Population structure of the bigtooth corvina Isopisthus parvipinnis from the Southwest Atlantic Ocean as determined by whole-body morphology

Abstract

Geometric morphometrics analysis provides evidence from the adaptive character of fish to the aquatic environment resulting from an evolutionary process. Thus, phenotypic variations among individuals are primarily due to heritability of genetic factors modulated by the surrounding environment. Analysis of body morphometry can provide important information on fish population structure, an essential prerequisite for conservation requirements and sustainable fisheries management. The “bigtooth corvina”, Isopisthus parvipinnis, is an euryhaline sciaenid fish widely distributed in the shallow and warm waters from the western Atlantic Ocean. It is often caught as bycatch of shrimp fisheries in Brazil. Although there is some basic ecological information about the species, knowledge about the stock structure is, at present, very limited. This work aims to investigate if the different environments of the South-Southeastern Brazilian coastal waters (São Paulo, Paraná, and Santa Catarina states) could affect the body shape of I. parvipinnis, allowing to define different population units through phenotypic geometric morphometrics. Juvenile fish, ranging between 66 and 139 mm of total length, were captured from September 2018 to May 2019 by research vessels and artisanal fleets using an otter trawl. Fish were photographed with 13 anatomical landmarks, and truss network analyses were performed using tpsUtil and tpsDig softwares. Data were analyzed through uni and multivariate statistical tests. Results showed significant differences among locations for all morphometric distances individually. Moreover, reclassification matrix presented a relatively high overall rate (79%). The hereby data suggest that I. parvipinnis in the study area is not a single and homogeneous stock, supporting the existence of a metapopulation structure. However, it is highly recommended to use complementary information, namely other natural tags, to corroborate these findings.