Trophic assessment and isotopic niches of the sympatric penaeids species Penaeus brasiliensis and P. paulensis in SW Atlantic estuarine systems

ABSTRACT

Penaeus brasiliensis and P. paulensis are shrimp species which overlap their distribution only in the Southwest Atlantic. In addition, they are fishery resources intensively exploited. The interactions between these two sympatric species, especially sharing of food resources, are still unknown. We have investigated the niche breadth of juvenile pink shrimps in two proximal coastal nurseries (Sepetiba and Guanabara bays) located in Southeast Brazil (∼23°W) by means of stable isotopes and stomach content analyses. These two bays are important nurseries for these species and are located in one of the most populous regions of Brazil. Diets were basically composed of benthic invertebrates (mollusks, crustaceans and polychaetes), particulate organic matter and benthic diatoms. We detected significant spatial differences in isotopic compositions (δ¹³C and δ¹⁵N), with pink shrimps from Guanabara Bay displaying the lowest values of both isotopes. The δ¹³C range and diet support that benthic microalgae are the primary producers in P. brasiliensis and P. paulensis food chains. Trophic diversity was higher in Guanabara Bay based on δ¹⁵N range, Standard Ellipse Area, and Centroid Distance metrics, displaying greater individual variability in isotopic signatures compared to Sepetiba Bay, probably due to enhanced food diversity and spatial heterogeneity in the former. The overlap in the ellipses areas between the two shrimp species was greater in Sepetiba Bay and indicates a greater sharing of resources that should be more abundant and available. Niche metrics analysis revealed greater spatial rather than interspecific differences. We advocate paying particular attention to monitoring the pink shrimps of Sepetiba Bay due to their smaller trophic niche width and lower δ¹⁵N range, which increases their sensitivity to changing habitat, mainly due to human actions.

KEYWORDS:

• Guanabara Bay
• Sepetiba Bay
• trophic ecology
• Penaeidae
• SIBER
• SE

Acknowledgements

The authors also thank Laboratório de Radioisótopos Eduardo Penna Franca of Instituto de Biofísica and Laboratório de Macroalgas of Instituto de Biologia, both at Universidade Federal do Rio de Janeiro (UFRJ), for lyophilizing samples. We also extend our gratitude to the Coordenação de Aperfeiçoamento Pessoal de Nível Superior (CAPES) for the D.Sc. fellowship (23038.000452/2017-16) to the first author and the Graduate Programme in Zoology from Museu Nacional (UFRJ). This article is part of the D.Sc. thesis of the first author. Thanks to Rafael B. de Moura for map drawing and to Marcelo Gomes de Almeida, Laboratory Technician at the Laboratório de Ciências Ambientais, Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF), for analysing isotopic compositions of shrimp muscle.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by grants from Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ-E26/111584/2014) and by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq - 403809/2012-6) to the Long Term Ecological Project of Guanabara Bay (PELD - Guanabara). The authors are grateful to Professor Jean L. Valentin, coordinator of PELD – Guanabara and his group that carried out the samplings. A.P.M. Di Beneditto thanks CNPq (301.259/2017-8) and FAPERJ (E-26/200.797/2021) for granting financial assistance. Shrimp samplings in Guanabara Bay were conducted under the authorization of Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), Brazilian Environmental Ministry (Licenses n° 27126-10).