Importance of hydrological parameters in egg and larva distribution of small pelagic fishes in the southern Moroccan Atlantic

The small pelagic fishes constitute a resource that overgoes 80% of the Moroccan fisheries in the southern Moroccan Atlantic region between Cape Blanc and Cape Boujdor (21 degree -26 degree 30'N). Two surveys were carried out in this area in March (winter) and July (summer) 1998. During cruises, the following environmental parameters were measured at 5 m depth: temperature, salinity, dissolved oxygen and phosphates. At each survey, 30 samples per season of ichthyoplankton were made using a small size Bongo net, 20 cm mouth diameter and 417 mu m mesh size, and equipped with a flowmeter to measure the volume of filtered water. The sampling was carried out with oblique hauls from surface to bottom, and no more than 100 m in depth for the stations that exceeded 100 m depth. The species studied were sardina, sardinellas, horse mackerels, chad mackerel and anchovy. The statistical analysis consisted of a one way anova to test significant spatial and temporal differences among the hydrological and biological parameters, a normalised principal analysis (PCA) for the hydrological parameters justified by the heterogeneous data, and a canonical correspondence analysis (CCA). The CCA analysis permitted to explain the structure of the biological data by mixing the two tables, biologic and hydrologic. The significance of CCA was tested by the Monte-Carlo test. A grouping of stations with the same hydrological characteristics was carried out and the main result in the two cruises was the separation between coastal and offshore stations at the isobath 80 m limit. In the coastal stations, the variation of temperature and phosphates was important and permitted the localisation of the upwelling areas in the cruise periods. These areas were characterised by a low temperature and a high content of phosphates observed principally in the north, between 24 degree 30'N and 26 degree 30'N in July. In the south, between 21 degree N and 22 degree 30'N, the upwelling was influenced by the ECSA current, which was rich in nutriments and relatively hot, and was more marked in March. In March, the spatial distribution of egg and larva densities (individual/10 m2) showed two separate high concentration areas in the north and in the south, essentially of sardina, sardinellas and anchovy. In July, the main characteristic was the occurrence of the eggs and larvae of almost all species in the area located between North Dakhla (24 degree 30'N) and Cape Barbas (22 degree 30'N). The choice of spa