Environmental factors influencing the recruitment and catch of tropical Panulirus lobsters in southern Java, Indonesia

Tropical Panulirus lobster fisheries in many parts of the world are open-access and poorly-regulated. This is in part because tropical Panulirus lobsters have an extended pelagic larval phase (up to 9 months) and their larval settlement may take place in different habitats and depths. When recruits of a fishery are believed not spawned locally, regulatory incentives are weak. We assessed the potential sources of recruits to a small, valuable fishery for six species of Panulirus lobster in southern Java, Indonesia with a larval advection model. The model predicted that between 1993 and 2007, 50–90% of the recruits were sourced locally compared to a mean of 25% from remote locations. The relative intensity of the Indonesian flow-through, the south Java current and seasonal onshore winds appear to be important in the local retention of recruits. Local fisheries records showed a strong seasonality in catch that we compared to potential environmental triggers with boosted regression trees. We found that the increased catch was associated with the rapid onset of increased rainfall (>90 mm) at the start of the monsoon (November–May). Fishers believe the coastal runoff during periods of high rainfall increases turbidity and thus enhanced catchability. Catches declined dramatically during an extended monsoon in 2010–2011, but recovered in early 2012 when rainfall patterns became more seasonal. These combined results show that there may be potential benefit of implementing local fisheries management regulations to increase sustainability. However, their effectiveness may be difficult to detect due to the strong influence of climate and oceanographic variability on both recruitment and subsequent catch.