Southeast Australian Waters Research Articles

Mysid subfamily Boreomysinae (Crustacea: Mysida: Mysidae) in the southeast Australian deep-sea

The deep-water mysid crustaceans of Australia have been barely known. Recent explorations of RV Investigator (CSIRO) in the southeast Australian waters discovered a unique fauna. In this special study of the marine subfamily Boreomysinae (family Mysidae) in Australia, five species from both genera Boreomysis and Neobirsteiniamysis are reported, including two new species for science: B. inopinata sp. nov., B. sibogae, B. sphaerops, B. urospina sp. nov. and N. inermis. Among the members of the subfamily, only B. sibogae has been previously known from Australia. The genus Neobirsteiniamysis and its bipolar-amphitropical species N. inermis are firstly recorded in Australia. Boreomysis inopinata sp. nov. has additional spinules on the outer spine of the antennal scale, which are not found in other species of the subfamily. Boreomysis urospina sp. nov. has the longest first segment of the uropodal exopod, laterally terminated by three spiniform setae; and its uropodal endopod is armed with up to five medial spiniform setae, the largest number in the subfamily. This species is included in a newly established subgenus Petryashovia subgen. nov., which unites epi-mesopelagic boreomysines, lacking the rostral projection, having rather small ventrolateral lobes of the carapace, and the 1-segmented propodus of the pereopods. The subfamily and generic diagnoses are updated. Additionally, a fragment of the mtDNA COI gene was sequenced for most of the studied species.

Coccolithophore assemblage changes over the past 9 kyrs BP from a climate hotspot in Tasmania, southeast Australia

Predicting phytoplankton responses to a changing climate on Tasmania's east coast is presently based on short-term plankton data sets (∼75 years). However, to better predict future phytoplankton composition, it is crucial to understand longer-term variations from geological records. A particularly important group are the coccolithophores given their vital contribution to the oceanic carbon pump.Here, we expand the archive of coccolithophores in southeast Australian waters by analysing coccolith assemblages in a 268 cm-long marine sediment core collected off Maria Island, Tasmania, using light and scanning electron microscopy in combination with sedimentary ancient DNA (sedaDNA) techniques.Coccoliths underwent a shift from a cold to warm-water adapted assemblage at ∼8.2 kyrs BP expressed by a transition in species dominance from the cold-water species Gephyrocapsa muellerae to the warmer-water species Emiliania huxleyi Type A. A period of coccolithophore community instability characterised by reduced diversity and species richness was also detected spanning ∼900 yrs. between 6 and 5 kyrs BP. The latter may be associated with a Mid-Holocene warm period in the Southern Ocean as well as sea-level rise changing the study site from a shallow coastal to deep water habitat.Emiliania huxleyi coccoliths displayed the highest total relative abundance, but less prevalent larger taxa (Calcidiscus, Coccolithus, Helicosphaera) accounted for >50% of total estimated coccolith CaCO3 sequestration, indicating that relatively scarce, densely calcified species do the ‘heavy-lifting’ of this process. Analysis of sedaDNA revealed coccolithophores contributed ∼44% to the total palaeo eukaryote composition, underlining their importance as part of the marine ecosystem in the study region. The detection of oceanographic shifts and subsequent coccolithophore assemblage composition, including past transitions of species dominance, offer valuable insight into the biological future of southeast Australian waters.

Testing the Influence of Seascape Connectivity on Marine-Based Species Distribution Models

Species distribution models (SDMs) are commonly used in ecology to predict species occurrence probability and how species are geographically distributed. Here, we propose innovative predictive factors to efficiently integrate information on connectivity into SDMs, a key element of population dynamics strongly influencing how species are distributed across seascapes. We also quantify the influence of species-specific connectivity estimates (i.e., larval dispersal vs. adult movement) on the marine-based SDMs outcomes. For illustration, seascape connectivity was modeled for two common, yet contrasting, marine species occurring in southeast Australian waters, the purple sea urchin, Heliocidaris erythrogramma, and the Australasian snapper, Chrysophrys auratus. Our models illustrate how different species-specific larval dispersal and adult movement can be efficiently accommodated. We used network-based centrality metrics to compute patch-level importance values and include these metrics in the group of predictors of correlative SDMs. We employed boosted regression trees (BRT) to fit our models, calculating the predictive performance, comparing spatial predictions and evaluating the relative influence of connectivity-based metrics among other predictors. Network-based metrics provide a flexible tool to quantify seascape connectivity that can be efficiently incorporated into SDMs. Connectivity across larval and adult stages was found to contribute to SDMs predictions and model performance was not negatively influenced from including these connectivity measures. Degree centrality, quantifying incoming and outgoing connections with habitat patches, was the most influential centrality metric. Pairwise interactions between predictors revealed that the species were predominantly found around hubs of connectivity and in warm, high-oxygenated, shallow waters. Additional research is needed to quantify the complex role that habitat network structure and temporal dynamics may have on SDM spatial predictions and explanatory power.

Prey preference, environmental tolerances and ichthyotoxicity by the red-tide dinoflagellate Noctiluca scintillans cultured from Tasmanian waters

AbstractThe large phagotrophic dinoflagellate Noctiluca has become a prominent red tide organism in southeast Australian waters since the 2000s, raising concerns for beach tourism, grazing impacts as well as ichthyotoxicity for finfish aquaculture. Satisfactory culture growth rates (0.23–0.56 per day) were obtained by feeding with small Thalassiosira diatom and Tetraselmis flagellate diets, while optimal growth rates sustained for up to 8 months (0.69 per day) were achieved by feeding in a plankton wheel with the large chain-forming dinoflagellate Gymnodinium catenatum. Noctiluca was highly tolerant towards salinities from 20 to 35 and growth was stimulated by temperatures increasing from 10 to 23°C, which in combination with the key factor of prey abundance explains the incidence in southeast Australia of predominantly summer and spring but occasionally also winter blooms. Fatty acid biomarkers suggest that Tasmanian field populations indiscriminately feed on available diatom and dinoflagellate mixtures. Noctiluca exhibited very limited ichthyotoxicity, and only at the highest cell concentrations of 2 000 000/L (50% reduction in RTgill W1 cell viability). Only the densest red tide surface slicks contained acutely toxic levels of unionized ammonia of 242 to 510 μg/L while inshore slicks generated oxygen concentrations as low as 0–1.5 ppm. Lipid phycotoxins (eicosapentaenoic acid, docosahexaenoic acid) did not appear to contribute to Noctiluca ichthyotoxicity. The fatty acid 20:0 eicosanoic acid may serve as a potential Noctiluca biomarker in marine food webs and sediments.

Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition

The taxonomy of the ocean sunfishes (Molidae) has a complicated history. Currently, three genera and four species are recognized, including two in the genus Mola (M. mola and M. ramsayi). In 2009, a genetic study revealed a potential third species, Mola species C, in Southeast Australian waters. Concentrating on this region, we obtained samples and morphological data from 27 Mola sp. C specimens, genetically confirmed the existence of this species (mtDNA D-loop and cytochrome c oxidase 1), and established its morphology across a size spectrum of 50–242 cm total length. Mola sp. C is diagnosed by clavus meristics [15–17 fin rays (13–15 principal, 2 minor), 5–7 ossicles, paraxial ossicles separate], clavus morphology (prominent smooth band back-fold, rounded clavus edge with an indent), and body scale morphology (raised conical midpoints, non-branching). This species does not develop a protruding snout, or swollen dorso- or ventrolateral ridges. Body proportions remain similar with growth. A review of the historic literature revealed that Mola sp. C is a new, hitherto undescribed species, M. tecta, which we describe and diagnose, and that it is the first proposed addition to the genus Mola in 125 years. Its core distribution is likely in the temperate waters of the Southern Hemisphere.

Distribution, reproduction and population structure of three gulper sharks (Centrophorus, Centrophoridae) in south-east Australian waters

Gulper sharks (Centrophorus spp.) are commercially fished in all oceans but the taxonomy and biology of many species are not clearly defined, and stocks are extremely vulnerable to over-exploitation. We present distributional, size-frequency and reproductive data for three species (Centrophorus harrissoni, C. moluccensis and C. zeehaani) that fishing has largely extirpated from the south-east Australian upper continental slope. Trawl-survey catches in 1976–77 from lightly exploited stocks comprised mostly mature males with few mature females or juveniles; a 2009 long-line survey caught higher proportions of mature females and, for C. harrissoni, more juveniles. Females of the three species grew larger and reached maturity at a greater size than males and, for both sexes, maturity sizes were more than 80% of their maximum observed lengths. Reproduction was continuous but data were insufficient to determine seasonality. Ovarian and uterine fecundity were singular for C. zeehaani whereas C. harrissoni and C. moluccensis developed two oocytes and produced one or two embryos; evidence suggests that the left-side uterus is less functional than the right-side. In response to these species’ inherent low productivity and continuing reduced numbers, managers have introduced landing restrictions and area closures to enhance Centrophorus stocks in southern Australian waters.

Phylogenetic placement and population structure of Indo‐Pacific bottlenose dolphins (Tursiops aduncus) off Zanzibar, Tanzania, based on mtDNA sequences

AbstractPhylogenetic placement of bottlenose dolphins from Zanzibar, East Africa and putative population differentiation between animals found off southern and northern Zanzibar were examined using variation in mtDNA control region sequences. Samples (n= 45) from animals bycaught in fishing gear and skin biopsies collected during boat surveys were compared to published sequences (n= 173) of Indo‐Pacific bottlenose dolphin, Tursiops aduncus, from southeast Australian waters, Chinese/Indonesian waters, and South African waters (which recently was proposed as a new species) and to published sequences of common bottlenose dolphin, Tursiops truncatus. Bayesian and maximum parsimony analyses indicated a close relationship between Zanzibar and South African haplotypes, which are differentiated from both Chinese/Indonesian and Australian T. aduncus haplotypes. Our results suggest that the dolphins found off Zanzibar should be classified as T. aduncus alongside the South African animals. Further, analyses of genetic differentiation showed significant separation between the T. aduncus found off northern and southern Zanzibar despite the relatively short distance (approximately 80 km) between these areas. Much less differentiation was found between southern Zanzibar and South Africa, suggesting a more recent common evolutionary history for these populations than for the northern and southern Zanzibar populations.

Assessing the stock status of holobenthic octopus fisheries: is catch per unit effort sufficient?

Abstract Leporati, S. C., Ziegler, P. E., and Semmens, J. M. 2009. Assessing the stock status of holobenthic octopus fisheries: is catch per unit effort sufficient? – ICES Journal of Marine Science, 66: 478–487. Holobenthic and merobenthic octopus fisheries are commonly treated as biological equivalents, regardless of their contrasting life-history strategies. This is the consequence of a lack of species identification and relevant biological information for many species, which has led to a reliance on catch per unit effort (cpue) data for stock status assessments. Using the commercial Octopus pallidus fishery in southeast Australian waters as a case study, the reliability of commercial cpue data as an indicator of stock status for holobenthic octopus fisheries was assessed. To achieve this, cpue and biological information from a fixed position experimental research line were investigated for consistency in stock status patterns and compared with commercial fishery cpue trends. Research line results revealed that cpue could remain stable regardless of size-selective fishing mortality potentially impacting recruitment. The cpue in the commercial fishery was very seasonal and dominated by females during autumn, when both cpue and spawning periods peaked, so increasing the potential for negative fishery impacts on egg production. The inability of cpue to account for the effects of continual fishing pressure on recruitment or seasonal changes in sex-specific catchability, however, indicates that cpue alone cannot provide sufficient information on the status of a holobenthic octopus fishery.

Cadmium, copper, mercury, and zinc concentrations in tissues of the King Crab ( Pseudocarcinus gigas) from southeast Australian waters

The concentrations of cadmium, copper, mercury, and zinc were determined in muscle (body, claw, and leg), hepatopancreas, and gill tissues of Pseudocarcinus gigas, an exceptionally large, long-lived, and deep-dwelling crab species. The accumulation patterns observed are discussed in terms of both intra- and interspecies variations, with particular attention to the possible consequences of the extreme size and depth range of P. gigas. Metal concentrations did not depend significantly on sex of the crab. Significant differences between tissues were detected for all metals, and the distribution of metal between the tissues was different for each metal. Significant correlations were found between metal concentrations in the various tissues and crab size, and these are discussed and rationalised. The concentrations of mercury and zinc in muscle tissue increased with crab size and were high compared to other crab species. The concentrations of cadmium and copper present in edible tissues were not especially high compared to other crab species, but the concentration of cadmium in the hepatopancreas is of dietary concern.

Age determination of orange roughy,Hoplostethus atlanticus (Pisces: Trachichthyidae) using210Pb:226Ra disequilibria

Natural levels of210Pb:226Ra in otoliths of orange roughy,Hoplostethus atlanticus, from south-east Australian waters, were measured to determine fish ages radiometrically. Up to maturity, radiometric age estimates were consistent with a single constant otolith growth rate. Radiometric ages for juveniles were comparable with, but greater than, those obtained in a recent, validated New Zealand study which employed counts of annuli on the surface of otoliths. Beyond maturity, radiometric ages were obtained by modelling with an otolith growth rate set at 45% of the juvenile rate. Radiometric ageing confirms that orange roughy is very slow-growing, with an age at maturity (32 cm standard length, SL) of ~ 32 yr, and is very long-lived, with fish 38 to 40 cm being 77 to 149 yr old. These results have important implications for the management of the fishery.

Recruitment variation in sympatric populations of Haliotis rubra (Mollusca. Gastropoda) in southeast Australian waters

Recruitment variation in sympatric populations of Haliotis rubra (Mollusca. Gastropoda) in southeast Australian waters

Population age structure and mortality rates of jackass morwong ( Nemadactylus macropterus) in Eastern Bass Strait, Australia

The catch-curve method was used to estimate the instantaneous rate of total mortality ( Z) of jackass morwong ( Nemadactylus macropterus) in south-east Australian waters. Age-frequency distributions were obtained for fish collected from eastern Bass Strait during the 3 years. March 1982–February 1985. Fish were obtained from: (1) demersal research fishing surveys stratified by depth; (2) commercial landings from eastern Bass Strait; (3) commercial landings from the adjacent New South Wales fishery. Jackass morwong were found in water 65–299-m deep, and almost half the biomass was in water 90–179-m deep. Our estimate of the total biomass (from the survey results) of the part of the population in eastern Bass Strait was 15 700 t. The oldest male morwong caught was 11 years old, the oldest female 13 years old. From the survey data, total mortality ( Z) was estimated as 0.45 for males, which is equivalent to an annual survival rate ( S) of 0.64, and as 0.47 for females, equivalent to an S of 0.63. There was substantial annual variation in estimates of Z. For the survey results, the annual mortality rate estimated for males was significantly different from that for females. The instantaneous rate of fishing mortality ( F) estimated from population biomass and mean commercial landings was very low (about 0.024; sensitivity analysis indicated a possible range of 0.012–0.072), and indicated that about 2% (by number; range 1–6%) of the part of the population in eastern Bass Strait was harvested annually. Z values estimated from samples of commercial landings were consistently larger than Z estimated from the survey samples. Using estimates of Z from commercial landings data resulted in high values of M (the instantaneous rate of natural mortality), which were inconsistent with the longevity of the species and the proportion of older fish found in the population. We believe this to be due to bias in the way commercial landings sample the population, and to be an inherent bias in the use of age-frequency data from commercial landings unless some correction for size-selectivity due to commercial fishing gear and fishing behaviour can be made.

Reversed-phase chromatographic separation and analysis of marine metal—organic complexes

Metal—organic complexes were isolated from seawater by adsorption on reversed-phase chromatographic supports such as C 18 Sep-Pak cartridges and XAD-2 resin and subsequent elution with methanol, acetonitrile or tetrahydrofuran. Preliminary results indicate that Sep-Pak cartridges packed with Styragel are also suitable, although back pressures are higher and low blank values are difficult to achieve. Analysis of the extracts by high-performance liquid chromatography with atomic fluorescence detection of trace metals showed that methanol extracts remain unchanged for up to three months in polypropylene at temperatures between −20°C and 20°C and in glass at −20°C. No changes were observed in acetonitrile extracts stored for one week at −20°C, even though the wet extract separated into two phases. Rapid freezing of C 18 Sep-Pak cartridges to /t-195°C also seemed to be a suitable method for preserving samples for future analysis. High-intensity lamps improved the sensitivity of the atomic fluorescence detector by 1/2-2 orders of magnitude and zinc, magnesium, copper, nickel and iron could be determined simultaneously with detection limits ranging from 0.05 μg l −1 (zinc) to 7 μg l −1 (iron). The chromatograms were calibrated by standard additions of trace metals. All the chromatographic columns investigated (C 18 Resolve, C 18 Nova-Pak, PRP-1 and Protein-Pak 125) contained impurity sites that could interfere with the analysis of metal—organic compounds at the ultra-trace level. As interference was most pronounced for magnesium—organic complexes, magnesium was used as an indicator of the presence of coordinating sites on the chromatographic support. Interference effects could be reduced by the addition of modifying agents containing alkali metal salts at a concentration of 50 m M. The most suitable salt was potassium trifluoromethanesulfonate. Metal—organic compounds were isolated on XAD-2 resin (waters from Storm Bay, Tasmania), and on C 18 Sep-Pak cartridges (waters from south-east Australian waters and the Fiji Basin). The concentrations of copper (410 p M), zinc (650 p M) and iron (800 p M) organic complexes from south-east Australian waters were higher than the values obtained for copper (60/2-120 p M), zinc (50/2-150 p M and iron (150/2-180 p M) organic complexes isolated from the Fiji Basin.

Trachymedusae and Narcomedusae of South-east Australian Waters

Thirteen species of Trachymedusae and seven of Narcomedusae are recorded from south-east Australian waters, where both orders were previously unknown. Eight Trachymedusae and four Narcomedusae are new records for the entire Australian region. Additions are made to the descriptions of some species. Eight species are epipelagic, seven bathypelagic, and five probably eurybathic in the upper 1000 m of the sea; the second and third groups contain several cosmopolitan species, but the species of the first (epipelagic) group tend to be restricted to tropical and, subtropical latitudes. One epipelagic species, Liriope tetraphylla (Chamisso & Eysenhardt), has not been found south of lat. 39� S. in south-east Australian waters and may serve as an indicator of one of the two main water masses which meet in that region. The most abundant species of either order is Aglauru hemistoma Peron & Lesueur, which is the commonest of all hydromedusae on the continental shelf off Queensland and New South Wales. Aglaura and Liriope are also recorded from the neighbourhood of Fremantle, W.A.