engleski

South Adriatic - potential spawning ground for scobrids inferred by genetics and modelling

In September 2011 during routine monitoring of commercial purse seine catches 87 fingerling specimens of scombrids were collected in the southern Adriatic Sea. Sequencing of mitochondrial control region locus inferred that specimens belonged to the Atlantic bluefin tuna, Thunnus thynnus (Linnaeus, 1758) (N=29), bullet tuna, Auxis rochei (Risso, 1810) (N=30) and little tunny, Euthynnus alletteratus, Rafinesque, 1810 (N=28). According to their body length and previously published growth parameters, we estimated their age to be approximately 30 days, which would suggest that they were spawned in the Adriatic Sea, contrary to standard knowledge. Hence, in order to determine possible location of the spawning we run coupled modelling system ROMS-ICHTHYOP. Realistic ROMS simulations were made to provide current and density fields for the ICHTHYOP model. ROMS model was forced with river inflows, tides, exchange through the Strait of Otranto and realistic surface air-sea fluxes calculated from fine resolution ALADIN model. ICHTHYOP was run in the backward mode for 30 days using published investigations on the studied species and its early stage dynamics, such as their growth and developmental stage thermal dependence, lethal temperatures, etc. Apart simulations with coupled modelling system, detailed analysis of prevailing meteorological and oceanographic conditions was made using all available data. Comparison to climatology of the area approved that 2011 had unusually prolonged warm and dry summer season. Occasional inflows of hot and dry air from the northern Africa additionally warmed up Adriatic atmosphere. Under these conditions sea surface temperature was up to 2 standard deviations above normal. In the deeper layers, high temperature and salinity were recorded.

ROMS; ICHTHYOP; bluefin tuna; bullet tuna; little tunny; Adriatic

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