Despite its economic and social importance for Namibia and South Africa, limited documented information exists regarding key aspects of the biology of deep-water hake, including its life cycle. This study utilizes data collected through the demersal surveys of the R/V Dr Fridtjof Nansen in South Africa and F/V Blue Sea 1 in Namibia to describe the migratory patterns of deep-water hake in space and time. Furthermore the study investigates aspects of the life cycle of this important species in the Benguela region. Results show that deep-water hake spawns between the western Agulhas Bank and Elands Bay in South Africa with the main nursery ground between Hondeklip Bay and the northern tip of Orange Banks. Deep-water hake in Namibia (up to the Kunene River) and along the south coast of South Africa (eastwards to Port Alfred) originate from these grounds, and undertake long-range migrations across latitudes and longitudes, respectively. This hypothesis is supported by the finding that spawning has not been observed in Namibia and there are no small juveniles along the South African south coast from the eastern border of the Agulhas Bank. The proposed pattern implies an interconnection between the Namibian and the South African components of the stock and the consequent need for a revision of the present management regime based on the assumption of stocks confined within the respective national jurisdictions. This study has used length frequency distributions in space and time in order to investigate the life cycle, in terms of origin, movement and population structure in particular, an approach that may also be useful for other widely distributed species.
23 December 2006 in Reviews in Fish Biology and Fisheries
Generalised additive models (GAMs) were applied to survey data to assess the influence of dissolved oxygen, water temperature and year of sampling upon the presence/absence of small (≤15 cm TL), me...
A new species of cuttlefish Sepia shazae n. sp. is described from South Africa. It is one of the commonest small Sepia species in South African waters occurring from 29°48'S in the north to 25°E in the east, between 200 and 700 m (only the third Sepia species recorded deeper than 600 m). It is recognised by: four papillae clusters dorsally on the head between the eyes; tubercles, warts and prominent clusters dorsally on mantle; skin between these structures smooth and shiny; cuttlebone lightly calcified, thin and fragile with thin inner cone and broad outer cone. S. shazae has been confused with Sepia dubia Adam et Rees, 1966 and is well represented in the holdings of the Iziko Museum, Cape Town (SAMC) as “S. dubia(?)”. S. dubia is re-described here on the basis of the second known individual, and is recognised by: four turret-clusters on dorsal head; two turrets transversely on mid-dorsal mantle; small warts covering dorsal body; cuttlebone heavily calcified, exceptionally broad, especially posterior phragmocone and outer cone. The holotype of S. shazae is deposited in the South African Institute of Aquatic Biodiversity (SAIAB) and paratypes in SAMC and the Natural History Museum (NHMUK), London. The new individual of S. dubia is deposited in SAIAB (the holotype is housed in NHMUK).
Two species of cuttlefish: Sepia robsoni (Massy) and Sepia faurei Roeleveld, are redescribed based on sexually mature males and females of both species. They were previously known only from their holotypes: male and female, respectively. They belong to a distinct group of small-sized sepiids, all near-endemics of southern African waters. The knowledge of the systematics and biology of this group is still limited despite the long time since the first description (1875). This is because, inter alia, of their small size: not larger than 4 cm mantle length at maturity. Twenty-one individuals of S. robsoni described here were scattered from Port Nolloth area to the Tsitsikamma coast (bottom depth <37–449 m). Eight known individuals of S. faurei came from the eastern Agulhas Bank (bottom depth 116–184 m). S. robsoni can be identified by extremely thinly calcified cuttlebone (transparent); smooth skin of dorsal mantle and head; tips of first pair of arms thick, finger-like, devoid of suckers. S. faurei can be distinguished by the following combination of characters: thick, heavily calcified cuttlebone but with flat and fused inner cone; skin of dorsal mantle and head very densely covered by characteristic warts; thin, whip-like tips of first pair of arms devoid of suckers. All described specimens of both species are deposited in the South African Institute of Aquatic Biodiversity (SAIAB) and in Iziko, South African Museum (SAMC).