Seasonal variations in wild fish aggregation near sea-cage fish farms in the Turkish Aegean Sea

• Published in: Aquaculture reports 2020-11, Vol.18, p.100478, Article 100478
• Main Authors: Akyol, Okan, Özgül, Aytaç, Düzbastılar, F. Ozan, Şen, Halil, Ortiz de Urbina, José M., Ceyhan, Tevfik
• Format: Article
• Language: English
• Subjects: Abundance; Biomass; Fish diversity; Mediterranean; Visual census
• ISSN: 2352-5134; 2352-5134
• DOI: 10.1016/j.aqrep.2020.100478

•Sparids, Carangids and Mugilids have greatest fish diversity beneath sea cages.•Boops boops is the most abundant fish species beneath sea cages.•Wild fish diversity is highest in summer lowest in winter.•Wild fish diversity increases towards to South. This study sought to determine seasonal variations in wild fish assemblage events associated with fish farms with respect to fish biodiversity, abundance and biomass along the Turkish Aegean Sea. Assemblages of wild fish were determined bimonthly with six rapid visual counts (RVCs) at six fish farms in both the Izmir (Northern Aegean Sea, NAS) and Mugla (Southern Aegean Sea, SAS) regions. Data were pooled based on each season. Thirty-nine total fish species representing 21 families were identified, with three particularly abundant families: Sparidae (seven species), Carangidae (six species) and Mugilidae (four species). The greatest fish diversity was recorded in the summer, followed by spring, autumn and winter. Regionally, the greatest fish diversity was observed in the southern Aegean Sea. Significant differences across seasons and regions were observed. Boops boops was very abundant at all stations, except for the first station in the NAS. Approximately 80.5 % of farm-associated fish were B. boops, followed by Atherina boyeri (4.14 %), Scomber colias (2.82 %), Sardinella aurita (2.78 %) and Oblada melanura (2.73 %). A total of 105,041 individual fish and 3637 kg.11,250 m−3 fish were identified in the NAS; 448,331 individual fish and 47,070 kg.11,250 m−3 fish were identified in the SAS. These results indicate that the diversity of wild fish communities is relatively high, and vary between regions. Boops boops represents the predominant species, although the Sparids, Carangids, Mugilids, Scombrids, Clupeids and Pomatomids are also highly represented throughout the Mediterranean.