Morphometric Analysis of Sagittal Otoliths in Coruh Trout (Salmo coruhensis Turan, Kottelat & Engin, 2010)

Abstract

The Coruh trout (Salmo coruhensis Turan, Kottelat & Engin, 2010) is a freshwater fish species endemic to Turkey. This study describes the allometric relationships between sagittal otolith (sagitta) measurements and total length (TL) of the Coruh trout collected from the Çam stream (Artvin, Turkey), and the length-weight relationship. A total of 82 individuals were caught with an electroshock device between May 2017 and April 2018. The length (LO), height (HO), weight (WO), perimeter (PO), and area (AO) of the otolith were recorded for each specimen. Shape indices such as shape factor, aspect ratio, circularity, roundness, rectangularity, ellipticity, surface density were calculated using these otolith measurements. Relationships between otolith variables and the somatic growth of fish were defined by the curvilinear function (power model). An analysis of covariance revealed that these relationships did not differ between the left and right sides, and between females and males. All regressions were highly significant (P < 0.001) and mean percent prediction error values were less than 7 %. The relationships of LO, HO, WO, and PO against TL were negative allometric, while the TL-AO relationship was positive allometric. In the analysis of relationships between the otolith shape indices and TL, the values of form factor, roundness, and rectangularity indices decreased with fish somatic growth. In contrast, the circularity and surface density indices increased with fish body length. The length-weight relationship was obtained as W = 0.0155*TL2.87 for overall samples. The difference between the slopes of LWRs of females and males was found insignificant. This study provides the first comprehensive data on the sagittal otolith morphometry of S. coruhensis.