The Black Sea Turtle (Chelonia mydas agassizii) at Lobos de Tierra Island, Northern Peru: High Densities in Small Areas

Abstract

Preliminary findings regarding black turtle (Chelonia mydas agassizii) occurrence in Lobos de Tierra Island, Northern Peru showed that 95% and 5% of turtles were juveniles and sub-adults, respectively, with an overall mean curved carapace length of 57.5 ± 7 cm (26.0-74.4 cm, n = 199). A total mean density of 180.4 turtles/km 2 was found with highest densities found in bays and inlets located in the southeast. Inshore densities in shallow waters (< 1.5 m) were almost one order of magnitude greater than offshore at ~ 1.5 km. In addition, based on structured qualitative interviews with fishermen, sea turtle capture and consumption still exists in the island, though occasional and sporadic. Jellyfish (Chrysaora plocamia) and green algae (Ulva sp.) consumption plays an important role in black turtle aggregations in the island, where densities are quite high compared to other feeding grounds elsewhere. We conclude that Lobos de Tierra constitutes an important Peruvian feeding ground, with high black turtle aggregations, close to the northern limit of the cold Humboldt Current.Resumen. Se presentan resultados preliminares sobre la ocurrencia de la tortuga negra (Chelonia mydas agassizii) en la isla Lobos de Tierra, Norte del Perú, se reportaron longitudes medias del Largo Curvo de Caparazón de 57.5 ± 7 (26-74.4 cm; n = 199), siendo el 95% juveniles y 5% sub-adultos. La disponibilidad alimenticia representada por sus presas: la medusa (Chrysaora plocamia) y algas verdes (Ulva sp.) juegan también un rol importante en sus agregaciones en la isla, las cuales son altas comparadas con otras zonas de forrajeo a nivel mundial, se determinó una densidad total media de 180.4 tortugas/km 2 , cuyos valores más altos fueron registrados en las bahías y ensenadas en el Sur Este, las densidades en aguas someras (< 1.5 m) fueron casi de un grado de magnitud por encima que en zonas localizadas a ~ 1.5 km de costa. Adicionalmente basados en entrevistas estructuradas cualitativas con pescadores, se determinó que la captura y consumo de tortugas aún existe en la isla, aunque estas son ocasionales y esporádicas. Se concluye que Lobos de Tierra constituye una importante zona de alimentación, con altas agregaciones muy cerca al límite norte de las aguas frías de la corriente de Humboldt.

New Record of Black Turtle Chelonia mydas agassizii in High Latitudes of Eastern South Pacific Ocean

“…It is also interesting to note that the measurement of the carapace (SCL: 50.2 cm) of our specimen was a juvenile [8,36,37], just like the specimen (SCL: 47 cm) reported at Desolation Island [23]. These measures would be in line with the life stage reported for feeding areas in Peru [38,39] and with the available size of measured specimens in Chilean waters (SCL mean: 49 cm; [14]), indicating that most are juveniles or subadult individuals.…”

Feeding ecology of the green turtle Chelonia mydas in northern Peru

“…The feeding ecology of this species has been studied throughout most of its distribution (Quiñones et al, 2015a). At their juvenile developmental habitats, green turtles can take on a herbivorous diet, feeding primarily on seagrass and algae (Plotkin et al, 1993;Seminoff et al, 2002aSeminoff et al, , 2003López-Mendilaharsu et al, 2005;Sampson & Giraldo, 2014).…”

“…Other studies have noted that C. mydas juveniles can also be carnivorous consumers, foraging mainly on cnidarians (Carrión-Cortez et al, 2010), sponges (Seminoff et al, 2002b), and tunicates (Amorocho & Reina, 2007. Additional studies have also identified an omnivorous diet, based mainly on algae but with an additional wide variety of animals, such as crustaceans, fish eggs, mollusks, and, to a lesser extent, jellyfish (Hays-Brown & Brown, 1982;De Paz et al, 2004;Kelez et al, 2004;Santillán, 2008;Quiñones et al, 2015aQuiñones et al, , 2015b.…”

“…This feeding strategy, where juveniles are herbivorous/omnivorous, allows for accelerated growth of recruits (Quiñones et al, 2015a). In the Eastern Pacific Ocean (EPO), there is baseline diet information for some green turtle feeding grounds, including those located in the Baja California Peninsula (Mexico) (Seminoff et al, 2002a(Seminoff et al, , 2003López-Mendilaharsu et al, 2005), the Galapagos Islands (Seminoff et al, 2002b;Carrión-Cortez et al, 2010), and the Gorgona Island (Colombia) (Amorocho & Reina, 2007.…”

“…In Peru, C. mydas feeding grounds have been identified in Tumbes (Rosales et al, 2010), El Ñuro (Velez-Zuazo et al, 2014), Sechura Bay and Virrilá estuary (Santillán, 2008;De Paz & Alfaro-Shigueto, 2008;Paredes et al, 2015), Isla Lobos de Tierra (Quiñones et al, 2015a), Chimbote (Alfaro-Shigueto et al, 2004), Pisco (Hays-Brown & Brown, 1982;Quiñones et al, 2010), and the Paracas Bay area (HaysBrown and Brown, 1982;De Paz et al, 2007;Paredes, 2015;Quiñones et al, 2010;Quiñones et al, 2015aQuiñones et al, , 2015b. Virrilá estuary and Sechura Bay are known to be important aggregation areas for juvenile and subadult green turtles (Santillán, 2008;Alfaro-Shigueto et al, 2011;Paredes et al, 2015;Ortiz et al, 2016).…”