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1
Turnbull, Alison, Juan José Dorantes-Aranda, Tom Madigan, Jessica Jolley, Hilary Revill, Tim Harwood e Gustaaf Hallegraeff. "Field Validation of the Southern Rock Lobster Paralytic Shellfish Toxin Monitoring Program in Tasmania, Australia". Marine Drugs 19, n. 9 (8 settembre 2021): 510. http://dx.doi.org/10.3390/md19090510.
Testo completoAbstract (sommario):
Paralytic shellfish toxins (PST) are found in the hepatopancreas of Southern Rock Lobster Jasus edwardsii from the east coast of Tasmania in association with blooms of the toxic dinoflagellate Alexandrium catenella. Tasmania’s rock lobster fishery is one of the state’s most important wild capture fisheries, supporting a significant commercial industry (AUD 97M) and recreational fishing sector. A comprehensive 8 years of field data collected across multiple sites has allowed continued improvements to the risk management program protecting public health and market access for the Tasmanian lobster fishery. High variability was seen in toxin levels between individuals, sites, months, and years. The highest risk sites were those on the central east coast, with July to January identified as the most at-risk months. Relatively high uptake rates were observed (exponential rate of 2% per day), similar to filter-feeding mussels, and meant that lobster accumulated toxins quickly. Similarly, lobsters were relatively fast detoxifiers, losing up to 3% PST per day, following bloom demise. Mussel sentinel lines were effective in indicating a risk of elevated PST in lobster hepatopancreas, with annual baseline monitoring costing approximately 0.06% of the industry value. In addition, it was determined that if the mean hepatopancreas PST levels in five individual lobsters from a site were <0.22 mg STX equiv. kg−1, there is a 97.5% probability that any lobster from that site would be below the bivalve maximum level of 0.8 mg STX equiv. kg−1. The combination of using a sentinel species to identify risk areas and sampling five individual lobsters at a particular site, provides a cost-effective strategy for managing PST risk in the Tasmanian commercial lobster fishery.
2
McMillan, M. N., C. Huveneers, J. M. Semmens e B. M. Gillanders. "Partial female migration and cool-water migration pathways in an overfished shark". ICES Journal of Marine Science 76, n. 4 (5 dicembre 2018): 1083–93. http://dx.doi.org/10.1093/icesjms/fsy181.
Testo completoAbstract (sommario):
Abstract Knowledge about reproductive movements can be of important conservation value for over-exploited species that are vulnerable when moving between and within key reproductive habitats. Lack of knowledge persists around such movements in the overfished school shark Galeorhinus galeus in Australia. Management assumes all pregnant females migrate between adult aggregations in the Great Australian Bight, South Australia, and nursery areas around Bass Strait and Tasmania. We tracked 14 late-term pregnant females tagged in South Australia using satellite-linked pop-up archival tags to investigate extent, timing, and routes of migrations. We found partial migration, with some females (n = 7) remaining near aggregating areas throughout the pupping season, some migrating to known nursery areas (n = 3), and one migrating ∼3 000 km to New Zealand. We conclude female movements and pupping habitats are less spatially constrained than assumed and propose females use cool-water routes along the shelf break to reduce energy costs of migration. Migrating females using these routes faced greater fishing pressure than sharks in inshore areas and were not protected by inshore shark fishing closures designed to protect them. This study demonstrates the complexity of reproductive movements that can occur in wide-ranging species and highlights the value of explicit movement data.
3
Frusher, S. D., e J. M. Hoenig. "Estimating natural and fishing mortality and tag reporting rate of southern rock lobster (Jasus edwardsii) from a multiyear tagging model". Canadian Journal of Fisheries and Aquatic Sciences 58, n. 12 (1 dicembre 2001): 2490–501. http://dx.doi.org/10.1139/f01-182.
Testo completoAbstract (sommario):
Fishing and natural mortality rates and tag reporting rate for rock lobsters (Jasus edwardsii) in northwest Tasmania, Australia, were estimated using multiyear tagging models. These estimates are necessary for assessment of the resource. Several models were examined that had either two or three tagging events each year, and either combined sexes or kept sexes separate. The model that best described the dynamics of the fishery utilized three tagging events within a year. The year was divided into discrete periods and, within each year, fishing effort and duration of period were used to apportion fishing and natural mortalities, respectively, to the periods. The separation of fishing mortalities by sex was not found to improve the models. Although high (1.01.2·year1), the instantaneous fishing mortality estimates were comparable to estimates obtained from other methods and the relative standard errors were low. Reporting rate estimates were also precise and indicated a lack of participation by the fishing industry. Estimates of natural mortality were low (0.000.02·year1) but imprecise.
4
Raoult, V., V. Peddemors, K. Rowling e J. E. Williamson. "Spatiotemporal distributions of two sympatric sawsharks (Pristiophorus cirratus and P. nudipinnis) in south-eastern Australian waters". Marine and Freshwater Research 71, n. 10 (2020): 1342. http://dx.doi.org/10.1071/mf19277.
Testo completoAbstract (sommario):
Sawsharks are one of the least well-known groups of sharks globally, yet they are caught in large numbers in south-eastern Australia. In this study we assessed spatiotemporal patterns of distribution of two co-occurring species of sawsharks, namely the common sawshark (Pristiophorus cirratus) and the southern sawshark (Pristiophorus nudipinnis), to guide future research in this area. To identify where the animals may occur in greater numbers, this study used the major commercial fishery datasets in the region, containing nearly 180000 catch records from 1990 to 2017. Several general patterns were evident. Sawsharks occurred at shallower and deeper depths than previously thought, and their geographical range was larger than documented in previous studies. Depth distributions of both species overlapped, but P. cirratus appeared more common in deeper water (at depths up to 500m), with peak common sawshark catch rates at ~400m. Seasonal standardised catch patterns across fishing methods suggested that migrations from deeper to shallower waters may occur in the Australasian autumn and winter. The greatest concentration of sawsharks, inferred by standardised catch rates, occurred to the east and west of Bass Strait between Tasmania and mainland Australia. Although standardised catch rates of sawsharks declined in gill-net fisheries by ~30%, primarily in the Bass Strait and Tasmania, sawsharks appear to be caught at consistent rates since the 1990s, inferring a possible resilience of these sharks to current levels of fishing pressure.
5
Ziegler, Philippe E. "Fishing tactics and fleet structure of the small-scale coastal scalefish fishery in Tasmania, Australia". Fisheries Research 134-136 (dicembre 2012): 52–63. http://dx.doi.org/10.1016/j.fishres.2012.08.011.
Testo completo
6
Knuckey, Ian A., e K. P. Sivakumaran. "Reproductive characteristics and per-recruit analyses of blue warehou (Seriolella brama): implications for the South East Fishery of Australia". Marine and Freshwater Research 52, n. 4 (2001): 575. http://dx.doi.org/10.1071/mf00022.
Testo completoAbstract (sommario):
Monthly samples of commercial catches of S. brama were collected between May 1996 and December 1997 in three regions of the fishery:off the east coast of Victoria; eastern Tasmania; and western Bass Strait. Sex ratio, gonadosomatic index, macroscopic and histological development, size at maturity and fecundity were estimated and combined with data on growth and mortality to perform per-recruit analyses. The main spawning period was during winter–spring and there was evidence of spawning in each of the three regions. Blue warehou reach maturity at 30–40 cm fork length. They have a determinate annual fecundity and spawn around three batches of eggs during a season. Eggs-per-recruit analyses revealed maximum egg production at ~40 cm (4–5 years) in an unfished population. Gill-net fishing, which targets fish >45 cm, was less likely to affect the relative eggs-per-recruit in a population than trawl fishing, which catches a wider range of smaller fish. These results are discussed in light of the current management arrangements in the fishery and will be used in models to assess the effect of fishing on the long-term sustainability of the blue warehou.
7
Wakamatsu, Lael, Gregory L. Britten, Elliot J. Styles e Andrew M. Fischer. "Chlorophyll-a and Sea Surface Temperature Changes in Relation to Paralytic Shellfish Toxin Production off the East Coast of Tasmania, Australia". Remote Sensing 14, n. 3 (30 gennaio 2022): 665. http://dx.doi.org/10.3390/rs14030665.
Testo completoAbstract (sommario):
Toxic phytoplankton have been detrimental to the fishing and aquaculture industry on the east coast of Tasmania, causing millions of dollars in loss due to contaminated seafood. In 2012–2017, shellfish stocks were poisoned by Alexandrium catenella, a dinoflagellate species that produces paralytic shellfish toxins (PST). Remote sensing data may provide an environmental context for the drivers of PST events in Tasmania. We conducted spatial and temporal trend analyses of the Multi-Scale Ultra-High-Resolution Sea Surface Temperature (MUR SST) and Ocean Color Climate Change Initiative chlorophyll-a (OC-CCI chl-a) to determine if SST and chl-a correlated with the major toxin increases from 2012 to 2017. Along with the trends, we compare the remotely sensed oceanographic parameters of SST and chl-a to toxin events off the east coast of Tasmania to provide environmental context for the high-toxin period. Spatial and temporal changes for chl-a differ based on the north, central, and southeast coast of Tasmania. For sites in the north, chl-a was 5.3% higher from the pre-PST period relative to the PST period, 5.1% along the central part of the coast, and by 6.0% in the south based on deviations from the coastal study area time series. Overall, SST has slightly decreased from 2007 to 2020 (tau = −0.011, p = 0.827) and chl-a has significantly decreased for the east coast (tau = −0.164, p = 1.58 × 10−3). A negative relationship of SST and PST values occurred in the north (r = −0.530, p = 5.32 × 10−5) and central sites (r = −0.225, p = 0.157). The correlation between satellite chl-a (from OC-CCI, Visible Infrared Imaging Radiometer Suite (VIIRS), and Moderate-Resolution Imaging Spectrometer (MODIS) Aqua) and in situ data is weak, which makes it difficult to assess relationships present between chl-a and toxin concentrations. Moving forward, the development of a regional chl-a algorithm and increased in situ chl-a collection and plankton sampling at a species level will help to improve chl-a measurements and toxic phytoplankton production monitoring around Tasmania.
8
Young, JW, RW Bradford, TD Lamb e VD Lyne. "Biomass of zooplankton and micronekton in the southern bluefin tuna fishing grounds off eastern Tasmania, Australia". Marine Ecology Progress Series 138 (1996): 1–14. http://dx.doi.org/10.3354/meps138001.
Testo completo
9
Crawford, C., G. Edgar, C. L. Gillies e G. Heller-Wagner. "Relationship of biological communities to habitat structure on the largest remnant flat oyster reef (Ostrea angasi) in Australia". Marine and Freshwater Research 71, n. 8 (2020): 972. http://dx.doi.org/10.1071/mf19171.
Testo completoAbstract (sommario):
Oyster reef restoration is a growing field in Australia, yet formal descriptions of associated biological communities for reefs created by native flat oysters (Ostrea angasi) do not currently exist. Native flat oysters once formed extensive and complex three-dimensional habitats in bays and estuaries across southern Australia until indiscriminate fishing, sedimentation and disease led to their near disappearance. To determine the diversity and abundance on naturally occurring oyster reefs, we sampled four sites on the last known naturally occurring oyster reef ecosystem, which resides in north-eastern Tasmania, and compared them to the surrounding soft sediment regions. Assemblages were related to environmental variables to determine whether consistent patterns were present. Oyster reef sites contained three times the faunal abundance of the surrounding soft sediment regions. Abundance among echinoderms, arthropods, molluscs and fish was much elevated, whereas annelids showed similar levels of abundance but differed in terms of species composition. These results show that oyster reefs do support abundant and diverse assemblages, emphasising the probable loss of community-level biodiversity associated with their historical decline around southern Australia.
10
Pocock, Celmara, David Collett e Joan Knowles. "False Promise: World Heritage, Ecotourism, and the Local Community of Strahan, Tasmania". Heritage 7, n. 2 (16 febbraio 2024): 1028–42. http://dx.doi.org/10.3390/heritage7020050.
Testo completoAbstract (sommario):
The inscription of properties on the World Heritage List often places restrictions on existing livelihoods. In these contexts, tourism is widely held to be a panacea for the economic and social wellbeing of local communities. Ecotourism, in particular, is regarded as addressing both environmental and social needs of communities. However, existing research demonstrates that tourism seldom delivers benefits to Indigenous peoples or local communities in developing countries. This paper suggests that such limitations are equally problematic for local communities in developed nations such as Australia. Through ethnographic research including participant observation and interviews, this paper describes the impacts of tourism on the local community of Strahan, a small logging, fishing, and mining town that transformed into a tourism village following the World Heritage listing of Southwest Tasmania. We suggest that contrary to the widely held view that tourism created employment and economic growth in the town, locals experience diminished quality of life, limited opportunities, and reduced amenity and services. This suggests that ecotourism overlooks its responsibilities for local communities in developed countries, with profound consequences for social sustainability.
11
Pecl, Gretta T., Sean R. Tracey, Leonid Danyushevsky, Simon Wotherspoon e Natalie A. Moltschaniwskyj. "Elemental fingerprints of southern calamary (Sepioteuthis australis) reveal local recruitment sources and allow assessment of the importance of closed areas". Canadian Journal of Fisheries and Aquatic Sciences 68, n. 8 (agosto 2011): 1351–60. http://dx.doi.org/10.1139/f2011-059.
Testo completoAbstract (sommario):
Movement of individuals over a range of temporal and spatial scales is a critical process in determining the structure and size of populations. For most marine species, a substantial amount of movement that is responsible for connecting subpopulations occurs when individuals are too small and numerous to be tagged using conventional methods. Using the elemental fingerprints of the statoliths of the squid Sepioteuthis australis and a robust machine learning classification technique, this study determined that newly hatched squid had elemental signatures that exhibited sufficient spatial variation to act as natural tags for natal origin and that elemental signatures can be used to allocate adult squid back to their natal site. Between 55% and 84% of the adult squid caught throughout the east and southeast of Tasmania, Australia, were classified back to an area that is closed to commercial fishing over much of the peak spawning period, and this was the only location with substantive evidence of natal recruitment. Although many studies have demonstrated the potential of this approach to discern connectivity between population units, few studies have successfully done so by then examining the trace element profiles of adults in addition to those of hatchlings as we have demonstrated with S. australis.
12
Henrich, Joseph. "Demography and Cultural Evolution: How Adaptive Cultural Processes Can Produce Maladaptive Losses—The Tasmanian Case". American Antiquity 69, n. 2 (aprile 2004): 197–214. http://dx.doi.org/10.2307/4128416.
Testo completoAbstract (sommario):
A combination of archeological and ethnohistorical evidence indicates that, over an approximately 8,000-year period, from the beginning of the Holocene until European explorers began arriving in the eighteenth century, the societies of Tasmania lost a series of valuable skills and technologies. These likely included bone tools, cold-weather clothing, hafted tools, nets, fishing spears, barbed spears, spear-throwers, and boomerangs. To address this puzzle, and the more general question of how human cognition and social interaction can generate both adaptive cultural evolution and maladaptive losses of culturally acquired skills, this paper constructs a formal model of cultural evolution rooted in the cognitive details of human social learning and inference. The analytical results specify the conditions for differing rates of adaptive cultural evolution, and reveal regimes that will produce maladaptive losses of particular kinds of skills and related technologies. More specifically, the results suggest that the relatively sudden reduction in the effective population size (the size of the interacting pool of social learners) that occurred with the rising ocean levels at the end of the last glacial epoch, which cut Tasmania off from the rest of Australia for the ensuing ten millennia, could have initiated a cultural evolutionary process that (1) kept stable or even improved relatively simple technological skills, and (2) produced an increasing deterioration of more complex skills leading to the complete disappearance of some technologies and practices. This pattern is consistent with the empirical record in Tasmania. Beyond this case, I speculate on the applicability of the model to understanding the variability in rates of adaptive cultural evolution.
13
Larcombe, James W. P., Kevin J. McLoughlin e Richard D. J. Tilzey. "Trawl operations in the South East Fishery, Australia: spatial distribution and intensity". Marine and Freshwater Research 52, n. 4 (2001): 419. http://dx.doi.org/10.1071/mf99169.
Testo completoAbstract (sommario):
Trawl areas and intensities were mapped at coarse (22 km 1986–99)and fine (1 km 1995–99)scales, and statistics reported by area and depth stratum. Total effort in hours was relatively stable to 1992, then increased substantially to 1999. The total distance trawled from fine-scale analysis showed a similar trend for the 1995–99 period. Coarse-scale analysis from 1986–99 indicated effort increases in north-east Bass Strait in particular, and also off western Tasmania and west of Bass Strait. There was little change in the total area of the fishery from 1995 to 1999, but grid cells on the periphery showed considerable interannual variation in the presence or absence of fishing. Increased or redistributed effort tended to further concentrate in the relatively small high-effort areas, rather than increasing equally across the grounds, or spreading to new grounds. In the total management area, a small proportion of the 1 km grids was fished. However, in 200–1000 m depth strata, ≥50%of the grids were fished with some intensity. The consequences and compromises of spatial scale are discussed in terms of data quality, the use of trawl effort as a surrogate for marine disturbance, and the interpretation of catch rates.
14
Raoult, Vincent, Troy F. Gaston e Jane E. Williamson. "Not all sawsharks are equal: species of co-existing sawsharks show plasticity in trophic consumption both within and between species". Canadian Journal of Fisheries and Aquatic Sciences 72, n. 11 (novembre 2015): 1769–75. http://dx.doi.org/10.1139/cjfas-2015-0307.
Testo completoAbstract (sommario):
Despite the global distribution of sawsharks, little is known about their diets or their role in the marine biosphere. As species in higher trophic positions are generally considered to be more at risk to perturbations such as fishing, understanding their role in the food chain will enable better conservation and management strategies for these species. Two sawshark species (Pristiophorus cirratus, Pristiophorus nudipinnis) co-occur in waters off east Tasmania, Australia. This study determined the trophic positions of these sawsharks and whether they avoided competing with each other through resource partitioning. Isotopic analysis of muscle tissue revealed that P. cirratus and P. nudipinnis had significantly different trophic levels, with P. cirratus likely to have a diet of primary consumers and P. nudipinnis likely to have a piscivorous diet. Owing to their different isotopic signatures, it is also likely that the sawshark rostrum has multiple functions. Both species shifted to higher trophic levels during ontogeny. Maternal isotopic signatures were detectable in P. cirratus juveniles.
15
Latour, Robert J., John M. Hoenig, Daniel A. Hepworth e Stewart D. Frusher. "A novel tag-recovery model with two size classes for estimating fishing and natural mortality, with implications for the southern rock lobster (Jasus edwardsii) in Tasmania, Australia". ICES Journal of Marine Science 60, n. 5 (1 gennaio 2003): 1075–85. http://dx.doi.org/10.1016/s1054-3139(03)00093-6.
Testo completoAbstract (sommario):
Abstract Multi-year tag-recovery models can be used to derive estimates of age- and year-specific annual survival rates and year-specific instantaneous fishing and natural mortality rates. The latter, which are often of interest to fisheries managers, usually can only be estimated when the tag-reporting rate (λ) and the short-term tag-induced mortality and tag-shedding rate (φ) are known a priori. We present a new multi-year tagging model that permits estimation of instantaneous mortality rates independently of φλ, provided tagged animals from two adjacent size groups are released simultaneously. If the two size groups comprise animals just above and below the minimum harvestable size limit, then it is possible to estimate year-specific instantaneous fishing and natural mortality rates after 2 yr of tagging and tag-recovery. In addition to the standard assumptions of multi-year tag-recovery models, it is necessary to assume that recruited animals have equal selectivity, pre-recruited animals become fully recruited in 1 or 2 yr, and the size groups experience the same natural mortality rate. Applicability of the model to the Tasmania southern rock lobster (Jasus edwardsii) fishery is evaluated using a simulation model and parameters based on data from the lobster fishery; assumptions are likely to be met and precision should be adequate if at least 1000 animals are tagged per year in each size group.
16
Frusher, S. D., S. D. Frusher, J. M. Hoenig e J. M. Hoenig. "Strategies for improving the precision of fishing and natural mortality estimates from multiyear tagging models: a case study". Marine and Freshwater Research 52, n. 8 (2001): 1649. http://dx.doi.org/10.1071/mf01196.
Testo completoAbstract (sommario):
Fisheries scientists and managers want precise estimates of fishing and natural mortality for assessments and management decisions. Because tagging can be an expensive option, maximizing potential benefits requires careful consideration of experimental design. We evaluated four options for improving the precision of estimates by conducting Monte Carlo simulations of a fishery patterned after that for the rock lobsters in north-western Tasmania, Australia. Improving tag-reporting rate and increasing the duration of the tagging study provided greater improvements in precision than increasing either the number of lobsters tagged per tagging event or the number of tagging events each year. A design based on twice-a-year tagging for three years to determine tagreporting rate followed by an additional two or more years of once-a-year tagging provided the most precise estimates of natural mortality of all the designs considered. This design was also cost effective relative to the other options, but tag-reporting rate must be constant over the period of the study. If constancy cannot be assumed, then years of multiple tagging events may have to be interspersed among the years with single tagging events. Further improvements in mortality estimates from this multiyear tagging model could be achieved with improved tagreporting rate.
17
Ziegler, Philippe E., Jeremy M. Lyle, Malcolm Haddon e Graeme P. Ewing. "Rapid changes in life-history characteristics of a long-lived temperate reef fish". Marine and Freshwater Research 58, n. 12 (2007): 1096. http://dx.doi.org/10.1071/mf07137.
Testo completoAbstract (sommario):
Banded morwong, Cheilodactylus spectabilis, a long-lived sedentary temperate reef fish, has undergone rapid changes in its growth and maturity characteristics along the east coast of Tasmania, Australia. Over a period of 10 years, growth of young males and females has consistently accelerated, such that in 2005, 3-year-old fish were up to 40 mm or 13% longer compared with 1996, and age at 50% maturity for females had declined from 4 to 3 years. The magnitude and speed of the observed changes were unexpected given the species’ longevity (maximum age of over 95 years). The underlying mechanisms for the changes remain unclear but density-dependent responses to changes in population size and age composition, possibly mediated through reduced competition for shelter and intra-specific interactions, may have been contributing factors. Increasing sea surface temperatures over part of the period of change does not appear to have been a major driver and a genetic response to fishing seems unlikely. Notwithstanding any uncertainty, C. spectabilis populations have become more productive in recent years, challenging the general approach towards stock assessment where life-history characteristics are assumed to remain stable across contrasting levels of stock abundance and environmental conditions.
18
Turnbull, Alison, Andreas Seger, Jessica Jolley, Gustaaf Hallegraeff, Graeme Knowles e Quinn Fitzgibbon. "Lobster Supply Chains Are Not at Risk from Paralytic Shellfish Toxin Accumulation during Wet Storage". Toxins 13, n. 2 (9 febbraio 2021): 129. http://dx.doi.org/10.3390/toxins13020129.
Testo completoAbstract (sommario):
Lobster species can accumulate paralytic shellfish toxins (PST) in their hepatopancreas following the consumption of toxic prey. The Southern Rock Lobster (SRL), Jasus edwardsii, industry in Tasmania, Australia, and New Zealand, collectively valued at AUD 365 M, actively manages PST risk based on toxin monitoring of lobsters in coastal waters. The SRL supply chain predominantly provides live lobsters, which includes wet holding in fishing vessels, sea-cages, or processing facilities for periods of up to several months. Survival, quality, and safety of this largely exported high-value product is a major consideration for the industry. In a controlled experiment, SRL were exposed to highly toxic cultures of Alexandrium catenella at field relevant concentrations (2 × 105 cells L−1) in an experimental aquaculture facility over a period of 21 days. While significant PST accumulation in the lobster hepatopancreas has been reported in parallel experiments feeding lobsters with toxic mussels, no PST toxin accumulated in this experiment from exposure to toxic algal cells, and no negative impact on lobster health was observed as assessed via a wide range of behavioural, immunological, and physiological measures. We conclude that there is no risk of PST accumulation, nor risk to survival or quality at the point of consumption through exposure to toxic algal cells.
19
Treloar, M. A., N. S. Barrett e G. J. Edgar. "Biology and ecology of Zearaja maugeana, an Endangered skate restricted to two south-western Tasmanian estuaries". Marine and Freshwater Research 68, n. 5 (2017): 821. http://dx.doi.org/10.1071/mf15478.
Testo completoAbstract (sommario):
The Endangered Maugean skate Zearaja maugeana is a relic species restricted to two isolated estuaries, Bathurst Harbour and Macquarie Harbour, in south-western Tasmania, Australia. Over a 1-year period, dive, tagging and net surveys provided information on the biology and ecology of this species. In all, 96 Maugean skates were caught during five trips to Macquarie Harbour, with four additional individuals observed underwater; however, no animals were located in the single trip to Bathurst Harbour. Morphometrics and the sex of the animals were recorded for 95 individuals. Crustaceans dominated the diet, with the majority of animals feeding on the crab Paragrapus gaimardii. Recapture rates were very low, with only one of 82 pit-tagged skates recaptured, and that occurred on the day of release. One acoustically tagged male skate was tracked for 5km along the harbour margin for 24h, whereas a female skate tracked for 46.5h showed high site fidelity, suggesting that multiple factors potentially influence habitat utilisation. Although Macquarie Harbour represents the stronghold for this species, this estuary is also experiencing major environmental disturbance and change. Conservation management of this Endangered skate requires specific consideration of aquaculture, recreational fishing and mine drainage effects, as well as ongoing monitoring.
20
Stevens, JD. "Blue and Mako Shark by-catch in the Japanese Longline Fishery off South-eastern Australia". Marine and Freshwater Research 43, n. 1 (1992): 227. http://dx.doi.org/10.1071/mf9920227.
Testo completoAbstract (sommario):
During the last 10 years, up to 70 Japanese longline vessels have fished Tasmanian waters of the Australian Fishing Zone each season, targeting bluefin tuna (Thunnus maccoyii). The average seasonal fishing effort in Tasmanian waters is about 3.3 million hooks, and data from observers suggests that, this results in a by-catch of some 34 000 blue sharks (Prionace glauca) each year, representing a weight of about 275 tonnes. In the last few years, fishing effort has increased as the catch rates of southern bluefin tuna have declined. The sharks are discarded after removal of the fins. The actual number of blue sharks hooked is much higher than 34000 because many are released by either shaking or cutting them off the line, although they are often damaged in the process. The majority of blue sharks caught are immature or adolescent females. Smaller numbers of shortfin mako sharks (Isurus oxyrinchus) are also caught and retained both for their fins and their meat. Tasmanian waters represent only one area of the Australian Fishing Zone fished by Japanese longliners.
21
Harrington, Julian J., Jayson M. Semmens e Malcolm Haddon. "Spatial distribution of commercial dredge fishing effort: application to survey design and the spatial management of a patchily distributed benthic bivalve species". Marine and Freshwater Research 58, n. 8 (2007): 756. http://dx.doi.org/10.1071/mf06101.
Testo completoAbstract (sommario):
The patchy spatial distribution of many benthic commercial bivalve species plays an important role in determining the fishing and management strategies applied within a fishery. This study used fisher catch-return data and high resolution Vessel Monitoring System (VMS) data to determine the distribution of fishing effort within a region opened to commercial dredge fishing during the 2003 Tasmanian commercial scallop (Pecten fumatus) fishery, Australia. Fisher catch return data suggested that most (88%) of the open region was fished, however, fine-scale VMS data showed that 50% of the fishing effort occurred within 0.85% of the total area available to fishing, and 95% of the effort occurred within ~12% of the open region. The distribution of VMS inferred that the fishing effort was found to be patchy at all measured spatial scales (5 × 5 km to 250 × 250 m grid cell sizes); however, the degree of patchiness decreased with lower spatial scale cell sizes. Significant differences in the dredged benthic communities recorded within regions exposed to different concentrations of fishing intensity (heavy, moderate and low) were observed, with low and moderately fished regions containing high abundances of screwshells and their associated hermit crabs. Water depth was found to explain some of these observed differences, suggesting that the results may be the consequence of fisher behaviour over pre-existing habitat types. The observed distribution of the fishing effort and scallop beds within the Tasmanian commercial scallop, Pecten fumatus, fishery suits a closed area spatial management strategy, with the areas opened to fishing potentially being of the same scale as scallop beds (km × km).
22
McLeod, David J., Alistair J. Hobday, Jeremy M. Lyle e Dirk C. Welsford. "A prey-related shift in the abundance of small pelagic fish in eastern Tasmania?" ICES Journal of Marine Science 69, n. 6 (18 maggio 2012): 953–60. http://dx.doi.org/10.1093/icesjms/fss069.
Testo completoAbstract (sommario):
Abstract McLeod, D. J., Hobday, A. J., Lyle, J. M., and Welsford, D. C. 2012. A prey-related shift in abundance of small pelagic fish in eastern Tasmania? – ICES Journal of Marine Science, 69: 953–960. Shifts in the relative abundance of small pelagic fish species have signalled a change in the ocean environment in a number of locations. Here we show that the replacement of jack mackerel, Trachurus declivis, with redbait, Emmelichthys nitidus, as the dominant small pelagic species from eastern Tasmania, following a period of high fishing pressure on jack mackerel, is consistent with altered zooplankton communities and long-term climate change. Stomach contents analysis and morphology measurements were conducted on both species to determine if they were functionally equivalent with regard to zooplankton prey. Diet varied between species and with fish size. Krill (Nyctiphanes australis) was consumed by both species, with redbait feeding more heavily on small copepods. The diet overlap and morphometric characteristics indicated that these species are not equivalent with regard to prey and therefore changes in prey availability may have contributed to the observed shifts in relative abundance. The continued poleward extension of the East Australian Current is expected to favour small warm-water copepods; thus, redbait may have an advantage over jack mackerel due to prey preferences. An increase in relative abundance of redbait has decreased effort in surface fisheries and may impact on surface-feeding higher predators in this region.
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Williams, H., e AH Schaap. "Preliminary results of a study into the incidental mortality of sharks in Gill-nets in two Tasmanian Shark Nursery Areas". Marine and Freshwater Research 43, n. 1 (1992): 237. http://dx.doi.org/10.1071/mf9920237.
Testo completoAbstract (sommario):
Since the early 1960s, certain sheltered bays and estuaries around Tasmania have been designated shark nursery areas, where the taking of either the school shark (Galeorhinus galeus) or the gummy shark (Mustelus antarcticus) has been prohibited. Recent assessments of Australian stocks of school and gummy sharks indicate that they are close to collapse, and the management of the fishery has come under review. With respect to shark nursery areas, concern has focused on the potential rate of incidental mortality of sharks caused by recreational gill-net fishing and poaching. In 1990, a study was begun in Frederick Henry Bay and Norfolk Bay, the largest proclaimed shark nursery areas in Tasmania, to estimate recreational net-fishing effort and incidental captures of sharks. School sharks were caught in waters deeper than 5 m; gummy sharks and dogfish were caught at all depths. The diversity and relative abundance of shark species increased with depth, whereas the diversity of teleosts decreased with depth. Most captured school and gummy sharks were between 1+ and 3+ years of age. Preliminary estimates of potential incidental mortality demonstrate that gill-netting in depths greater than 5 m may be a significant source of mortality for both species.
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Emery, Timothy J., Klaas Hartmann, Bridget S. Green, Caleb Gardner e John Tisdell. "Fishing for revenue: how leasing quota can be hazardous to your health". ICES Journal of Marine Science 71, n. 7 (26 febbraio 2014): 1854–65. http://dx.doi.org/10.1093/icesjms/fsu019.
Testo completoAbstract (sommario):
Abstract Fisheries management decisions have the potential to influence the safety of fishers by affecting how and when they fish. This implies a responsibility of government agencies to consider how fishers may behave under different policies and regulations in order to reduce the incidence of undesirable operational health and safety outcomes. In the Tasmanian southern rock lobster fishery, Australia, the expansion of the quota lease market under individual transferable quota (ITQ) management coincided with a rise in the number of commercial fishing fatalities, with five between 2008 and 2012. A discrete choice model of daily participation was fitted to compare whether physical risk tolerance varied between fishers who owned the majority of their quota units (quota owners) and those who mainly leased (lease quota fishers). In general, fishers were averse to physical risk (wave height), however this was offset by increases in expected revenue. Lease quota fishers were more responsive to changes in expected revenue than quota owners, which contributed to risk tolerance levels that were significantly higher than those of quota owners in some areas. This pattern in behaviour appeared to be related to the cost of leasing quota. Although ITQs have often been considered to reduce the incentive for fishers to operate in hazardous weather conditions, this assumes fishing by quota owners. This analysis indicated that this doesn't hold true for lease quota fishers in an ITQ system, where in some instances there remains an economic incentive to fish in conditions with high levels of physical risk.
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Alderman, R., R. Gales, G. N. Tuck e J. D. Lebreton. "Global population status of shy albatross and an assessment of colony-specific trends and drivers". Wildlife Research 38, n. 8 (2011): 672. http://dx.doi.org/10.1071/wr10199.
Testo completoAbstract (sommario):
Context Monitoring the status of albatross populations and identifying the factors driving observed trends remain international conservation and management priorities. The shy albatross is endemic to Australia and breeds only on three Tasmanian islands. Aims To provide a reliable total population estimate for shy albatross, including an assessment of demographic trends for each of the three populations where possible. We consider also key drivers of population trends for each population, particularly the potential role of fisheries by-catch, with an overall aim of determining the status of the species. Methods Aerial photography and ground surveys were used to estimate the number of annual breeding pairs and trends in adult and juvenile survival rates were calculated using mark–recapture methods. At-sea distribution data was used to identify population specific trends in the overlap of shy albatross and fisheries to evaluate the potential influence of fisheries by-catch on the populations. Key Results The Albatross Island population increased post-harvesting but has recently stabilised at around 5200 breeding pairs, less than half its estimated historic size. This trajectory change appears driven by a decrease in juvenile survival. The small (170 breeding pairs) Pedra Branca population has recently declined, probably due to reduced breeding success associated with the increasing population of Australasian gannets (Morus serrator) on the island. The largest population (on Mewstone) comprises at least 9500 breeding pairs. Trends for this population are unknown. However, this paper demonstrates that these birds have greater overlap with trawl and longline fishing effort and are consequently at higher risk of fishing-related mortality. Conclusions Given the extent of fisheries overlap, survival rates for Mewstone individuals are likely to be lower than the Albatross Island population. Combined with recent trends on Pedra Branca and Albatross Island, we suggest that the current status of the shy albatross is likely to be stable at best and quite possibly decreasing. Implications The concerns raised about the conservation status of shy albatross reinforce the importance of continued population monitoring focussed particularly on establishing the trend of Mewstone. A thorough assessment of interactions with trawl fishing operations also is a management priority for this species.
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Barrett, Neville, Colin Buxton e Caleb Gardner. "Rock lobster movement patterns and population structure within a Tasmanian Marine Protected Area inform fishery and conservation management". Marine and Freshwater Research 60, n. 5 (2009): 417. http://dx.doi.org/10.1071/mf07154.
Testo completoAbstract (sommario):
As reference sites to better understand characteristics such as movement patterns, depletion of natural resources and ecosystem interactions, Marine Protected Areas (MPAs) are crucial in fishery and conservation management. The southern rock lobster (Jasus edwardsii) is an important reef predator in temperate Australasia and subject to heavy exploitation. In a Tasmanian MPA, 90% of individuals were recaptured less than 200 m from the point of release over weekly to annual time scales, regardless of size or sex. This lack of movement resulted in a substantial build-up of biomass and of large mature individuals in the MPA relative to adjacent fished locations. Although there was little spillover of individuals to the fishery, a 4-fold increase in female fecundity potentially enhanced larval export. Comparison of fished and unfished biomass of legal-sized animals suggested that exploitation had reduced biomass in the adjacent fishery to <10% of natural values. Overall, the demographic and movement patterns illustrate the extent of depletion of stocks in the absence of historical baseline data and the potential need for spatial management resulting from limited movement. Our data indicate that within MPAs, this predator can potentially recover in abundance to natural levels despite adjacent fishing pressure.
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Yick, Jonah L., Chris Wisniewski, John Diggle e Jawahar G. Patil. "Eradication of the Invasive Common Carp, Cyprinus carpio from a Large Lake: Lessons and Insights from the Tasmanian Experience". Fishes 6, n. 1 (23 febbraio 2021): 6. http://dx.doi.org/10.3390/fishes6010006.
Testo completoAbstract (sommario):
Common carp (Cyprinus carpio, L. 1758) are the most abundant pest fish species in Australia, detrimental to ecosystem integrity and values, and in need of suitable management solutions. In January 1995, this destructive pest was discovered in two large, connected Tasmanian lakes—Lakes Crescent (23 km2) and Sorell (54 km2). After an initial assessment, carp were immediately contained to these waters using screens to prevent their escape down-stream, followed by swift legislation to enforce closure of the lakes to the public. Assessment and evaluation of carp numbers occurred throughout the eradication program, with effort focused on Lake Crescent. Beginning with undirected removal, techniques progressively evolved to more sophisticated targeted removal with assistance from biotelemetry, in conjunction with gill netting and electro-fishing. Real-time population estimates and in situ observations resulted in a detailed cumulative understanding of carp population dynamics, behaviour and seasonal habitat choice. This allowed strategic deployment of fences to block access to marshes, and the installation of steel traps within the fences. These gears specifically prevented spawning opportunities, while concurrently capturing mature fish. Following 12 years of adaptive and integrated effort, 7797 carp (fry, juvenile and adult) were captured from Lake Crescent, with the last carp being caught in December 2007. The subsequent 14 years of monitoring has not resulted in the capture of any carp, confirming the successful eradication of carp from Lake Crescent. These management practices have been successfully replicated in the larger Lake Sorell, where 41,499 carp (fry, juvenile and adult) have been removed. It is now estimated that there are few, if any carp remaining. Collectively, the techniques and strategies described here were reliable, and can be applied as a model to control or eradicate pest populations of carp in freshwater lakes elsewhere.
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Geraghty, Pascal T., William G. Macbeth e Jane E. Williamson. "Aspects of the reproductive biology of dusky, spinner and sandbar sharks (Family Carcharhinidae) from the Tasman Sea". Marine and Freshwater Research 67, n. 4 (2016): 513. http://dx.doi.org/10.1071/mf14228.
Testo completoAbstract (sommario):
Increased harvest pressure exerted on sharks worldwide has created a necessity for more information concerning the basic biology of targeted species. This study marks the first dedicated assessment of the reproductive biology of Carcharhinus obscurus, C. brevipinna and C. plumbeus in eastern Australian waters, where these species support a demersal longline fishery. We found all three to be late maturing species of low reproductive output, suggestive of an overarching susceptibility to stock depletion in the region. Length- (L50, cm LT) and age-at-maturity (A50, years), for females and males were respectively 281.1 and 15.5, and 271.9 and 14.6 for C. obscurus; 224.9 and 10.1, and 208.9 and 8.5 for C. brevipinna; and, 174.8 and 9.5, and 164.5 and 7.0 for C. plumbeus. Uterine fecundity (i.e. litter size) was observed at 5–12 (=9.6), 5–14 (=10.6) and 3–12 (=7.8) for the same three species respectively, and increased significantly with maternal length in C. brevipinna. Length-at-birth (L0, cm LT) ranged from 92 to 96 for C. obscurus, 79–82 for C. brevipinna and 66–76 for C. plumbeus, and all three species exhibited lengthy gestation periods, overall embryonic sex ratios of 1:1 and synchronous parturition in autumn. However, given limitations with respect to sample size and temporal distribution inherent in this study, the reproductive parameters defined herein are necessarily preliminary. Nevertheless, this research challenges a range of findings emanating from other parts of the world and, in doing so, raises pertinent questions relating to the resilience to targeted fishing activities of these species in New South Wales waters compared to other oceanic regions. Moreover, it reinforces the importance of locally derived demographic parameters for population modelling and stock assessment.