Caracterização e refrigeração do sêmen de Cynoscion acoupa (Lacepède, 1801), (Perciformes: Sciaenidae): informações básicas para reprodução e conservação da espécie

Abstract

Fish represent the most diverse group of vertebrates on the planet, encompassing approximately 37,553 described species. Within marine biodiversity, the acoupa weakfish (Cynoscion acoupa) stands out as a strategic resource of significant commercial and ecological value, particularly in the North and Northeast regions of Brazil. Despite its importance, intense anthropogenic pressure has caused a sharp decline in its natural stocks, raising its status on the IUCN Red List to Vulnerable (VU). Faced with the threat of a fishery collapse, the development of reproductive biotechnologies emerges as a crucial tool for conservation and cultivation. The objective of this study was to characterize and refrigerate the semen of C. acoupa, determining the post-capture viability window of gametes under refrigeration and evaluating the physicochemical and morphological parameters of fresh semen. The study was conducted at LARAQUA/UEMA, with 18 male specimens captured in the RESEX of Cururupu - MA, using gillnets (200 mm mesh), under an ICMBio/SISBio license and CEUA approval. The animals were euthanized by hypothermia, subjected to biometry, and the gonads were extracted. For the viability test (n=8), the gonads were kept under refrigeration (4 to 6 °C) and the semen was evaluated at 0, 30, 60, 90, 120, and 150 minutes. For characterization (n=10), color, pH, motility rate and duration, sperm concentration, and morphology (Rose Bengal staining, 200 cells/slide) were evaluated. Data were analyzed via ANOVA and Tukey's test (𝑝 < 0.05). The results showed: specimens with a mean weight of 11.4 ± 1.6 kg and a mean length of 87.8 ± 4.7 cm, characterizing them as mature adults. In the viability assay, fresh semen (time 0 min) exhibited motility rates above 90% and movement duration exceeding 5 minutes. No statistically significant differences were detected in the motility rate between 0, 30, and 60 minutes, and at 90 minutes the semen still exhibited a robust rate of 76.3%, demonstrating practical viability for onboard processing. Characterization revealed white semen with a milky appearance, a pH of 6.8, and a mean sperm concentration of 1.75 X 108 cel.mL-1. Morphological analysis demonstrated a high index of normal spermatozoa (74.3 ± 13.5%), with predominantly primary abnormalities (short and coiled tail) and low rates of secondary alterations (8.8 ± 3.7%). It is concluded that the male gonads of the acoupa weakfish present a critical viability window of up to 90 minutes under post-capture refrigeration, and that the observed physicochemical parameters and high morphological integrity consolidate fundamental data for the refinement of artificial insemination and cryopreservation protocols for the species.