Commercial and recreational harvests of fish from two eastern Australian coastal rivers, the Richmond and the Clarence, have been compared for the period from March 1988 to May 1989, using commercial fisheries statistics and a roving creel census of daytime recreational anglers. For both rivers, sea mullet (Mugil cephalus) made up about 70% of the commercial catch by weight but was not caught in significant numbers by anglers. Fish species harvested in large numbers by both sectors were yellowfin bream (Acanthopagrus australis), dusky flathead (Platycephalus fiscus), luderick (Girella tricuspidata), sand whiting (Sillago ciliata), mulloway (Argyrosomus hololepidotus) and tailor (Pomatomus saltatrix). For the Richmond River, yellowfin bream, dusky flathead and tailor were harvested principally by recreational anglers; sand whiting were equally shared between fishing sectors, and harvests of luderick and mulloway were dominated by commercial fishers. For the Clarence River, which supports one of the largest estuarine-based commercial fisheries in Australia, tailor were harvested principally by recreational anglers; yellowfin bream, dusky flathead and mulloway were equally shared between fishing sectors, and sand whiting and luderick were taken predominantly by commercial fishers. Although data on recreational fishing throughout Australia are limited, anglers now appear to be the dominant harvesters of several estuarine fish species. As in other parts of the world, the numbers of recreational anglers in Australian waters appear to be increasing, and this situation is likely to lead to both heightened conflict between the user groups and increased exploitation of a limited resource. The need for sustained and cost-effective monitoring of recreational angler effort and harvests is emphasized.

1. Planning for the conservation of river biodiversity must involve a wide range of management options and account for the complication that the effects of many actions are spatially removed from these actions. Reserve design algorithms widely used in conservation planning today are not well equipped to address such complexities. 2. We used process-based models to estimate the expected persistence of river biodiversity under alternative catchment-wide management scenarios and applied it in the Hunter Region (37 000 km 2 ) in southeastern Australia. 3. The biological condition of 12 197 subcatchments was estimated using a multiple linear regression model that related assessments of the integrity of macroinvertebrate assemblages to human-induced disturbances at river sites. The best-fit model (R 2 = 0.76) used measures of both local and catchment-wide disturbances as well as elevation and distance from source as predictor variables. Based on the outputs of this model, we estimated that substantial loss of river biodiversity had occurred in some parts of the coastal fringes and the lower parts of the larger river systems. The most affected river type was small, lowgradient streams. 4. The predicted biodiversity condition together with river types based on macroinvertebrate assemblages and abiotic attributes was used to estimate a biodiversity persistence index (BDI). 5. A priority value for each subcatchment was calculated for different actions by changing the disturbance values for that subcatchment and calculating the resulting marginal change in regional BDI. Maps were thereby created for three different types of priority: catchment protection priority, catchment restoration priority and river section conservation priority. 6. The subcatchments of high catchment protection priority for river biodiversity were mostly in the uplands and within protected areas. The river sections of high conservation priority included many coastal lowland rivers in and around protected areas as well as many upland headwater streams. Subcatchments of high priority for catchment restoration were mostly in coastal areas or lowland floodplains. 39 7. This approach may be particularly well suited to guide the integrated implementation of three place-based protection strategies proposed for freshwaters: focal areas, critical management zones and catchment management zones.

Environmental flows were released to the Macquarie Marshes (*210,000 ha) in north-west NSW of Australia between October and December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black rolypoly. At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a 6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7-14.8 mg l -1 , followed by more gradual increases in total phosphorus (mean concentrations 0.6-0.8 mg l -1 ) and DOC (26.1-50.2 mg l -1 ) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations of nutrients and DOC, attaining mean densities of (6.0-6.9) 9 10 6 cells ml -1 of planktonic bacteria and (80.7-81.4) 9 10 3 cells ml -1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes, over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton.

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Eastern king prawns (Penaeus plebejus) migrate north from estuaries along the eastern coast of New South Wales and are subject to fishing during this migration. A constant-parameter deterministic compartmental model of the northward migration is described in which the compartments are zones of constant latitudinal width. Assumptions made for each zone are similar to those made for the Baranov catch equation, in which the population decays exponentially through constant instantaneous rates of natural mortality, fishing mortality and emigration. However, in addition to these assumptions, emigration from each zone is assumed to replenish the population in the next zone to the north. This results in the dynamics of the population being described by a system of constant-coefficient linear first-order differential equations. The solutions of this system and of equations for cumulative catch are given in a form that allows the model to be generalized to other migration patterns as a multi- zone analogue of the Baranov catch equation. A discretized form of the model with a restricted parameterization is used to analyse tag-return data from four tag releases. Estimated parameters are used in a yield-per-recruit analysis of prawns recruited to the ocean fishery from Botany Bay.