Assignment of Gilthead Seabream Sparus aurata to Its Origin through Scale Shape and Microchemistry Composition: Management Implications for Aquaculture Escapees

Abstract

This study tests the suitability of the gilthead seabream scales as a proxy for origin selection in wild and anthropogenically pressured environments. Scale morphology and microchemistry were used to discriminate the habitat selection of two wild, farmed and wild farm-associated populations where landmark and outline-based scale morphometrics, trace-element chemistry and scale microstructure characteristics were analysed. The morphometric techniques successfully differentiated between the farmed and wild origin scale phenotypes. Reduced discrimination sensitivity between the wild and wild farm-associated origin was, however, reported. The discrimination based on microchemistry (B, Ba, Mn, K, Sr and Zn) classified the scales with high accuracy according to their origin (wild vs. farmed vs. wild farm-associated) and sampling locations, thus proving itself as a powerful tool in provenance study of gilthead seabream. Disparity in scale microstructure characteristics accounted for radii, circuli and inter-circulus spacing, hence unveiling the differences in growth and environmental conditions between the wild and farmed fish. In brief, scale shape was found to be a potent exploration tool for farmed fish identification, whereas scale microchemistry yielded a good resolution in identifying gilthead seabream membership among different habitats. Considering the importance of this species in aquaculture and fisheries throughout the Mediterranean, more research is needed to assess the usefulness of scales as nonlethal biogeochemical tags.

Genetic discrimination of wild versus farmed gilthead sea bream Sparus aurata using microsatellite markers associated with candidate genes

“…The simplest yet cheapest way to distinguish fish origin is to use external characteristics in combination with morphometrics (e.g., body and otolith shape, condition index) and organoleptic descriptors, but their use is limited to early escaped fish (Arechavala-Lopez et al, 2013;Šegvić-Bubić et al, 2014;Talijančić et al, 2019Talijančić et al, , 2021. Recent studies have shown that when analysing body shape and otolith characteristics, attribution of farm seabream to their true origin is more than 75% correct (Talijančić et al, 2019(Talijančić et al, , 2021, while Šegvić-Bubić et al (2020) showed that the pattern of scale shape, supported by scale microchemistry, can serve as a discriminator in controlling recent escapes.…”

Scale regeneration in reared Gilthead seabream: Revisiting the use of scales in identifying aquaculture escapees

“…Several different methodologies have been applied for the identification of aquaculture escapees in wild‐caught Gilthead seabream samples, mainly involving morphological and genetic traits (e.g. Arechavala‐Lopez, Sanchez‐Jerez, et al, 2012; Segvic‐Bubic et al, 2014; Šegvić‐Bubić et al, 2020; Zuzul et al, 2019). Among them, scale regeneration has been suggested as a cost‐effective and rapid morphological index.…”

“…Furthermore, it is frequently used to estimate differences in growth patterns reflected in morphological variability between fish of different spatial distribution or/and wild versus reared origin (e.g. Arechavala‐Lopez, Sanchez‐Jerez et al, 2012; Ibanez et al, 2017; Lund & Hansel, 1991; Poulet et al, 2005; Šegvić‐Bubić et al, 2020). Handling manipulations (e.g.…”

“…Similar to other commercially farmed fish species, accidental escape events of reared seabreams, due to mainly technical or operational failures, are not rare (Arechavala‐Lopez, Uglem et al, 2012; Glaropoulos et al, 2012). These escape events might be considered as a potential threat to the natural populations, due to genetic, physiological and morphological differences between reared and wild fish (Alarcon et al, 2004; Arechavala‐Lopez et al, 2013; Carrillo et al, 2001; Fragkoulis et al, 2017; Geladakis et al, 2021; Karaiskou et al, 2009; Segvic‐Bubic et al, 2014; Šegvić‐Bubić et al, 2020; Zuzul et al, 2019). The ability to discriminate different origins (wild vs. farmed) in the wild represents a first step towards functional management of escapees.…”