Abstract
A successful discrimination of fish populations is essential for sustainable management and assessment. Otolith shape analysis has been used on several species to reveal their population structure. Our aim was to use the otolith shape of European sprat (Sprattus sprattus) to investigate large- and small-scale geographical variability across the Greater North Sea ecoregion. The otolith shape was extracted from digitalised images and transformed into Wavelet coefficients to be analysed with multivariate statistics. Otolith shape was observed to follow the genetic population structure recently defined for the region, supporting the latest revision of the stock boundaries. Four main groups were identified based on phenotypic variability: (i) Norwegian fjords; (ii) North Sea and offshore Skagerrak–Kattegat; (iii) coastal Skagerrak–Kattegat; and (iv) Uddevalla fjord. However, 4-fold cross-validations based on Linear Discriminant Analysis resulted in low accuracy limiting at the moment the ability to use otolith shape analysis for population identification at an operational basis. Our results show the importance of coastal areas, which might be inhabited by distinct populations of sprat that are currently not acknowledged in the management and assessment.
Highlights
An accurate understanding of the population structure underlying a fish stock is of vital importance for sustainable management
Our results show the impor tance of coastal areas, which might be inhabited by distinct populations of sprat that are currently not acknowledged in the management and assessment
Otolith shape compared among sprat from the Norwegian fjords (NW), North Sea (NS), offshore Skagerrak (SK), coastal Skagerrak (CS), and offshore Kattegat (KA) by CAP and ANOVA-like permutation tests showed significant differences between areas (P < 0.05, Fig. 2)
Summary
An accurate understanding of the population structure underlying a fish stock is of vital importance for sustainable management. A prerequisite for investigating population structure in marine fish species is a successful discrimination of populations, either based on genetic or phenotypic differences. Body size and age (Campana and Casselman, 1993), temperature (Gagliano and McCor mick, 2004), diet (Mille et al, 2016), salinity (Berg et al, 2018), and habitat depth (Lombarte and Lleonart, 1993) have been shown to be important variables affecting otolith shape, making it a successful marker for stock discrimination in several fish species (Libungan et al, 2015a; Stransky et al, 2008)
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