Can movement explain spatial patterns in demography of red-throat emperor?

Ashley Williams, Campbell R Davies, Bruce D Mapstone, Ian Montgomery and Garry R Russ

CRC Reef Research Centre, TOWNSVILLE, AUSTRALIA

THEME: ASFB

The red throat emperor (Lethrinus miniatus) is an important commercial reef fish species of the Great Barrier Reef (GBR) Line Fishery. We examined the spatial patterns in demographic parameters of red throat emperor populations among reefs closed to fishing in three regions (Townsville, Mackay and Storm Cay) spread over 3º of latitude on the GBR. In contrast to other coral reef fish, results indicated that age, growth and mortality rates of red throat emperor were relatively similar at the spatial scale of individual reefs within regions, but differed significantly among regions. The Townsville region was characterised by the greatest proportion of older fish, the smallest maximum size, and the lowest rates of mortality. In contrast the Mackay region was characterised by the highest proportion of younger fish, the largest maximum size, and the highest rates of mortality. Demographic parameters for the Storm Cay region were intermediate between the other two regions. Recent genetic studies using microsatellite markers indicate red throat emperor populations on the GBR constitute a single homogenous stock, indicating the significant regional patterns in demography may be a result of regional differences in environmental conditions or historic fishing pressure. Using an age-structured model we explore the potential of adult movements between reefs as a further explanation for the significant regional