Biologia reprodutiva e ecologia trófica de Conodon nobilis (linnaeus, 1758) e Bagre bagre (linnaeus, 1766) capturados no golfão maranhense – Brasil

Abstract

Knowledge of fish biology provides data for the correct management of fishing resources, enabling the formulation of conservation measures and fishing management. Considering existing gaps in the explored ichthyofauna, this research aimed to analyze the reproductive biology and trophic ecology of Conodon nobilis (Linnaeus, 1758) and Bagre bagre (Linnaeus, 1766) from artisanal fishing captured in the fishing community of Raposa, located in the Gulf Maranhão. 360 specimens were acquired for each species, between January and December 2021. In the laboratory, the biometric data of each specimen were recorded and then they were sectioned to remove the tissues, stomach and gonad. The gonadosomatic index (IGS), condition factor (K), sex ratio, type of spawning and spawning season were evaluated. Stomach contents were conditioned and preserved in 10% formaldehyde for analysis, identification and classification of food items at the lowest possible taxonomic level. The degree of repellency and feeding strategies of each species were analyzed. For C. nobilis the length ranged from 11 to 31.8 cm. The sex ratio was 1 Male:1.51 Female and negative allometric growth (b<3). Five stages of gonadal maturation were confirmed throughout the sampling period, for both species, namely: Immature phase (IM); Development phase (DP); Spawning capacity phase (SP); Regression phase (RP); Regeneration phase (RGP). The length of first sexual maturity (L50) for males was 18.94cm, for females it was 18.91cm and for the grouped sexes it was 18.92cm and according to the gonadosomatic indices, individuals in spawning capacity were found in the months of January, April, May, July, September and December, indicating which species has split spawning. This species adopts a generalist feeding strategy, with greater consumption of fish and crustaceans. However, due to the predominance of fish in the diet, C. nobilis can be characterized as a species with a carnivorous eating habit and a piscivorous tendency. For the Bagre bagre species, the length varied between 22.08 and 57.6 cm. The sex ratio found was 1 Male:1.29 Females and negative allometric growth (b<3). The length of first sexual maturity (L50) for males was 33.51cm, for females it was 29.40cm and for the grouped sexes it was 31.21cm and the highest gonadosomatic peaks in females were recorded in the months of January and August to December, while for males these peaks varied in the months of January, May, August and December, indicating split spawning. B. catfish demonstrates a generalist, predominantly carnivorous feeding strategy, with a preference for fish. Given this information, it is possible to define closed periods, minimum catch size, in addition to evaluating the impact of fishing on food chains with a view to proposing measures that minimize disturbances in ecosystems and help preserve fish populations at sustainable levels.