Brief presentation of the results of echo surveys in the Strait of Sicily in period Sergey Goncharov

STRAIT OF SICILY – PHYSICAL BACKGROUND The general surface circulation pattern is locally controlled by the motion of the Modified Atlantic Water (MAW), which bifurcates in the Atlantic Ionian Stream (AIS), a meandering surface current inflowing towards the Ionian Sea and the Atlantic Tunisian Current (ATC) (Lermusiaux and Robinson, 2001; Béranger et al., 2004). It has been shown (Garcia Lafuente et al., 2002) how AIS acts as a transport mechanism for displacing fish eggs and larvae from the more important northern spawning grounds towards the southern limit of the region. During summer, the Atlantic water advected by the AIS to the South of Sicily is warmer than the surrounding waters north of it at the same depth, a fact that is the consequence of the presence of the Adventure Bank Vortex (ABV) (Robinson et al., 1991, 1999) and the frequent wind-induced upwelling events along the southern shore of the island (Piccioni et al., 1988). Atlantic Ionian Stream (AIS) Adventure Bank Vortex Ionian Shelf Vortex Upwelling Spawning grounds Cape Passero Front A. I. S. A. I. S. A. T.T. C.

STRAIT OF SICILY – PHYSICAL BACKGROUND If the AIS path is distant offshore, the central-northern coasts can show a greater upwelling extension, thereby, producing drastic changes in the temperature regime of the surface waters. The contrary would happen if the AIS is pushed against the shore: the size of ABV would reduce and water in coastal zone would increase the temperature because of the AIS influence. Therefore, year to year variability of AIS path have consequences on the predominant hydrological phenomena occurring in the region, such as, on the extension of upwelling and on the formation of frontal structures. All these hydrological features have shown their influence on the spawning strategy of the European anchovy Engraulis encrasicolus (Linnaeus, 1758) and the survival of the early life stages (Garcia Lafuente et al., 2002). Atlantic Ionian Stream (AIS) Adventure Bank Vortex Ionian Shelf Vortex Upwelling Spawning grounds Cape Passero Front A. I. S. A. I. S.

The maps of transects and anchovy and sardine biomass distribution by results of echo survey in July 2002.

The maps of transects and anchovy and sardine biomass distribution by results of echo survey in June 2003.

The maps of transects and anchovy and sardine biomass distribution by results of echo survey in July 2004.

The maps of transects and anchovy and sardine biomass distribution by results of echo survey in July 2005.

The maps of transects and anchovy and sardine biomass distribution by results of echo survey in October 2005.

The maps of transects and anchovy and sardine biomass distribution by results of echo survey in June 2006.

Thanks for attention

TS(dB/kg)=-14.90*LogL(cm) (sardine) TS(dB/kg)=-12.15*LogL(cm) (anchovy) For recalculation the formula from dimension dB/kg to dB per individual fish I used the formula TSкг = TS – 10Log, is the weight of one fish, kg. =0.0059*L (anchovy) TS=20LogL (anchovy) TS=20Log (sardine) Barange, M., Hampton, I. and Soule, M. Empirical determination of in situ target strengths of three loosely aggregated pelagicsh species. ICES Journal of Marine Science, 53, 225–232, TS(dB/kg)=-14.90*LogL(cm) (sardine) TS(dB/kg)=-12.15*LogL(cm) (anchovy) For recalculation the formula from dimension dB/kg to dB per individual fish I used the formula TSкг = TS – 10Log, is the weight of one fish, kg. =0.0059*L (anchovy) TS=20LogL (anchovy) TS=20Log (sardine)