The upper ocean temperatures in the Angolan-Namibian coastal waters were anomalously high during March 1995, with positive temperature anomalies of up to 8°C. Maximum temperature differences were 30-50 m deep, reflecting a deepening of the thermocline from normal depths of 10-30 m. The unusually warm water mass covered the Angolan coast from Cabinda (5 0 S), the northern limit of the survey area, to at least 24°S off central Namibia. Higher than norma] temperatures were observed as far south as Ltideritz (27°S). Satellite-derived SST and direct observations indicated that the seaward distribution of warm water extended more than 300 km from the coast. Surface drogues released inshore along the central Namibian shelf suggested a maximum southward extension by 3 March 1995. The warm event was associated with observed mortalities in sardine Sardinops sagax, horse mackerel Trachurus trachurus capensis and kob Argyrosomus inodorus off the coast. It also caused a southward displacement of sardine stocks from Ango]a, resulting in an increased availability of pelagic fish in Namibian waters. Conditions have occasionally been anomalously warm in Angolan and Namibian waters in the past, with the last major event in 1984. These events are known as Benguela Nifios, because of their resemblance to the well known Pacific El Niiio. The 1995 Benguela Nino appeared to be associated with a positive subsurface salinity anomaly of 0.5 x 10-3 in Namibian waters and a negative (-4.0 x 10-3) surface salinity anomaly in Angolan waters, thought to be derived from the freshwater input of the Congo River.

No abstract

No abstract

In the present study, a modelling experiment is conducted to simulate the transport of sardine (Sardinops sagax) eggs and larvae in the Northern Benguela. Based on historical and newly obtained data, different scenarios of vertical and horizontal distribution are applied and the effects on retention are discussed. The simulations showed that vertical and horizontal distribution were important for retention of sardine larvae in the Northern Benguela. By using age‐dependent data on vertical distribution, it was shown that retention of particles in the simulation was substantially enhanced compared with a scenario where particles were distributed in the offshore moving Ekman layer. Retention was lowest during October–December (when upwelling intensity is high) and highest during February–April (when upwelling intensity is somewhat lower). When different spawning areas were considered, highest retention was observed in an area near Walvis Bay. It is concluded that the behaviour of sardine larvae is adapted to the circulation system in the Northern Benguela in a way that promotes retention of the larvae in inshore nursery areas.

No abstract