Morphological and molecular differentiation of wild and farmed gilthead sea bream Sparus aurata: implications for management

Abstract

A combination of molecular and morphological characteristics was used to investigate populations of wild and farmed gilthead sea bream Sparus aurata from the largest Croatian shellfish production area, Mali Ston Bay. Identification of farmed escapees was performed in the wild in order to evaluate and compare the detection sensitivity of molecular and morphological tools. Using a traditional set of measurements and a truss network system, morphometric trait analysis of gilthead sea bream showed clear body shape differences between individuals from the wild and farmed populations. Microsatellite markers only revealed weak neutral genetic differentiation between farmed and wild samples from Mali Ston Bay (Wright's F ST = 0.019, p > 0.05; Jost's D EST = 0.022), despite the fact that the farmed gilthead sea bream were of Atlantic origin. Using assignment tests, morphological (16%) and molecular (25%) analysis identified farmed escapees in the samples of wild gilthead sea bream in the vicinity of aquaculture sites. Morphological data showed good potential for distinguishing recent escapees in wild populations, since these characteristics are affected by the environment. This study demonstrates the presence of escapees in the local wild population in this region, and suggests the potential for genetic interaction.

Morphological and ecophysiological adaptations of wild gilthead seabream Sparus aurata associated with tuna farms

“…body and otolith shape, condition index), have proven to be highly accurate and easily manageable tools for discriminating the origins of gilthead seabream Sparus aurata due to their simplicity in de ployment, which does not require broader expert knowledge or specialisation (Arechavala-Lopez et al 2013). However, morphological resemblance between populations can also be viewed as a proxy measure for similarities in habitat use (Olsson et al 2007), suggesting that morphometry analysis is primarily sensitive in the detection of recent escape events before the convergence from the farmed to the wild morphotype 'sets' in the natural habitat (Šegvić-Bubić et al 2014).…”

Phenotypic plasticity in wild marine fishes associated with fish-cage aquaculture

“…Independently of ecological and taxonomical considerations, comparative studies between reared and wild fish have usually shown a smaller head and a blocky-belly body in the farmed fishes. This has been found in coho salmon Oncorhynchus kitsutch (Walbaum, 1792) (Swaine et al, 1991), turbot Scophthalmus maximus (Linnaeus, 1758) (Ellis et al, 1997), sharpsnout seabream Diplodus puntazzo (Walbaum, 1792) (Sarà et al, 1999), gilthead seabream (Loy et al, 1999;Grigorakis et al, 2002;Arechavala-Lopez et al, 2011;Š egvić-Bubić et al, 2014), European sea bass (Loy et al, 2000;Arechavala-Lopez et al, 2011), European perch Perca fluviatilis Linnaeus, 1758 (Mairesse et al, 2005), sterlet Acipenser ruthenus Linnaeus, 1758 (Lenhardt et al, 2012) and silversides Odontesthes spp. (Crichigno et al, 2014).…”

Assessing the influence of gilthead sea bream escapees in landings of Mediterranean fisheries through a scale‐based methodology

“…At a regional level, a highly admixed wild population structure has indeed already been detected (Šegvić‐Bubić et al . 2011b, ), as well as cultured fish spawning while in sea cages (Somarakis et al . ).…”

“…There are also ecological implications arising from the presence of escapees in the wild, for example reduction of genetic diversity of wild conspecific populations through hybridisation (Šegvić‐Bubić et al . 2011b, ) and increased competition for food and habitat with other organisms (Toledo‐Guedes et al . ; Arechavala‐Lopez et al .…”