Thea Linke

This study has explored the extent to which the predominant faunal component of the diet (benthic macroinvertebrates) of the large, long-lived estuarine-resident Acanthopagrus butcheri is related to particular prey and predator traits. Focus is placed on the location (infaunal vs epifaunal) and species size category (small vs medium vs large) of the prey and feeding behaviour of A. butcheri. Data on the benthic macroinvertebrates in the stomach contents of A. butcheri in a microtidal estuary (Swan-Canning, Western Australia) are compared with those of macroinvertebrates sampled in the benthos at the same sites and times in eight consecutive seasons using an Ekman grab. The eight most abundant small macroinvertebrate species in the benthic samples were infaunal and, apart from the bivalve Arthritica semen that was ingested by only a few fish, were not fed on by A. butcheri. In contrast, the three most abundant medium and large-sized species in the benthos, the epifaunal bivalves Xenostrobus securis and Fluviolanatus subtortus and infaunal nereidid polychaete Simplisetia aequisetis, were preyed on substantially, with the first ingested by 54% of A. butcheri and contributing over 51% to dietary volume. Although the eunicid polychaete Marphysa sanguinea occurred in only 7% of benthic samples and contributed <0.1% to abundance, this large infaunal species ranked second in contribution to dietary volume (12%). This species and S. aequisetis were preyed on when they emerged in part or wholly above the substrata. The above results imply that, in terms of prey, A. butcheri selects predominantly medium and large epifaunal macroinvertebrate species and those medium to large infaunal polychaetes which, at times, move out of the substrata. This reflects non-emergent infauna being present in essentially all benthic samples and contributing 66% to total abundance, whereas this group was found in only 8% of stomach samples of A. butcheri and contributed only 2% to dietary volume. In contrast, emergent infauna and epifauna contributed 12 and 22%, respectively, to abundance in the benthos, but as much as 22 and 75%, respectively, to the diets of A. butcheri. It is concluded that the marked selectivity of A. butcheri for prey was related to certain prey and predator traits, i.e. size category of prey species, and prey located above the substrata, either permanently or at frequent intervals, and to visual acuity and a fast-swimming angled attack by the predator.

Expectations and patterns of publication have changed markedly with evolving online availability and associated development of new citation gathering databases. Perhaps the most vulnerable components of the scientific literature to ongoing change are books and book chapters, given their elongated publication timelines and generally more limited online availability. To test this, we applied citation analyses and assessments of library holdings to determine the use of the natural history books published by Surrey Beatty & Sons between 1987 and 2010. We (i) evaluated the relative use of book chapters and journal papers by comparing citations to chapters in the five books of the Nature Conservation series by Surrey Beatty & Sons to citations of journal chapters in four Australian journals published in the same years, (ii) determined the efficacy of four different databases in retrieving citations to book chapters by comparing their recovery of citations to the five books of the Nature Conservation series, and (iii) quantified noncitation measures related to library holdings to evaluate the use of the books on the entire Surrey Beatty & Sons list. Mean citations/chapter to the first three books in the Nature Conservation series were similar to the mean citations/paper in four Australian journals published in the same years. However, the mean citations/chapter of the last two books declined relative to citations/paper for the journals, suggesting a fall in book use evident by early this century. Citation retrieval varied across databases; Google Scholar retrieved most citations, followed by Scopus, Web of Science (Cited Reference Search) and Web of Knowledge. Contrary to published concerns, no citations retrieved by Google Scholar were in questionable sources such as contents pages - many were from highly ranked journals. Each book in the full Surrey Beatty & Sons list was held by an average of 45.3 libraries in Australia and 36.1 in the USA, and less than five in each of the UK, New Zealand, Hong Kong, Canada, Germany and South Africa. This was a similar coverage to another Australian publisher, the Royal Zoological Society of New South Wales, and indicated strong markets in Australia and the USA. It was less, though, than the number of libraries with current or past subscriptions to five Australian journals publishing nature conservation content. We conclude that citation data for books and book chapters are available and that library holdings provide another measure of use. The online ‘visibility’ of books may be a problem, but can be improved through better marketing and improved author search techniques.

This presentation will focus on a quantitative scheme for classifying nearshore habitat types and predicting their fish faunas, which has been developed for a range of estuaries in south-western Australia that differ widely in their geographical and geomorphological characteristics. This scheme provides a reliable framework for managers and ecologists to (i) investigate relationships between habitat types and faunal composition at local to regional scales and under different geographic and estuarytype scenarios, (ii) establish benchmarks against which the impact of future environmental change can be assessed and (iii) predict the habitat type and characteristic fauna of any nearshore site of interest within those systems. The habitat classification scheme has been based on the use of enduring environmental criteria that can be easily measured in GIS from mapped data sources such as satellite imagery and bathymetric charts, and has employed novel applications of relatively new multivariate routines. The results of this classification scheme, and the relationships between the derived habitat types and their fish assemblages, will be presented for five estuaries across south-western Australia, namely the permanently open Swan-Canning and Peel-Harvey estuaries, the seasonally-open Broke and Wilson inlets and the normally-closed Wellstead Estuary. Questions regarding the importance of geographical location and estuary type in structuring habitat types and their fish faunas will also be addressed.

The Swan-Canning Estuary is highly valued for its ecological, recreational, commercial and indigenous importance (e.g. Seddon 1972, Swan River Trust 2008, 2009). It supports a diverse range of fish species (several of which complete their life cycles in the system and/or are recreationally or commercially important, e.g. Loneragan et al. 1989, Kanadjembo et al. 2001, Hoeksema and Potter 2006), migratory and resident waterbirds (Bamford et al. 2003), submerged and fringing vegetation (e.g. Hillman et al. 1995, Astill and Lavery 2001, McMahon 2001) and a dolphin population (Lo 2009). The Swan-Canning Estuary and its large (ca 125 000 km2) catchment have been subjected to substantial anthropogenic change since European settlement in the early to mid 1800s, and the system is now classified as highly modified (Commonwealth of Australia 2002). These artificial modifications, combined with the ongoing effects of local population growth and climate change, continue to have a wide range of implications for the water quality of this system. For example, reduced river flow due to damming or diversion of the major tributaries and the effects of climate change, increased tidal exchange through widening and deepening of the estuary mouth and extensive clearing of catchment vegetation, have all contributed to rising salinity throughout this system (Hamilton et al. 2001, Thomson et al. 2001, Chan et al. 2002, CSIRO 2009). Changes in the volumes of marine vs riverine flow have also exacerbated the stratification of salinity and dissolved oxygen concentration within the water column, particularly in the upper estuarine reaches where bottom waters become hypoxic during drier periods of the year (Hamilton et al. 2001, Thomson et al. 2001, http://www.swanrivertrust.wa.gov.au/science/river/Content/plots.aspx). This lack of dissolved oxygen has become so extensive that remedial oxygenation of both the Swan and Canning rivers is now undertaken mechanically (http://www.swanrivertrust.wa.gov.au/ science/river/content/oxygenation.aspx). Widespread land clearing, shoreline modification and the growth of surrounding urban and agricultural activity have also resulted in increased surface runoff from the catchment, and thus also of the sediment, nutrient and pollutant loads entering the estuary. These loadings have also risen due to the vast network of drains servicing residential, farming and industrial areas that discharge into the system, and their impacts are further compounded by the reduced flushing of the estuary due to diminishing rainfall (Jakowyna et al. 2000, Swan River Trust 2003, 2009, Foulsham 2009). The system, and particularly its upper reaches, is now considered to be eutrophic to hypereutrophic (Swan River Trust 2009), and the levels of various non-nutrient contaminants in the sediment exceed ANZECC and ARMCANZ Interim Sediment Quality Guideline Trigger Values at several locations throughout the estuary (Nice 2009).

Three complementary, quantitative approaches, i.e. gut content analyses, stable isotope analyses (δ15N; δ13C) and fatty acid composition, were employed to investigate the extent to which the diets of four abundant species of teleost occupying different feeding niches, i.e. Leptatherina wallacei (pelagic feeder), Acanthopagrus butcheri (bentho-pelagic feeder), Pseudogobius olorum and Favonigobius punctatus (benthic feeders) differed within and among species and within species on temporal and spatial scales in a permanently-open (the Swan-Canning estuary) and a seasonally-open estuary (Wilson Inlet) in south-western Australia. The stable isotope analyses and analyses of fatty acid composition were used to elucidate the origin of energy and the possible pathways of nutrient transfer from potential prey items to these four species of fish. Multivariate methods (non-metric multidimensional scaling ordination and associated tests, such as PERMANOVA, ANOSIM and SIMPER) were used to detect any significant differences in the dietary and biochemical compositions of the fish. Stomach content data for each species demonstrated size-related changes in diet and that the dietary compositions of each species varied among estuaries. Each species was classed as opportunistic and omnivorous, consuming fauna as well as flora, but to differing extents. Leptatherina wallacei fed in the water column as well as on the benthos, while P. olorum almost exclusively consumed benthic prey. The baseline δ15N values of primary producers were higher, in general, in the Swan-Canning estuary than in Wilson Inlet, and the δ15N values in the former system were also higher in each prey and fish species. This fact provided evidence to suggest that anthropogenically introduced nitrogen was present at the system level. The δ13C values showed a higher influence of terrestrially derived carbon and a lesser influence of marine derived carbon in the diet of each prey and fish species in the Swan-Canning estuary than in the aquatic macrophyte fuelled (Ruppia megacarpa) Wilson Inlet. The docosahexaenoic : eicosapentaenoic (DHA:EPA) fatty acid ratio was highest in the pelagic feeder (L. wallacei), lowest in the benthic feeder (P. olorum) and intermediate in the bentho-pelagic feeder (A. butcheri) in both the Upper Swan River and Wilson Inlet, and it was higher in pelagic (e.g. seston, calanoid and cyclopoid copepods, mysids) than in benthic (e.g. annelids, molluscs, harpacticoid copepods) prey in both estuaries, indicating that L. wallacei fed, to a certain extent, on pelagic prey, while P. olorum fed on benthic prey. Therefore, the DHA:EPA ratio may provide a useful indicator of the respective feeding niches occupied by estuarine fish species. The findings from these studies suggest that (1) the food resources are partitioned within and among species and among estuaries, (2) both terrestrial and aquatic sources of organic material support food chains in two estuaries, (3) the DHA:EPA ratio can be a useful indicator of feeding mode and (4) the food resources and the pathways of material transfer from primary producers to consumers differ among these species.

Although Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a valued component of the Swan-Canning Estuary and the Swan Canning Riverpark, little is known about the health and ecology of the small community of dolphins inhabiting the estuary. To improve the scientific basis for management, we examined the population genetics, trophic associations, and contaminant exposure of dolphins within the estuary. This Swan Canning Research Innovation Program (SCRIP) study had the following objectives: (1) detail contaminant concentrations in dolphins (as a baseline for future monitoring); (2) provide a preliminary assessment of health risk posed by contaminants to dolphins; (3) examine trophic pathway associations for Swan River bottlenose dolphin community; (4) use genetic information to examine whether bottlenose dolphins from the Swan-Canning Estuary and adjacent waters (Cockburn Sound) represent one homogenous population or (alternatively) if fine-scale population structuring occurs; and (5) put project findings into the perspective of system ecology and management implications. Tissue samples for this study were obtained through remote biopsy sampling of free-ranging dolphins and the collection of tissues during post-mortem examinations under permits and licences from the WA Department of Environment and Conservation and the Murdoch University Animal Ethics Committee.

Bottlenose dolphins are valued feature of the Swan Canning river system. Sighting data indicate that dolphins use the rivers year-round and range throughout their extent. The 2009 mortality event emphasised the need to improve our understanding of the connections between dolphins and the estuary ecosystem. We address three elements of an ecosystem-based approach to dolphin conservation: (1) environmental influences on dolphins; (2) interactions between dolphins and other biological components; and (3) dolphins as a means to increase community understanding about river health. To investigate environmental influences, we are investigating: (a) the prevalence and severity of tattoo skin disease lesions on known dolphins from the river system and adjacent waters (e.g. Cockburn Sound); (b) spatial and temporal patterns in lesion occurrence; and (c) associations with salinity and other environmental factors. A preliminary investigation into dolphin foraging ecology in 2009 indicated differences between the stable isotope ratios of dolphins associated with the river system and dolphins associated with two coastal sites, and also supported behavioural observations indicating that dolphins associated with the river system are likely to feed on both marine and estuarine-based prey. Climate change and population growth will continue to alter the Swan Canning river system, suggesting that the long-term retention of dolphins as functioning ecological components of this ecosystem will on-going adaptation and change, both by dolphins and by human managing the environment around them.

This technical report reviews findings from an investigation into the mortalities of six bottlenose dolphins (Tursiops aduncus) in the Swan Canning Riverpark in 2009. The report: (a) describes the epidemiology and pathology of these mortalities; (b) presents background information on the ecology of dolphins in the Swan Canning Riverpark and factors known to affect dolphin health; and (c) discusses the potential role of chemical contaminants in the mortalities. These mortalities were investigated in context of dolphin deaths in the Swan Canning Riverpark prior to 2009 and a series of mortalities of dolphins in the Bunbury area between 2008-10, as well as marine mammal mortality events in other locations.