Morphological discreteness of the estuarine croaker Pseudotolithus elongatus (Teleostei: Sciaenidae).

Abstract

The estuarine croaker (Pseudotolithus elongatus, Sciaenidae) has long-term socio-economic and ecological significance in tropical and subtropical regions of the world, but little has been reported on the population demographics of this species. In this study, a traditional morphometric approach was used to test the hypothesis that island samples are morphologically distinctive from adjoining estuarine waters. The study involved a total number of 612 specimens from four islands (Alligator, Tobacco, Parrot and James) of the lower Cross River, Nigeria as well as from the mouth of the Cross River estuary, sampled from January to July 2020. Each specimen was subjected to morphometric measurements consisting of 14 allometrically modified characters. Results of principal component analysis explained 85.6% of the total variance. The pooled between-groups discriminant function analysis correctly classified 66.0% of individuals into two distinct stocks (Island and Estuary mouth). The present finding demonstrates that the Cross River Islands hold a unit stock of P. elongatus that is morphologically separable from the adjoining estuarine waters. We therefore recommend that the croaker population in Cross River should be managed as separate stocks.