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greatest. Periphyton is mostly composed of diatoms, epiphytic algae, bacteria, fungi and protozoa and builds up as a food source for snails on submerged waterplants and on the undersides of floating plants. Highest densities of Gyraulus gilberti (15/m) occurred in permanent creeks such as Ross River. Thus, rather fortuitously, likely recreational sites such as Big Bay and Ti-Tree Bay along the northern foreshore were relatively safe, especially if some vegetation cleating was added. Austropeplea was never collected from bare areas. Although infected snails were collected at all times of the year, the greatest densities of Austropeplea occurred during the late dry season. Blair and Finlayson (1981) noted the catastrophic effect of heavy wet season rainfall on Austropeplea populations at the Ross River dam in 1978 due to substrate scouring and vegetation clearing. It is likely that since Austropeplea were mainly associated with ponded habitats, maximum densities were influenced considerably by dry season habitat shrinkage as well as by food concentration. In contrast, peak densities of Amerianna and Gyraulus were recorded during the late wet seasons of 1992 and 1993. In terms of surveillance, the prevalence of infection within each size class of snail provided a handy indicator to streamline efforts. For Austropeplea lessoni, for example, 80 per cent of snails of 20 mm or greater shell length were infected with trematodes, 39 per cent of these being with Trichobilharzia spp. For the Ross River dam, smaller snails, i.e. < 3 mm for Gyraulus gilberti, < 6 mm for Amerianna carinata and < 10 mm for Austropeplea lessoni, need not be collected (Hurley et al. 1994).
DOI link for greatest. Periphyton is mostly composed of diatoms, epiphytic algae, bacteria, fungi and protozoa and builds up as a food source for snails on submerged waterplants and on the undersides of floating plants. Highest densities of Gyraulus gilberti (15/m) occurred in permanent creeks such as Ross River. Thus, rather fortuitously, likely recreational sites such as Big Bay and Ti-Tree Bay along the northern foreshore were relatively safe, especially if some vegetation cleating was added. Austropeplea was never collected from bare areas. Although infected snails were collected at all times of the year, the greatest densities of Austropeplea occurred during the late dry season. Blair and Finlayson (1981) noted the catastrophic effect of heavy wet season rainfall on Austropeplea populations at the Ross River dam in 1978 due to substrate scouring and vegetation clearing. It is likely that since Austropeplea were mainly associated with ponded habitats, maximum densities were influenced considerably by dry season habitat shrinkage as well as by food concentration. In contrast, peak densities of Amerianna and Gyraulus were recorded during the late wet seasons of 1992 and 1993. In terms of surveillance, the prevalence of infection within each size class of snail provided a handy indicator to streamline efforts. For Austropeplea lessoni, for example, 80 per cent of snails of 20 mm or greater shell length were infected with trematodes, 39 per cent of these being with Trichobilharzia spp. For the Ross River dam, smaller snails, i.e. < 3 mm for Gyraulus gilberti, < 6 mm for Amerianna carinata and < 10 mm for Austropeplea lessoni, need not be collected (Hurley et al. 1994).
greatest. Periphyton is mostly composed of diatoms, epiphytic algae, bacteria, fungi and protozoa and builds up as a food source for snails on submerged waterplants and on the undersides of floating plants. Highest densities of Gyraulus gilberti (15/m) occurred in permanent creeks such as Ross River. Thus, rather fortuitously, likely recreational sites such as Big Bay and Ti-Tree Bay along the northern foreshore were relatively safe, especially if some vegetation cleating was added. Austropeplea was never collected from bare areas. Although infected snails were collected at all times of the year, the greatest densities of Austropeplea occurred during the late dry season. Blair and Finlayson (1981) noted the catastrophic effect of heavy wet season rainfall on Austropeplea populations at the Ross River dam in 1978 due to substrate scouring and vegetation clearing. It is likely that since Austropeplea were mainly associated with ponded habitats, maximum densities were influenced considerably by dry season habitat shrinkage as well as by food concentration. In contrast, peak densities of Amerianna and Gyraulus were recorded during the late wet seasons of 1992 and 1993. In terms of surveillance, the prevalence of infection within each size class of snail provided a handy indicator to streamline efforts. For Austropeplea lessoni, for example, 80 per cent of snails of 20 mm or greater shell length were infected with trematodes, 39 per cent of these being with Trichobilharzia spp. For the Ross River dam, smaller snails, i.e. < 3 mm for Gyraulus gilberti, < 6 mm for Amerianna carinata and < 10 mm for Austropeplea lessoni, need not be collected (Hurley et al. 1994).
ABSTRACT