Stock delineation of striped snakehead, Channa striata using multivariate generalised linear models with otolith shape and chemistry data

Abstract

Otoliths are commonly used to discriminate between fish stocks, through both elemental composition and otolith shape. Typical studies also have a large number of elemental compositions and shape measures relative to the number of otolith samples, with these measures exhibiting strong mean–variance relationships. These properties make otolith composition and shape data highly suitable for use within a multivariate generalised linear model (MGLM) framework, yet MGLMs have never been applied to otolith data. Here we apply both a traditional distance based permutational multivariate analysis of variance (PERMANOVA) and MGLMs to a case study of striped snakehead (Channa striata) in India. We also introduce the Tweedie and gamma distributions as suitable error structures for the MGLMs, drawing similarities to the properties of Biomass data. We demonstrate that otolith elemental data and combined otolith elemental and shape data violate the assumption of homogeneity of variance of PERMANOVA and may give misleading results, while the assumptions of the MGLM with Tweedie and gamma distributions are shown to be satisfied and are appropriate for both otolith shape and elemental composition data. Consistent differences between three groups of C. striata were identified using otolith shape, otolith chemistry and a combined otolith shape and chemistry dataset. This suggests that future research should be conducted into whether there are demographic differences between these groups which may influence management considerations. The MGLM method is widely applicable and could be applied to any multivariate otolith shape or elemental composition dataset.

Major population’s separation area for sardine (Sardina pilchardus) and hake (Merluccius merluccius) revealed using otolith geochemistry on the Atlantic coast of Morocco

“…The analysis of whole otolith chemical compositions has been used in several studies to characterize the chemical signatures of fish groups at large spatial scales (Moreira et al, 2018;Soeth et al, 2019;Correia et al, 2021). They are mainly used in studies focusing on fish population structure and dynamics (Correia et al, 2014;Hägerstrand et al, 2017;Khan et al, 2021). Although the whole otolith chemical composition integrates the overall fish life history, methods based upon whole otolith chemistry have been successfully used to identify fish stock units with low levels of connectivity (Correia et al, 2021).…”

“…However, factors that affect the elemental incorporation into otoliths are not yet completely understood and various factors other than ambient water chemistry may also play important roles in elemental incorporation: dietary sources, physiological processes or genetic variations (Clarke et al, 2011;Sturrock et al, 2015;Izzo et al, 2018;Hüssy et al, 2020). The success in the use of the whole otolith chemistry (i.e., entire life-history prior to capture) to investigate fish population structure at large geographic scale (Moreira et al, 2018;Soeth et al, 2019 ;Correia et al, 2021;Khan et al, 2021) allows for an increase in sample size due to a reduction in the time invested in otolith processing procedures and chemical analyses.…”

Feeding and reproduction of striped snakehead Channa striata (Bloch, 1793) inhabiting the Gangetic river system

“…As a result, the feeding and natural breeding habitats of this economically important fish species have been limited, resulting in a reduction in wild populations. There is no report available on the feeding habits and reproductive biology of the C. striata population from the Ganga River, Yamuna River, and Gomti River at the selected sampling stations, which harbour its distinct stocks (Khan et al 2021). In the context of a changing environment, it is important to comprehend the changes in food, feeding habits, and reproductive biology of the C. striata population for appropriate management.…”