a long period of time, it is tough for phytoplankton to remain in the euphotic zone. Calm periods allow for stratification to develop, which means that phytoplankton can grow and multiply while held in the shallow mixed layer. In other words, there is a miniature spring bloom during each calm period (Mann & Lazier, 1996). Upwelling and zooplankton Upwelling and primary production follow the onset of a strong wind within a few days (Mann & Lazier, 1996). Zooplankton, such as copepods, take longer to respond to the abundance of food available because they have life cycles of weeks rather than days. Zooplankton in the Canary Current reach their peak density in autumn when upwelling intensity decreases. The decrease in upwelling allows the zooplankton to stay over the shelf where their food supply exists. Due to the rapid response of phytoplankton to upwelled nutrients, zooplankton are seldom food-limited. Upwelling and fish Four types of fish comprise 75% of total catch in the Cap Blanc region (Mann & Lazier, 1996). Clupeids (Sardina pilchardus, the sardine, and Sardinella aurita) were the most abundant. S. pilchards dominate in the cooler northern waters while S. aurita are prevalent in warmer southern waters. Next most abundant were Jack mackerel (Trachurus spp.) and Redfish (Sparidae). Ansa-Emmin (1982) found that in 1974, the total fish landings reached 2.68 million tons. Nearly 1 million tons were Clupeidae with .67 million tons being sardines. Nutrient recycling Phytoplankton over the shelf area either sink to the bottom or are consumed by zooplankton. If they settle to the bottom, phytoplankton release ammonia during their decomposition, which returns nitrogen to the waters. Consequently, the phytoplankton remains could be consumed by benthic dwellers, which also excrete ammonia. If consumed by zooplankton, nitrogen from the phytoplankton will be returned to the environment via excreted ammonia or fecal pellets, which settle to the bottom. Regardless of the mechanism, a high proportion of phytoplankton nitrogen ends up being released in the shoreward-moving lower layer of the water column (Mann & Lazier, 1996). This water will later be upwelled and can stimulate further primary production. Barber and Smith (1981) estimated that on the shelf off Cap Blanc, regenerated nitrogen accounted for 72% of total nitrogen. See also Portugal Current Christopher Columbus Madeira Elmina Castle Voyages of Christopher Columbus Eastern boundary current References Ansa-Emmin, M. (1982) Fisheries in the CINECA region. Rapp. P.-v. Reun. Cons. Int. Explor. Mer. 180: