Distribution and abundance of pelagic fish off Spanish Sahara during CUEA expedition JOINT-I

Abstract

Abstract The distribution and abundance of pelagic fish was investigated during Expedition JOINT-I of the Coastal Upwelling Ecosystem Analysis Program. The studies were conducted off Spanish Sahara, primarily along 21° 40′N between 17°05′ and 17°40′W from 31 March to 10 May, 1974. Data on fish abundance were collected with a hydroacoustic system consisting of 120- and 38-kHz echo sounders and a computerized signal processing system. Two congregations of fish were observed, one associated with the upper continental slope and the second at midshelf. The upper slope congregation was primarily horse mackerel (Trachurus sp.) and was associated with high abundance of large (over 500 μm) zooplankton. The second congregation was primarily sardine (Sardina pilchardus) and was distributed coincident with maximum abundance of small zooplankton and phytoplankton. The mean abundance of fish was estimated at 60 g m−2 wet weight over an area of about 4000 km2.