Distribution of juvenile penaeid prawns in mangrove forests in a tropical Australian estuary, with particular reference to Penaeus merguiensis

Abstract

Several species of prawns, including juveniles of Penaeus merguiensis, will move into mangrove forests when the forests are inundated by flood tides. However, we do not know how extensively the prawns use the forests or whether some parts of the forests are more valuable to the prawns than others. We assessed the distribution of juvenile prawns in 3 different mangrove communities in intertidal forests adjacent to a small creek and a river in northern Australia between December 1993 and February 1995. The 3 mangrove communities were dominated, respectively, by the structurally complex Rhizophora stylosa, and the more open Ceriops tagal and Avicennia marina. We used stake nets (100 m long, 2 mm mesh) to sample discrete areas of the mangrove forests, and fyke nets (2 mm mesh) to sample prawns moving through the forests. The area of each stake net site ranged from 430 to 650 m 2 and the distance of the midpoint of each site inland from the creek or river mangrove fringe ranged from 13 to 225 m. A large size range of juvenile P. merguiensis (2 to 21 mm carapace length, CL) was caught in the mangroves and prawns were caught as far as 200 m into the forests. In the creek forest, there was no clear relationship between mangrove community type and prawn catches. The highest densities of P. merguiensis were recorded in the creek and were 28.1 and 27.6 prawns 100 m -2 in Rhizophora sp. and Ceriops sp. forest respectively. The highest mean catches were taken 59 m from the creek mangrove fringe. In contrast to the creek, in the river mangrove forest, there was a clear pattern of catches: the number of P. merguiensis caught decreased with distance into the mangroves and at shallower water depths. We have hypothesised that the distribution of juvenile P. merguiensis inside the mangroves depends largely on the local topography and pattern of water currents within each forest. Large numbers of unidentified Metapenaeus spp. and smaller numbers of M. ensis and P. monodon were also recorded from the samples inside the mangrove forests.

Assessing patterns of fish zonation in temperate mangroves, with emphasis on evaluating sampling artefacts

“…Mangroves have generally been treated as a single habitat unit, the value of which has been inferred from samples taken at 1 stratum (or zone), usually along the seaward edge (Hindell & Jenkins 2004), but fish and invertebrate assemblages may vary strongly with distance into mangrove forests. Fish abundances and biomass may be greater at 'inland' mangrove positions (Ronnback et al 1999), with juvenile fish and prawns moving considerable distances into mangrove forests (Vance et al 1996), depending on topography and current patterns (Vance et al 2002). Conversely, assemblages of epibenthic nekton may be more abundant and diverse along the edge than inner forest regions of mangroves (Vance et al 1996, Meager et al 2003.…”

“…Fish abundance differed little between forest and edge, but species richness and biomass were lower in forest than along the edge. Recent work by Vance et al (2002) shows that differences in faunal abundances among regions within mangrove forests largely depend on local topography and water currents. In our study, water depth within a zone was a poor predictor of fish abundance, species richness, or biomass among sampling occasions.…”

Spatial and temporal distribution of decapod larvae in the subtropical waters of the Arvoredo archipelago, SC, Brazil

“…There is good information on the blue crab in Cheasapeake Bay, USA (EPIFANIO & GARVINE, 2001) and shrimps in Carpentaria Gulf, Australia (VANCE et al, 1990(VANCE et al, , 1998(VANCE et al, , 2002. Decapod larval ecology studies are scarce in Brazil and a proportion of these studies remain as unpublished thesis and monographs of limited availability.…”

Juvenile Penaeid Shrimp Density, Spatial Distribution and Size Composition in four adjacent habitats within a Mangrove-Fringed Bay on Inhaca Island, Mozambique

“…Water depth and sediment type, among others, were the factors most responsible for differences in shrimp abundances between habitats. However, water currents, as suggested by Vance et al (2002), Loneragan et al (1998) and Dall et al (1990) may also have an important influence on shrimp abundance.…”

“…Smaller shrimps are expected to be less active swimmers than bigger shrimps, therefore may be a tendency for net transport to the mangrove edges and mud flats (Vance et al, 2002;Rönnbäck et al, 2002;Loneragan et al, 1998). Data collected during 14 months near the mangrove forest (sand flat habitat) at Saco da Inhaca, also found that sizes smaller than 3 mm CL dominated the catches (Macia, unpublished data).…”