Stable isotopes reveal tissue-specific nutrient assimilation and energy allocation during ovarian maturation in the pink shrimp Farfantepenaeus brasiliensis

Abstract Stable isotope analysis provides an effective approach for investigating patterns of nutrient assimilation and resource use in aquatic organisms. Dietary assimilation in the pink shrimp Farfantepenaeus brasiliensis was assessed across four ovarian maturation stages using δ 13 C and δ 15 N. Muscle and ovarian tissues from 121 individuals were analysed to estimate the relative contributions of seven dietary source groups—algae, zooplankton, molluscs, crustaceans, fish, bivalves, and polychaetes—using the Bayesian mixing model MixSIAR. Algae represented the predominant dietary source in both tissues across all maturation stages, although their estimated contribution to muscle declined with advancing maturation. Zooplankton showed a probabilistic trend toward greater contribution to ovarian tissue during the developing and mature stages, whereas its contribution to muscle varied without a consistent directional pattern. Bivalves represented a secondary dietary source, with greater contributions to muscle during advanced maturation, while fish and polychaetes generally showed comparatively low contributions. Multivariate analysis revealed contrasting assimilation patterns between tissues, with muscle showing substantial overlap among maturation stages and ovarian tissue displaying greater stage-associated variation, particularly along the algae–zooplankton gradient. Overall, these results indicated tissue-specific differences in dietary assimilation associated with ovarian maturation. As maturation stages were unevenly represented across the sampling period, some seasonal influences may also be reflected in these stage-associated patterns. Differences between tissues may likewise reflect tissue-specific isotope turnover and temporal integration of dietary signals. These findings expand knowledge of trophic dynamics during reproduction in wild F. brasiliensis and provide a basis for future controlled studies on reproductive nutrition and broodstock diet formulation.