História de vida de Aetobatus narinari (Myliobatiformes) capturada pela pesca artesanal no litoral da Paraíba e Pernambuco, Brasil

Abstract

The spotted eagle ray, Aetobatus narinari, occurs in coastal and island tropical regions of the Atlantic Ocean. The recent taxonomic redefinition of the species has reduced the available literature on its biology and fishing, as well as made its conservation status (Near Threatened - NT) obsolete worldwide. In Brazil, this ray is caught by artisanal fisheries in several regions; even so there is no information about its basic biology in these areas, being classified as a Data Deficient species (DD). Therefore, the present work aimed to estimate age and growth; characterize aspects of reproductive biology and eating habits; and study the linear and geometric morphometry and population structure of the ray A. narinari in the coast of Paraíba and Pernambuco (07°30'S; 34°49'W / 07°47'S; 34°51'W), Northeast Brazil. The samples were collected in May and July of 2015 and monthly from April 2016 to August 2018 by artisanal fishing. The individuals were identified, sexed, photographed, the disc width (DW, cm) and total mass (TM, kg) were taken. For the study of growth, age was estimated by counting the translucent bands of the vertebrae for 26 females (DW: 53.2 - 155 cm) and 24 males (DW: 44.2 - 136 cm), so the growth model with the best fit for both sexes was von Bertalanffy (females: L8 = 164.2; k = 0.18 e t0= -2.4; males L8 = 153.3; k = 0.25 e t0= -1.9); and the older individuals were a nine-year-old female (DW: 155 cm) and a five-year-old male (DW: 136 cm). For reproductive biology, based on the analysis of secondary sex macroscopic structures, 27 females (DW: 53.2 - 155 cm) and 27 males (DW: 39.5 - 141 cm) were analyzed, females body size at which 50% of the individuals are mature (DW50) at 130.15 cm and males at 116.42 cm. The highest mean values of the hepatosomatic index (IHS) and gonadosomatic index (IGS) for males occurred in the third bimester of the year, and for females occurred in the last bimester for IHS and in the fourth bimester for IGS. Regarding the study of diet, based on the analysis of stomach contents, the Whitespotted Eagle Ray presented a specialist diet based on prey from the Chordata and Mollusca group, where females fed mainly on Fish (IRI %: 46.4) and Ascidians (IRI %: 27.9); and the males on Ascidians (IRI %: 57.2) and Gastropoda (IRI %: 20.3). For linear morphometry, besides DW, 29 additional morphometric measurements were taken for comparison between males and females; therefore the results of Covariance Analyses (ANCOVA) performed for the separate sexes showed a significant difference in linear regressions between each measurement and the DW of individuals. For the geometric morphometry, photographs of the dorsal and ventral view of the chondrochraniums of 38 individuals (15 males and 23 females) were used; and according to the statistical of Principal Component analysis and Linear Discriminant analysis there were significant differences for the sexes in both dorsal and ventral views. Finally, to study the population structure, 42 individuals were used and concatenated COI-Cytb-ND4 sequences of mitochondrial genes were analyzed; and the sample presented 14 different haplotypes, with diversity hd= 0.646; low fixation index (FST) values per site; indicating weak population structure. In the study area the small-scale artisanal fishery catches A. narinari specimens of all ages and different stages of maturity throughout the year, so the study can contribute to the management of fishing and conservation of the species in the region.