Small fish and crustaceans demonstrate a preference for particular small-scale habitats when mangrove forests are not accessible

Availability of large areas of complex habitat (particularly mangrove forest) is an important reason why fish use estuaries as nursery areas. However for aquatic species, access to much of the complex habitat in tidal systems is restricted to short periods of time. Consequently, aquatic species must spend considerable time in ex-forest habitats; habitats available when mangrove forests are not accessible. The objective of this study was to determine the extent to which the availability of particular small-scale, ex-forest habitats influenced the distribution of small fish (< 100 mm FL) and crustaceans. Substantially higher numbers of small fish and crustaceans were recorded from muddy substrata than from sandy substrata. Over muddy substrata, bank architecture such as drains returning water to sub-tidal areas and water depths < 0.375 m strongly influenced the distributions of abundant species, whereas areas of low current velocity and hydrodynamic features had only minor influence on distributions. Similarly, water depths < 0.375 m and bank architecture, such as drains, strongly influenced the distribution of the abundant crustacean taxa. Current velocity and hydrodynamic features had little influence on the distribution of crustaceans. Most of the abundant taxa showed a positive response to small-scale ex-forest habitats that either provided longer access time to complex intertidal habitat and/or shallow water. However it was unclear whether those habitat preferences also provided feeding opportunity, refuge from predation or energetic advantage.