Age and Stock Analysis Using Otolith Shape in Gags from the Southern Gulf of Mexico

Abstract

On Campeche Bank (CB) in the southern Gulf of Mexico, Gags Mycteroperca microlepis are captured as part of a sequential multispecies fishery. Limited scientific data suggest that the Gag is the third most important commercial species in the region, contributing 21% (total weight) of the overall grouper catch. Neither age nor stock data are currently available for Gags in this region, making it impossible to determine how this species is affected by current fishing practices. Such information is vital for the CB stock since it acts as a genetic source for a mixed Gag population on the west Florida shelf through a constant unidirectional flow of larvae. The goal of this study was to generate baseline age and stock structure data for Gags on CB. Age was quantified from otoliths by counting the number of annuli (indicated by the number of opaque zones from the otolith core to the margin) in thin sections. Otolith shape was analyzed by using discrete wavelet transforms, linear otolith morphometrics, and shape indices. In each of 198 specimens, age was determined based on examination of the right sagittal otolith, and shape analysis was conducted on the left sagittal otolith. Individual age ranged from 4 to 17 years, and otolith opaque band deposition occurred annually between December and February. Using principal components analysis and linear discriminant analysis, two distinct groups were identified (discrimination success = 98%), indicating the presence of substructure in the CB stock of Gags. Otolith analysis clearly assisted in achieving a better understanding of the CB Gag stock and in identifying the complexity within the stock, demonstrating that otolith analysis is a useful tool in characterizing fish populations. The study results highlight the urgent need for Gag stock assessment in this region and for the application of a cautious approach to fishery management given the immense gaps in biological data for this species. Received January 13, 2016; accepted July 18, 2016 Published online October 7, 2016

Otolith Shape Analysis of Bluefish, Pomatomus saltatrix (Linnaeus, 1766) in the Black Sea Region (Samsun, Turkey)

“…FF, C, RD, R, E and AR for sagitta were calculated and the realtionships between otolith length and shape descriptors were revealed. The usefulness of otolith shape analysis for stock identification and differentiation have already been supported for several fish species (Campana 1999;Tuset et al 2006;Ferguson et al 2011;Zengin et al 2015;Renán et al 2016;Avigliano et al 2017;Teimori and Eslami 2017). Otolith shape can be described in some ways, one of the simplest and useful method is distance measurement.…”

The use of Fourier analysis as a tool for Oblada melanura (Linnaeus, 1758) stock unit separation in the south central Mediterranean Sea

“…Taking into account the environmental factors which impact some inter- and intra-specific otolith differences (Lombarte, 1992) and the genotypic aspects which specify the otolith morphology, Avigliano et al . (2015) revealed that the method of otolith shape analysis applied for this study was among the successful tools for stock discrimination (Campana & Casselman, 1993; Burke et al ., 2008; Cañás et al ., 2012; Avigliano et al ., 2014) of different species worldwide (Begg & Brown, 2000; Begg et al ., 2001; Brophy & Danilowicz, 2002; Turan, 2004; Galley et al ., 2006; Megalofonou, 2006; Mérigot et al ., 2007; Duarte-Neto et al ., 2008; Renán et al ., 2010; Vieira et al ., 2014; Jemaa et al ., 2015; Libungan et al ., 2015; Jawad et al ., 2017; Mapp et al ., 2017).…”

“…Our findings are consistent with those relating to other species (Campana & Casselman, 1993; Duarte-Neto et al ., 2008; Renán et al ., 2010; Vieira et al ., 2014; Jemaa et al ., 2015). Elliptic Fourier descriptors (EFD) and principal component analysis (PCA), using SHAPE, can accurately detect small shape variations and evaluate the shape independently of size (Iwata et al ., 1998; Yoshioka et al ., 2004).…”

“…The morphology of the otolith varies clearly between species and within species from different regions (Campana & Casselman, 1993; Lombarte & Lleonart, 1993; Renán et al ., 2010). The sampled Oblada melanura specimens in the south central Mediterranean presented a clear discrimination between three different Tunisian areas.…”

Stock Discrimination of Northern Pike Esox lucius L., 1758 Inhabiting Lakes Simenlik and Ladik (Samsun-Turkey) Using Otolith Biometry and Shape Analysis

“…and have been described as a "flight recorder" of fish (Lecomte-Finiger 1992). They are considered as valuable markers for distinguishing different fish populations (Tuset et al 2003;Petursdottir et al 2006;Zengin et al 2015;Renán et al 2016;Avigliano et al 2019;Mahè et al 2019;Vu and Kartavtsev 2020;Labidi et al 2020;Ghanbarifardi and Zarei 2021;Chen et al 2021). It is critical to determine the phenotypic variations produced by environmental influences in fisheries management and biology.…”