Transect widths were previously disregarded as a serious source of bias in aerial censuses of Iarge game in northern Namibia. The cumulative number of sightings per species was recorded at increasing distance away from the airraft in recent aerial censuses in our region.
Simulated samples from totaI aerial censuses in Etosha National Park were used to assess inexpnsive sample count methds designed for most large game species in northern Namibia. Random transect samples yielded population estimates with greater precision than systematic or weighted transect samples.
Environmental conditions in the Fish River affect several ecological aspects of Barbus hospes which emphasised the importance of the link between populations in the Fish and Orange Rivers. Higher growth and mortality rates were found for this species in the Fish River compared to those in the Orange River.
A concrete canal, built in 1972 to supply water from the Kunene River to the central parts of Owamboland, is responsible for the transfer of 32 fish species from the Kunene River to Owambo. Most of these fish are at present limited to artificial reservoirs. Only one cichlid species has so far succssfully invaded the oshana system. Turbidity is believed to be the main factor preventing the invasion of Kunene River fish into the oshanas.
Observations were made on a population of dik-dik in Etosha NationaI Park from 1983 to 1986. Most sightings were of an adult pair or a pair and one offspring. More family groups and single females were seen in the cold-dry season than during other seasons. Birth of lambs usually occurred in December and January.
Damara Terns Sterna balaenarum laid two-egg clutches in less than 0.9% of over 500 nests reported in coastal Namibia since 1975. In 1991, during renewed efforts to completely survey Damara Tern population throughout Namibia, a colony was re-discovered at Hottentot Bay in southwestern Namibia.Of 12 nests with eggs at least 4 (33%) had two eggs.
A singIe brown hyaena Hyaena brunnea was found on the fresh carcase of a Cape fur seal Arctocephalus pusillus in the Meob Bay area of the Namib-Naukluft Park, Namibia. Evidence showed that the hyaena approached the seal and killed it by biting and crushing its skull. Although no previous records of this type of predation could be traced, brown hyaena may hunt seals more commonly than is known.
Wild sycamore fiys Ficus sycomorus suffered extensive frost damage in 1989, being the first known occurrence in 25 years. Twenty-five fig trees were monitored for 21 months and the effects of frost were related to minimum temperatures in the riverbed. Sub-zero temperatures affected 20 of the trees and caused up to 90% frost damage to leaves. Foliage affected by frost remained moribund and attached to the branches for the monitoring period. Frost may limit the distribution of sycamore figs in the Namib.
This paper examines some of the more important characteristics of Namibia's commercially important pelagic fish stocks exploited during the 1990 and 1991 seasons. Comparisons of landings in recent years and some broad speculations on the future state of the Namibian pelagic fish stocks are made.
A survey of fishes of the Kunene River along the Namibia-Angola border in 1990-1991 resulted in a total of 69 freshwater and 19 marine species being recorded. Previously Bell-Cross (1982) reported 70 species, Bethune and Roberts (1991) 69 species and Van der Waal(1991) 63 species. The absence of several species not collected during the survey is attributed to the limited sampling done in floodplain and swampy areas.
Experimental counts of elephants in Etosha National Park wereused to estimate the bias associated with low intensity counting methods developed for this species. Repeated counting of the same area showed that precise population estimates can be obtained from the method used, and that elephants react to survey aircraft by breaking up into smaller groups.
At the present time, resurgence in interest on the part of the ornithological community in conservation issues in general has included, inter alia, a welcome re-awakening in the necessity for the re-appraisal of parapatric pairs and assemblages of species in an avifauna as potentially harbouring currently unrecognised and even undescriptionbed full species!
Most of the recorded specimens of Hemirhagerrhis viperina (Bocage) have been examined and compared with abundant material of H. nototaenia from central Africa. H. viperina can he most readily distinguished by its relatively short tail and colour pattern, but there are also average differences in several head shield characters.
A new species of Coluber (sensu lato) is descriptionbed from near the Cunene River in northern Namibia. The genus has not previously been recorded south of Kenya. This snake appears to be most closely related to C. florulentus which occurs 3 000 km to the north, but it differs in its strongly-handed pattern, suggesting mimicry of the Zebra Spitting Cobra Naja nigricollis nigricincta.