Large and small-scale movement patterns of the West Coast rock lobster, Jasus lalandii.

The primary focus of this thesis was to investigate the movement patterns of the South African West Coast rock lobster, Jasus lalandii, using a diverse range of techniques. These were (1) an examination of long-term data from an ongoing tag-recapture program, (2) observations on rock lobsters in a mesocosm aquarium, (3) surveys that monitored the seasonal fluxes in activities and abundance of rock lobsters in the field, (4) video recordings of movement behaviour in small aquaria and (5) acoustically tracking the movements of four individual rock lobsters. On the West Coast of South Africa, large-scale movement (Le. > 10 km) of J. lalandii (> 70 mm carapace length), was examined using a database of tag-recaptures from 1968 to 2000. Only 0.5 % of rock lobsters recaptured over this period had moved more than 10 km, with 0.3 % moving southeastwards and 0.2 % north-westwards. The data fail to provide evidence for the hypothesized largescale south-eastward migration of rock lobsters from the West Coast to settle on the South Coast, east of Cape Hangklip. Rock lobsters were monitored in a mesocosm aquarium that closely resembled the natural habitat of the species, but contained a high density of predatory fish. Shelter fidelity, tendency to aggregate with conspecifics and crepuscular movements were observed under these conditions. The rock lobsters displayed high levels of shelter fidelity, rarely exchanging shelters more than once. They tended to aggregate in the largest shelters available, and there was no indication of crepuscular foraging behaviour. In this environment, they consumed predominantly algae, which were available in or near shelters. The behaviour of rock lobsters in this experiment was considered to be strongly influenced by the intense predation levels in the aquarium. Monthly observations of rock lobsters in the field in the area east of Cape Hangklip were used to examine seasonal small-scale movement patterns, hole andlor site fidelity, activities and changes in the abundance of lobsters of different size and sex, comparing a marine reserve and a non-reserve area. No fidelity to shelters was evident, nor was site fidelity detected at the scale examined (an area of 1250 m 2 ). Ovigerous females moved inshore during winter months, but as summer approached and females reached the stage where they would release their larvae, males became more abundant inshore at both the reserve and non-reserve sites. Large rock lobsters (> 80 mm CL) were more abundant at the reserve site compared to the non-reserve site during both the open and closed recreational fishing seasons. The lobsters in this area had relatively low gut-fullness indices and predominantly fed on algae, which reflects the apparent scarcity of more suitable prey items. The influence of acoustic transmitters on the movements of J. lalandii (> 85 mm CL) was tested in laboratory aquaria in the absence of predators. Simultaneously their behaviour was observed near to vs. far from shelters. The acoustic transmitters had no effects on the behaviour of the rock lobsters which moved equal distances and at equal speeds whether they carried transmitters or not. Lobsters moved significantly faster when far from shelters, compared to movements near shelters. Unless the lobsters were foraging on food placed far from shelters, most of their time was spent in or near shelters. These behaviour patterns are probably means of minimizing risks associated with exposure. Acoustic tracking of four rock lobsters for up to 32 days revealed an average rate of movement of 15.5 mlday and a maximum movement of212 mlday. The furthest distance moved by a rock lobster tracked over 32 days, was 1146 m. The results showed that the acoustic tracking technique has excellent potential for monitoring the movements of J. lalandii. Future studies using this technique are strongly recommended and should include extended tracking periods, tracking experimentally displaced rock lobsters and the movements of rock lobsters in response to a red tide.