Prevalence and survival of escaped European seabass Dicentrarchus labrax in Cyprus identified using genetic markers

Abstract

The escape of European seabass Dicentrarchus labrax (L.) from fish farms is considered to be a widespread problem in the Mediterranean area, where this species is produced in large quantities in offshore cages. Whilst estimates of the number of escaped seabass in the wild have been made previously, the actual distribution, long-term survival and the potential effects on native populations remain largely unknown. This study characterises the genetic profiles of all contemporary and some historic aquaculture sources of European seabass in Cyprus and uses these profiles to identify escaped fish in seabass collected from the wild around the island. Significant differences in the microsatellite and mitochondrial DNA marker profiles were found between farmed and wild fish. The number of escapees identified was 15% of the total number of wild-caught fish sampled. However, escapees were not equally distributed; at one location ~70% of wild-caught fish were escapees while in other areas escapees only accounted for up to 4%. Escapees were present in all size classes of fish, but the majority were of commercial size (300−500 g) typical of seabass farmed in seacages. This indicates that they may have escaped recently and during normal aquaculture operations as no escape event was reported in the course of the study. Two large, egg-bearing females and some juvenile fish were also classified as escapees, which suggests that long-term survival and interbreeding with wild fish is possible in Cypriot waters.

Metapopulation patterns of additive and nonadditive genetic variance in the sea bass (Dicentrarchus labrax)

“…However, sea bass would could be a rare example of heterosis for a marine fish as-to our knowledge-heterosis was suggested only in hybrids of coastal and Arctic cod (Gadus morhua) (Bangera, Ørdegård, Praeble, Mortensen, & Nielsen, 2011), while many cases were reported for marine invertebrates (Bierne, David, Boudry, & Bonhomme, 2002;Edmands, 1999;Pereira, Barreto, & Burton, 2014;Wang & Cote, 2012). et al, 2005), and in open waters around Cyprus (Brown, Miltiadou, & Tsigenopoulos, 2015). The capacity of foreign progeny to outcompete local individuals could be partly mediated by nonadditive effect for survival (Hänfling, 2007).…”

Siblingship tests connect two seemingly independent farmed Atlantic salmon escape events

“…In addition, DNA methods have been successfully tested and implemented to identify escapees back to their farms of origin for a range of other aquaculture species, including rainbow trout Oncorhynchus mykiss (Glover 2008, Consuegra et al 2011, European seabass Dicentrarchus labrax (Brown et al 2015), Asian sea bass Lates calcarifer (Yue et al 2012, Noble et al 2014 and Atlantic cod Gadus morhua (Glover et al 2011a). In the present study, we implemented siblingship tests for the first time, which led to an increase in the accuracy and confidence of assignment of the salmon escapees back to their farm(s) of origin.…”

Site fidelity of farmed gilthead seabream Sparus aurata escapees in a coastal environment of the Adriatic Sea

“…Recent studies have demonstrated that escaped European seabass and gilthead seabream are able to move away from their original farm to coastal fishing areas up to 20 km away, and that escapees may survive for relatively long periods (> 6 mo) by feeding on natural resources (ArechavalaLopez et al 2011, 2012, Toledo-Guedes et al 2014. The ability of escapees to exploit natural resources was evident in the relatively high proportion of gilthead seabream and European seabass escapees in wild populations in the Adriatic Sea and in the waters of Cyprus (13−15%) (Šegvić- Bubić et al 2011b, Brown et al 2015, and in the western Mediterranean (11−20%) (Izquierdo-Gómez et al 2017). It seems that farmed escapees successfully introgressed and changed the genetic profile of certain wild populations, which were then characterized by decreased allelic diversity in comparison to unaffected wild populations (Šegvić-Bubić et al 2017).…”