Phenotypic Convergence in Sea Bass (Dicentrarchus labrax) Escaping From Fish Farms: The Onset of Feralization?

The impact of fish escaping from farms may depend on the extent to which escapees adapt natural environment, resemble wild conspecifics, and become feral. Yet, little is known about process feralization in marine fish. We examined phenotypic changes body shape, condition, scale growth profiles sea bass Canary Islands quantified had diverged farmed conspecifics. Most feral sizes that overlapped with those fish, indicating they escaped throughout production cycle. However, 29% were larger than maximum size at harvesting, wild. Analysis showed some grown as fast cultured albeit more variable rates. Feral tended converge towards a similar having streamlined bodies, lower hepatosomatic indices (HSI) cages. Although our study cannot discriminate between plasticity differential mortality escapees, we interpret convergence likely result period initial starvation, plasticity, selection against maladapted phenotypes. Our results warn risks rearing open-net cages suggest could pose threat shallow coastal assemblages, particularly areas where species not naturally found.