Population Structure and Reproductive Biology of the Atlantic Seabob(Xiphopenaeus kroyeri) Caught off the Northeastern Coast of Brazil

Abstract The Atlantic seabob, Xiphopenaeus kroyeri is one of the most important marine fishery resources along the Brazilian coast, particularly in Northeastern Brazil, where it plays a key economic and social role. Despite its relevance, long-term, species-specific information on population structure and reproductive dynamics remains limited due to the aggregation of official fisheries statistics. This study analyzed the population structure, sex ratio, growth pattern, and reproductive biology of X. kroyeri captured off the coast of Pirambu, Sergipe State, Northeastern Brazil. Shrimp were sampled monthly between February 2020 and November 2025 by semi-industrial trawl fisheries operating at depths of 5–20 m, except during the legally established closed season. A total of 28,437 individuals were analyzed. Females exhibited significantly greater carapace length and body weight than males, indicating clear sexual dimorphism. Length–frequency distributions showed a predominance of females in larger size classes and males in smaller classes, with the presence of juvenile cohorts suggesting continuous recruitment. The overall sex ratio differed significantly from the expected 1:1 proportion, with a predominance of males in several years. The carapace weight–length relationship indicated negative allometric growth for both sexes, with coefficients of determination exceeding 0.90. Estimates of length at first sexual maturity (CL₅₀) revealed that males reached maturity at smaller sizes (11.40 mm) than females (12.07 mm). Notably, the female CL₅₀ observed in this study was substantially lower than previously reported for the same locality, indicating a temporal reduction in size at maturity over the last decade. This shift may reflect demographic responses to sustained fishing pressure and environmental variability, with potential implications for spawning stock biomass and recruitment dynamics. Overall, while several biological patterns confirm previous findings for X. kroyeri, the documented reduction in female size at first maturity represents a relevant update to the species’ reproductive parameters in Sergipe and provides important inputs for local stock assessment and fisheries management. These findings emphasize the importance of long-term, localized biological monitoring to support adaptive management of this heavily exploited resource.