Re-establishing recreational prawning in the Swan-Canning Estuary

This project builds on the work of a previous Recreational Fishing Initiatives Fund Project to pilot the culture and of the Western School Prawn (Metapenaeus dalli) in to the Swan-Canning Estuary and increase interest in prawning via a citizen science/community engagement project. Having developed, for the first time, successful aquaculture techniques for this species in the former project, the current project utilised these techniques to release ~2 million hatchery-reared post-larval M. dalli in to the Swan-Canning Estuary. It also produced good-quality data to inform the management of this iconic species, re-engaged community with the prawns and stewardship of the estuary through a citizen science program (Prawn Watch) and developed a refined citizen science monitoring program for M. dalli that could be used in the future

Estimating predation rates of restocked individuals: The influence of timing-of-release on metapenaeid survival

Abstract The success of aquaculture-based enhancement programs is greatly influenced by the survival of released individuals. Immediate post-release mortality through predation is one of the greatest obstacles to the success of releases, and the choice of a release site or time-of-release can be critical in maximising survival. This paper develops a quantitative method of estimating predation rate to inform release programs, and describes its use in determining whether hatchery-reared Western School Prawns Metapenaeus dalli should be released into the Swan-Canning Estuary in temperate south-western Australia during the night or day. Fish faunal composition was determined during the day and night, both before and after the release of ∼130,000 postlarval M. dalli. Far greater numbers of species and individuals were recorded at night. Stomach contents of 16 abundant teleost species were estimated volumetrically (%V) and any postlarval M. dalli counted. Although diet varied among species, diel phase and size class, crustaceans (including M. dalli) were a key dietary component (>10%V) of 12 species. The data on the abundance of these fish species and the number of M. dalli they consumed were combined and bootstrapped to estimate the total relative number of M. dalli consumed at the time-of-release. The results indicated that while six species consumed M. dalli, two species, Ostorhinchus rueppellii (Apogonidae) and Atherinomorus vaigiensis (Atherinidae), were responsible for ∼99% of the predation, and that the total number of postlarval prawns consumed was 288% higher at night than in the day. These findings suggest that releasing M. dalli during the day will greatly reduce predation and consequently allow a greater survival rate at this release site. The simple methodology developed here could be readily employed to inform release strategies for other species

Influence of physico-chemical and biotic factors on the distribution of a penaeid in a temperate estuary

The distribution, abundance and size structure of a penaeid with tropical affinities (Metapenaeus dalli) was investigated in a temperate, microtidal estuary in south-western Australia. Sampling was conducted every lunar month for two years at 20 sites across five regions (nine subregions) in nearshore waters by hand trawl, and at 16 sites across four regions (eight subregions) in offshore waters by otter trawl. Densities of M. dalli changed markedly seasonally, with greatest values recorded in nearshore waters from October to February, and in offshore waters from March to July. These densities also varied spatially, with the highest recorded in the Lower Canning, Middle Swan, and Upper Melville Water regions. Spearman's rank correlation showed a positive relationship between the density of M. dalli in nearshore waters and surface water temperature in all nine subregions, whilst densities of M. dalli in offshore waters were negatively correlated with bottom water temperature in most of the estuary; these correlations reflect the movement of adult prawns into shallow waters for breeding in summer, as well as the subsequent recruitment and movement back into deeper waters over the winter months. Mean carapace lengths remained relatively unchanged over the late autumn and winter months (May to August), before rapidly increasing with temperature in late spring. The spatial and temporal distribution of M. dalli differed significantly from those of other crustaceans in the estuary, particularly the penaeid Penaeus latisulcatus, which was concentrated mainly in the Lower and Upper Melville Water regions. The distribution of M. dalli was statistically indistinct from that of the apogonid Ostorhinchus rueppellii, which predates heavily on postlarval M. dalli, and very similar to those of two scyphozoans, Aurelia aurita and Phyllorhiza punctata, that likely predate on larval M. dalli. These findings highlight the partitioning of species within the estuary and the significance of site selection for maximising the post-release survival of hatchery-reared M. dalli produced by aquaculture-based enhancement programs

Restocking of the Western School Prawn (Metapenaeus dalli) in the Swan Canning Riverpark

This report provides the first comprehensive investigation into the biology and ecology of the Western School Prawn (Metapenaeus dalli) in the Swan-Canning Estuary in south-western Australia. It provides knowledge to help manage the fishery and evaluate release strategies for the aquaculture-based enhancement of this species. The study involved Murdoch University, the Department of Biodiversity, Conservation and Attractions (DBCA) (formerly Department of Parks and Wildlife and the Swan River Trust) and the Australian Centre for Applied Aquaculture Research (ACAAR). It was designed to complement a concurrent project to develop aquaculture techniques to produce and release M. dalli and re-engage the local community with prawning and the estuary (led by ACAAR, DBCA’s Parks and Wildlife Service and the West Australian Fish Foundation), funded by the Recreational Fishing Initiatives Fund. The Fisheries Research and Development Corporation provided matching funds for the current study. Biological data on M. dalli were collected from 20 sites in nearshore and 16 in the offshore waters of the Swan-Canning Estuary, ranging from the mouth of the system to ~40 and 30 km upstream in the Swan and Canning rivers, respectively, in every lunar month between October 2013 and March 2016. Laboratory studies were also completed to investigate the survival and growth of larval prawns in different salinity, water temperature and algal food conditions. Results were presented as part of the Prawn Watch program to engage the community in the research and encourage stewardship of the fishery and the estuary

Forestry impacts and the vertical distribution of stream invertebrates in south-western Australia

1. Vertical distributions of invertebrates (> 53 μm) were compared between two logged and two undisturbed headwater streams in south-western Australia. The abundance and composition of invertebrates from core samples (4 cm diameter, 30 cm depth) were determined at intervals of 0-1 cm, 1-5 cm, 5-15 cm and 15-30 cm. 2. In addition to examining the effects of clearfell logging, this study provides the first description of the interstitial communities of Australian sandy streams. The interstitial fauna of the undisturbed streams were concentrated in the upper 5 cm of the bed and were numerically dominated by nematodes, a characteristic more typical of marine and lentic habitats than lotic systems. 3. The invertebrate community structure was substantially altered in the logged streams, with fewer taxa collected than in undisturbed streams. Invertebrate densities in the logged and undisturbed streams did not differ in the upper 5 cm of the bed, but, below this, densities were significantly lower in the logged streams. Increased sedimentation did not appear to be responsible for the differences in community structure between logged and undisturbed streams. 4. The impact of clearfell logging to the extent shown here has not previously been demonstrated in south-western Australia. As a consequence it is strongly recommended that sampling of the benthic meiofauna is included in future biomonitoring protocols for the sandy streams of this regio

Sensitivity of Daphnia carinata Sensu Lato to the Insect Growth Regulator, Pyriproxyfen

This paper reports the sensitivity ofDaphnia carinatasensu lato to pyriproxyfen, a promising chironomid control agent. Neonates exposed to pyriproxyfen in acute toxicity trials produced 48-hr LC50of 0.08 ppm, eight times the concentration known to control the emergence of nuisance chironomids. However, continuous exposure to pyriproxyfen (0.01 ppm) during a 3-brood, 14-day life cycle test, suppressed the growth ofD. carinataand reduced reproduction by as much as 80%

The Fish Community Index: A Practical Management Tool for Monitoring and Reporting Estuarine Ecological Condition

Indicators of ecological health based on biological communities, including numerous multimetric indices, are used worldwide to assess and report the condition of aquatic ecosystems such as estuaries. Yet, these tools have rarely been applied to support estuary management in Australia. We present a case study of one such multimetric indicator, the Fish Community Index (FCI), which was developed and applied to quantify the ecological condition of estuaries in southwestern Australia (SWA). We outline the rationale, development, and implementation of the FCI for annual monitoring and reporting of the ecological condition of a highly urbanized estuary, highlighting the key research and management outcomes that it has delivered, and evaluating its potential future applications to support estuary management more broadly, both across Australia and internationally. The FCI is founded upon a conceptually simple and scientifically robust rationale and is sensitive to the ecological stressors that affect many estuaries across the region (e.g., hypoxia, algal blooms). Together with an accompanying annual fish monitoring regime, the FCI provides managers with a consistent, robust basis for quantifying and reporting spatiotemporal changes in estuary condition, with easily comprehensible outputs that facilitate communication with stakeholders, ranging from politicians to the general public. We attribute the successful implementation of this management tool to several characteristics, namely 1) support from a long‐term, collaborative partnership between managers and researchers; 2) comprehensive testing and validation of the index prior to implementation; 3) a robust, standardized monitoring regime; and 4) sustained resourcing from managers to implement the index as part of a reporting framework. The FCI has also been applied to other SWA estuaries and could provide a platform for more coordinated assessment and reporting of estuarine condition at the bioregional scale, thereby helping to improve the gap in reporting on the biotic integrity of Australian estuaries

Evaluation of the Juvenile Hormone Mimic Pyriproxyfen (S-31183) Against Nuisance Chironomids (Diptera: Chironomidae), with Particular Emphasis on Polypedilum nubifer (Skuse)

Laboratory bioassays of the juvenile hormone mimic pyriproxyfen against late instar larvae of the nuisance chironomid Polypedilum nubifer revealed that 0.01 ppm pyriproxyfen caused a 90% inhibition of emergence of this species. A field trial of pyriproxyfen at 0.01 ppm was conducted using in situ enclosures. Pyriproxyfen significantly reduced the emergence of P. nubifer and another chironomid, Kiefferulus intertinctus (Skuse), for 24 d. Larval abundances of these species were not affected by the pesticide application. Pyriproxyfen may provide a satisfactory alternative pesticide to organophosphate control agents currently in use, particularly in highly eutrophic wetlands

Opportunistic foraging by three species of cormorants in an Australian estuary

Aspects of the feeding biology of three species of cormorant (Phalacrocorax melanoleucos, P. sulcirostris and P. varius) were investigated in the large Peel-Harvey Estuary in south-western Australia in April and October 1986 and January 1987. The duration of dives by each species increased with depth and at each depth was greater in P. varius than in the two smaller species. Differences in the ranges of depths in which the similarly sized P. melanoleucos and P. sulcirostris fed would have reduced any potential interspecific competition for feeding space and food. The dive-rest ratio was similar (2.6–2.8) in all three species. Comparisons between the diet of each cormorant species and the potential prey where foraging occurred demonstrated that all three cormorant species were opportunistic feeders, ingesting predominantly small, slow-swimming, benthic-feeding fish and crustaceans. The small size of the prey was limited by the small dimensions of the gullet. There was no evidence that any of the three cormorant species were likely to exert a pronounced adverse effect on the abundance of the major commercial fish in the estuary or on the food of these teleosts

Aquatic fauna of the Warren bioregion, south-west Western Australia: Does reservation guarantee preservation?

The Warren Bioregion, in the extreme south-west of Western Australia, has a unique assemblage of aquatic invertebrates, fish and amphibians. Current literature indicates that 192 fully described species have been collected, of which 10 invertebrate, 1 fish and 6 frog species could be considered locally endemic. We estimate that secure nature reserves (A-Class and National Parks) in the Warren Bioregion provide a refuge for 86% of the aquatic faunal elements. Reservation alone, however, may not be sufficient to protect certain of the aquatic fauna. Adverse impacts occurring within catchments, including erosion and deposition of sediment, salinization, fire, land clearing, the presence of dams and the introduction of exotic fish, may adversely affect the aquatic fauna within a reserve. Management of protected habitats must ensure that only anthropogenic activities which are sympathetic to the long term persistence of all elements of the biota occur within, and adjacent to, the reserve system