Investigating spatial heterogeneity of von Bertalanffy growth parameters to inform the stock structuration of common sole, Solea solea, in the Eastern English Channel

Abstract

In fisheries science, a mismatch between the delineation of a fish stock and the underlying biological population can lead to inaccurate assessment and management. Previous results suggested a potential spatial structuration of the Eastern English Channel (EEC) stock of common sole, Solea solea, in three sub-populations. In this article, we propose to investigate the spatial population structure of common sole in the EEC using the von Bertalanffy Growth Function parameters as indicators of population segregation. In order to test the sub-population hypothesis and evaluate its robustness to data sources, we developed three models, all including an area effect on growth parameters. The first model was aimed at testing a potential data source effect (in addition to the area effect) using commercial and scientific survey data jointly. The two other models used either scientific survey or commercial fishery data and focused on spatial differences in growth parameters. Our results showed that the growth parameter estimates indeed differed depending on the type of data used, with higher estimated asymptotic length and length at age two (L2) using commercial data. They also highlighted spatial differences in asymptotic length, consistent between models, which tend to confirm a spatial structuration of sole in the EEC. While these results need to be strengthened by marking and genetic studies, they constitute a first step towards a better understanding of the population spatial structuration of common sole in the EEC. Highlights► Von Bertalanffy growth parameters are used to inform the spatial structuration of an exploited species. ► Spatial differences in asymptotic length reinforce the metapopulation hypothesis. ► Growth parameters estimates differ depending on the type of data used -scientific survey or commercial fisheries.

State-space modeling of multidecadal mark–recapture data reveals low adult dispersal in a nursery-dependent fish metapopulation

“…Our results provide evidence of low connectivity among common sole subpopulations within the EEC, and no inputs from the adjacent spatial management areas. This evidence of local segregation is consistent with recent studies using patterns in key life history traits (Du Pontavice et al 2018;Randon et al 2018) for the common sole in the EEC.…”

“…These natural barriers consist of deep gravel grounds, which occur centrally in the EEC (separating UK from FrW & FrE), and wide rocky reefs from the coasts out into deeper waters (separating FrW from FrE). These natural delineations could potentially define the spatial structure of the common sole population within the EEC and have recently been used to study its connectivity in the EEC (Du Pontavice et al 2018;Randon et al 2018).…”

“…Although Du Pontavice et al (2018) and Archambault et al (2016) suggested heterogeneity of fishing mortality within the EEC, with the fishing pressure in FrE being higher than in the UK and FrW areas, no spatial variability of fishing mortality within the three EEC areas was considered in our approach. However, because the EEC common sole stock is considered homogeneous, no stock assessment results were available for the individual 'sub-stock' areas (UK, FrW, FrE), and no spatialized catch data were available in the time series.…”

“…Otoliths are also extensively used in connectivity studies, either through otolith morphology (Bacha et al 2016;Hüssy et al 2016;Mahe et al 2016) or otolith chemistry (Tanner et al 2016;Callicó Fortunato et al 2017;Régnier et al 2017;Moreira et al 2018). Morphometry and meristics (Allaya et al 2016;Sley et al 2016), parasites (Catalano et al 2014;MacKenzie & Abaunza 2014) and life history traits Erlandsson et al 2017;Du Pontavice et al 2018;Randon et al 2018) have also been used to assess stock structure. In the past decade, stock delineation studies have resulted in revised stock boundaries for numerous stocks (e.g.…”

“…Observed contrast in key life history traits (density-at-age and length-at-age data) have suggested potential spatial structuring within the adult component of the EEC common sole stock within three discrete spatial areas (Du Pontavice et al 2018;Randon et al 2018). However, the movements of adult sole between these areas remain largely unknown.…”