Academic literature on the topic 'Fish populations – Western Australia – Perth'

Within Western Australia, Perca fluviatilis is restricted to the south-western corner and is found in the Swan, Murray, Harvey, Collie, Capel, Carbunup, Margaret, Blackwood, Donnelly and Warren river systems. Age data suggest it was released into Big Brook Dam (Warren River) in 1992 or 1993, where it has since played a role in eliminating the native teleosts. Its success here is attributed to a young age at maturity, rapid growth (compared with populations elsewhere), predatory nature, large size (compared with native fish), broad environmental and habitat tolerances, and absence of predators. Gonadal development initiates in late summer, with peak spawning between August and September. Males and females attained maturity in their first and second years, respectively, which is earlier than reported for most Northern Hemisphere populations and can be attributed to their rapid growth here because of the warmer climate. At ages 1, 2, 3, 4 and 5, males, on average, attained 102, 159, 206, 246 and 280 mm total length (TL) and females had attained 104, 166, 228, 290 and 351 mm TL at the respective ages. Diets of fish 50–200 mm TL comprised mainly small aquatic invertebrates, whereas larger fish preyed almost exclusively on decapods, mainly marron (Cherax tenuimanus), and teleosts.

The reproductive biology, age, growth, food and habitat of Nannoperca australis are described from samples collected from fringing macrophyte beds of the Macquarie River, Tasmania. Comparisons are made with the same species at Narrandera in New South Wales and other nannopercids, mainly in south-western Australia. Nannoperca australis spawned at the end of its first year, predominantly between October and December, inclusive. The peak mean gonadosomatic index of males occurred in August at 8.0 and that of females two months later at 11.5. The largest oocytes, of running-ripe females collected in October and December, were 1.15 mm in diameter. Fecundities ranged from 78 for a 1-year-old 37-mm fish to 679 for a 2-year-old 63-mm fish. Spawning is presumed to occur in the macrophyte habitat, since adults did not emigrate from these areas at this time. Otoliths and length-frequency histograms indicated that populations were dominated by 0+ fish. Amphipods and ostracods predominated in the guts of N. australis and prey items were mostly either benthic invertebrates or plant epifauna. Plankton was consumed by small fish in greater quantities than by larger fish, whereas the opposite was true for benthic and epifaunal prey. Fish were virtually always associated with aquatic macrophytes and almost always with shallow, still water.

Increasing salinities throughout southwestern Western Australia, facilitated by extensive land clearing, have compromised the region's highly endemic freshwater fishes. Salinization of the Blackwood River has resulted in the main channel and upper cleared catchment being dominated by estuarine and halotolerant teleosts. The non-halotolerant species are restricted to the forested non-saline tributaries of the lower catchment. Of the 12 943 fish (13 species) captured in 113 sites, the halotolerant introduced Mosquitofish Gambusia holbrooki was widespread and the most abundant, representing almost 52% of fish caught. The estuarine Western Hardyhead Leptatherina wallacei, which was also widespread throughout the main channel and upper catchment, was the next most abundant, representing ca. 24% of fish caught. Freshwater endemics represented ca. 23% of captures, with the Western Minnow Galaxias occidentalis and Western Pygmy Perch Edelia vittata accounting for most (i.e., ca. 20%). There were significant differences in teleost communities among the naturally vegetated, low salinity tributaries of the river compared with the main channel and upper cleared catchment. While the forested tributaries still contain populations of E. vittata, Nightfish Bostockia porosa and Mud Minnow Galaxiella munda, the elevated salinities in the upper reaches of the Blackwood River system appear to have caused a massive decline in, or extinction of, populations of these species. The protection of the region's unique freshwater teleosts relies on the preservation of their remaining habitat in both the uncleared catchments of the region and in the low salinity forested tributaries within largely cleared systems, such as those in the Blackwood River catchment.

Saffron thistle (Carthamus lanatus L.), an erect spiny annual herb, is a weed of pasture and cereal crops in some agricultural areas of southern Australia. Cypselas (achenes or seeds) were collected from mature plants at three sites near Salmon Gums, Moorine Rock and Greenough in Western Australia and grown at South Perth. Two forms were observed and could be distinguished by differences in their phenology and the shape of cotyledons and achenes. After two generations at South Perth, germination in the presence or absence of leaching with water or after storage at daily fluctuating temperatures of 15-60�C indicated that there were differences between forms as well as between different accessions of the same form. This result suggests that genetic as well as environmental factors influence the breakdown of dormancy and promote germination. Differences in germination were detected when a single accession was sown at two sites, one in the south and the other in the north of the cereal-growing region of Western Australia. Low rainfall and temperatures in autumn were primarily responsible for slow and staggered germination at the more southern site. The protracted germination of saffron thistle in the southern cereal-growing districts creates a problem for cultural control and correct timing of herbicide applications.

The Australian Government's Coastal Catchment Initiative (CCI) seeks to achieve targeted reductions in nutrient pollution to key coastal water quality hotspots, reducing algal blooms and fish kills. Under the CCI a Water Quality Improvement Plan (WQIP) is being prepared for targeted estuaries (Swan–Canning, near Perth, and the Vasse–Geographe, 140 km south of Perth) to address nutrient pollution issues. A range of projects are developing, testing and implementing agricultural Best Management Practices (BMPs) to reduce excessive loads of nutrients reaching the receiving waters. This work builds on progress-to-date achieved in a similar project in the Peel–Harvey Catchment (70 km south of Perth). It deals with the necessary steps of identifying the applicability of BMPs for nutrient attenuation, developing and promoting BMPs in the context of nutrient use and attenuation on farm and through catchments and estimating the degree to which BMP implementation can protect receiving waters. With a range of BMPs available with varying costs and effectiveness, a Decision Support System (DSS) to guide development of the WQIP and implementation of BMPs to protect receiving waters, is under development. As new information becomes available the DSS will be updated to ensure relevance and accuracy for decision-making and planning purposes. The DSS, calibrated for application in the catchments, will play a critical role in adaptive implementation of the WQIP by assessing the effect of land use change and management interventions on pollutant load generation and by providing a tool to guide priority setting and investment planning to achieve agreed WQIP load targets.

Objective: Recent Australian Government initiatives have emphasised problems with service provision to the ethnic mentally ill. This study aims to address the paucity of contemporary data describing the disposition of the ethnic mentally ill in hospital settings. Method: Patterns of admissions for psychiatric disorders to all hospitals in Perth, Western Australia, for the 3 years from 1990 to 1992, of migrants and the Australian born were compared using data from the Western Australian Mental Health Information System. Results: The overall rates for European migrants showed a ‘normalisation’ towards those of the Australian-born. There were high rates for the schizophrenic spectrum disorders in Polish and Yugoslavian (old terminology) migrants. There were low admission rates for South-East Asian migrants, predominantly those from Vietnam and Malaysia. Rates for alcoholism were low in Italian and all Asian migrants. There were high rates of organic psychosis, especially in those older than 75 years, among the Italian and Dutch migrants. The relative risk of a first admission in the 3 years being an involuntary admission to a mental hospital was almost twice that of the Australian-born for migrants from Poland, Yugoslavia, Malaysia and Vietnam. Conclusions: The results imply the possibility of significant untreated and/or undiagnosed psychiatric morbidity in the South-East Asian-born. They also indicate a need for further exploration of the unexpectedly high levels of psychiatric morbidity among some ethnic elderly groups, specifically the Dutch- and Italian-born. The findings demonstrate the persistence of high rates of presentation for psychotic disorders among Eastern European-born populations, many years post migration.

Abstract The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is one of the most economically important pest insects of fruit crops worldwide. Mediterranean fruit fly can cause up to 100% crop loss in susceptible fruit. In order to formulate best management practices, it is critical to understand how Mediterranean fruit fly overwinters in a given geographical location and bridge the gap between autumn and spring populations. In this study, we evaluated the overwintering potential of Mediterranean fruit fly immature and adult stages in two locations in Perth Hills, Western Australia. We also monitored wild adult Mediterranean fruit fly populations for 2 yr. Adults were present year-round with captures very low in winter to early spring relative to summer and autumn. Field experiments revealed that immature stages in apples (eggs/first instar) and soil (pupae) remained viable in winter, emerging as adults at the onset of warmer weather in spring. In field cages, adults survived 72–110 d, and female laid viable eggs when offered citrus fruit, though only 1–6% eggs survived to emerge as adults. Adults survived longer in field cages when offered live citrus branch. The findings suggest that all Mediterranean fruit fly life stages can survive through mild winter, and surviving adults, eggs in the fruit and/or pupae in the soil are the sources of new population that affect the deciduous fruit crops in Perth. We recommend that Mediterranean fruit fly monitoring is required year-round and control strategies be deployed in spring. Furthermore, we recommend removal of fallen fruit particularly apple and other winter fruit such as citrus.

Genetic variation within and among populations of an outcrossing stoloniferous perennial legume, strawberry clover (Trifolium fragiferum L.), was studied using seed collected from 5 different locations in Western Australia. The sites ranged from Badgingarra to the north of the wheatbelt to Karridale in the southwest of the state. Seed was collected randomly at each site and was grown out at the University of Western Australia Field Station at Shenton Park, Perth. Thirteen morphological plant traits were measured and analysed. Results show that within-population variation was extremely high. In contrast, among-population variation was generally low with most characters showing only 8–15% of the total variation. Despite this, all but 1 of the measured plant traits differed among populations. Principal components analysis highlighted the large amount of variation within the populations with the first 3 principal components accounting for only 59% of the total variation. We suggest that the populations have begun to differentiate into ecotypes more suited to those habitats into which they have been sown but that within-population variation remains high due to the outcrossing nature of strawberry clover.

Paropsis charybdis (Coleoptera Chrysomelidae) an Australian pest of Eucalyptus in New Zealand is subject to biological control by Enoggera nassaui (Hymenoptera Pteromalidae) a solitary egg parasitoid sourced from Western Australia ( Perth Strain) in 1987 Erratic control in inland regions of New Zealand led to the introduction and release in 2000 of two Tasmanian E nassaui strains to attempt expansion of the climatic range of biocontrol Samples recovered a year later were analysed using partial sequences of the Cytochrome oxidase I (COI) mitochondrial gene to test for establishment This method detected a haplotype corresponding with a Tasmanian (Florentine Valley) strain However as sequences could not be obtained from original Perth strain stocks some doubt remains as to the genetic source of the other current E nassaui populations in New Zealand COI proved adept at distinguishing between different parasitoid populations and shows promise for similar studies

The Roe’s abalone (Haliotis roei) fishery near Perth, Western Australia, is uniquely accessible, and highly vulnerable to overexploitation. The sustainability of this intensively utilized fishery requires robust assessment. To facilitate an assessment, this research aimed to provide rigorous and detailed biological information with appropriate interpretation. Four critical aspects of the species’ biology and population dynamics were investigated: (1) the stock structure; (2) the recreational catch; (3) an appropriate growth curve and description of size at age; and (4) abundance measures against which to assess the impact of fishing mortality. Allozyme electrophoresis was used to investigate stock structure across the species’ distribution. Standardized variance in allelic frequencies between 10 sites in south-western Australia indicated high levels of gene flow across the 3000 km sampled (mean FST = 0.009). An isolation-by-distance was evident when pairwise measures of GST were related to geographic distance (r=0.45, P<0.001). The area of complete genetic mixing was estimated from samples within the Perth fishery to be less than the distance between the two nearest sites, or 13 km. Consequently, the Perth fishery comprises numerous discrete stocks, each requiring independent assessment. A possible mechanism for this population structure is the retention of larvae in the wind driven currents oscillating in the near-shore lagoons, with rare pulses of long distance dispersal via the southerly Leeuwin current, running further offshore. The presumed impact of intensive recreational fishing, combined with substantial commercial quotas for the Perth fishery, had led to tight restrictions on fishing effort, without any quantitative measure of the recreational catch. A stratified creel survey was adapted to estimate the effort, catch rate and mean weight of abalone harvested by the recreational sector. Catches were estimated for reef complexes, or stocks, of less than 10 nautical miles (18.5 km) of coast. Between 1997 and 2000 the recreational catch varied from 30 to 45 tonnes whole weight, approximately equivalent to the commercial quota of 36 tonnes. On average 88% of the recreational catch came from two stocks, while 98% of the commercial catch came from these two, and one additional, stocks. The incidental mortality from recreational fishing, measured as the number of abalone left dead on the reef as a proportion of the estimated catch, was approximately 7% and 20% at two sites surveyed. Spatial and temporal patterns of growth were examined on the west coast of Western Australia. Growth increments were measured for abalone larger than about 30 mm from tagging studies at five sites in the Perth fishery, a site at the northern extent of the species’ distribution and a site in the southwest. Mean annual growth increments of the 0+ year class were obtained by fitting components to length frequencies from five sites in the Perth fishery, and combined with growth increments from each Perth tag site for model fitting. A von Bertalanffy growth curve provided a slightly better fit to the tag data, but a Gompertz growth curve was a much better fit when the mean increment from the 0+ to 1+ cohort was included, with the inflection occurring at about 40 mm, the size at sexual maturity. There was no difference in annual growth between the two years studied. There was significant variation in growth between the reef platform and adjacent sub-tidal reef, but this variation was site specific and faster growth rates were not consistently associated with either habitat. There was no latitudinal trend in growth rate. Growth at the Perth sites was the fastest and similar at all five sites with growth increments greater in summer than in winter. Size and abundance of abalone were measured using fixed transects and quadrats. Abalone densities were highest on the outer edge of the platform, intermediate in the middle of the reef platform, and lowest on both the inner platform and the sub-tidal reef. The pattern of mean lengths of abalone was the inverse of the density. Mean length and abundance were driven by the presence of post-settlement juveniles on the outer and middle reef habitats. There was a high spatial variation in abundance, with densities varying between transects at the same site, but the trend between years for each transect at a site was not significantly different. Abalone abundances, by size class, were examined from sites sampled between 1996 and 2002. A low density of post-settlement juveniles at all sites in 1997 was reflected in low densities of the 1+ and 2+ year classes in subsequent years. Abalone abundances at an unfished site were steady over the seven years. Two sites were located within each of the main stocks utilised by the recreational fishery. Abundance was stable or increasing in one stock, corresponding to a stable total catch. In the second stock the total catch increased over time and abundances declined. Perth is the focus of the Roe’s abalone fishery, with recreational and commercial fishers take about equal shares of the annual catch. Stocks are highly subdivided, with most of this catch coming from only 3 stocks occupying about 20 nautical miles of coast. Growth rates were found to be lower than previous estimates, and more similar to other commercial species of abalone. All life history stages are highly habitat specific, particularly the recruits, and the distribution and abundance through time indicate that the main stocks are near, or slightly over, the limit of sustainable fishing.

Latitudinal patterns in reef fish assemblages reflect the influence of long-term environmental conditions, evolutionary processes and the recent, short-term influence of fishing. Long-term processes generate the typically common latitudinal patterns in reef fish assemblages, such as decreases in diversity and herbivory towards higher latitudes. These patterns reflect the global gradient in water temperature and the isolation of temperate regions from the tropics. Fishing also influences reef fish assemblages in that it decreases the abundance of large-bodied carnivore species on reefs, often leading to over-exploitation, depletion and in some cases the extirpation of populations. Indirectly, the removal of these large-bodied carnivores can influence the abundance of their prey, leading to an increase in non-target species. This study examines the latitudinal patterns in reef fish assemblages across a unique biogeographic region, the temperate Western Australian coast, and incorporates an investigation of the influence of fishing on the structure of these assemblages. Seven regions across seven degrees of latitude and seven degrees of longitude covering approximately 1500 km of coastline were sampled. Fish assemblages were characterised at each region using diver operated stereo-video transects. At each region, four locations, and within each location, four reefs were surveyed totalling 1344 transects. A significant gradient in water temperature exists with latitude and longitude. Along the Western Australian coast, and in contrast to other regions species diversity of reef fish increased towards higher latitudes and there was no evidence for a decrease in the biomass and abundance of herbivorous reef fish. The presence of the poleward flowing warm water Leeuwin current combined with the absence of major extinction events means the temperate Western Australian coast contrasts with global latitudinal trends in reef fish assemblage structure. The unique biogeographic history of temperate Western Australia has also generated a high degree of endemism among reef fish. Nearly 30 % of the species found along the west coast in this study are endemic to Western Australia, with the narrow range of these species playing an important role in the large scale patterns and spatial vi heterogeneity in reef fish assemblage structure. Furthermore, many of these endemic species are large-bodied carnivores and targeted by fishers. The impact of fishing on the abundance of large-bodied carnivores throughout the Western Australian temperate region is clear both spatially and temporally. The distribution of fishing effort is greatest along the west coast and decreases towards the south following the gradient in SST. Along the west coast, high levels of fishing effort have reduced the biomass and abundance of target carnivores to well below the standing biomass of the south coast where a low level of fishing effort occurs. This reduction in biomass is related to the historical declines in catch per unit effort (CPUE) of many key target species. These target species include endemic species such as Choerodon rubescens, Glaucosoma herbraicum, Epinephilides armatus Nemadactylus valenciennesi and Achoerodus gouldii.