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

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

“…The Atlantic Morocco coastal geomorphology, together with distinct climatic and environmental characteristics, results in singular upwelling patterns (Benazzouz et al, 2014), whereas in northern and central coast regions, the upwelling is seasonal (with low and high activity, respectively), and on the southern region, a permanent and intense upwelling activity is present. That oceanographic characteristic could isolate the south of Morocco location from the remaining, as has already been defended and observed by Labonne et al (2022) for the same species, using an otolith chemical signature. Finally, such pronounced morphological disparities could also be attributed to phenotypic plasticity in response to extrinsic conditions, such as environmental or exploitation factors (Cadrin, 2000), as previously suggested for this species (Neves et al, 2021).…”

“…For this reason, individuals living in distinctive environments are likely to develop unique demographic dynamics and establish discrete demographic stocks, even if they are genetically homogeneous (Neves et al, 2021). Because the European sardine has shown limited genetic differentiation over wide regional scales (Baibai et al, 2012;Kasapidis, 2014), the authors consider that the phenotypic variations observed are likely attributable to environmental factors, as stated by Campana and Casselman (1993), or even to oceanographic phenomena that might function as an obstacle to planktonic migration (Labonne et al, 2022), promoting isolation and resulting in distinct populations.…”

“…For this reason, individuals living in distinctive environments are likely to develop unique demographic dynamics and establish discrete demographic stocks, even if they are genetically homogeneous (Neves et al ., 2021). Because the European sardine has shown limited genetic differentiation over wide regional scales (Baibai et al ., 2012; Kasapidis, 2014), the authors consider that the phenotypic variations observed are likely attributable to environmental factors, as stated by Campana and Casselman (1993), or even to oceanographic phenomena that might function as an obstacle to planktonic migration (Labonne et al ., 2022), promoting isolation and resulting in distinct populations. The Atlantic Morocco coastal geomorphology, together with distinct climatic and environmental characteristics, results in singular upwelling patterns (Benazzouz et al ., 2014), whereas in northern and central coast regions, the upwelling is seasonal (with low and high activity, respectively), and on the southern region, a permanent and intense upwelling activity is present.…”

“…That oceanographic characteristic could isolate the south of Morocco location from the remaining, as has already been defended and observed by Labonne et al . (2022) for the same species, using an otolith chemical signature. Finally, such pronounced morphological disparities could also be attributed to phenotypic plasticity in response to extrinsic conditions, such as environmental or exploitation factors (Cadrin, 2000), as previously suggested for this species (Neves et al ., 2021).…”

“…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).…”