Mangroves as nursery sites: comparisons of the abundance and species composition of fish and crustaceans in mangroves and other nearshore habitats in tropical Australia

Daytime sampling of mangrove and seagrass (Halophila/Halodule community) habitats every 7 wk at Alligator Creek, Queensland, Australia, over a period of 13 mo (February 1985–February 1986) using two types of seine net, revealed distinct mangrove and seagrass fish and crustacean faunas. Total abundance of fish and relative abundance of small and large fish also varied between habitats and seasonally. Post-larval, juvenile and small adult fish captured with a small seine-net (3 mm mesh) were significantly more abundant (4 to 10 times) in the mangrove habitat throughout the 13 mo of sampling. Mangrove fish abundance showed significant seasonality, greatest catches being recorded in the warm, wet-season months of the year. Relative abundances of larger fish (captured in a seine net with 18 mm mesh) in the two habitats varied throughout the year, but did not show a seasonal pattern. At the same site, small crustaceans were significantly more abundant in the mangroves in all but one dryseason sample. Similar comparisons for three riverine sites, sampled less frequently, in the dry and wet seasons of 1985 and 1986, respectively, showed that in general mangrove habitats had significantly more fish per sample, although the relative abundance of fish in mangroves and other habitats changed with season. Crustacean catches showed a similar pattern, except that densities among sites changed with season. Fish and crustacean abundance in mangroves varied among sites, indicating that estuaries differ in their nursery-ground value. The juveniles of two commercially important penaeid prawn species (Penaeus merguiensis and Metapenaeus ensis) were amongst the top three species of crustaceans captured in the study, and both were significantly more abundant in the mangrove habitat. By contrast, mangroves could not be considered an important nursery for juveniles of commercially important fish species in northern Australia. However, based on comparisons of fish catches in other regions, the results of the present study indicate the importance of mangroves as nursery sites for commercially exploited fish stocks elsewhere in South-East Asia

On the Edge: Coastal Governance and Risk

Coastal zones are not only some of the most populous areas of the planet, but are also some of the most hazardous, facing a wide range of hazards alongside environmental degradation and increasing development pressures. The inter-connectivity of coastal systems, both human and physical, provides particular challenges to risk management, especially in the context of the complex governance regimes of such areas, where contrasting land and marine institutions and policies come together. After a brief overview of traditional approaches to coastal risk management, the chapter focuses on the role and potential of integrated planning and management in facilitating a more balanced and sustainable approach to coastal risk management. Within such discussions the value and potential of Integrated Coastal Zone Management (ICZM) alongside other integrated and spatial planning approaches is explored. ICZM has frequently been endorsed as a means of managing competing resources and ‘wicked’ (multi-dimensional) coastal problems, and so potentially has a valuable role to play. Drawing on a range of examples, particularly from European experiences, the chapter evaluates the extent to which ICZM contributes to coastal risk management. Whilst not a panacea, the chapter concludes that ICZM may be able to facilitate the development of more adaptable and palatable approaches for local communities, much needed in the context of coastal climate change impacts