South Australian Waters Research Articles

Age‐related movement patterns and population structuring in southern garfish, Hyporhamphus melanochir, inferred from otolith chemistry

Abstract The southern garfish, Hyporhamphus melanochir (Val.), is an important inshore fishery species in South Australia. Over the past few years there have been concerns with this fishery, which is now considered to be over‐exploited. Currently, the fishery is assumed to consist of two separate stocks, but there is no understanding of movement patterns both within and between these two stocks to justify this assumption. Otolith chemistry was used to infer age‐related patterns of movement, delineate potential sub‐populations and determine the extent of mixing within South Australian coastal waters. Results indicated that the population structuring of garfish is more complex than previously assumed and it seems that stocks can be discriminated at a much finer spatial scale. Garfish collected from sites separated by <60 km displayed significantly different chemical signatures (relative concentrations of 7Li, 24Mg, 55Mn, 88Sr and 138Ba) in their otoliths, especially during their second year of growth, indicating that they had inhabited different water bodies. From a broader perspective, South Australian garfish can be partitioned into six regional components with various levels of inter‐mixing. From these results, it was suggested that assessment and management of the fishery may have to be restructured to align with the smaller spatial units.

DNA barcoding reveals overlooked marine fishes

With more than 15000 described marine species, fishes are a conspicuous, diverse and increasingly threatened component of marine life. It is generally accepted that most large-bodied fishes have been described, but this conclusion presumes that current taxonomic systems are robust. DNA barcoding, the analysis of a standardized region of the cytochrome c oxidase 1 gene (COI), was used to examine patterns of sequence divergence between populations of 35 fish species from opposite sides of the Indian Ocean, chosen to represent differing lifestyles from inshore to offshore. A substantial proportion of inshore species showed deep divergences between populations from South African and Australian waters (mean=5.10%), a pattern which also emerged in a few inshore/offshore species (mean= 0.84%), but not within strictly offshore species (mean=0.26%). Such deep divergences, detected within certain inshore and inshore/offshore taxa, are typical of divergences between congeneric species rather than between populations of a single species, suggesting that current taxonomic systems substantially underestimate species diversity. We estimate that about one third of the 1000 fish species thought to bridge South African and Australian waters actually represent two taxa.

Estimating historical commercial rock lobster (Jasus edwardsii) catch inside Australian State territorial waters for marine protected area assessment: the binomial likelihood method

The rock lobster (Jasus edwardsii) fishery of South Australia is the State’s most valuable fisheries resource with an export value exceeding ~AU$100 million. The fishery operates primarily inshore (<60 m), and overlaps with a series of marine protected areas (MPAs) currently proposed for State territorial waters. As a result, the need to quantify the impact of proposed MPAs on commercial landings of rock lobster within territorial waters is an integral part of the MPA assessment process. Removing fishing effort displaced by MPAs prevents a corresponding increase in exploitation outside protected zones. We describe a binomial likelihood method that utilises historical commercial catch data to estimate catch totals of rock lobster inside South Australian State waters. Lobster catches per km2 showed a high level of spatial variation with estimated historical lobster catch in State waters spanning approximately three orders of magnitude. The method identified key areas where high lobster catch (up to 500 kg/km2) overlapped with State waters. Binomial likelihood outputs have particular application to the estimation of net catch loss in situations where fishery buy-back or financial compensation are a considered option as part of the MPA implementation process.

Comparative phylogeography reveals host generalists, specialists and cryptic diversity: Hexabothriid, microbothriid and monocotylid monogeneans from rhinobatid rays in southern Australia

The phylogeography and host specificity of three monogenean species infecting different sites on the southern fiddler ray, Trygonorrhina fasciata (Rhinobatidae) in South Australia (SA) were studied: Branchotenthes octohamatus (Hexabothriidae: gills), Calicotyle australis (Monocotylidae: cloaca) and Pseudoleptobothrium aptychotremae (Microbothriidae: skin). Five rhinobatid species ( Aptychotrema vincentiana, T. fasciata, Trygonorrhina sp. A, Aptychotrema rostrata and Rhinobatos typus) with distributions spanning west, south and east Australian coastal waters, were surveyed for monogeneans resembling the three species documented from T. fasciata in SA. The identities of hosts and parasites collected were investigated using the mitochondrial genes ND4 and Cytochrome b (cyt b), respectively, in addition to the nuclear marker, Elongation factor 1-alpha (EF1a) for Pseudoleptobothrium. Genetic analyses confirmed that B. octohamatus is geographically widespread and displays little genetic structure, suggesting high levels of gene flow. It was collected from four rhinobatid species throughout its distribution and is not, therefore, host specific. For C. australis, genetic analyses revealed two discrete populations with a genetic divergence of ∼4%, one population occurring west of Bass Strait on two sympatric host species and the other population on the east coast, also occurring on sympatric host species. Similarly, for Pseudoleptobothrium, specimens collected west of Bass Strait were genetically distinct (∼3.5%) from those collected to the east. However, on the east coast, a third Pseudoleptobothrium population was revealed, separated by a genetic distance of >11%, indicating a morphologically cryptic species. Host preferences were indicated for each Pseudoleptobothrium lineage. These genetic discoveries are discussed in relation to life history characteristics of each monogenean species, highlighting the value of phylogeographic analyses to understand the parasite–host relationship.

A Tagging Study on Yellowtail Kingfish (Seriola Lalandi) and Samson Fish (S. Hippos) in South Australian Waters

SummaryWild yellowtail kingfish (Seriola lalandi Valenciennes, 1833) and Samson fish (S. hippos Günther, 1876) were tagged with nylon-headed, single-barbed dart tags between December 1, 2004 and December 31, 2006 in Spencer Gulf and offshore from the west coast of Eyre Peninsula, South Australia. Two-hundred and forty-one S. lalandi and 73 S. hippos were tagged. Twenty-four S. lalandi were recaptured and the maximum distance between capture points was 130 km and the maximum time at liberty was 442 days. Two S. hippos were recaptured, of which one was at liberty for a maximum of 378 days. Both S. hippos were recaptured at the original capture site. Recapture results indicate that large S. lalandi remain in, or return to, northern Spencer Gulf. This region may be important for aggregations of large, reproductively mature S. lalandi. One large S. lalandi tagged at Port Augusta was recaptured near Fitzgerald Bay, indicating that wild fish may move past S. lalandi sea-cage farms in this region. This course of movement may provide opportunities for disease and parasite interactions between wild and farmed fish. An additional outcome of this research was the residual impact that it has had on sustainable fishing practices in South Australia with increased recreational fisher participation in the tag and release of S. lalandi and S. hippos.

Application of a 'case-building approach' to investigate the age distributions and growth dynamics of Australian sardine (Sardinops sagax) off South Australia

Like many pelagic fish, sardine Sardinops sagax is difficult to age by counting structures in otoliths. Of 12968 whole otoliths analysed in the present study, &lt;25% could be counted with accuracies of greater than ±1 zone. Estimates of average percentage error (APE) were high (11.37%). We used a ‘case building approach’ to corroborate a method for estimating age. Regressions of otolith weight–age from otoliths with high readabilities were used to estimate the age of fish with lower or unreadable otoliths. Growth rates determined from daily increments ranged from 0.36 to 0.75 mm day–1 for larvae and from 0.22 to 0.47 mm day–1 for juveniles. Estimates of von Bertalanffy growth coefficients were k = 0.32–1.07 year–1 and L∞ = 166.96–195.68 mm. Growth parameters estimated during the present study support previous assertions that levels of pelagic production in South Australian (SA) waters lie between those recorded in the predominantly oligotrophic waters off Western Australia (WA) and the productive waters off southern California and South Africa. Disparities in the age distributions of inshore and offshore samples suggest that age data from commercial catch samples may not be representative of the population. This finding has implications for the use of age-structured models to assess of stocks of S. sagax and other small pelagic fishes.

The impact of recalcitrant organic character on disinfection stability, trihalomethane formation and bacterial regrowth: An evaluation of magnetic ion exchange resin (MIEX®) and alum coagulation

Research Article| November 01 2003 The impact of recalcitrant organic character on disinfection stability, trihalomethane formation and bacterial regrowth: An evaluation of magnetic ion exchange resin (MIEX®) and alum coagulation Mary Drikas; Mary Drikas 1CRC for Water Quality and Treatment, Australian Water Quality Centre, Private Mail Bag 3, Salisbury, South Australia, 5108, Australia E-mail: mary.drikas@sawater.com.au Search for other works by this author on: This Site PubMed Google Scholar Christopher W. K. Chow; Christopher W. K. Chow 1CRC for Water Quality and Treatment, Australian Water Quality Centre, Private Mail Bag 3, Salisbury, South Australia, 5108, Australia Search for other works by this author on: This Site PubMed Google Scholar David Cook David Cook 1CRC for Water Quality and Treatment, Australian Water Quality Centre, Private Mail Bag 3, Salisbury, South Australia, 5108, Australia Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2003) 52 (7): 475–487. https://doi.org/10.2166/aqua.2003.0043 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll JournalsThis Journal Search Advanced Search Citation Mary Drikas, Christopher W. K. Chow, David Cook; The impact of recalcitrant organic character on disinfection stability, trihalomethane formation and bacterial regrowth: An evaluation of magnetic ion exchange resin (MIEX®) and alum coagulation. Journal of Water Supply: Research and Technology-Aqua 1 November 2003; 52 (7): 475–487. doi: https://doi.org/10.2166/aqua.2003.0043 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Two South Australian reservoir waters, Hope Valley and Myponga, were selected in this study based on the differences in the character of their organic matter. Four treatment options: (a) alum coagulation without pH adjustment; (b) alum coagulation at pH 6; (c) magnetic ion-exchange (MIEX®) resin; and (d) combined alum/MIEX® treatment, were used to compare the removal of dissolved organic carbon (DOC) and treated water quality, particularly the formation of disinfection by-products and bacterial regrowth potential. Improved DOC removal was achieved with the inclusion of MIEX® treatment in the process. Removal of DOC under optimised treatment conditions indicated combined alum and MIEX® treatment was very similar to MIEX® alone but much better than conventional and enhanced coagulation with alum. Combined treatment (alum and MIEX®) removed 2.3 and 1.4 times the DOC of enhanced coagulation with alum from Hope Valley and Myponga respectively.The DOC remaining after each treatment strategy was different in character. The molecular weight distribution results indicated that MIEX® treatment removed a broad range of compounds, whilst alum treatment targeted the removal of high molecular weight compounds. In addition, the DOC remaining after MIEX® treatment consisted of compounds with lower specific UV absorbance (SUVA). Including MIEX® in the treatment stream provided better DOC and bromide removal thus reducing chlorine decay and trihalomethane (THM) formation. The ability of the water to support bacterial growth as measured by bacterial regrowth potential (BRP) was the lowest after MIEX® treatment (option c) compared with the three other treatments (options a, b & d). In summary, laboratory tests show that including MIEX® in the treatment process can improve treated water quality. bacterial regrowth potential, chlorine decay, coagulation, MIEX®, natural organic matter, trihalomethane formation This content is only available as a PDF. © IWA Publishing 2003 You do not currently have access to this content.

A model of spatially evolving herpesvirus epidemics causing mass mortality in Australian pilchard Sardinops sagax.

In 1995 mass mortality of pilchards Sardinops sagax occurred along >5000 km of Australian coast; similar events occurred in 1998/99. This mortality was closely associated with a herpesvirus. The pilchard is an important food source for larger animals and supports commercial fisheries. Both epidemics originated in South Australian waters and spread as waves with velocities of 10 to 40 km d(-1). Velocity was constant for a single wave, but varied between the epidemics and between the east- and west-bound waves in each epidemic. The pattern of mortality evolved from recurrent episodes to a single peak with distance from the origin. A 1-dimensional model of these epidemics has been developed. The host population is divided into susceptible, infected and latent, infected and infectious, and removed (recovered and dead) phases; the latent and infectious periods are of fixed duration. This model produces the mortality patterns observed locally and during the spread and evolution of the epidemic. It is consistent with evidence from pathology. The wave velocity is sensitive to diffusion coefficients, viral transmission rates and latent period. These parameters are constrained using the local and large-scale patterns of epidemic spread. The relative roles of these parameters in explaining differences between epidemics and between east- and west-bound waves within epidemics are discussed. The model predicts very high levels of infection, indicating that many surviving pilchards recovered following infection. Control appears impracticable once epidemics are initiated, but impact can be minimised by protecting juvenile stocks.

Opportunity cost of ad hoc marine reserve design decisions: an example from South Australia

Like many states and territories, South Australia has a legacy of marine reserves considered to be inadequate to meet current conservation objectives. In this paper we configured exploratory marine reserve systems, using the software MARXAN, to examine how efficiently South Australia's existing marine reserves contribute to quantitative biodiversity conservation targets. Our aim was to compare marine reserve systems that retain South Australia's existing marine reserves with reserve systems that are free to either ignore or incorporate them. We devised a new interpretation of irreplaceability to identify planning units selected more than could be expected from chance alone. This is measured by comparing the observed selection frequency for an individual planning unit with a predicted selection frequency distribution. Knowing which sites make a valuable contribution to efficient marine reserve system design allows us to determine how well South Australia's existing reserves contribute to reservation goals when representation targets are set at 5, 10, 15, 20, 30 and 50% of conservation features. Existing marine reserves that tail to contribute to efficient marine reserve systems constitute 'opportunity costs'. We found that despite spanning less than 4% of South Australian state waters, locking in the existing ad hoc marine reserves presented considerable opportunity costs. Even with representation targets set at 50%, more than halt of South Australia's existing marine reserves were selected randomly or less in efficient marine reserve systems. Hence, ad hoc marine reserve systems are likely to be inefficient and may compromise effective conservation of marine biodiversity.

Comparison of the spawning patterns and fisheries biology of the sardine, Sardinops sagax, in temperate South Australia and sub-tropical southern Queensland

South Australia is the centre of the Australian distribution of Sardinops sagax, whereas southern Queensland is the northeastern edge of its local range. In South Australia, eggs were collected during all months and the peak in abundance coincided with the upwelling period in summer–autumn (January–April). In contrast, eggs were collected from southern Queensland only during winter–spring (August–November), when water temperatures fell below 23 °C. In South Australia, eggs were found throughout shelf waters, whereas in southern Queensland most eggs were collected from a small area between Noosa Heads and Caloundra. The South Australian fishery was confined mainly to the waters of southern Spencer Gulf and the Coffin Bay Peninsula, and the Queensland fishery was centred on the area of high egg density. Catch rates in the South Australian fishery were high throughout the year, whereas low catch rates were recorded in southern Queensland outside the spawning season. In South Australia, 50% of males and females were mature at approximately 146 and 150 mm FL, respectively. Over 70% of fish in all size classes collected from southern Queensland were sexually mature. Fish less than 145 mm FL comprised over 30% of South Australian catch, but less than 3% of fish taken from southern Queensland. Evidence is consistent with the hypothesis that S. sagax is a widely distributed resident of South Australian waters, but only migrates into southern Queensland during winter–spring to spawn.

Effects of the 1995 and 1998 mass mortality events on the spawning biomass of sardine, Sardinops sagax, in South Australian waters

This paper estimates and compares the effects of the mass mortalities of Sardinops sagax that occurred in South Australian waters in 1995 and 1998. After the 1995 event, the spawning biomass of S. sagax in South Australian waters fell by over 75% from approximately 165 000 tonnes to approximately 37 000 tonnes. No juvenile mortality was observed during 1995 and the population recovered quickly, with spawning biomass reaching 147 000 (70 000 to 234 000, 95%CI) tonnes in 1998. After the mass mortality event in October–November, spawning biomass fell by over 70% to 36 000 (19 000 to 67 000, 95%CI) tonnes; significant numbers of juveniles were also killed. The mortality of juveniles in 1998 and the recent increase in the abundance of Engraulis australis suggest that the population may recover more slowly from the 1998 mortality event than did after 1995. The initiation of the two largest mono-specific mass mortalities of fish ever recorded in South Australian waters within a period of less than four years suggests that the timing and location of the events was non-random. Both events occurred since 1993–1994, when large-scale tuna farming began in South Australia, and less than 250 km from Port Lincoln, where large quantities of untreated imported frozen S. sagax are fed to caged tuna. The introduction of untreated imported frozen fish products into the marine environment may be one of the mechanisms that has facilitated the range shifts of pathogens that have been associated with the increased frequency of mass mortalities due to disease in the ocean.

Metal Levels in Seston and Marine Fish Flesh Near Industrial and Metropolitan Centres in South Australia

Port Pirie is the site of the largest lead smelter in the world, depositing 250 t of zinc, and 100 t of lead annually into Spencer Gulf. Barker Inlet is adjacent to metropolitan Adelaide, and receives unknown quantities of urban and industrial discharges. Both areas are sites of major commercial and recreational fisheries, contained within delicately balanced marine wetland ecosystems, comprising large areas of mangrove and seagrass habitats. Aldrichetta forsteri and Sillago schomburgkii are major species within these fisheries and as estuarine-dependent species were chosen for this study as indicator species for the detection and monitoring of pollutant impacts in the nearshore marine ecosystems of South Australia. Seston sediment collectors were deployed at each site and analysed seasonally for the presence of cadmium, lead and copper. Flesh samples from A. forsteri and S. schomburgkii were examined seasonally for the presence of cadmium, lead and copper and the results correlated with levels found in the seston sediment at each site. Metal concentrations were also correlated with a biomarker of genotoxicity measured in the same animals (micronuclei in erythrocytes) that were reported previously. Seston levels of cadmium, lead and copper were highest at Port Pirie, followed by Barker Inlet and were lowest at Wills Creek, with cadmium undetectable at the latter site. Metals in seston varied considerably with season, with generally higher levels in winter samples. In fish flesh, metal levels followed broadly similar trends as for seston. Spearman rank correlations between metals in seston and in flesh were strongly positive. There was also a significant correlation between flesh concentrations of each metal and the frequency of micronuclei in erythrocytes. This study has shown that seston concentration of pollutant metals are high in areas of industrial activity, and that these levels are also reflected in metal content of fish flesh. Mean flesh levels of cadmium and copper did not exceed Australian health based maximum permitted levels of fish for human consumption, whereas flesh levels of lead in fish from Port Pirie and Barker Inlet exceeded these standards in each of the seasons monitored. This may represent a significant dietary source of lead in humans, especially at Port Pirie where human lead exposure from terrestrial sources is important. There may also be the potential for accumulation of metals in residents of metropolitan Adelaide whose diets are high in fish (and/or crustaceans), particularly estuarine-dependent species, such as A. forsteri and S. schomburgkii. The study also showed that a non-specific biomarker of genotoxicity (micronuclei in erythrocytes) is potentially useful as a monitoring technique in fish species to evaluate their exposure and genotoxic responses to pollutants in South Australian waters. These data represent a snapshot of the current situation in this area and may act as background levels against which future improvements or decrements in water quality may be compared.

Development of a nested-PCR assay for the detection of cryptosporidium parvum in finished water

A nested-PCR assay, incorporating an internal positive control, was developed for Cryptosporidium monitoring in finished water. This assay was capable of reproducibly detecting 8 oocysts in spiked-filtered water samples collected from 5 South Australian water treatment plants. The RT-PCR assay of Kaucner and Stinear (Appl. Environ. Microbiol. 64(5) (1998) 1743) was also evaluated for the detection of Cryptosporidium parvum. Initially, under our experimental conditions, a detection level of 27 oocysts was achieved for spiked reagent water samples. This level was improved to 5 oocysts by modification of the method. Untreated South Australian source waters concentrated by calcium carbonate flocculation were found to be highly inhibitory to the RT-PCR assay. Concentration of similar samples using Envirochek filters appeared to eliminate PCR inhibition. While both methods possessed similar sensitivities the nested-PCR assay was more reproducible, more cost effective, simpler to perform and could detect both viable and non-viable intact Cryptosporidium parvum oocysts, which is an important consideration for plant operators. These factors make the nested-PCR assay the method of choice for screening large numbers of potable water samples, where a reliable low level of detection is essential.

Have recent mass mortalities of the sardine Sardinops sagax facilitated an expansion in the distribution and abundance of the anchovy Engraulis australis in South Australia?

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 220:241-251 (2001) - doi:10.3354/meps220241 Have recent mass mortalities of the sardine Sardinops sagax facilitated an expansion in the distribution and abundance of the anchovy Engraulis australis in South Australia? T. M. Ward, F. Hoedt, L. McLeay, W. F. Dimmlich, G. Jackson, P. J. Rogers, K. Jones South Australian Research and Development Institute (Aquatic Sciences), PO Box 120, Henley Beach 5022, Adelaide, South Australia *E-mail: ward.tim@saugov.sa.gov.au Present Addresses: **Department of Marine Biology and Aquaculture, James Cook University, Townsville 4811, Queensland, Australia ***Fisheries Western Australia. WA Marine Research Laboratories, PO Box 120 North Beach WA 6020 ABSTRACT: This paper examines the hypotheses (1) that Sardinops sagax and Engraulis australis are spatially segregated and do not interact directly, and (2) that recent mass mortalities of S. sagax have facilitated an expansion in the distribution and abundance of E. australis. In South Australian waters, S. sagax and E. australis both spawn during summer and autumn. Eggs and larvae of both species occur over the continental shelf, and are abundant in areas where upwelling occurs (e.g. off the Coffin Bay Peninsula and the western tip of Kangaroo Island) and frontal systems form (e.g. in Investigator Strait and the entrance of Spencer Gulf). After the mass- mortality events in 1995 and 1998, eggs and larvae of S. sagax were confined mainly to these areas, and estimates of the total abundance of S. sagax eggs and larvae in South Australian waters fell by between 48 and 83% respectively. Between 1996 and 1999, densities of E. australis eggs and larvae increased in both key spawning areas and the central and eastern Great Australian Bight, and total abundance of eggs and larvae increased by over 215 and 285% respectively. These results indicate that (1) S. sagax and E. australis are not spatially segregated and may interact directly, and (2) the mass mortalities of S. sagax may have facilitated an expansion in the distribution and abundance of E. australis. Hence, fluctuations in the relative abundance of S. sagax and Engraulis spp. observed in the world¹s productive boundary-current systems may also be possible in Australian waters. KEY WORDS: Sardine · Anchovy · Distribution and abundance · Eggs and larvae · depth · Temperature · Spawning Season · Spawning Area · Competition Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 220. Online publication date: September 27, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Phylogeography of the invasive polychaete Sabella spallanzanii (Sabellidae) based on the nucleotide sequence of internal transcribed spacer 2 (ITS2) of nuclear rDNA

Genetic relationships between different populations of the invasive species Sabella spallanzanii (Gmelin, 1791) (Polychaeta, Sabellidae) are investigated through the use of the internal transcribed spacer 2 (ITS2) of the nuclear ribosomal DNA (285 bp). Samples were taken from South Australian waters (3 populations), the Mediterranean Sea (8 populations) and the French Atlantic coast (1 population). The ITS2 sequences were analyzed using both maximum parsimony and unweighted pair-group mean analysis (UPGMA) algorithms; results showed genetic disjunction between the Australian and the Mediterranean populations. Within the Mediterranean populations, 3 different sub-groups, corresponding to different sub-basins, could be clearly detected (Northwest- ern, Central and Eastern basins). The Atlantic population showed strong differences with the Mediterranean and Australian populations, but did not allow the identification of the source of intro- duction from Europe to Australia. Data also suggest the occurrence of a reduced genetic variability of the Australian populations, probably due to the 'founder effect' of one introduction, either via ballast waters or hull fouling. The recent description of the life cycle and larval development of S. spallan- zanii in the Mediterranean Sea, with a long pelagic larval phase and a post-settlement stage of meta- morphosis (approx. 25 d), supports the hypothesis of introduction via ballast waters (larval pool). Our data show high consistency when compared with the allozyme analysis previously performed by Andrew & Ward (1997; Mar Ecol Prog Ser 152:131-143) on a reduced number of populations and emphasize the importance and suitability of ITS sequences as markers to study the genetic structure at the population level in S. spallanzanii.

Pathologic Features of Fatal Shark Attacks

To examine the pattern of injuries in cases of fatal shark attack in South Australian waters, the authors examined the files of their institution for all cases of shark attack in which full autopsies had been performed over the past 25 years, from 1974 to 1998. Of the seven deaths attributed to shark attack during this period, full autopsies were performed in only two cases. In the remaining five cases, bodies either had not been found or were incomplete. Case 1 was a 27-year-old male surfer who had been attacked by a shark. At autopsy, the main areas of injury involved the right thigh, which displayed characteristic teeth marks, extensive soft tissue damage, and incision of the femoral artery. There were also incised wounds of the right wrist. Bony injury was minimal, and no shark teeth were recovered. Case 2 was a 26-year-old male diver who had been attacked by a shark. At autopsy, the main areas of injury involved the left thigh and lower leg, which displayed characteristic teeth marks, extensive soft tissue damage, and incised wounds of the femoral artery and vein. There was also soft tissue trauma to the left wrist, with transection of the radial artery and vein. Bony injury was minimal, and no shark teeth were recovered. In both cases, death resulted from exsanguination following a similar pattern of soft tissue and vascular damage to a leg and arm. This type of injury is in keeping with predator attack from underneath or behind, with the most severe injuries involving one leg. Less severe injuries to the arms may have occurred during the ensuing struggle. Reconstruction of the damaged limb in case 2 by sewing together skin, soft tissue, and muscle bundles not only revealed that no soft tissue was missing but also gave a clearer picture of the pattern of teeth marks, direction of the attack, and species of predator.

Spatial variation in size and age structures and reproductive characteristics of the King George whiting (Percoidei : Sillaginidae) in South Australian waters

Adult King George whiting were sampled at 12 localities representing a range of habitat types across South Australia. Sampling was undertaken between March and May for a minimum of 2 years between 1995 and 1998. Fish were aged by otolith interpretation, and reproductive maturity was determined by gonad analysis using macroscopic and histological techniques. In total, 6961 fish comprising 3678 females and 3283 males were considered from four localities in each of three geographic regions. In both Gulf St Vincent and Spencer Gulf, age structures became more complex from north to south, associated with a shift in size towards larger fish. In the simplest age structures, &gt;90% of fish were from the 3-year age class, whereas the age range of the most complex was 3–17 years, with the 3–5 age classes most numerous. Males were more abundant in smaller size classes and females in the larger. Although some fish from each locality showed some gonad development, only at three localities did spawning occur. At these places, populations had the broadest age and size distributions and were in deep water that experienced medium to high wave energy. Since spawning grounds and nursery areas are up to several hundred kilometres apart, the processes of larval advection and adult movement are implicated as obligate processes of the life history.

Comparative ecophysiology of the harmful alga Chattonella marina (Raphidophyceae) form South Australian and Japanese waters

The raphidophyte flagellate Chattonella marina was successfully cultured from Boston Bay (South Australia), coincident with mass mortality of farmed bluefin tuna (Thunnus maccoyii) in April 1996. Grown under laboratory conditions at 150 µmol m-2 s-1 irradiance, optimal growth (>0.5 day-1) occurred at a temperature of 25°C and a salinity of 30 p.s.u., but good growth (>0.3 day-1) also occurred between a temperature of 10 and 30°C and at a salinity of 15-45 p.s.u. However, cultures grew much faster at an irradiance of 450 µmol m-2 s-1 (1.08 day-1). While Australian C.marina had similar temperature and salinity requirements as well-studied Japanese cultures from the Seto Inland Sea, the Australian strains exhibited a light saturation level for growth four times higher than that reported from Japan (150 µmol m-2 s-1). An adaptation to higher light intensities was reflected in higher concentrations of microsporine-like amino acids in the Australian strains. The different light adaptation phenotypes were still apparent after long-term culturing under similar physiological conditions. Potential growth habitats for this ichthyotoxic flagellate in the Australian region and impli- cations for finfish aquaculture industries are discussed.

Spatial variation in mean growth rates at size of southern rock lobster, Jasus edwardsii, in South Australian waters

Size-specific growth rates of Jasus edwardsii were estimated from 16 000 recaptures of tagged lobsters during a 3-year mark–recapture study. The von Bertalanffy growth model was fitted to observed increases in carapace length. A normal likelihood of predicted length increment as a function of starting length and time-at-large was maximized. Estimated standard deviation of the likelihood, taken as an allometric function of predicted length increment, quantified individual growth variation. The distributions of residuals indicated satisfactory fits. von Bertalanffy parameters of growth were estimated at three levels of spatial resolution: 18 statistical reporting blocks, 6 growth subregions, and 2 fishery management zones. Among blocks, the mean annual growth of lobsters of 100 mm carapace length was 7–20 mm for males and 5–15 mm for females. Females grew more slowly after reaching sexual maturity. Growth rates declined by approximately 1 mm year –1 per 20 m increase in depth of habitat, at depths of 20 m and deeper. Density-dependent growth was indicated by spatial anti-correlation between male growth rates at 100 mm and fishery catches by number per unit effort. Regression implied that a 10% decrease in catch rate corresponded to increased growth by weight of 2–5%.

Ecological sustainability of the South Australian coastal aquaculture management policies

Coastal aquaculture in South Australia has been going through a period of unprecedented growth during the past seven years. The value of the South Australian aqua‐culture industry has increased from US$1.3 million in 1990–1991 to an estimated US$31 million in 1996–1997. This growth has led to the implementation of planning and management policies by the state government. South Australian coastal waters have been divided into regions, and regional aquaculture management plans have been prepared. These management policies have generated concerns among interest groups and the community. The recent coastal aquaculture planning and management policies are described and analyzed, focusing on their contribution to the development of an ecologically sustainable industry. The need for an integrated approach to management is emphasized, especially given the great interest of the state government on the development of the industry.