Distribution of two species of sea snakes, 'Aipysurus laevis' and 'Emydocephalus annulatus', in the southern Great Barrier Reef: metapopulation dynamics, marine protected areas and conservation

Abstract

'Aipysurus laevis' and 'Emydocephalus annulatus' typically occur in spatially discrete populations, characteristic of metapopulations; however, little is known about the factors influencing the spatial and temporal stability of populations or whether specific conservation strategies, such as networks of marine protected areas, will ensure the persistence of species. Classification tree analyses of 35 years of distribution data (90 reefs, surveyed 1-11 times) in the southern Great Barrier Reef (GBR) revealed that longitude was a major factor determining the status of 'A. laevis' on reefs (present = 38, absent = 38 and changed = 14). Reef exposure and reef area were also important; however, these factors did not specifically account for the population fluctuations and the recent local extinctions of 'A. laevis' in this region. There were no relationships between the status of 'E. annulatus' (present = 16, absent = 68 and changed = 6) and spatial or physical variables. Moreover, prior protection status of reefs did not account for the distribution of either species. Biotic factors, such as habitat and prey availability and the distribution of predators, which may account for the observed patterns of distribution, are discussed. The potential for inter-population exchange among sea snake populations is poorly understood, as is the degree of protection that will be afforded to sea snakes by the recently implemented network of No-take areas in the GBR. Data from this study provide a baseline for evaluating the responses of 'A. laevis' and 'E. annulatus' populations to changes in biotic factors and the degree of protection afforded on reefs within an ecosystem network of No-take marine protected areas in the southern GBR.