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

Tanja Šegvić-Bubić,Branimir Šegvić,Lena Vulić,Igor Talijančić,Ivana Radonić,Iva Žužul,Leon Grubišić

doi:10.3390/w12113186

Tanja Šegvić-Bubić, Branimir Šegvić + Show 5 more

Open Access

https://doi.org/10.3390/w12113186

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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.

Highlights

Population connectivity and spatial structure information provide a basis for understanding fish population dynamics and play a key role in conservation and fisheries management [1]
canonical variate analysis (CVA) output based on fish origin partially segregated individuals according to the specified groups (W, Wild farm-associated (WF), F) with no significant difference in shape of wild and wild farm-associated groups as measured by both Procrustes and Mahalanobis distances (Supplementary Table S1)
Shape changes related to variation along the first canonical variate (CV1, 96.9% of cumulative variation) showed that the scales of the farmed group were relatively wider and shorter, while scales of the wild and wild farm-associated groups were elongated, with a larger distance between the focus and anterior edge, and a straighter posterior edge as opposed to the convex edge observed in the farmed group (Figure 3a)

Summary

Introduction

Population connectivity and spatial structure information provide a basis for understanding fish population dynamics and play a key role in conservation and fisheries management [1]. Several recent studies have confirmed that Adriatic tuna farms are areas of permanent residency of highly abundant wild seabream [7,8] This aggregative behaviour has been attributed to the permanent and increased availability of tuna baitfish losses, composed of small pelagic species. Such an altered environment has triggered the temporarily stable adaptation of both morphological and physiological traits, where wild farm-associated populations show a different head profile, body shape and enhanced reproductive fitness in comparison to those of wild or farmed fish origin [8]. Plastic and genetic variation are considered two unique ways of adapting to local environmental conditions [2], and in this case, gilthead seabream plasticity response might have facilitated the observed genetic changes among populations

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