Meager, J.J.; Loneragan, N.R.; Vance, D.J. and Williamson, I. (2000). Microhabitat distribution of juvenile banana prawns (Penaeus merguiensis) within a mangrove forest and selection for vegetative structure. Meeting on Mangrove Macrobenthos, Mombasa Kenya. September 7-11, 2000.

The microhabitat distribution of juvenile banana prawns (Penaeus merguiensis) was examined in a mangrove forest in southeast Queensland, Australia. The mangrove forest was dominated by Avicennia marina and Aegiceras corniculatum, with a dense cover of mangrove pneumatophores, leaf litter, small seedlings and mangrove debris. The overall objective was to test whether banana prawns chose different microhabitats within a mangrove forest during high tide. Both field and laboratory experiments were carried out to test the hypothesis that banana prawns selected mangrove structure over non-vegetated substrate.

Densities were compared between vegetated and non-vegetated (cleared) microhabitats, in sites located on the mangrove-creek fringe (5-8 metres into the forest) and a further 25 metres into the forest (termed inland). Prawns were sampled by 3 m x 3 m lift-nets, that were activated at the top of the flood tide. Two nets were set in each treatment and sampling was repeated fortnightly over three spring tides (March and April, 2000). A further three samples were taken fortnightly from the mangrove-creek fringe during April and May, 2000 when diurnal tidal heights were lower. The distribution and abundance of banana prawns in the adjacent creek were also monitored during both high and low tide using a small beam trawl.

A large size range of banana prawns moved into the mangrove forest at high tide (2 to 13.5 mm carapace length) and the maximum density recorded was 100 prawns 100m-2. Significantly greater numbers of prawns were caught at the mangrove-creek fringe (mean ± SE: 29.17 ± 6.05 prawns 100m-2), than at the inland sites (0.93 ± 0.93 prawns.100m-2). However, catch rates of banana prawns did not differ between vegetated and cleared sites and no interaction of microhabitat and position occurred.

The habitat preferences and behaviour of juvenile prawns were further investigated in the laboratory. These experiments took place in a tank (1.8 m diameter) divided into four habitats; simulated A. marina pneumatophores, leaf litter, debris and non-vegetated substrate. The behaviour and location of 10 prawns were monitored over a two-hour period and the experiment was repeated with different prawns five times for each prawn size class (3-6 mm, 6-10 mm and 10-14 mm carapace length), and during both day and night. ANOVA indicated that juvenile banana prawns of all sizes demonstrated a preference for simulated mangrove structure over non-vegetated substratum (during day and night).

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