The current knowledge status of the genetic population structure of the European sardine (Sardina pilchardus): uncertainties to be solved for an appropriate fishery management

Abstract

To achieve sustainable fisheries implies that resources' management is carried out in accordance with biologically and ecologically relevant processes. In this context, to infer the boundaries of the genetic stocks along their distribution is crucial to avoid the depletion of genetic diversity induced by fishing pressure. Despite its remarkable ecological role and commercial interest, there are still many uncertainties about the genetic population structure and local adaptation processes of the European sardine (Sardina pilchardus) along its distributional range. Our analysis revealed that in addition to the uneven genetic study effort throughout its distribution, there are discrepancies when it comes to delimiting populations, especially in the waters surrounding the Iberian Peninsula. Also, powers of the genetic markers applied in the studies were examined, showing that allozymes detected a larger number of significant pairwise values of genetic differentiation, while mtDNA-RFLP detected a greater degree of differentiation among genetic stocks. Moreover, large values of genetic diversity in all the locations were identified regardless of marker type. Thereby, we provide a discussion of updated knowledge, contributing to shape long-term and genetically sustainable harvest strategies for this pelagic fish, since our findings indicate a mismatch between the genetic stocks and the managed stocks currently defined.

Sardines at a junction: Seascape genomics reveals ecological and oceanographic drivers of variation in the NW Mediterranean Sea

“…Highly mobile sardine, similarly to other clupeids, display localized batch spawning behaviour and migratory patterns that may result in restricted gene flow between populations and subsequent divergence (Bacha et al, 2014). This has already been demonstrated within the Mediterranean and to a lesser extent in the eastern Atlantic, mainly reflecting the levels of environmental heterogeneity of the two regions (Caballero‐Huertas et al, 2022, and references therein; Ganias et al, 2004). The prevailing conditions are distinct in the two areas in terms of productivity, circulation patterns, wind events, water temperature, and biogeochemical and biological components but also topographic features that greatly impact the species' spatiotemporal variability in spawning (Ganias, 2009; Lima et al, 2022).…”

“…Environmental variables were selected considering evolutionary history, climate variability or change, and fishing activity as the dominant processes affecting small pelagic fish. Variables were selected to include all previously reported variables and their trends with significant impact on sardines, such as temperature (Garrido et al, 2017; Gordó‐Vilaseca et al, 2021), salinity (Santos, Ré, et al, 2006) and hydrodynamics (for a review see Caballero‐Huertas et al, 2022), as well as variables related to the biology of the species whose impact has never previously been assessed. Given that the impacts of climate change are a rather complex issue that refers to more than one parameter (e.g., an increase in temperature), we tested whether there are any environmental variables related to topography, hydrodynamics, and biochemical and biological components at different layers (i.e., surface, water column, bottom), different types of exploitation tools and food availability acting as selective agents in sardines of the Northwestern Mediterranean (Table 1; Table S2, see Supplementary Information for a detailed description).…”

“…Environmental variables were selected considering evolutionary history, climate variability or change and fishing activity as the dominant processes affecting small pelagic fish. Variables were selected as to include all previously reported variables and their trends with significant impact on sardines such as temperature (Garrido et al, 2017;Gordó-Vilaseca, Pennino, Albo-Puigserver, Wolff, & Coll, 2021), salinity (Santos, Ré, Dos Santos, & Peliz, 2006) and hydrodynamics (for a review see Caballero-Huertas et al, 2022), as well as variables related to the biology of the species whose impact has never been assessed before. Given that the impacts of climate change are a rather complex issue that refers to more than one parameter (e.g.…”

Comparing otolith shape descriptors for population structure inferences in a small pelagic fish, the European sardineSardina pilchardus(Walbaum, 1792)

“…Understanding the population structure of fish species is fundamental for developing appropriate fisheries management strategies. For that purpose, several approaches are presently used to describe fish population structure (e.g., Caballero-Huertas et al, 2022;Cadrin, 2013;Catalano et al, 2014;Kristoffersen & Magoulas, 2008;Labonne et al, 2022;Moura et al, 2020;Muniz et al, 2020;Neves & Garrido, 2020;Neves et al, 2021;Reis-Santos et al, 2015). Among them, otolith shape analysis is an efficient methodology for studying fish population structure (Campana & Neilson, 1985;Izzo et al, 2017;Mapp et al, 2017) and is one of the most used methods (Bird et al, 1986;Campana & Neilson, 1985;Doering & Ludwig, 1990;Libungan et al, 2015a;Parisi-Baradad et al, 2005;Tuset et al, 2021).…”

Population genomics reveals the underlying structure of the small pelagic European sardine and suggests low connectivity within Macaronesia

“…Recently reported low biomass levels (ICES, 2020) led to recommendation to reduced fishing in Southern Europe, with great economic impact. It also prompted us to reevaluate the current population structure of S. pilchardus aiming at the ongoing discussion on how genetic information can contribute to stock delineation for management purposes (Caballero-Huertas et al, 2022).…”