|Origin of predators attracted by aquaculture facilities on the Mediterranean coast: insights on aquaculture impacts at community level|
Mrugala, A. (2011). Origin of predators attracted by aquaculture facilities on the Mediterranean coast: insights on aquaculture impacts at community level. MSc Thesis. University of Oviedo. Department of Functional Biology: Oviedo. 43 pp.
Aquaculture techniques > Cage culture
Aquatic organisms > Heterotrophic organisms > Predators
MED, Mediterranean [Marine Regions]
Coastal sea-cage fish farms seem to be particularly attractive for marine fish species due to a constant supply of uneaten feed pellets and particulate organic matter. Consequently, the dense prey assemblages allure predators, as for example marine mammals, which were observed to prey upon farmed fish. Until now bluefish (Pomatomus saltatrix L.) is the only documented predatory finfish species in the Mediterranean Sea feeding on cultured fish. Samples of bluefish caught inside cages of farmed seabream in Guardamar, Alicante (NW Mediterranean Sea) were genetically analyzed to determine their geographical origin. For the comparison two reference populations from the NE Atlantic Ocean (Gulf of Cadiz, near the Gibraltar Strait) and Eastern Mediterranean Sea have been used. The population structure of bluefish in the studied region was first assessed in order to explore the power of assignment tests. Molecular markers were as follows: hypervariable microsatellite loci and mtDNA sequences of cytochrome b. The analysis revealed homogenous genetic structure across the Gibraltar Strait, with no differentiation between the Atlantic and Western Mediterranean samples, although with moderate differentiation of the population from the Eastern Mediterranean Sea. The bluefish caught inside seabream cages seems to originate partially from the local population, including the Gulf of Cadiz in the Atlantic Ocean, and in the lesser extent from the Eastern Mediterranean/Black Sea region, which is consistent with the highly migratory behaviour of this species. The presence of individuals of Turkish origin confirms the attractive character of aquaculture sites; however the extent of such across- Mediterranean attraction remains unclear. New approaches to further investigate this aspect are suggested, like physical tagging and wider sampling coverage of the Mediterranean Sea.