Patch dynamics of the gastropod Strombus luhuanus provides insights on alternative population states of heavily exploited species from the Philippines

Strombus luhuanus is a gastropod species widely distributed in the Indo-West Pacific commonly exploited for food by coastal community.  The species is gregarious with size of aggregations largely determined by habitat... [ view full abstract ]

Strombus luhuanus is a gastropod species widely distributed in the Indo-West Pacific commonly exploited for food by coastal community.  The species is gregarious with size of aggregations largely determined by habitat factors and season.  The aggregating behavior facilitates exploitation of the species with a computed rate of 86.2% which is higher than the rate computed from other exploited species within Southeast Asia.

Population modeling using PRESENCE where aggregations were considered patches, however, showed  a persistence value of  1.01 to 1.25.  While the value may be due to a low detection probability (0.087 to 0.599) as well as low detection probability (0.05 to 0.5) mainly from crypsis and burrowing, aggregations were found to have lower density relative to unexploited ones.  Low density aggregations may be an alternative state to high density aggregations of exploited species occurring as patches in a landscape. High density aggregations are maintained by biological attributes such as seasonal dispersion, high colonization rate and high occupancy probability.   The change from high density state to low density state is facilitated by high harvesting pressure while low detection probability and low extinction rate serve as the sill for change in state.