A new species of electric ray of the genus Narcine Henle, 1834 from the South-Western Indian Ocean (Chondrichthyes: Torpediniformes: Narcinidae)     

《African Journal of Marine Science》2013,35(1):135-144

The Namibian linefishery is a multisector fishery, with recreational and commercial sectors targeting overlapping species. Prior to 1990, catch data were recorded for the boat sector, but little research was done on the population dynamics of any of the species. Hence, none of the stocks were assessed owing to the lack of parameter estimates for fisheries modelling. Current management regulations for the Namibian linefishery are therefore not based on scientific investigations but, for historical reasons, were adapted from South African legislation for similar species. From 1994, linefish research in Namibia focused on the life history and population dynamics of silver kob Argyrosomus inodorus and West Coast steenbras Lithognathus aureti, important species in both commercial and recreational sectors. A roving-roving creel survey was used to determine effort and catches of recreational shore-anglers. Both species were assessed using yield-per-recruit models. Based on the results, reduced daily bag limits and the implementation of size limits for the recreational sector were proposed. For the commercial sector, the introduction of a total allowable catch would seem to be the best option. Results from an economic survey indicated that the recreational sector earns six times more for the country annually than the commercial sector.  相似文献   

The effects of Qatar crude oil on reproductive success in the sand-prawn Callianassa kraussi under static aquarium conditions     

《African Journal of Marine Science》2013,35(1):89-97

The reproductive success of Callianassa kraussi exposed to a water-soluble fraction of Qatar crude oil was investigated on the basis of embryonic development, hatching success, larval development and survival of post-larval stages. Embryos showed a number of abnormalities, of which only one occurred in numbers that could be related to oil exposure (concentration and duration). These abnormalities were directly reflected in the reduced hatching success (as little as 25 per cent under the worst conditions). The percentage of larvae surviving the two moults to become juveniles was also considerably reduced, while the survival of juveniles at the sublethal experimental levels was found to be directly linked to their history of exposure. It is anticipated that C. kraussi populations, because of several unusual features in their breeding ecology, would suffer long-term damage should the extent of larval recruitment to adult populations be reduced as a result of chronic exposure to oil.  相似文献