedio de largo curvo de caparazón (LCC) de 79.6±0.9cm. Se recapturó una hembra que había sido previamente marcada en el Archipiélago de Galápagos. Mientras que ninguna de las tortugas marcadas en el Golfo Dulce fue reportada anidando en alguna playa. Nuestros resultados sugieren que el Golfo Dulce es un área importante para la tortuga verde, en donde se congregan individuos adultos o subadultos para alimentase de los pastos marinos y las partes carnosas de los mangles. Asimismo, el área representa un gran reto para la conservación internacional, ya que posiblemente las hembras adultas que capturamos provienen de playas de anidación de Panamá y Colombia, lo que requiere de acuerdos multilaterales que propicien la recuperación de la tortuga verde del Pacífico Este. Sugerimos la continuación de este proyecto de conservación para utilizar a las tortugas marinas como especie sombrilla para la protección de los ecosistemas del Golfo Dulce.

Abstract The Golfo Dulce is one of the few tropical fjords in the world, and has recently been declared a Marine Area for Responsible Fisheries (AMPR), harboring mangrove ecosystems, coral reefs and seagrass beds, which are important feeding areas for green turtles (Chelonia mydas). In this study we estimate the catch per unit effort (CPUE) and population structure in a site in the western sector of the Golfo Dulce. Between August 2010 and March 2013, were captured a total of 253 green turtles (including 20 recaptures) using entanglement nets. The annual CPUE (CPUE, 1 unit: 100m of net for 7h) during the study ranged between 0.19 and 0.45, decreasing gradually over the years, possibly prompted by mass mortality occurred in January 2013. We found that seasonality and temporality influence the CPUE according to the best-fit model. About 78.17% were considered adult females, with an average length of curved carapace (LCC) of 79.6±0.9cm. The female recaptured has been tagged previously in the Galapagos Archipelago. While none of the turtles tagged in the Golfo Dulce was reported nesting on any other beach. Our results suggest that the Golfo Dulce is an important area for green turtles, where individuals congregate for adults and subadults would feed on seagrasses and the fleshy parts of the mangroves. The area also represents a major challenge for international conservation, possibly because we captured adult females from nesting beaches of Panama and Colombia, which requires multilateral agreements that promote the recovery of the East Pacific green turtle. We suggest the continuation of this conservation project to use sea turtles as umbrella species to protect ecosystems in the Golfo Dulce. Rev. Biol. Trop. 63 (Suppl. 1): 363-373. Epub 2015 April 01.