Modelling the transport of important artisanal fishery species in the Mozambique Channel

Downey-Breedt, NJ (1), Sauer, WHH (2), Roberts, MJ (3)

1 Rhodes University, Department of Ichthyology and Fisheries Science, PO Box 94, Grahamstown, 6140, South Africa,

2 Rhodes University, Department of Ichthyology and Fisheries Science, PO Box 94, Grahamstown, 6140, South Africa,

3 Oceans and Coasts Research, Department of Environment Affairs, PO Box 52126, Cape Town, 8002, South Africa,

Twenty four regional climate change hotspots have been identified around the globe. These areas are warming faster than 90% of the ocean. One such hotspot occurs in the Mozambique Channel, with a large area affecting the EEZ of Madagascar. Madagascar’s marine environment is an essential source of both food and income to coastal communities. Small scale and artisanal fishing is mainly for subsistence or for local markets. The availability and stability of marine and coastal resources in the region, have already been affected by climate change. This study focuses on two species/groups targeted by artisanal fishers in south- western Madagascar: Octopus cyanea and rock lobster. Individual-based modelling (Ichthyop 3.2) was used to model the transport of the planktonic stages to settlement age (octopus) and puerulus stage (rock lobster) in the Mozambique Channel. Model results are being used to determine main drift routes and the potential impact of climate change; dispersal distance and links to marine reserve size; the potential impact of  climate  change  on  source  and  sink  relationships;  and  genetic  connectivity  between  Mozambique Channel populations. Preliminary data analysis indicates hatching site and season significantly affect successful recruitment. Most octopus paralarvae were recruited to the southwest coast of Madagascar (dispersal distance of ~140 km), with fewer transported to areas further north. Results indicated transport across the Mozambique Channel to the Mozambique coast is possible. The majority of rock lobster phyllosoma were transported to the east African continental shelf, with fewer returning to the southwest coast of Madagascar.

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