Horse Mackerel Hydroacoustic Survey on the Africana Voyage 107, October 1992

The Horse Mackerel Hydroacoustic Survey was conducted on the Africana Voyage 107 from 07-23 October 1992. The objectives of the survey were to obtain a hydroacoustic estimate of horse mackerel abundance in the area between East London and Mossel Bay; to obtain acoustic estimates of anchovy and pilchard abundance east of Mossel Bay to assist in the design of the pelagic spawner biomass survey in November; to obtain a target strength/length relationship for horse mackerel and target strength data for anchovy and pilchard; to collect biological data pertaining to horse mackerel; to investigate the foraging behaviour of horse mackerel and food preference of pilchard; to test for relationships between horse mackerel movement and near-surface and mid-water currents, and to add to the ADCP data base for the southeast coast; to measure thermal salinity structure of the water column and to measure basic biotic parameters (oxygen, nutrient and chlorophyll); to collect data from the satellite imager on the large-scale influence of the Agulhas current; to sample mesopelagic fauna off the shelf with a number of ad hoc deep trawls; and to characterise zooplankton patches acoustically on a number of cross-shelf transects.