Description
Acoustic survey, conducted with an annual periodicity, to assess and map the small- and mid-sized pelagic (neritic) species¿ resources and the oceanographic and biological conditions of the Gulf of Cadiz continental shelf (both Spanish and Portuguese waters, ICES Subdivision IXa South, from Cape Trafalgar to Cape San Vicente, between 20 and 200 m depth). The survey season coincides with the anchovy (Engraulis encrasicolus) peak spawning in order to estimate the anchovy SSB by echo-integration. The acoustic sampling for assessment by echo-integration is performed during daylight hours (at a 10-knot speed). Biological characterization of the pelagic community is sampled by opportunistic pelagic trawls (for identification of echo-traces), which are also performed during the day (at a 4-knot speed). Ancillary biological information (fish eggs) sampled with CUFES (Continuous Underway Fish Egg Sampler) and coupled to the acoustic sampling. Occurrence of sea birds, turtles, and mammals is also recorded along the acoustic transects through census techniques. Oceanographic characterization of the surveyed area from both discrete (CTD profiles in night stations) and continuous sampling (Thermosalinometer-fluorimeter) coupled to the CUFES sampling. This year, ad hoc Bongo 40 stations arranged in two additional transects were also carried out in order to characterize the ichthyoplankton and mesozooplankton species assemblages in the eastern sector of the study area (Guadalquivir river mouth-Trafalgar) and their relationships with environmental conditions.
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