Evaluation of otolith shape as a tool for stock discrimination in marine fishes using Baltic Sea cod as a case study

Abstract

In the Western Baltic Sea two genetically distinct cod stocks "Eastern Baltic cod" and "Western Baltic cod" occur with considerable mixing of stocks. In this study we evaluated the applicability of otolith shape analysis for classification of individuals caught in the mixed stock cod fishery, using SNP (Single nucleotide polymorphism) based genetic assignment of otolith shape baselines. We further developed a management aimed approach for mixed stock assignment by robust stochastic baseline selection and posterior bias correction by individual reassignment of the least likely classifications into the alternate stock. Classification criteria selected by Monte Carlo runs of Linear Discriminant Analysis were captured by otolith area and 20 Elliptic Fourier Descriptors of primarily low frequency harmonics. Classification success was considerably lower when using a baseline of spawning individuals only, compared to the better spatial coverage of a combined baseline also including genotyped individuals from the mixed stock area. Furthermore, the inclusion of genotyped individuals balanced the baseline size composition and to a large extent removed a strong size related bias in classification success. These results demonstrate the interplay of environmental, ontogeneticand genetic influences on otolith shape, which complicates the application of otolith shape for stock discrimination in mixed-stock scenarios. Rigours genetic validation and further studies on the temporal dynamics of shape formation are necessary.

Spawning time of Atlantic herring ( Clupea harengus ) populations within a restricted area reflects their otolith growth at the larval stage

“…Further, the exact knowledge of genetic and environmental origin is an enormous benefit, in contrast to natural samples where the origin can only be assumed. This knowledge was used for an individual assignment of otoliths achieving highest classification success when assigning the otoliths to their genetic origin (87.2-91.9%) being comparable to other classification studies among populations using otolith shape [30,61,62]. Only a minor part of the otolith shape variation could be explained by salinity differences in the absence of genetic variation.…”

“…The low vertebral count of LV herring and the late timing of spawning is an indication of spawning and adaptations to the environmental conditions of the lake habitat. However, this also implies that natal homing [62,63] of Landvik herring occurs on an annual basis. The vertebral number for LV herring in May has been remarkably stable (55.5-55.8) since 1984 [43], supporting natal homing.…”

IDENTIFIKASI STRUKTUR STOK IKAN CAKALANG (Katsuwonus pelamis Linnaeus, 1758) DI SAMUDRA HINDIA (WPP NRI 573) MENGGUNAKAN ANALISIS BENTUK OTOLITH

“…Pemahaman tentang struktur stok merupakan hal yang fundamental dalam pengelolaan perikanan (Hussy et al, 2016). Saat ini pengelolaan perikanan di Indonesia telah diterapkan berdasarkan wilayah perairan yang dikenal sebagai Wilayah Pengelolaan Perikanan (WPP).…”

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

“…Stock identification is a basic requirement to describe the stock status and to support better stock assessment of fishery (Cadrin et al, 2005).Otolith shape analysis is a basic method for seperating fish stocks. Also there are a lot of studies about intraspecific variations of fish stocks from otolith shape (Vignon and Morat, 2010;Bostancı et al 2015;Zengin et al, 2015;Hüssy et al, 2016;Avigliano et al, 2017;Saygin et al, 2017;Bostancı and Yedier, 2018;Song et al, 2018;Yedier et al, 2019). Otoliths are innate data archives that document information in their microstructure and chemistry at different spatial and temporal scales related to their growth and environment (Miyan et al, 2016).…”