Journal articles on the topic 'Sharks – Effect of fishing on – Australia'
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1
McAuley, Rory B., Colin A. Simpfendorfer, and Norm G. Hall. "A method for evaluating the impacts of fishing mortality and stochastic influences on the demography of two long-lived shark stocks." ICES Journal of Marine Science 64, no. 9 (September 20, 2007): 1710–22. http://dx.doi.org/10.1093/icesjms/fsm146.
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Abstract McAuley, R. B., Simpfendorfer, C. A., and Hall, N. G. 2007. A method for evaluating the impacts of fishing mortality and stochastic influences on the demography of two long-lived shark stocks. — ICES Journal of Marine Science, 64. Stochastic demographic models were developed for Carcharhinus obscurus and C. plumbeus populations off the west coast of Australia by resampling the input parameters for life tables from empirical biological data collected from commercial target fisheries and fishery-independent surveys. The models were used to examine the effects of multiple scenarios of age-specific survival, derived from the fishing mortality rates estimated from a tagging study on sharks and indirect estimates of natural mortality. In the absence of fishing, median estimates of the rates of intrinsic population increase (r) were 0.025 for both species. Inclusion of the age-specific fishing mortality rates estimated for C. obscurus recruits born in 1994 and 1995 resulted in the median estimates of r declining to 0.007 and 0.012, respectively, suggesting that recent harvest levels of mainly neonates by the target fishery were probably sustainable. However, the model also suggested that the population was more susceptible to exploitation of older sharks than was previously believed. The C. plumbeus model indicated that fishing mortality between 2001 and 2004 was probably unsustainable. The increasingly negative trend in median r estimates (from –0.032 to –0.049), and the population’s apparently limited capacity for density-dependent compensation through changes in fecundity, somatic growth and longevity, suggests that management intervention is necessary to prevent continued stock depletion.
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Drew, Michael, Paul Rogers, and Charlie Huveneers. "Slow life-history traits of a neritic predator, the bronze whaler (Carcharhinus brachyurus)." Marine and Freshwater Research 68, no. 3 (2017): 461. http://dx.doi.org/10.1071/mf15399.
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Intra-species plasticity in the life-history characteristics of sharks leads to the need for regional estimates to accurately determine resilience to anthropogenic effects. The present study provides the first length-at-age, growth and maturity estimates for the bronze whaler (Carcharhinus brachyurus) from southern Australia. Age estimates were obtained from vertebral sections of 466 individuals spanning 50–308-cm total length. Maximum estimates of age for males and females were 25 and 31 years respectively. The three-parameter logistic model for females (L∞=308cm LT, k=0.15, α=742) and for males (L∞=317cm LT, k=0.13, α=782) provided the best fit to the size at age data. Males matured at a similar age (16 years), but smaller size than females (224v. 270cm LT). Growth parameters and age-at-maturity estimates were similar to those for genetically isolated C. brachyurus populations, and the sympatric dusky shark (C. obscurus). The southern Australian C. brachyurus population is long-lived, slow growing and late maturing. These growth parameters are needed to undertake demographic analyses to assess the resilience of C. brachyurus to fishing, and provide an example of a wide-ranging elasmobranch with similar life-history characteristics across isolated populations.
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Moulton, PL, TI Walker, and SR Saddlier. "Age and growth studies of Gummy Shark, Mustelus antarcticus Gunther, and School Shark, Galeorhinus galeus (Linnaeus), from Souther Australian Waters." Marine and Freshwater Research 43, no. 5 (1992): 1241. http://dx.doi.org/10.1071/mf9921241.
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Age-length data were derived from counting stained bands on whole vertebral centra obtained from gummy shark, Mustelus antarcticus, captured by gill-nets during 1973-76 in Bass Strait and from gummy shark and school shark, Galeorhinus galeus, captured during 1986-87 in Bass Strait and waters off South Australia. The data were fitted to the von Bertalanffy growth equation after adopting the Francis reparametrization and correcting for sampling bias caused by the selectivity effects of the gill-nets of various mesh sizes used to capture the sharks. The von Bertalanffy growth curves of male and female gummy shark were significantly different, but the growth curves of male and female school shark were not. The growth curves suggest that growth rates of male and female gummy shark in Bass Strait were lower during 1986-87 than during 1973-76 and that the growth rates of male and female gummy shark and school shark in Bass Strait during 1986-87 were lower than those in South Australia at the same time. These apparent temporal and spatial differences in growth patterns of gummy shark are explained by the 'Phenomenon of Apparent Change in Growth Rate'. It is concluded that the growth curves determined for 1986-87 are distorted by the effects of a long history of high and length-selective fishing mortality and that actual growth patterns of gummy shark are better represented by the von Bertalanffy growth equation determined for shark caught in Bass Strait during 1973-76, when fishing mortality was much lower. Verification of age estimates was attempted by comparing von Bertalanffy growth curves derived from age-length data with those derived from tag release-recapture length-increment data, but these comparisons highlight the limitations of using tag data for this purpose. Although reasonable agreement was found between such growth curves for gummy shark, it appears that school shark older than 11 years cannot be aged accurately from stained whole or sectioned vertebrae. Sectioned vertebrae from a school shark recaptured 35.7 years after being tagged and released and calculated as having an age exceeding 45 years gave estimates of only 18-20 years of age.
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Zhou, Shijie, Ross M. Daley, Michael Fuller, Cathy M. Bulman, and Alistair J. Hobday. "A data-limited method for assessing cumulative fishing risk on bycatch." ICES Journal of Marine Science 76, no. 4 (January 28, 2019): 837–47. http://dx.doi.org/10.1093/icesjms/fsy206.
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Abstract To assess fishing effects on data-poor species, impact can be derived from spatial overlap between species distribution and fishing effort and gear catchability. Here, we enhance the existing sustainability assessment for fishing effect method by estimating gear efficiency and heterogeneous density from sporadic catch data. We apply the method to two chondrichthyan bycatch species, Bight Skate and Draughtboard Shark in Australia, to assess cumulative fishing mortality (Fcum) from multiple fisheries. Gear efficiency is estimated from a Bayesian mixture distribution model and fish density is predicted by a generalized additive model. These results, combined with actual fishing effort, allow estimation of fishing mortality in each sector and subsequently, the Fcum. Risk is quantified by comparing Fcum with reference points based on life history parameters. When only the point estimates were considered, our result indicates that for the period 2009 and 2010 Bight Skate caught in 14 fisheries was at high cumulative risk (Fcum ≥ Flim) while Draughtboard Shark caught by 19 fisheries was at low cumulative risk (Fcum ≤ Fmsy). Because of the high cost of conducting cumulative risk assessments, we recommend examining the distribution of fishing effort across fisheries before carrying out the assessments.
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Volep, E., A. R. Carroll, D. Strauss, J. O. Meynecke, and D. Kobashi. "Effect of environmental conditions on cetacean entanglements: a case study from the Gold Coast, Australia." Marine and Freshwater Research 68, no. 11 (2017): 1977. http://dx.doi.org/10.1071/mf16302.
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Entanglement of marine mammals in fishing gear is recognised worldwide and is a continuous management concern. Gill-net entanglement data from the Queensland Shark Control Program (QSCP) on the Gold Coast, Australia, from 1990 to 2012 were analysed in the present study. Environmental drivers that may affect entanglements of humpback whales (Megaptera novaeangliae) and common dolphins (Delphinus delphis) were selected. M. novaeangliae entanglements coincided with their annual migration, with the greatest occurrences in September. D. delphis were mostly entangled from March to November, with the greatest occurrences in June. For both species, entanglements primarily occurred when the wave height was between 0.5 and 1.25m, the wave power was between 0 and 5kWm–1 and the wind speed was between 12 and 19kmh–1. M. novaeangliae entanglements were significantly more likely to occur in low rainfall (<6mmh–1), and D. delphis entanglements were more likely to occur during spring tides. There was a correlation between entanglements and the position of the East Australian Current’s (EAC) maximum velocity, with 73% of M. novaeangliae entanglements and 79% of D. delphis entanglements occurring when the EAC’s maximum velocity was west (shoreward) of its average position at 154°E. The present study provides the first set of possible management intervention targets associated with environmental conditions.
6
Bansemer, C. S., and M. B. Bennett. "Retained fishing gear and associated injuries in the east Australian grey nurse sharks (Carcharias taurus): implications for population recovery." Marine and Freshwater Research 61, no. 1 (2010): 97. http://dx.doi.org/10.1071/mf08362.
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Incidental hooking of Carcharias taurus is a threat to their populations’ recovery on the east coast of Australia. Photo-identification techniques were used to investigate the frequency of hooking at 25 aggregation sites along the east coast of Australia between 2006 and 2008. Of the 673 sharks identified, 113 sharks were identified with signs of 119 incidences of hooking. For sharks with both their left and right flank photographed during a single survey day, up to 29% of females and 52% of males were identified with retained fishing gear or an attributed jaw injury. The largest number of sharks identified (222) were from a year-round aggregation of immature and mature sharks at Fish Rock, New South Wales, Australia. Forty-eight per cent of all sharks identified with retained fishing gear were first identified at this site. Fish Rock, a designated critical habitat for C. taurus, allows most forms of line fishing except fishing with bait or wire trace while anchored or moored. As interactions with fishing gear can result in debilitating disease, morbidity and death, the high incidence of hooked individual C. taurus is considered a key threatening process that is likely to reduce this shark population’s ability to recover.
7
Walker, TI. "Fishery simulation model for sharks applied to the Gummy Shark, Mustelus antarcticus Gunther, from Southern Australian waters." Marine and Freshwater Research 43, no. 1 (1992): 195. http://dx.doi.org/10.1071/mf9920195.
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A dynamic pool simulation model is derived and applied to the gummy shark stock of the southern shark fishery. Inputs to the model are fishing effort reported by fishers for hooks and for gill-nets with mesh sizes of 6 inches (152 mm), 7 inches (178 mm) and 8 inches (203 mm) along with estimates for growth, natural mortality, catchability, hook and gill-net mesh selectivity, size at maturity and fecundity of females, sex ratio at birth, and length-weight relationships. Growth is described by the von Bertalanffy equation; hook selectivity is constant with length for sharks recruited to the fishery; gill-net selectivity is based on the probability density distribution of the gamma function where selectivity varies with the mesh size of the gill-nets and the length of the sharks; number of births is related to the proportion of females mature at each length, and the relationship between number of births and maternal weight is linear; parturition is annual and time is standardized so that parturition occurs at the beginning of each year; sex ratio at birth is based on observations of a 1: 1 sex ratio of embryos; and allometric weight-length is based on the power curve. Natural mortality of recruits, catchability, reproduction and growth parameters are held constant, but density-dependent natural mortality of prerecruits is varied in proportion to stock abundance. The model is used to simulate effects of historical longline fishing effort and gill-net fishing effort for each mesh size on stock biomass, numbers of sharks in the stock, and numbers of births. The performance of the model is evaluated by comparing simulated annual catches and the simulated mean weight of sharks captured with annual catches reported by the fishers and the mean weight of sharks sampled in commercial landings. Uncertainties surrounding estimates of some of the parameters are discussed. Notwithstanding its shortcomings, the model indicates that the stock of gummy shark has been severely reduced and is in danger of further depletion unless immediate action is taken to reduce the commercial catch.
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Taylor, S. M., J. M. Braccini, B. D. Bruce, and R. B. McAuley. "Reconstructing Western Australian white shark (Carcharodon carcharias) catches based on interviews with fishers." Marine and Freshwater Research 69, no. 3 (2018): 366. http://dx.doi.org/10.1071/mf17140.
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The assessment of fisheries-related effects on protected species, such as white sharks (Carcharodon carcharias), is often hampered by a lack of historical catch information. In the present study, historical catch estimates derived from interviews with fishers operating in the Western Australian Temperate Demersal Gill-net and Demersal Longline Fisheries were matched with fishing effort data reported in statutory fishing returns. Catch estimates obtained from interviewed fishers were extrapolated to account for total catch in two different ways, resulting in mean (95% confidence intervals) estimates of 1232 (476–2245) and 1039 (505–2096) white sharks caught between 1988 and 2012. These estimates were then used to reconstruct catches over a 59-year period, from the start of commercial gillnetting in the mid-1950s. The reconstructed catch trend reflected the history of gill-net fishing effort, peaking in the late 1980s at a level approximately fourfold greater than the estimated catch of ~30 sharks year–1 in 2014. More than one-third of fishers interviewed expressed doubts about the accuracy of self-reported white shark catch data, a requirement of current legislation. Given the benefits of reporting data from protected species bycatch, efforts to accurately record this information should be continued and improved.
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Stevens, JD. "Blue and Mako Shark by-catch in the Japanese Longline Fishery off South-eastern Australia." Marine and Freshwater Research 43, no. 1 (1992): 227. http://dx.doi.org/10.1071/mf9920227.
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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.
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Diana, Farah, Hafinuddin Hafinuddin, and Muhajir Ansar. "PENGARUH JENIS UMPAN YANG BERBEDA TERHADAP HASIL TANGKAPAN KEPITING BAKAU (Scylla serrata) DENGAN MENGGUNAKAN ALAT TANGKAP BUBU." JURNAL PERIKANAN TROPIS 5, no. 2 (October 1, 2018): 119. http://dx.doi.org/10.35308/jpt.v5i2.1031.
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Mangrove crab (Scylla serrata) is one of the fishery commodities that have higheconomic value. In addition, mangrove crab is one of export commodities to several countries such as United States, Europe, Australia, Japan, Hongkong,Taiwan, Singapore and South Korea. In general, the fishing activities of mangrove crabs in the general waters of many fishermen use different baits,it's just not known which bait is best for catching mangrove crabs. The purpose ofthis study is to determine the effect of using different types of bait to the mangrove crab catch by using bubu and know the type of bait that is most effective against the catching of mangrove crab. This research method used Completely Randomized Design (RAL) with three treatments and three replications: P1 = shredded fish, P2 = Shark skin bark, and P3 = Chicken head bait. The parameters in this study are the number of catches, the feed response and the water quality parameters, the results of this study indicate the number of catches P1 = 55.55%, P2 = 22.22% and P3 = 33.33%. While feed response time in this research P1 = 1.61, P2 = 12.03, and P3 = 11.74. From the results of this study showed the use of different baits have a very significant effect on the number of mangrove crabs (scilla serata). While the feedback response also shows the results are very real (Fcal> Ftab).
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Stevens, J. D., G. J. West, and K. J. McLoughlin. "Movements, recapture patterns, and factors affecting the return rate of carcharhinid and other sharks tagged off northern Australia." Marine and Freshwater Research 51, no. 2 (2000): 127. http://dx.doi.org/10.1071/mf98158.
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Between February 1983 and May 1985, ~10 500 sharks of 23 species were fin-tagged off northern Australia. Tagging concentrated on the commercially important Carcharhinus tilstoni and C. sorrah. Most recaptures were made in 1984 and 1985, but returns continued until May 1997. In all, 579 tags (5.5%) were recovered. Tag shedding was estimated to be low (0.025 year –1 for C. tilstoni) and tagging mortality was significantly lower for sharks caught by hand-line than by gill-net. Australian gill-netters, Taiwanese gill-netters (fishing in the Australian Fishing Zone) and Australian prawn trawlers accounted for most of the returns. The maximum distance between the release and recapture positions was >1100 km, but most returns were made within 50 km of the tagging site. Nearly all the releases were in inshore waters fished by Australian vessels. Although many recaptures were made by the offshore Taiwanese fishery, the Taiwanese fishing effort was much higher than for the inshore Australian fishery, so that relative to fishing effort, relatively few sharks moved from inshore to offshore waters.
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Pepperell, JG. "Trends in the distribution, species composition and size of sharks caught by Gamefish Anglers off South-eastern Australia, 1961-90." Marine and Freshwater Research 43, no. 1 (1992): 213. http://dx.doi.org/10.1071/mf9920213.
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Records of shark captures were extracted from the archives of 10 of the major New South Wales gamefishing clubs that operate from ports located between latitudes 33�s and 37�s. Although organized game fishing began off eastern Australia in 1936, the majority of catches were made after 1960. Data normally recorded by these clubs included common name of shark, whole weight, locality of capture, boat name and angler. Recognized single species of sharks recorded by these clubs were blue (Prionace glauca), tiger (Galeocerdo cuvier), white (Carcharodon carcharias), shortfin mako (Isurus oxyrinchus) and grey nurse (Carcharias taurus). Species identified only to generic level, and recorded by clubs, were whalers or requiem sharks (Carcharhinus spp.), hammerheads (Sphyrna spp.) and threshers (Alopias spp.). Analysis of catch records indicated that the mako shark was the most common species caught overall, although whaler sharks dominated the catch in the northern part of the study area and hammerhead sharks dominated the catch in the south. Grey nurse and white sharks were relatively rare in the southern part of the study area. Whaler sharks dominated the catch in the 1960s, and the proportions of blue and tiger sharks in the catch increased in the 1980s. Size ranges and distributions of some species also varied through time and by area. Some of the observed changes could be attributed to changed fishing practices, particularly the increasing popularity of tag-and-release and an increasing tendency to fish further from the coast. A marked decline in the number and proportion of white sharks in the catch since the 1970s gives cause for some concern regarding the status of that species off south-eastern Australia.
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Braccini, Matias, Simon de Lestang, and Rory McAuley. "Dusky sharks (Carcharhinus obscurus) undertake large-scale migrations between tropical and temperate ecosystems." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 9 (September 2018): 1525–33. http://dx.doi.org/10.1139/cjfas-2017-0313.
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Understanding the large-scale migrations of marine predators can allow better representation of their population dynamics. The migration biology of dusky sharks (Carcharhinus obscurus), a cosmopolitan large marine predator with very low resilience to fishing, was quantified using a large-scale network of acoustic receivers deployed across Western Australia. Time-series plotting of individual shark detections and modified logistic modelling were used to determine the timing of acoustically tagged sharks’ seasonal migration, the proportion of the population migrating, and the size at which sharks start to migrate. Large (>200 cm fork length) dusky sharks migrated between areas closed (north) and open (south) to commercial shark fishing. There was limited evidence that smaller sharks occurred in the northern study area, whereas several larger individuals of both sexes undertook repeated north–south displacements, moving between disparate ecosystems within the Indian Ocean (21.7°S–35.4°S) and covering round-trip distances of 2000–3000 km per migratory event. For migrating individuals, the probability of occurring in the north was high in the austral winter–spring and low (males) to moderate (females) during the austral summer–autumn.
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Solihin, Akhmad. "KONFLIK ILLEGAL FISHING DI WILAYAH PERBATASAN INDONESIA-AUSTRALIA." Marine Fisheries : Journal of Marine Fisheries Technology and Management 1, no. 2 (February 21, 2012): 29. http://dx.doi.org/10.29244/jmf.1.2.29-36.
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The habits of Indonesian fisher who ride into the territory of the Australian fisheries often causing fluctuative relations between two countries, because repressive action of the Australian Government's apparatus. Therefore, the purpose of this study are: to assess the economic interest of fisher when get into the fishery regions of Australia, to analyze the offense of illegal fishing, and to get the eradication strategies of illegal fishing in two countries agreement areas. This study is a descriptive analysis, using a normative juridical approach which is equipped with comparative approaches. Based on the analysis yielded that 1) sea cucumbers and sharks are the main target of Indonesian fisher, wherein the value of profits from sea cucumbers of AU $ 14,000-AU $ 30,000, 2) illegal fishing violation occurred, i.e.; breach of the agreement not only operating areas, the utilization of fishery resources, environmental pollution, but also agents of illegal immigrants, 3) eradication of illegal fishing through the establishment of a legal approach by arbitration forming, and economic approach with alternative livelihoods development.
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Savina, Marie, Robyn E. Forrest, Elizabeth A. Fulton, and Scott A. Condie. "Ecological effects of trawling fisheries on the eastern Australian continental shelf: a modelling study." Marine and Freshwater Research 64, no. 11 (2013): 1068. http://dx.doi.org/10.1071/mf12361.
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The New South Wales Offshore Trawl Fishery began to expand in 1976, following a large exploratory trawl survey carried out on the fishing grounds of the upper continental slope. This survey was repeated 20 years later with the same vessel and using similar protocols. Comparison of the survey results suggested that the overall fish biomass in the survey area had substantially decreased after 20 years. We have implemented an ecosystem model using the Atlantis framework to (1) emulate the evolution of the shelf ecosystems from 1976 to 1996 and (2) explore the effects of alternative fishing pressures on those ecosystems. We have been able to emulate the observed decline of most of the commercial groups of fish species in the Offshore Trawl Fishery, including sharks, and our results confirmed that fishing pressure was the most important cause of these observed changes. Fourteen fishing scenarios highlight the competing nature of some of the ecosystem-based sustainable fishing objectives.
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Van Houtan, Kyle S., Tyler O. Gagné, Gabriel Reygondeau, Kisei R. Tanaka, Stephen R. Palumbi, and Salvador J. Jorgensen. "Coastal sharks supply the global shark fin trade." Biology Letters 16, no. 10 (October 2020): 20200609. http://dx.doi.org/10.1098/rsbl.2020.0609.
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Progress in global shark conservation has been limited by constraints to understanding the species composition and geographic origins of the shark fin trade. Previous assessments that relied on earlier genetic techniques and official trade records focused on abundant pelagic species traded between Europe and Asia. Here, we combine recent advances in DNA barcoding and species distribution modelling to identify the species and source the geographic origin of fins sold at market. Derived models of species environmental niches indicated that shark fishing effort is concentrated within Exclusive Economic Zones, mostly in coastal Australia, Indonesia, the United States, Brazil, Mexico and Japan. By coupling two distinct tools, barcoding and niche modelling, our results provide new insights for monitoring and enforcement. They suggest stronger local controls of coastal fishing may help regulate the unsustainable global trade in shark fins.
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Braccini, Matias, Brett Molony, and Nick Blay. "Patterns in abundance and size of sharks in northwestern Australia: cause for optimism." ICES Journal of Marine Science 77, no. 1 (October 10, 2019): 72–82. http://dx.doi.org/10.1093/icesjms/fsz187.
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Abstract Reliable information for population assessments is rare for sharks. We quantified patterns in catch rates and mean size for numerous tropical and subtropical species from 15 years of fishery-independent surveys (2002–2017) in northwestern Australia. This study region represents an area of ~0.8 million km2 which was closed to commercial shark fishing from 1993 or 2005 onward due to the very high State-wide catches of sandbar (Carcharhinus plumbeus) and dusky (Carcharhinus obscurus) sharks. A total of 43 shark and ray species were sampled, with sandbar shark being the most commonly caught species, followed by milk (Rhizoprionodon acutus), spot-tail (Carcharhinus sorrah), tiger (Galeocerdo cuvier), blacktip (Carcharhinus limbatus and Carcharhinus tilstoni), dusky and sliteye (Loxodon macrorhinus) sharks, and scalloped hammerhead (Sphyrna lewini). For sandbar shark, catch rates increased between 2008 and 2017 whereas for other taxa catch rates were mostly stable (albeit fluctuating). Mean size at capture fluctuated across years with no particular trends. Unlike for other parts of the world, catch rates and mean size of northwestern Australian sharks have been stable or increased in recent years. Though most shark species have conservative life histories, when science, management and enforcement work synergistically, sustainable resource use, recovery and conservation outcomes can all be achieved.
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Grant, Scott M., Jenna G. Munden, and Kevin J. Hedges. "Effects of monofilament nylon versus braided multifilament nylon gangions on catch rates of Greenland shark (Somniosus microcephalus) in bottom set longlines." PeerJ 8 (December 3, 2020): e10407. http://dx.doi.org/10.7717/peerj.10407.
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The Greenland shark (Somniosus microcephalus) is the main bycatch species in established and exploratory inshore longline fisheries for Greenland halibut (Reinhardtius hippoglossoides) on the east coast of Baffin Island, Canada. Bycatch and entanglement in longline gear has at times been substantial and post-release survival is questionable when Greenland sharks are released with trailing fishing gear. This study investigated the effect of the type of fishing line used in the gangion and gangion breaking strength on catch rates of Greenland shark and Greenland halibut in bottom set longlines. Circle (size 14/0, 0° offset) hooks were used throughout the study. Behavior of captured sharks, mode of capture (i.e., jaw hook and/or entanglement), level of entanglement in longline gear, time required to disentangle sharks and biological information (sex, body length and health status) were recorded. Catch rates of Greenland shark were independent of monofilament nylon gangion breaking strength and monofilament gangions captured significantly fewer Greenland sharks than the traditional braided multifilament nylon gangion. Catch rates and body size of Greenland halibut did not differ significantly between gangion treatments. Although most (84%) of the Greenland sharks were hooked by the jaw, a high percentage (76%) were entangled in the mainline. The mean length of mainline entangled around the body and/or caudal peduncle and caudal fin was 28.7 m. Greenland sharks exhibited cannibalistic behavior with 15% of captured sharks cannibalized. All remaining sharks were alive and survived the disentanglement process which can be attributed to their lethargic behavior and lack of resistance when hauled to the surface. Thus, as a conservation measure fishers should be encouraged to remove trailing fishing gear prior to release. Our results are used to demonstrate benefits to the fishing industry with regard to an overall reduction in the period of time to disentangle sharks and damage to fishing gear by switching from braided multifilament to monofilament gangions in Greenland halibut longline fisheries.
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Raoult, V., V. Peddemors, K. Rowling, and J. E. Williamson. "Spatiotemporal distributions of two sympatric sawsharks (Pristiophorus cirratus and P. nudipinnis) in south-eastern Australian waters." Marine and Freshwater Research 71, no. 10 (2020): 1342. http://dx.doi.org/10.1071/mf19277.
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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.
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Braccini, Matias, and Hilario Murua. "Quantifying shark and ray discards in Western Australia’s shark fisheries." Marine and Freshwater Research 73, no. 3 (November 9, 2021): 283–91. http://dx.doi.org/10.1071/mf21159.
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Commercial fisheries can discard a considerable volume of sharks and rays, which, as a group, are of high conservation concern. In Western Australia (WA), commercial shark fishing commenced in the 1940s; however, catch time series are not available for discarded species. The present study quantified catch (i.e. dead individuals) time series of discarded sharks and rays in WA’s shark fisheries using on-board observer information collected since 1993 and testing assumptions through sensitivity analysis. Overall, 18 shark and ray taxonomic groups were discarded, comprising ~20% of the observed catch by number. Port Jackson shark, southern eagle ray and spurdogs were the most commonly discarded elasmobranchs, followed by western wobbegong, angel sharks, stingrays, and guitarfish and shovelnose rays. For the base case scenario, the catch of these species was small, peaking at 12.6, 5.6, 1.3, 1.8, 4, 1.3 and 2.7 tonnes (Mg) respectively, given their low post-release mortality (PRM). Current catch levels were even lower (e.g. <5 Mg for Port Jackson shark). Other discarded elasmobranchs were rarely caught. Assuming 100% PRM resulted in higher annual catches, highlighting the need for further research on the PRM of sharks and rays. The reconstructed catch series will be used in risk assessments to determine the sustainability of discarded species.
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Lowry, Michael, and Jeff Murphy. "Monitoring the recreational gamefish fishery off south-eastern Australia." Marine and Freshwater Research 54, no. 4 (2003): 425. http://dx.doi.org/10.1071/mf01269.
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The east coast Australian gamefish fishery is a diverse, multi-species fishery that targets billfish, sharks, tuna and other pelagic fish along the east Australian seaboard. A Gamefish Tournament Monitoring Program (GTMP) was undertaken, and 39021 angler trips from 1996 to 2000 were analysed. The program reports on trends in fishing effort, catch rates, catch composition, proportions of captures tagged and released and spatial distribution of catches for the principal recreational billfish species: black marlin (Makaira indica), striped marlin (Tetrapterus audax) and blue marlin (Makiara nigricans).The GTMP was principally designed as part of an integrated program to monitor the recreational gamefish fishery. The spatial and temporal design of the program restricted statistical analyses however, there were trends in fishing effort, directed effort, catch rates, catch composition, proportions of fish tagged and spatial distribution of catches for the principal recreational billfish species over seven successive years (1994–2000). Analysis of catch data, stratified by directed effort, indicated significant differences in catches of target species, demonstrating the importance of calculating catch rate estimates according to the main target preference. Analysis of tournament based tagging information indicated that while overall tournament tagging rates remained high (88%) there were significant differences in the number of fish tagged between species groups highlighting the impact that angler attitude and the competition point score structure has on the harvest of gamefish target species.
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Harry, Alastair V., Paul A. Butcher, William G. Macbeth, Jess A. T. Morgan, Stephen M. Taylor, and Pascal T. Geraghty. "Life history of the common blacktip shark, Carcharhinus limbatus, from central eastern Australia and comparative demography of a cryptic shark complex." Marine and Freshwater Research 70, no. 6 (2019): 834. http://dx.doi.org/10.1071/mf18141.
Full textAbstract:
Common and Australian blacktip sharks (Carcharhinus limbatus and Carcharhinus tilstoni) occur sympatrically in Australia, where they are reported as a complex because of their morphological similarities. This study provides the first description of the life history of C. limbatus using samples from central eastern Australia, where C. tilstoni is rare. Females (68–267cm total length (TL); n=183) and males (65–255cm TL; n=292) both matured at 8.3 years and 200cm TL, which exceeds the maximum length of C. tilstoni. Vertebral ageing revealed that female and male C. limbatus lived to 22 and 24 years respectively, exceeding known longevity in C. tilstoni. The mean (±s.d.) intrinsic rate of population increase calculated using a Euler–Lotka demographic method was 0.11±0.02year–1 for C. limbatus, compared with 0.17±0.02 and 0.20±0.03year–1 for two C. tilstoni stocks. Despite their similar appearance, these species differed in both their biological productivity and susceptibility to fishing activities. Monitoring of relative abundance should be a priority given they are likely to have divergent responses to fishing.
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Cliff, Geremy, and Sheldon F. J. Dudley. "Reducing the environmental impact of shark-control programs: a case study from KwaZulu-Natal, South Africa." Marine and Freshwater Research 62, no. 6 (2011): 700. http://dx.doi.org/10.1071/mf10182.
Full textAbstract:
Large-scale shark-control programs at popular beaches in New South Wales and Queensland, Australia, and KwaZulu-Natal (KZN), South Africa, provide protection against shark attack. Although these programs have enhanced bathing safety, reducing the environmental impacts of decades of fishing for large sharks and the associated by-catch remains a challenge. Over the past three decades, there have been several interventions to reduce such impact in the KZN program. The first was the release of all live sharks, including those species known to be responsible for fatal shark attacks. Measures to reduce catches of sharks associated with the winter influx of shoals of sardines, Sardinops sagax, have been increasingly successful. In addition, extensive removal of nets has resulted in a major reduction in effort. Collectively, these initiatives reduced mortalities of sharks by 64%. Baited lines, termed drumlines, were introduced at 18 beaches, where they replaced some of the nets. The former had a far lower by-catch of rays, turtles and cetaceans and significantly lower catches of certain shark species. Replacement of some nets with drumlines is planned for the remaining beaches. Only two attacks, both non-fatal, have occurred at protected beaches in KZN over the past three decades, indicating that the program has maintained its public safety mandate while it has succeeded in reducing its impact on the environment.
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McMillan, M. N., C. Huveneers, J. M. Semmens, and B. M. Gillanders. "Partial female migration and cool-water migration pathways in an overfished shark." ICES Journal of Marine Science 76, no. 4 (December 5, 2018): 1083–93. http://dx.doi.org/10.1093/icesjms/fsy181.
Full textAbstract:
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.
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Raoult, V., V. Peddemors, and J. E. Williamson. "Biology of angel sharks (Squatina sp.) and sawsharks (Pristiophorus sp.) caught in south-eastern Australian trawl fisheries and the New South Wales shark-meshing (bather-protection) program." Marine and Freshwater Research 68, no. 2 (2017): 207. http://dx.doi.org/10.1071/mf15369.
Full textAbstract:
Two species of angel shark (Squatina australis, S. albipunctata) and two species of sawshark (Pristiophorus nudipinnis, P. cirratus) are frequently caught in south-eastern Australia. Little is known of the biology of these elasmobranchs, despite being caught as secondary target species in large numbers. The present study collected morphometric and reproductive data from sharks caught in shark-control nets, commercial fishing trawlers and research trawlers in south-eastern Australia. All four species had female-biased sexual size dimorphism, but growth curves between sexes did not differ. Male S. australis individuals were fully mature at ~800-mm total length, male P. nudipinnis at ~900mm, and male P. cirratus at ~800mm. Anterior pectoral margins could be used to determine total length in all species. No morphometric measurement could reliably separate Squatina spp. or Pristiophorus spp., although S. albipunctata over 1000-mm total length had larger eyes than did S. australis.
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Rogers, P. J., C. Huveneers, S. D. Goldsworthy, W. W. L. Cheung, G. K. Jones, J. G. Mitchell, and L. Seuront. "Population metrics and movement of two sympatric carcharhinids: a comparison of the vulnerability of pelagic sharks of the southern Australian gulfs and shelves." Marine and Freshwater Research 64, no. 1 (2013): 20. http://dx.doi.org/10.1071/mf11234.
Full textAbstract:
The dusky shark Carcharhinus obscurus and the bronze whaler Carcharhinus brachyurus are large-bodied, marine predators that inhabit coastal and shelf waters of southern Australia. C. obscurus is considered to be among the most vulnerable pelagic sharks to overexploitation. This study focussed on population metrics and movement patterns of these sympatric species. Litters from two pregnant C. brachyurus were examined; these comprised 20 and 24 embryos, respectively. Tagging data indicated that 75% of whaler sharks tagged in this region by recreational fishers were juveniles, and 58% of recaptures occurred within 50 km of the tagging locations. Fishery catch samples comprised 99% juvenile C. brachyurus and C. obscurus. Our findings suggested that semi-protected gulf waters represented ecologically significant habitats of juveniles. A fuzzy-logic model showed that in terms of relative vulnerability to fishing, C. brachyurus ranked in the mid to lower end of the spectrum, when compared with six sympatric pelagic shark species, including the white shark, Carcharodon carcharias. Our findings emphasised a need for improvement to management measures for these carcharhinids, which are likely to play a significant role in the functioning of the temperate gulf and shelf ecosystems.
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Arifin, Yusuf Nur. "Analysis of Law Enforcement Against Criminal Action on Illegal Fishing (Case Study of MV Hai Fa)." Hang Tuah Law Journal 4, no. 1 (June 10, 2020): 14. http://dx.doi.org/10.30649/htlj.v4i1.146.
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<p>The MV Hai Fa case has taken the public's attention for almost the last 5 years after the court ruling was issued by the Ambon Court. MV Hai Fa was declared proven to have captured 15 tons of spike shark (<em>Carcharhinus spp</em>) and hammerhead shark (<em>Sphyrna lewini</em>) which are some of the protected species of marine animals as stated in the Minister of Maritime Affairs and Fisheries Regulation Number 59 of 2014 concerning Prohibition of Fish Expenditures Cowboy sharks (<em>Carcharhinus spp</em>) and hammerhead sharks (<em>Sphyrna lewini</em>) outside the territory of the Republic of Indonesia and violating Article 100 in conjunction with Article 7 paragraph (2) letter m law No. 45 of 2009 concerning amendments to Law No.31 of 2004. This study uses normative legal research methods with a case, concept, law and comparison approach with the aim of knowing and analyzing the law enforcement process against illegal fishing cases by MV Hai Fa in Indonesian waters as well as analyzing comparative reviews of national law and international law in MV Hai Fa case and the government system owned by Vietnam and Australia. The results of the study concluded that the need for a government institution which is appointed by the President could carry out full coordination and supervision until the judicial process and that the revision of fisheries law which has more severe sanctions were adjusted to international law and the material and immaterial losses caused by the crime.</p>
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Grant, Scott M., Rennie Sullivan, and Kevin J. Hedges. "Greenland shark (Somniosus microcephalus) feeding behavior on static fishing gear, effect of SMART (Selective Magnetic and Repellent-Treated) hook deterrent technology, and factors influencing entanglement in bottom longlines." PeerJ 6 (May 17, 2018): e4751. http://dx.doi.org/10.7717/peerj.4751.
Full textAbstract:
The Greenland Shark (Somniosus microcephalus) is the most common bycatch in the Greenland halibut (Reinhardtius hippoglossoides) bottom longline fishery in Cumberland Sound, Canada. Historically, this inshore fishery has been prosecuted through the ice during winter but winter storms and unpredictable landfast ice conditions since the mid-1990s have led to interest in developing a summer fishery during the ice-free season. However, bycatch of Greenland shark was found to increase substantially with 570 sharks captured during an experimental Greenland halibut summer fishery (i.e., mean of 6.3 sharks per 1,000 hooks set) and mortality was reported to be about 50% due in part to fishers killing sharks that were severely entangled in longline gear. This study investigated whether the SMART (Selective Magnetic and Repellent-Treated) hook technology is a practical deterrent to Greenland shark predation and subsequent bycatch on bottom longlines. Greenland shark feeding behavior, feeding kinematics, and variables affecting entanglement/disentanglement and release are also described. The SMART hook failed to deter Greenland shark predation, i.e., all sharks were captured on SMART hooks, some with more than one SMART hook in their jaw. Moreover, recently captured Greenland sharks did not exhibit a behavioral response to SMART hooks. In situ observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25–35 cm. This method of feeding is suggested to negate the potential deterrent effects of electropositive metal and magnetic alloy substitutions to the SMART hook technology. The number of hooks entangled by a Greenland shark and time to disentangle and live-release a shark was found to increase with body length.
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Naz, Graham M. "Effect of Covid-19 Pandemic to the Fishers in a Coastal Municipality in the Philippines." International Journal of Multidisciplinary: Applied Business and Education Research 3, no. 6 (June 11, 2022): 967–76. http://dx.doi.org/10.11594/ijmaber.03.06.02.
Full textAbstract:
The fishing industry was not spared by threats of Covid-19 pandemic, despite being considered as part of essential industry. This study determined the effects of the pandemic to the fishing industry, particularly the fishers, in terms of their cost of operation, sales and volume of catch. It also identified their problems encountered and the strategies used to deal with the problems. The study employed descriptive quantitative research design. Respondents, who are the local fishers in a coastal municipality of Bulan, Sorsogon, Philippines, are randomly chosen through stratified random sampling. Survey questionnaire was used and data were analyzed through descriptive statistics. Results revealed that respondents had been heavily affected by the pandemic, particularly in their cost of operation among the three areas of concern. This was due to increase in prices of crude oil/gasoline, food commodities, and fishing gears and equipment. Only few respondents, however, expressed that there are effects on sales and volume of catch. Findings of the study revealed that most common problems were price increase in gasoline/crude oil and fishing gears, as well as price volatility of fish. Study found that respondents took loans (from loan sharks/brokers), repaired their fishing gears by themselves (instead of buying or paying for repair) and attend more to their alternative source of income, to overcome the challenges of pandemic to their livelihood. It recommends that local government must consider providing fishers with relief/loan assistance, particularly during state of calamities, as well as providing livelihood programs and skills training for more sustainable alternative source of income.
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Chin, Andrew, Colin Simpfendorfer, Andrew Tobin, and Michelle Heupel. "Validated age, growth and reproductive biology of Carcharhinus melanopterus, a widely distributed and exploited reef shark." Marine and Freshwater Research 64, no. 10 (2013): 965. http://dx.doi.org/10.1071/mf13017.
Full textAbstract:
Inadequate life-history information can compromise management of shark populations. The present study examined the life history of blacktip reef sharks (Carcharhinus melanopterus) from north-eastern Australia with predictions that they would show life-history patterns similar to those of other reef sharks species. Age and growth estimates were derived from vertebrae and five growth models. Males were 543–1390 mm total length (LST) and females were 514–1600 mm LST. Longevity was 10 years (males) and 15 years (females). Chemical marking confirmed annual band pair deposition but indicated probable age underestimation of large individuals. The logistic model was preferred (second-order Akaike information criterion (AICc) weight 0.7536), with growth parameter estimates of length at birth (L0) = 617 mm LST; asymptotic length (L∞) = 1585 mm LST; k (from logistic model) = 0.251 year–1. Males matured at 4.2 years (1050 mm LST) and females at 8.5 years (1335 mm LST), although further verification is needed. Mating and parturition occurred in summer and autumn, females having three or four pups per litter. Data were inconclusive in determining reproductive periodicity. These data contribute to the species management and conservation and suggest that the species may be sensitive to fishing pressure and habitat loss. The study also demonstrated potential complications in using vertebrae to estimate age and growth of chondrichthyan fishes.
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Navia, Andrés Felipe, and Paola Andrea Mejía-Falla. "Fishing effects on elasmobranchs from the Pacific Coast of Colombia." Universitas Scientiarum 21, no. 1 (January 27, 2016): 9. http://dx.doi.org/10.11144/javeriana.sc21-1.feoe.
Full textAbstract:
<p>During 1995, 2001, 2003, 2004 and 2007; we studied the temporal variation in the structure of the elasmobranch assemblage along the Colombian Pacific coast using: the community index of diversity, heterogeneity, equitability, species composition, average catch sizes, and mean trophic levels. A total of 1 711 specimens from 19 species<br />(7 sharks and 12 rays) were collected during the 90 trawling operations. The number of species captured varied between 7 (1995) and 12 (2007) demonstrating a trend towards an imbalance in the assemblage attributes. In 1995, the mean trophic level (TLm) of the assemblage was 3.60, but in 2007 it decreased to 3.55 when the functional level of large predators was absent (TL ≥ 4). These results suggest changes in species composition, structural attributes, and a reduction of the highest functional level. Alterations to the catch proportions were also found: i.e. a greater abundance of rays of lower trophic levels. This study suggests an effect of trawling on the stability of this tropical coastal ecosystem.</p>
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Tovar-Ávila, Javier, Terence I. Walker, and Robert W. Day. "Reproduction of Heterodontus portusjacksoni in Victoria, Australia: evidence of two populations and reproductive parameters for the eastern population." Marine and Freshwater Research 58, no. 10 (2007): 956. http://dx.doi.org/10.1071/mf06230.
Full textAbstract:
Significant differences in the length–frequency composition of catch samples, mass–length relationships and length-at-maturity found between Heterodontus portusjacksoni from western and far-eastern Victoria, suggest the presence of at least two separate breeding populations off south-eastern Australia, with some mixing between these regions. In each region females attain a larger size than males, and collectively those sharks in western Victoria are smaller, present higher mass-at-length, and lower length-at-maturity than those in far-eastern Victoria. These regional differences might be a result of sampling bias, length-selective fishing mortality, environmental conditions, or genetic differences. However, tagging evidence from previous studies and the presence of two bio-geographic provinces in the region support the hypothesis of two separate breeding populations. The essential reproductive parameters for H. portusjacksoni population analysis in far-eastern Victoria were determined, using a novel method to estimate fecundity and the ovarian cycle of an egg-laying species. In this region, females have between 6 and 20 pre-ovulatory oocytes (average = 14, n = 29, standard deviation = 3.71) before the reproductive season. The species has an annual reproductive cycle correlated with water temperature, with ovulation starting during late winter to early spring and a ~6 month egg-laying period. The period from the onset of vitellogenesis to ovulation of oocytes is ~18 months.
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Lucifora, Luis O., Roberto C. Menni, and Alicia H. Escalante. "Reproduction and seasonal occurrence of the copper shark, Carcharhinus brachyurus, from north Patagonia, Argentina." ICES Journal of Marine Science 62, no. 1 (January 1, 2005): 107–15. http://dx.doi.org/10.1016/j.icesjms.2004.09.003.
Full textAbstract:
Abstract The copper shark, Carcharhinus brachyurus, is the only member of its genus with a preferred habitat in temperate waters, and it usually gives birth in the cooler extremes of its range. Maturation patterns, reproductive condition, monthly sex ratios, and seasonal occurrence of copper sharks were analysed, mostly from Anegada Bay (Argentina), a presumed nursery area for the species. Males mature between 200 and 220 cm total length (LT), with a 50% size at maturity (L50) of 216.18 cm LT. Females mature between 215 and 223 cm LT (with an L50 of 222.16 cm LT). Maturity off Argentina is at a slightly smaller size than off South Africa and Australia. There is no sexual dimorphism in size at maturity. Only two pregnant females, each carrying 16 advanced embryos, were caught. The hepatosomatic index (IH) of adult males showed significant monthly changes, related possibly to an increase in the gonadosomatic index (IG). IH and IG of adult females showed no significant trend throughout the fishing season. The IH of adult females was significantly correlated with maximum diameter of ovarian follicles. Small translucent ovarian follicles in two gravid females indicated that ovarian and gestation cycles run sequentially, with maturation of oocytes subsequent to parturition. Neither newborns nor significant numbers of females bearing term embryos were recorded, and there was no evidence of a copper shark primary nursery area in Anegada Bay. However, most copper sharks in Anegada Bay were large juveniles and sub-adults. The species is found off Argentina from October to late March, but they do not move southwards to Anegada Bay until December, and they leave the bay again by April. These movements appear to be related more to water temperature rather than to migration of potential prey. Monthly variation in sex ratios is associated mainly with fluctuations in the sex ratios of juveniles.
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Barton, Diane P., Laura Taillebois, Jonathan Taylor, David A. Crook, Thor Saunders, Mark Hearnden, Alan Greig, et al. "Stock structure of Lethrinus laticaudis (Lethrinidae) across northern Australia determined using genetics, otolith microchemistry and parasite assemblage composition." Marine and Freshwater Research 69, no. 4 (2018): 487. http://dx.doi.org/10.1071/mf17087.
Full textAbstract:
The grass emperor Lethrinus laticaudis is a conspicuous element of the commercial and recreational catch from nearshore reef systems across northern Australia. The nearshore reef systems across northern Australia are exposed to increasing levels of fishing pressure from commercial and recreational fishers. To inform ongoing management of this species, the present study examined the stock structure of L. laticaudis across northern Australia using a combination of complementary techniques. In all, 342 L. laticaudis samples were collected from 13 locations in the coastal waters of northern Australia ranging from the Pilbara region of Western Australia to Moreton Bay in south-east Queensland. Population genetic analyses using microsatellite markers demonstrated that there were at least four genetically distinct populations across northern Australia with gene flow between management jurisdictions (with significantly more separation between Western Australian and Northern Territory locations than between Northern Territory and Queensland locations). An isolation by distance effect was evident (genetic differences increasing linearly with distance). Otolith microchemistry and parasitology analyses indicated some spatial structuring of populations within broader regions. These findings of restricted connectivity at small spatial scales suggest that L. laticaudis is vulnerable to localised depletion in areas where fishing effort is concentrated. This conclusion is consistent with recent observations of fishery declines in heavily fished locations.
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Glaister, JP, SS Montgomery, and VC McDonall. "Yield-per-recruit analysis of Eastern King Prawns Penaeus plebejus Hess, in Eastern Australia." Marine and Freshwater Research 41, no. 1 (1990): 175. http://dx.doi.org/10.1071/mf9900175.
Full textAbstract:
The eastern king prawn, P. plebejus, has been commercially exploited for over 50 years. Controversy has arisen over the presumed effect of increasing fishing effort on reported declining catch per vessel and the need for further management of the fishery. The present study develops the information necessary to evaluate this presumption by analysing landing statistics, data developed from a log-book programme, commercial catch composition and data from a series of mark-recapture experiments conducted on part of the fishing grounds. Population parameters (growth, mortalities and other losses) were calculated via a series of tagging experiments. Recapture rates of tagged prawns were examined for each point release (local recapture) and for the state as a whole (sequentially applied effort), the difference providing estimates of emigration rate. Weekly values chosen for these parameters allowed calculation of yield-per-recruit estimates. For 1979 and 1980, respectively, fishing mortality estimates ranged between 0.04 and 0.08 per week, depending upon number of vessels per port; emigration was estimated to be 0.13 and 0.18 per week for the two years, tagging mortality (0.08 per week), and all other losses other than by tagging and emigration at 0.06 and 0.08 per week. A compartmented, time-lagged model of the fishery was used to predict changes in yield per recruit as a consequence of changes in management strategy and to describe the relationship between fishing effort and yield per recruit. The analyses suggested that limited benefits in terms of yield per recruit would eventuate from substantial increases in effort but that substantial decreases in catch per effort were likely.
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Otway, N. M., and M. T. Ellis. "Pop-up archival satellite tagging of Carcharias taurus: movements and depth/temperature-related use of south-eastern Australian waters." Marine and Freshwater Research 62, no. 6 (2011): 607. http://dx.doi.org/10.1071/mf10139.
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Knowledge of migratory movements and depth/temperature-related use of coastal waters by sharks can lead to more sustainable fisheries and assist in managing the long-term conservation of those species now considered threatened. Pop-up archival satellite tags (PATs) provide an alternative to conventional tagging for documenting migratory movements. This study focussed on the migratory movements of Carcharias taurus, a critically endangered shark found along the east coast of Australia. From October 2003 to July 2008, 15 C. taurus individuals were tagged with PATs with varying deployments (60–150 days) and acoustic tags linked to an acoustic monitoring system providing accurate geo-location. Distances moved by C. taurus individuals ranged from 5 to 1550 km and varied according to sex and season. Migrations north and south were punctuated en route by occupation of sites for varying periods of time. The deepest depth recorded was 232 m off South West Rocks on the New South Wales mid-north coast. On average, C. taurus males and females spent at least 71% of their time in waters <40 m and 95% of their time in waters 17–24°C. By mainly occupying inshore waters, C. taurus is exposed to potentially adverse fishing-related interactions that may be difficult to mitigate.
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Keller, Krystle, James A. Smith, Michael B. Lowry, Matthew D. Taylor, and Iain M. Suthers. "Multispecies presence and connectivity around a designed artificial reef." Marine and Freshwater Research 68, no. 8 (2017): 1489. http://dx.doi.org/10.1071/mf16127.
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A goal of designed artificial reefs (ARs) is to enhance fish abundance, species diversity and fishing opportunities by providing food and refuge for fish. Quantifying the contribution of ARs to coastal ecosystems and fisheries productivity requires an understanding of fish presence at the structure and connectivity with surrounding habitats. In the present study, the movements and presence of 10 eastern fiddler rays (Trygonorrhina fasciata), 17 Port Jackson sharks (Heterodontus portusjacksoni) and 18 bluespotted flathead (Platycephalus caeruleopunctatus) were monitored using acoustic telemetry around a designed AR in 38-m depth near Sydney, Australia. Fiddler rays exhibited an average short-term presence of 43% at the AR, and 26% over the ~20-month monitoring period, which was significantly higher than the other two species. Fish tagged at the AR showed high affinity to the site at which they were tagged compared with fish tagged on natural reef. All three species moved frequently between the AR and the other reefs in the area, indicating that the AR may increase the connectivity between adjacent habitats and aid the dispersion of benthic species. The moderate presence at the AR suggests that these species may contribute to some biomass production at this AR by incorporating this reef in their natural range.
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Foster, Scott D., Piers K. Dunstan, Franziska Althaus, and Alan Williams. "The cumulative effect of trawl fishing on a multispecies fish assemblage in south-eastern Australia." Journal of Applied Ecology 52, no. 1 (October 3, 2014): 129–39. http://dx.doi.org/10.1111/1365-2664.12353.
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Zemah-Shamir, Ziv, Shiri Zemah-Shamir, Aviad Scheinin, Dan Tchernov, Teddy Lazebnik, and Gideon Gal. "A Systematic Review of the Behavioural Changes and Physiological Adjustments of Elasmobranchs and Teleost’s to Ocean Acidification with a Focus on Sharks." Fishes 7, no. 2 (February 28, 2022): 56. http://dx.doi.org/10.3390/fishes7020056.
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In recent years, much attention has been focused on the impact of climate change, particularly via ocean acidification (OA), on marine organisms. Studying the impact of OA on long-living organisms, such as sharks, is especially challenging. When the ocean waters absorb anthropogenic carbon dioxide (CO2), slow-growing shark species with long generation times may be subjected to stress, leading to a decrease in functionality. Our goal was to examine the behavioral and physiological responses of sharks to OA and the possible impacts on their fitness and resilience. We conducted a systematic review in line with PRISMA-Analyses, of previously reported scientific experiments. We found that most studies used CO2 partial pressures (pCO2) that reflect representative concentration pathways for the year 2100 (e.g., pH ~7.8, pCO2 ~1000 μatm). Since there is a considerable knowledge gap on the effect of OA on sharks, we utilized existing data on bony fish to synthesize the available knowledge. Given the similarities between the behaviors and physiology of these two superclasses’ to changes in CO2 and pH levels, there is merit in including the available information on bony fish as well. Several studies indicated a decrease in shark fitness in relation to increased OA and CO2 levels. However, the decrease was species-specific and influenced by the intensity of the change in atmospheric CO2 concentration and other anthropogenic and environmental factors (e.g., fishing, temperature). Most studies involved only limited exposure to future environmental conditions and were conducted on benthic shark species studied in the laboratory rather than on apex predator species. While knowledge gaps exist, and more research is required, we conclude that anthropogenic factors are likely contributing to shark species’ vulnerability worldwide. However, the impact of OA on the long-term stability of shark populations is not unequivocal.
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Marriott, Ross J., Brent Wise, and Jill St John. "Historical changes in fishing efficiency in the west coast demersal scalefish fishery, Western Australia: implications for assessment and management." ICES Journal of Marine Science 68, no. 1 (November 9, 2010): 76–86. http://dx.doi.org/10.1093/icesjms/fsq157.
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Abstract Marriott, R. J., Wise, B., and St John, J. 2011. Historical changes in fishing efficiency in the west coast demersal scalefish fishery, Western Australia: implications for assessment and management. – ICES Journal of Marine Science, 68: 76–86. The west coast demersal scalefish fishery off the southern part of Western Australia has experienced technological creep over the past 20 years, resulting in improved fishing efficiency. The aim of this study was to obtain quantitative measures of efficiency improvements arising from the historical adoption of several important technologies from the surveys of experienced skippers. Survey results suggest that the relatively rapid adoption of Global Positioning Systems from 1989 to 1991 had a large and overriding effect on fleet-wide fishing efficiency. Additive effects from the fleet-wide adoption of colour sounders and hydraulic reels on effective fishing effort and the catch rates of West Australian dhufish (Glaucosoma hebraicum) and pink snapper (Pagrus auratus) were also demonstrated. Historical logbook data were independently analysed as a secondary check of these findings for three of the surveyed skippers, which identified that GPS adoption had a significant, positive influence on the catch rate for two vessels, but not for the third, highlighting potential variation in this response among skippers. The results have contributed towards improved understanding of the historical dynamics of the fishery and of the factors that have affected, at least in part, historical changes or, in some instances, a lack of change in observed effort and catch rates.
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Knuckey, Ian A., and 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, no. 4 (2001): 575. http://dx.doi.org/10.1071/mf00022.
Full textAbstract:
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.
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Spaet, JLY, A. Manica, CP Brand, C. Gallen, and PA Butcher. "Environmental conditions are poor predictors of immature white shark Carcharodon carcharias occurrences on coastal beaches of eastern Australia." Marine Ecology Progress Series 653 (October 29, 2020): 167–79. http://dx.doi.org/10.3354/meps13488.
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Understanding and predicting the distribution of organisms in heterogeneous environments is a fundamental ecological question and a requirement for sound management. To implement effective conservation strategies for white shark Carcharodon carcharias populations, it is imperative to define drivers of their movement and occurrence patterns and to protect critical habitats. Here, we acoustically tagged 444 immature white sharks and monitored their presence in relation to environmental factors over a 3 yr period (2016-2019) using an array of 21 iridium satellite-linked (VR4G) receivers spread along the coast of New South Wales, Australia. Results of generalized additive models showed that all tested predictors (month, time of day, water temperature, tidal height, swell height, lunar phase) had a significant effect on shark occurrence. However, collectively, these predictors only explained 1.8% of deviance, suggesting that statistical significance may be rooted in the large sample size rather than biological importance. On the other hand, receiver location, which captures geographic fidelity and local conditions not captured by the aforementioned environmental variables, explained a sizeable 17.3% of deviance. Sharks tracked in this study hence appear to be tolerant to episodic changes in environmental conditions, and movement patterns are likely related to currently undetermined, location-specific habitat characteristics or biological components, such as local currents, prey availability or competition. Importantly, we show that performance of VR4G receivers can be strongly affected by local environmental conditions, and provide an example of how a lack of range test controls can lead to misinterpretation and erroneous conclusions of acoustic detection data.
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Adams, S., B. D. Mapstone, G. R. Russ, and C. R. Davies. "Geographic variation in the sex ratio, sex specific size, and age structure of Plectropomus leopardus (Serranidae) between reefs open and closed to fishing on the Great Barrier Reef." Canadian Journal of Fisheries and Aquatic Sciences 57, no. 7 (July 1, 2000): 1448–58. http://dx.doi.org/10.1139/f00-076.
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Variation in reproductive parameters of Plectropomus leopardus populations between coral reefs open and closed to fishing was examined in two geographic regions (off Townsville (19°S) and in the Swains (22°S)) of the Great Barrier Reef, Australia. The reproductive parameters that were examined included the operational (reproductive) sex ratio and size and age structure of mature females, sex-changing individuals (transitionals), and mature males. There was a greater proportion of males above the minimum size and age of harvest on reefs closed to fishing for 8-10 years than on reefs open to fishing, although the effect varied with geographic region. Nevertheless, neither the sex ratio, mean age, nor mean size of males or transitionals varied significantly with reef closure status. Females, however, were significantly older and larger on closed than on open reefs in both regions. Marked regional variations in the sex ratio and average age of transitionals were found independent of reef closure status, suggesting regional variation in reproductive strategies. Controlled manipulations, inclusion of broad spatial scales, and detailed studies of intra- and inter-specific variation in serranid reproductive biology are necessary to resolve such complexities in the responses of protogynous serranids to fishing pressure and management strategies.
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Ihsan, Evi Nurul, Siti Yasmina Enita, Kunarso, and Anindya Wirasatriya. "Oceanographic Factors in Fishing Ground Location of Anchovy at Teluk Cenderawasih National Park, West Papua : Are These Factors Have an Effect of Whale Sharks Appearance Frequencies?" IOP Conference Series: Earth and Environmental Science 116 (February 2018): 012017. http://dx.doi.org/10.1088/1755-1315/116/1/012017.
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Dowling, Natalie A., Stephen J. Hall, and Richard McGarvey. "Assessing population sustainability and response to fishing in terms of aggregation structure for greenlip abalone (Haliotis laevigata) fishery management." Canadian Journal of Fisheries and Aquatic Sciences 61, no. 2 (February 1, 2004): 247–59. http://dx.doi.org/10.1139/f03-165.
Full textAbstract:
The greenlip abalone (Haliotis laevigata) population in Waterloo Bay, South Australia, has undergone collapse and fishery closure twice since 1978. A rich data set, including survey measures of degree of spatial aggregation, has been gathered over that time and provides a unique opportunity to identify factors accounting for persistence or collapse, an issue that is of significance to abalone fisheries worldwide. Statistical analyses of fishery and survey data were undertaken to infer functional relationships between catch, effort, recruitment, adult density, and extent of aggregation. Catch rates were hyperstable, an observation consistent with the targeting of large aggregations. Statistical analysis of recruitment showed a significant year effect, implying an environmental signal, and suggested that aggregation size impacts fertilization success. Aggregation size grew under closure, suggesting an impact of fishing on this demographic feature. Aggregative behaviour appears to be critical for subpopulation sustainability. Fishery collapse may be triggered by depletion of larger abalone aggregations by heavy fishing, resulting in declines in fertilized egg production. When heavy fishing coincides with unfavourable environmental conditions, recruitment may be insufficient to sustain the subpopulation. If aggregation is similarly critical for other subpopulations, management strategies could be adapted according to the extent of aggregation in each subpopulation.
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Brown, Paul, Taylor L. Hunt, and Khageswor Giri. "Effects of gear type, entrance size and soak time on trap efficiency for freshwater crayfish Cherax destructor and C. albidus." Marine and Freshwater Research 66, no. 11 (2015): 989. http://dx.doi.org/10.1071/mf14284.
Full textAbstract:
Freshwater crayfish support significant commercial and recreational fisheries worldwide. The genus Cherax is fished in Australia with a variety of fishing gears, yet little is known of the relative efficiency of the different fishing gears and methods. Additionally, freshwater-crayfish traps can pose a risk to air breathing by-catch such as aquatic mammals, reptiles and birds, so by-catch mitigation is important. We sought to understand whether freshwater-crayfish fishing can be undertaken efficiently, using passive traps and nets, without undue risk to air-breathing by-catch species. In field-experiments, we compared the efficiency of six gear types and tested the effect of five exclusion rings on catch performance over three soak times. The efficiency of gear types varied significantly by soak times. In productive locations, catch can be maximised by repeatedly deploying open-topped gear for short soak times. Opera-house traps fitted with fixed entrance rings (45–85-mm diameter) were not size-selective for yabbies. Encouragingly, open-topped gear and opera-house traps fitted with fixed ring entrances much smaller than many commercially available (45-mm diameter) still fish effectively for yabbies. We believe that smaller fixed ring-entrance size is likely to be correlated with a reduced risk of by-catch for air-breathing fauna.
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Huveneers, Charlie, Sasha Whitmarsh, Madeline Thiele, Lauren Meyer, Andrew Fox, and Corey J. A. Bradshaw. "Effectiveness of five personal shark-bite deterrents for surfers." PeerJ 6 (August 31, 2018): e5554. http://dx.doi.org/10.7717/peerj.5554.
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The number of shark-human interactions and shark bites per capita has been increasing since the 1980s, leading to a rise in measures developed to mitigate the risk of shark bites. Yet many of the products commercially available for personal protection have not been scientifically tested, potentially providing an exaggerated sense of security to the people using them. We tested five personal shark deterrents developed for surfers (Shark Shield Pty Ltd[Ocean Guardian]Freedom+ Surf, Rpela, SharkBanz bracelet, SharkBanz surf leash,andChillax Wax) by comparing the percentage of baits taken, distance to the bait, number of passes, and whether a shark reaction could be observed. We did a total of 297 successful trials at the Neptune Islands Group Marine Park in South Australia, during which 44 different white sharks (Carcharodon carcharias) interacted with the bait, making a total of 1413 passes. The effectiveness of the deterrents was variable, with theFreedom+ Surfaffecting shark behaviour the most and reducing the percentage of bait taken from 96% (relative to the control board) to 40%. The mean distance of sharks to the board increased from 1.6 ± 0.1 m (control board) to 2.6 ± 0.1 m when theFreedom Surf+was active. The other deterrents had limited or no measureable effect on white shark behavour. Based on our power analyses, the smallest effect size that could be reliably detected was ∼15%, which for the first time provides information about the effect size that a deterrent study like ours can reliably detect. Our study shows that deterrents based on similar principles—overwhelming a shark’s electroreceptors (the ampullae of Lorenzini) with electrical pulses—differ in their efficacy, reinforcing the need to test each product independently. Our results will allow private and government agencies and the public to make informed decisions about the use and suitability of these five products.
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Mohamed, Kolliyil S., Thayyil Valappil Sathianandan, Elayaperumal Vivekanandan, Somy Kuriakose, U. Ganga, Saraswathy Lakshmi Pillai, and Rekha J. Nair. "Application of biological and fisheries attributes to assess the vulnerability and resilience of tropical marine fish species." PLOS ONE 16, no. 8 (August 17, 2021): e0255879. http://dx.doi.org/10.1371/journal.pone.0255879.
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Taking advantage of published data on life-history traits and short-term information on fishery parameters from 3132 records for 644 fish stocks along the coast of India, we calculated resilience (R) and vulnerability (V). Further, we developed an Index of Resilience and Vulnerability (IRV) for 133 species of tropical finfishes, crustaceans, and molluscs. Using 7 resilience and 6 vulnerability attributes, two-dimensional scatter plots of the resilience and vulnerability scores were generated and the Euclidean distance and angle from the origin to each point were calculated to determine IRV and the effect of fishing on fish species. By ranking the species, the top 10 highly resilient, highly vulnerable, and high-risk species (low IRV) were identified. While small-sized species with fast growth rate and low trophic level were among the highly resilient species, large predatory species such as sharks and barracudas were among the highly vulnerable and high-risk species. More than 100 of the 133 species were resilient-yet-vulnerable, and most crustaceans showed high resilience. Differences in IRV scores among species within the same family were discernible, indicating the differences in the biological characteristics and response to fishing. Sensitivity analysis indicated that an abridged IRV with 6 attributes works similar to 13 attributes and can be used in data-deficient situations. Comparison of R and V of IRV with other assessments showed different results because of divergences in the objectives, number and types of attributes, and thresholds used. These assessments do not convey the same information and therefore great care must be taken for reproducing these frameworks to other fisheries. The results of IRV analysis can be useful for stock assessments and in developing effective management measures in combination with other complementary information.
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Flowers, KI, EA Babcock, YP Papastamatiou, ME Bond, N. Lamb, A. Miranda, R. Nuñez, et al. "Varying reef shark abundance trends inside a marine reserve: evidence of a Caribbean reef shark decline." Marine Ecology Progress Series 683 (February 3, 2022): 97–107. http://dx.doi.org/10.3354/meps13954.
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Spatial comparisons of reef shark abundance inside and outside marine protected areas (MPAs) are common and generally report positive MPA effects, yet few studies have tracked abundance trends over long time periods. This is problematic because inside:outside comparisons at a single point in time cannot evaluate whether populations are declining. In Belize, the Caribbean reef shark Carcharhinus perezi is one of the most fished shark species and is more abundant inside MPAs. Although the relative abundance of C. perezi was stable inside Glover’s Reef Marine Reserve (GRMR) from 2001 to 2013, using standard baited remote underwater video station surveys, we document a decline in relative abundance inside the no-take marine reserve from 2009 to 2019. We used a negative binomial generalized linear model and model averaging to test the effect of year, depth, and water temperature on C. perezi and nurse shark Ginglymostoma cirratum relative abundance. While model-averaged results indicated a C. perezi decline, G. cirratum remained stable from 2009 to 2019. We hypothesize that the C. perezi decline is a result of fishing along the edge of GRMR, while G. cirratum stability is related to their behavior and nationwide protection. Given the dynamic nature of fisheries regulations, economic pressures, and site-specific environmental conditions, our results emphasize the need for standardized long-term monitoring of reef sharks inside and around MPAs globally.
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Kuzminykh, Zh O., and N. V. Krasilnikova. "COMMUNICATIVE AND PRAGMATIC FEATURES OF A SPEECH GENRE IN BUSINESS MASS MEDIA DISCOURSE: A CASE STUDY OF ENTREPRENEURIAL PITCHES FROM ENGLISH MEDIA." Bulletin of Udmurt University. Series History and Philology 32, no. 2 (April 29, 2022): 286–94. http://dx.doi.org/10.35634/2412-9534-2022-32-2-286-294.
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The paper considers the phenomenon of the entrepreneurial pitch as a speech genre of the mass media subtype of business discourse. The communicative and pragmatic specificity of the genre was explored using a sample of 30 entrepreneurial pitches from the television reality shows "Dragons' Den" (Great Britain) and "Sharks Tank" (USA, Australia). The methodology is based on studying semantics, pragmatics and style characteristics of the pitches, as well as on the methods of cognitive analysis and linguistic interpretation. The findings show that the genre of the entrepreneurial pitch, from the mass media discourse perspective, is distinguished by such discourse features as semantic and pragmatic richness, focus on a high degree of persuasive impact on the audience during the short time of a pitch session. To achieve the effect, all communication strategies and tactics employed by the speaker must be purposefully planned and implemented in accordance with the communication settings and the target audience. The results obtained can be applied in the process of teaching English, as well as in linguistic research.