Environmental determinants of faunal ecology in estuarine and low-wooded island mangrove habitats of northeastern Queensland

Three trips were made to Cape York to sample fish in estuarine and low-wooded island mangrove habitats:Trip 1 (December 1995): Jacky Jacky Creek, Olive River, Lockhart River, McIvor River, Night Island Trip 2 (February 1996 - wet season): McIvor River, Lockhart River, Pascoe River, Escape River, Jacky Jacky CreekTrip 3 (June 1996 - dry season): Jacky Jacky Creek, Escape River, Bird Islands, Pascoe River, Lockhart River, King Island, McIvor River, Port Douglas.Water quality parameters were measured at all locations. These included NH4, NO3, TDN, DON, PON, PO4, TDP, DOP, POP, SiO, Chlorophyll a, Phaephyton and suspended solids.In Jacky Jacky Creek, Escape River, Pascoe River, Lockhart River and the McIvor River, fish were sampled with groups of monofilament gill nets, each 33 m long by 4.5 m deep, with stretched mesh sizes of 152, 102 and 51 mm. Multi-panel nets, 30 m long by 2 m deep, with stretched mesh sizes of 19, 25 and 32 mm were also deployed. Upstream sites (2-10km) from the mouth and downstream sites (within 1 km of the mouth) were sampled. Nets were set for up to 11 daylight hours. Catch was recorded on each hourly check by species, size and abundance. Most fish that were alive when removed from the nets were measured and released. Dead fish and unknown species were frozen and retained for identification and gut contents analysis. Food items were identified to general taxa and summarised by frequency of occurrence (percentage of all fish in a taxa having consumed a particular food item). Catch per hour of net deployment was calculated for each net set.At upstream and downstream sites, centered on net deployment stations, continuous measurements were taken using logging instrumentation while nets were in place. DataSonde Hydrolab units were used to track turbidity, oxygen, salinity, temperature and pH. A flow velocity meter (Starflow) was used to track water depth, flow rate and direction. Jacky Jacky Creek, Escape River, Pascoe River, Lockhart River and the McIvor River, were also classified according to bioregion, relative influence of tide at the entrance to the estuary, geomorphology, fishing exploitation, latitude (decimal degrees), direction of outfall and name of receiving waters, tidal range (m), water depth at mouth at midtide (m), salinity (ppt), water temperature (°C), composition of the estuary substrate, area of open water (km²), total area of mangroves (km²), width of estuary mouth (km), catchment area (km²), percent of catchment cleared, maximum elevation in the catchment (m) and average annual rainfall (mm).
 This study was undertaken to:1. quantify relationships between environmental characteristics of watersheds and the relative abundance and community structure of associated faunal communities in mangrove-dominated riverine estuaries of northeastern Queensland2. quantify relationships between environmental characteristics of offshore mangrove islands and the relative abundance and community structure of associated faunal communities on low-wooded islands of the Great Barrier Reef3. determine changes in faunal assemblages in riverine and low-wooded islands over time by comparing past and current surveys, and to provide an opportunity for future comparisons by establishing baseline information4. identify and compare trophic relationships in a variety of mangrove ecosystems5. develop a model for relating the conditional of mangrove faunal assemblages to environmental conditions toward the ultimate goal of predicting the potential impacts associated with proposed developments and resource users.
 Some of these data are used in the publication:Ley JA (2005) Linking fish assemblages and attributes of mangrove estuaries in tropical Australia: criteria for regional marine reserves. Marine Ecology Progress Series 305: 41-57.

Organization: Australian Ocean Data Network