Palmeira-Nunes, Ana Rita Onodera, de Souza Rosa, Ricardo, Nunes, Jorge Luiz Silva, Piorski, Nivaldo Magalhães, de Luna Sales, João Braullio, Santos, Jamerson Aguiar, Barbosa Martins, Ana Paula, Hauser-Davis, Rachel Ann, Rincon, Getulio, Coelho, Keyton Kylson Fonseca, Rodrigues-Filho, Luís Fernando, and Wosnick, Natascha (2025) Salinity-driven habitat use of marine-estuarine batoids on the Amazon Coast. Environmental Biology of Fishes, 108. pp. 1763-1782.

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Abstract

The behavioral plasticity of non-marine elasmobranch species allows these animals to strategically inhabit areas where salinity aligns with their physiological needs. Thus, this study aimed to investigate habitat use by rays in an Amazonian estuary, following a categorization of non-marine species based on the type of environment in which critical life history phases occur. Data on the capture of ray species in fishing weirs were acquired through a monitoring program conducted from March 2011 to April 2012. One hundred and forty-five coastal-estuarine rays, representing seven species, were sampled over 1 year in the estuary, across a salinity range from 12.9 to 41.3 ppt (26.8 ± 11.6 ppt). The dominant presence of neonates and juveniles, constituting approximately 70% of the total rays captured year-round, is noteworthy. Additionally, the presence of pregnant females with embryos at various developmental stages indicates the importance of the study area for the life cycle of various elasmobranch species. Our data suggest that Hypanus guttatus and Hypanus geijskesi fit into the estuarine generalist category, and Gymnura aff. micrura fits into the non-marine transient category. We identify salinity as a key driver of ray temporal distribution within the Amazonian coast, a crucial region for elasmobranch conservation. Future studies should, therefore, aim to understand how climate change might impact elasmobranch habitat use in this region.

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