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Marine Ecology Progress Series

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MEPS 232:225-238 (2002)  -  doi:10.3354/meps232225

Long-distance migration of South African deep-water rock lobster Palinurus gilchristi

Johan C. Groeneveld1,2,*, George M. Branch2

1Marine and Coastal Management, Private Bag X2, Rogge Bay 8012, Cape Town, South Africa
2Marine Biology Research Institute, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa

ABSTRACT: Long-term movement patterns of deep-water rock lobster Palinurus gilchristi were investigated off the south coast of South Africa using tag recapture data. Over a 12 yr period (1988 to 1999), 30 043 lobsters were tagged at 5 sites. From west to east, these were Cape Agulhas, West and East Agulhas Bank, Mossel Bay to Port Elizabeth, and Port Alfred. The overall recapture rate was 7.51%, with individuals remaining at large for up to 10.3 yr. Overall, 547 (25.8%) tagged lobsters of both sexes moved >20 km within or between sites. We hypothesized that counter-current migration of juveniles would occur to redress downstream dispersal of phyllosoma larvae by the westerly flowing Agulhas Current. The vast majority of migrants (72.6%) did prove to be immature (carapace length <72 mm) and did migrate eastwards against the prevailing flow of the Agulhas Current. The Cape Agulhas population (at the western extreme) comprised juveniles only. Over 97% migrated >50 km, either southeastwards offshore to the West and East Agulhas Bank sites (106 lobsters, covering a mean distance of 154 km), or eastwards alongshore to the Mossel Bay to Port Elizabeth site near the center of the range (33 lobsters, 461 km). The fastest 5% of migrants moved at 0.43 to 0.78 km d-1. In general, Cape Agulhas migrants reached West Agulhas Bank within 1 yr, East Agulhas Bank within 2, and Mossel Bay to Port Elizabeth within 3 yr. The West Agulhas Bank population comprised mostly juveniles and small mature individuals, and 38% migrated, all moving eastwards, either to East Agulhas Bank (66 lobsters, 46 km), or to Mossel Bay to Port Elizabeth (73 lobsters, 426 km). The easterly migration of P. gilchristi was evident but diminished at East Agulhas Bank, virtually absent at Mossel Bay to Port Elizabeth and non-existent at Port Alfred (at the eastern extreme). There was no evidence suggesting a westwards or return migration at any of the 5 sites. It is concluded that Cape Agulhas is an important settlement area for post-larvae originating between Port Elizabeth and West Agulhas Bank, and that juveniles migrate eastwards to redress the downstream displacement. The Port Alfred population is non-migratory and receives no immigrants from elsewhere, adding to other evidence that it is a separate stock, and it is inferred that phyllosoma larvae from this area use a different larval dispersal and return mechanism.

KEY WORDS: Rock lobster · Migration · Contranatant · Recruitment · Phyllosoma · Agulhas Current · Tag recapture

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