Genetic variation of Atlantic horse mackerel (Trachurus trachurus) in the Turkish waters

Geographic variations of Truchurus trachurus based on mitochondrial 16S rDNA gene from 8 locations, including the Black, Marmara, Aegean and north-eastern Mediterranean Seas, were investigated. Restriction fragment length polymorphism (RFLP) analyses revealed 14 different composite haplotypes for 307 individuals and diagnostic restriction sites for discriminating among populations. The distribution of haplotypic groups mostly followed the geographic origin of populations. Average haplotype diversity within populations was high (0.7311), and nucleotide diversity was low (0.0071). Mean nucleotide divergence among samples of T. trachurus was 0.00271. The highest value of pairwise inter-group nucleotide divergence was detected between the West and East Black Sea samples (0.01119), and the lowest (-0.00018) between the two North-eastern Mediterranean samples. In Monte Carlo pairwise comparisons of haplotype frequencies genetically different populations were detected. The distribution of haplotypes and the pairwise estimate of nucleotide divergence exposed high differentiation of the Black Sea (BS2) population with respect to the others. Mantel's test showed that the genetic distances between these Populations were not associated with their geographical distances (r = 0.326; P > 0.05)

Relative body condition of red mullet (Mullus barbatus) and its applicability as an indicator of environmental status

This study examines the ratio between length and body weight of 4191 specimens of a prevalent, tertiary tropic level Teleost fish, red mullet (Mullus barbatus) sampled using a standard survey protocol from more than 2500 km by the coasts of Turkey extending along the Mediterranean, Aegean, and the Black Sea. The study's primary aim was to investigate whether there is a correspondence between the body condition of the red mullet and the environmental status independently determined based on lower trophic levels of the water masses the species inhabits. Possible impacts of some intrinsic (fish length), extrinsic factors (bathymetry, abundance, and site), and numerical condition expressions on the outcomes were analyzed and eliminated. The results displayed a strong positive correlation between the fish condition index values and the ecosystem descriptor; the body condition of fish increased as ecological status improved from "bad" to "good/high". Based on this relationship and to facilitate the use of red mullet body condition as an ecosystem indicator, a set of target reference values addressing different ecological states have been proposed. (C) 2021 Elsevier B.V. All rights reserved