O uso do hábitat por juvenis do Mero Epinephelus itajara (Lichtenstein, 1822) (Perciformes: Epinephelidae) no estuário do Rio Cricaré, norte do Espírito Santo

Abstract

The Atlantic goliath grouper Epinephelus itajara is an estuarine-dependent reef fish that discontinuously inhabits the Atlantic Ocean and is currently classified as Critically Endangered in Brazil. The species is considered to be of rare occurrence and shows habitat use shifts, inhabiting estuaries and mangroves in the juvenile stage, living associated to coral and rocky reefs, shipwrecks, and oil platforms in the adult stage. The species is protected since 2002 in Brazil, but still being captured even after ban. In this context of imminent extinction, the present study sought to understand important ecological traits about the Atlantic goliath grouper juvenile stage in the Cricaré estuary, northern Espírito Santo state, southeastern Brazil. The main goals of the study were: 1. Report the occurrence of juveniles in study area; 2. Verify the occurrence of recapture of individuals over time; 3. Determine the length-weight relationship and juvenile growth pattern; 4. Investigate the existence of juvenile preferential habitats; 5. Determine how the water abiotic variables influence the presence/absence of juveniles in the estuary. Individuals were collected in field campaigns carried out for 35 months between the years 2015, 2018, 2019, 2021 and 2022 using blue crab traps, in addition to receiving individuals incidentally captured by local artisanal fishers. Individuals had biometric data collected (total length, standard length, and weight), and individuals larger than 10 cm were tagged subcutaneously with pit tags containing unique numbers to obtain data on recapture. The research showed the occurrence of 305 captures of juveniles in the study area, with a total length range from 5.4 to 50.5 cm, of which 148 individuals were marked. The recapture rate of individuals in the estuary was 11.5% (n=17) and the length-weight relationship resulted in a negative allometric growth pattern (n=265, b=2.876). The Kruskal-Wallis test confirmed the hypothesis that juveniles are not randomly distributed in the estuary and Dunn’s post hoc test showed that juveniles prefer wide lagoon environment (320 m maximum width) to the detriment of medium creek (40 m maximum width) and narrow creek environments (10 m maximum width). The Generalized Linear Models (GLM) analysis reaffirmed the hypothesis that juveniles are not randomly distributed in the estuary, however, it did not identify a significant influence of abiotic variables (pH, temperature, depth, salinity and dissolved oxygen) on the presence/absence of juveniles in the three environments sampled. Despite this, the present study reports that Atlantic goliath grouper juveniles shows tolerance to very low dissolved oxygen concentrations (<1 mgL-1) and a wide range of salinity (1.5 to 30.7 ppt). According to the abundance of juveniles and the occurrence of recaptures of individuals over time in the same area, the present work suggests that the Cricaré estuary acts as an important nursery for the critically endangered species and juveniles show site fidelity and, in this context, to understand the habitat use by juveniles in mangroves is an important strategy to support actions aimed at the conservation of the Atlantic goliath grouper in Brazil, since the juvenile stage is a critical phase for the continuity of the species life cycle.