Gulf of Cadiz - Ecology

The nutrient enrichment of coastal waters comes from two main sources: Portuguese upwelling (S. Vicente Cape, Sta. Maria Cape) and river discharges (related to local and regional rainfall patterns). The intensity of the Portuguese upwelling system has been weakening for the last 50 years, causing a progressive reduction in the amount of nutrient-rich waters flowing onto the western shelf of the Gulf of Cadiz when westerlies blow. On the other hand, the combination of warm, nutrient-rich waters (discharged by the Guadiana and Guadalquivir Rivers) and the cool advected waters coming from the Portuguese upwelling area creates, in the cyclonic cell, a suitable environment for spawning and recruitment of small pelagic and demersal fish species.

On the Huelva shelf, two hydrodynamic patterns can be observed during the year. In the autumn-winter period, waters are well mixed showing similar conditions in temperature (slightly colder in the west due to the inland cold water river discharges), while in the spring-summer period the Portuguese upwelling favors the development of the two cells described above (see environment section). The interannual variability in those seasonal patterns has great influence on the recruitment of major fishery species.

Spatially, two important recruitment areas can be distinguished in the coastal waters of the cyclonic cell formed in the eastern shelf, and off-shore near the Huelva front. The shallow waters close to the Guadalquivir River mouth is the preferred habitat for Sparidae (e.g. Diplodus bellottii), Haemulidae, Soleidae and the crustacean stomatopod Squilla mantis. The deeper areas are preferred habitats of some clupeids (sardine, sardinella), cephalopods, hake, and scaldfish.

Sardine and anchovy are considered to be key species for the trophodynamic functioning of the marine ecosystems in the Huelva region.