The potential for using acoustic tracking to monitor the movement of the West Coast rock lobster Jasus lalandii

Although acoustic tracking has been used to study the movement of several species of clawed and spiny lobsters, only recent technological advances have provided sufficiently small transmitters to examine the utility of using acoustic tracking as a means to analyse the movement of relatively small spiny lobsters, such as Jasus lalandii. The effect of the transmitter on the mobility of J. lalandii was tested in aquarium experiments and was shown to have no influence on movement in three separate experiments. Thereafter, adult male rock lobsters (86–98mm carapace length) were tracked in field trials for up to 32 days at Betty's Bay (n = 4) and Hermanus (n = 5) off the Western Cape, South Africa. Tracking J. lalandii in the field using acoustic tags was successful, even in areas with dense kelp beds and rocky outcrops. The signal from the transmitters was readily detectable from the surface and subsequent use of underwater tracking equipment enabled visual confirmation of the position of the rock lobsters. Lobsters moved significantly longer distances (>45m day^?1) in the first two days following tagging than during any subsequent time period (<10m day^?1). This suggests that transmitter attachment and/or handling altered the movement pattern for the first 72 hours after tagging. During the period of observation, J. lalandii displayed classical nomadic behaviour.     

Partitioning of a goby resource amongst four avian predators and evidence for altered trophic flow in the pelagic community of an intense,perennial upwelling system

Pelagic gobies Sufflogobius bibarbatus were numerically the most important prey of jackass penguins Spheniscus demersus. Cape cormorants Phalacrocorax capensis and bank cormorants P. neglectus sampled at islands off the South West African coast during the period 1978–1982. These three seabirds feed on small gobies near the surface and some of them can also dive sufficiently deep to catch larger gobies. Their populations at islands north of Lüderitz, where gobies are abundant, have been increasing. Cape gannets Morus capensis feed only on large gobies that are infrequently at the surface, and the gannet population off South West Africa has shown a large decrease since the collapse of the pilchard Sardinops ocellata resource in the late 1960s and early 1970s. In the intense perennial upwelling system situated between 22 and 27°S gobies are believed to have partially replaced pilchards during the 1970s. Both pilchards and gobies are able to feed on large diatoms of the genera Chaetoceros and Delphineis, which dominated the inshore phytoplankton in the early 1970s when biomass levels of both pilchards and gobies were low.     

Exchange of the Wandering Albatross Diomedea Exulans Between the Prince Edward and Crozet Islands: Implications for Conservation

Exchange of 61 wandering albatrosses Diomedea exulans has been recorded between the French Crozet Islands and the South African Prince Edward Islands, 1 068 km apart in the Southern Ocean. Most movements of banded birds (57) have been westwards, from the Crozets to the Prince Edwards. In all, 18 fledglings banded at Possession Island, Crozets, have bred at Marion Island, Prince Edwards, but only one fledgling from Marion Island has been recorded breeding on Possession. The wandering albatrosses of the two island groups form a metapopulation that ideally should be conserved as a single unit. It is suggested that France and South Africa collaborate through the Agreement on the Conservation of Albatrosses and Petrels to effect an improved conservation status for the wandering albatrosses of the two island groups.     

An Analysis of a Modified van der Grinten Equatorial Arbitrary Oval Projection

The choice of a projection for world distributions depends on a number of considerations. Primarily this involves the properties of equivalence and conformality. But there are instances where requirements regarding the use of these mutually exclusive properties would allow a compromise projection. This article presents the mathematical basis, a construction procedure, and an analysis of area and angular deformation of one such projection, a modified van der Grinten.

Mathematical expressions are derived which are used to locate parallels and meridians. Parallels of the modified grid are straight lines located at an increasing distance from the equator. Meridians are arcs of circles intersecting the construction equator truly. Distribution of S and 2ω are shown.