Zooplankton and epibenthic fauna in shrimp ponds: factors influencing assemblage dynamics

Abstract

The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial shrimp (penaeid prawn) pond in subtropical Australia. Physicochemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 mm mesh) varied from 111.7 ind. L À1 (324 mg L À1 ) to 8.3 ind. L À1 (44.2 mg L À1 ). Immediately after the ponds were stocked with shrimp postlarvae there was a rapid decline in zooplankton numbers, particularly the dominant larger copepods. We attributed this to predation by the shrimp postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. Changes in abundance and biomass of the zooplankton assemblage were not correlated with physicochemical characteristics. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m À2 and the biomass at 0.8 g m À2 . Unlike zooplankton, the peaks in abundance of epibenthos did not correspond to the peaks in biomass. This was due to the large differences in the size of the dominant taxa across the season. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples, with amphipods abundance increasing towards the end of the growout. Negative correlations were found between epibenthos abundance and pH and temperature. These relationships were strongly influenced by the high abundances of amphipods and may reflect an effect on the growth of macroalgae in the pond rather than a direct effect on the epibenthos. No correlations were found between epibenthic fauna biomass and physicochemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities, indicating that this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes in abundances of zooplankton or epibenthos assemblages. Zooplankton clearly contribute to the nutrition of shrimp postlarvae immediately after stocking. The establishment of an abundant assemblage of zooplankton before stocking shrimp postlarvae would appear to be beneficial, if not essential. Later in the season, zooplankton and epibenthos apparently contribute little to shrimp biomass. Owing to their relatively low biomass, the consumption of shrimp feeds by epibenthos is likely to be insignificant compared with that of the shrimp.

Feeding behaviour, efficiency and food preference in yabbies Cherax destructor

“…Therefore, it is not surprising that numerous studies have indicated that a diet including zooplankton increases the growth and survival rates in juvenile crayfish and shrimp (Penaeid sp.) (Coman et al, 2003;Geddes et al, 1991;Mitchell & Collins, 1989;Smallridge et al, 1989;Verhoef et al, 1998). It is commonly believed that following the juvenile stage crayfish no longer posses the dexterity to capture zooplanktonic prey (Sierp & Qin, 2001).…”

Zooplankton from shrimp culture ponds in Northeastern Brazil

“…In general, little is known about the zooplankton dynamics in tropical estuaries, and according to Buskey [11], zooplankton rarely have been studied concurrently in tropical or temperate estuaries, even less studies exists on shrimp ponds. Studies of zooplankton in shrimp ponds have shown that these are complex assemblages with rapid temporal changes in structure [4]. The main factors influencing these changes are variations in source of food, predation and the influences of variations in physical and chemical water quality parameters.…”

“…The assemblages found in the studied ponds have a variety of roles within the pond ecosystem. Grazing zooplankton influences the dynamics of pond phytoplankton [4]. Predation of zooplankton by shrimp [22] may transfer a significant proportion of the nutrients from natural biota to the shrimp [23].…”

“…Consequently, this research would provide more data on the use of zooplankton as indicators of water quality. Zooplankton clearly contributes to the nutrition of shrimp postlarvae immediately after stocking [4]. Overall, this paper will be able to provide useful baseline water quality data that may enable the improvement of farm management processes.…”

Limnological assessment of anthropogenic activities of River Henwal

“…Because contamination-resistant species in nutrient-rich water can become dominant, the growth of other species can be inhibited, which can decrease diversity. However, many researchers warn against using the zooplankton diversity index as a measure of water quality and have indicated the drawbacks of using the Shannon-Wiener (H) and Simpson (d) indices to calculate zooplankton diversity (Thessen, 2005;Tiwariand Nair, 1998;Senthil, 2002;Coman, 2003).…”