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1
Campana, Steven E., Linda Marks, Warren Joyce, and Nancy E. Kohler. "Effects of recreational and commercial fishing on blue sharks (Prionace glauca) in Atlantic Canada, with inferences on the North Atlantic population." Canadian Journal of Fisheries and Aquatic Sciences 63, no. 3 (March 1, 2006): 670–82. http://dx.doi.org/10.1139/f05-251.
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The nominal catch of blue sharks (Prionace glauca) reported for the Canadian Atlantic grossly underestimates the annual catch mortality of about 1000 tonnes (t), making blue sharks the most frequently caught large shark in Canadian waters. Although blue sharks accounted for 99% of all sharks landed at recreational shark fishing tournaments, tournament catches accounted for only 3% of total fishing mortality. Standardized catch rate indices suggested a decline in blue shark abundance of about 5%6%·year1 since 1995. An increased mortality rate in recent years was suggested by a decline in the median size of blue sharks in the commercial catch. Two independent calculations suggest that North Atlantic catches exceeded 100 000 t, with catch mortalities ranging between 26 000 and 37 000 t. Because tagging studies indicated that blue sharks are highly migratory with a single population in the North Atlantic, the Canadian contribution to overall population mortality accounts for only 2% of the total. The fact that blue shark populations are relatively productive and resilient may help explain their persistence in the face of high international catch mortality and a decline in relative abundance.
2
Estrada, James A., Aaron N. Rice, Molly E. Lutcavage, and Gregory B. Skomal. "Predicting trophic position in sharks of the north-west Atlantic Ocean using stable isotope analysis." Journal of the Marine Biological Association of the United Kingdom 83, no. 6 (December 2003): 1347–50. http://dx.doi.org/10.1017/s0025315403008798.
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Trophic positions (TP) were estimated for the blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), thresher shark (Alopias vulpinus), and basking shark (Cetorhinus maximus) using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N). The basking shark had the lowest TP (3·1) and δ15N value (10·4‰), whereas the thresher shark had the highest values (4·5, 15·2‰). Mako sharks showed considerable variation in TP and isotopic values, possibly due to foraging from both inshore and offshore waters. Thresher sharks were significantly more enriched in δ15N than blue sharks and mako sharks, suggesting a different prey base. The δ13C values of thresher sharks and mako sharks varied significantly, but neither was significantly different from that of blue sharks. No statistical differences were found between our TP estimations and those derived from published stomach contents analyses, indicating that stable isotope data may be used to estimate the trophic status of sharks.
3
Rochman, Fathur, Gussasta Levi Arnenda, Arief Wujdi, and Roy Kurniawan. "Vertical distribution of blue Shark (Prionace glauca) in The Indian Ocean." E3S Web of Conferences 322 (2021): 01009. http://dx.doi.org/10.1051/e3sconf/202132201009.
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Each fish species tends to choose a suitable environment suitable for its survival and reproduction horizontally and vertically. Blue shark (Prionace glauca) is the dominant catch of pelagic sharks by-catch in the Eastern Indian Ocean longline tuna fishery, with about 70% of the total sharks caught in this fisheries. This study aims to provide the information and the vertical analysis distribution of blue sharks based on temperature and depth in the Indian Ocean. The scientific observer collected 2,951 set-by-set longline fishing data based on Research Institute For Tuna Fisheries (RITF) from January 2006 to December 2018, on which the present analysis was made. The mini logger was used to measure the vertical distribution of blue sharks in the longline fisheries. This result indicated that blue shark was caught between 75.18-445.46 m depth, with 84% of which live at thermocline area (70-300 m depth), and 16% lived in underlayer area (>300 m depth). Blue sharks distributed in the underlayer area have a larger body size than those in the thermocline area with a size >180 cmFL compared to 50-170 cmFL in the thermocline area.
4
Wells, R. J. David, Natalie Spear, and Suzanne Kohin. "Age validation of the blue shark (Prionace glauca) in the eastern Pacific Ocean." Marine and Freshwater Research 68, no. 6 (2017): 1130. http://dx.doi.org/10.1071/mf16054.
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The blue shark (Prionace glauca) is subjected to high levels of fishery catch and by-catch worldwide; thus, knowledge of their productivity and population status is vital, yet basic assumptions of band-pair deposition rates in vertebrae used for age and growth models are being made without direct validation studies in the Pacific Ocean. As such, the purpose of the present study was to validate vertebral band-deposition rates of blue sharks tagged and recaptured in the eastern Pacific Ocean. Vertebrae of 26 blue sharks marked with oxytetracycline (OTC) were obtained from tag–recapture activities to determine timing of centrum growth-band deposition. Results from band counts distal to the OTC mark on each vertebra indicated that a single band pair (1 translucent and 1 opaque) is formed per year for blue sharks ranging from 1 to 8 years of age. Length–frequency modal analysis was also used to obtain growth estimates from a dataset spanning 26 years of research and commercial catch data. Results provide support for annual band-pair deposition in blue shark vertebrae and will aid in future blue shark age and growth studies in the Pacific Ocean.
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Chodrijah, U., and R. Faizah. "Population parameter, size distribution and sex ratio of the blue shark (Prionace glauca Linnaeus, 1758) caught in the southern of Nusa Tenggara." IOP Conference Series: Earth and Environmental Science 890, no. 1 (October 1, 2021): 012054. http://dx.doi.org/10.1088/1755-1315/890/1/012054.
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Abstract The blue shark (Prionace glauca Linnaeus, 1758) was a targeted shark caught in the artisanal fisheries in Tanjung Luar, West Nusa Tenggara. This species was caught by drifting longline. The study aims to obtain the parameter population, size distribution and sex ratio of the blue shark from these waters. The research was conducted in Tanjung Luar during 2019-2020, and a total of 1676 blue sharks were caught by drift longline. The data were analyzed by using ELEFAN II. The size blue sharks varied from 73 cm to 397 cm total length (TL), with mean length was 266 cm for males and 72-390 cm with mean length 255,61 cm TL for females. Male was dominated sex ratio. The equation growth for blue shark for male was Lt = 400 (1 – e−0.28 (t-0.2921)) and female was Lt = 390 (1 – e−0.25 (t-0.3307)) . The first captured (Lc ) length for males and females are 267.76 cm and 250.98 cm, respectively. Natural mortality (M) = 0.42/year, the fishing mortality (F ) = 0.50/year. The exploitation rate was > 0.55/year it means that utilization rate of blue sharks in Southern of Nusa Tenggara waters was susceptible to overfishing. This condition needs good management actions for this species.
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Zhu, Jizhang, Zhe Geng, Jiangfeng Zhu, and Kindong Richard. "Reproductive Biology and Distribution of the Blue Shark (Prionace glauca) in the Western Indian Ocean." Biology 12, no. 8 (August 14, 2023): 1128. http://dx.doi.org/10.3390/biology12081128.
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Due to the limited biological research on the blue shark in the Indian Ocean, such as the lack of a clear understanding of its reproductive biology and distribution, our study analyzed and evaluated the fork length distribution, sexual maturity length, reproductive capacity, and spatiotemporal distribution of blue sharks based on biological data and capture location information collected in the western Indian Ocean from 2010 to 2020. The objective of this study is to provide reliable biological information important in performing future stock assessments vital for species conservation in this region. A total of 791 male (33–249.5 cm FL) and 803 female (12–349.6 cm FL) blue sharks were collected in the West Indian Ocean. We used the morphology of the sexual organs to ascertain their sexual maturity. Results show that the observed size at 50% sexual maturity of male blue sharks in the West Indian Ocean was 161.4cm FL (192.4 cm TL) for males and 179.3 cm FL (213.9 cm TL) for females based on logistic curve analysis. The average litter size of pregnant blue sharks was 33.7 pups. There were significant differences in the distribution of blue shark individuals with different sexual maturity levels in different quarters (p < 0.05). This study suggests that the area near the equator in the Indian Ocean from October to March of the following year may be the mating ground for blue sharks, while the temperate waters in the Indian Ocean are the nursery ground and parturition ground for pregnant and juvenile throughout the whole year. Therefore, it is recommended to adopt a more scientific and reasonable operational method in these areas.
7
Francis, Malcolm P. "New Zealand shark fisheries: development, size and management." Marine and Freshwater Research 49, no. 7 (1998): 579. http://dx.doi.org/10.1071/mf97076.
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New Zealand’s shark fisheries have increased steadily since 1975 to reach 17 000–19 000 t per year. Commercial fisheries catch mainly spiny dogfish (Squalus acanthias), school shark (Galeorhinus galeus), skates (Raja nasuta and R. innominata), ghost sharks (Hydrolagus novaezealandiae and Hydrolagus sp.), rig (Mustelus lenticulatus) and elephantfish (Callorhinchus milii). School shark, rig and elephantfish fisheries have long histories, and catches are limited by Individual Transferable Quotas. Fisheries for spiny dogfish, skates and ghost sharks have only developed since 1979. Spiny dogfish and skate landings are partially regulated by total quotas. Other sharks are prohibited target species. Blue (Prionace glauca), porbeagle (Lamna nasus) and mako (Isurus oxyrinchus) sharks are taken as by-catch of the tuna longline fishery. There is a small recreational catch of spiny dogfish, school shark, rig, mako shark and blue shark. Historically important Maori fisheries for spiny dogfish, school shark and rig are now minor. A beach netting programme has operated off Dunedin beaches since 1969 to protect swimmers from shark attacks. Fisheries management measures include commercial quotas, prohibitions on target fishing many species, recreational bag limits, limits on set-net length, mesh size and soak time, and closure of many inshore waters to set-netting, trawling and Danish seining.
8
Varghese, Sijo P., N. Unnikrishnan, Deepak K. Gulati, and A. E. Ayoob. "Size, sex and reproductive biology of seven pelagic sharks in the eastern Arabian Sea." Journal of the Marine Biological Association of the United Kingdom 97, no. 1 (March 9, 2016): 181–96. http://dx.doi.org/10.1017/s0025315416000217.
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Studies on reproduction in sharks are important for their management, since the attainment of sexual maturity has a substantial impact on their distribution, behaviour and biology. However, reproductive biology of large oceanic sharks is poorly studied in the Indian seas. In this study, the size structure, sex and maturity of pelagic thresher (Alopias pelagicus), bigeye thresher (A. superciliosus), oceanic whitetip shark (Carcharhinus longimanus), tiger shark (Galeocerdo cuvier), shortfin mako (Isurus oxyrinchus), longfin mako (I. paucus) and blue shark (Prionace glauca) in the eastern Arabian Sea are described based on 1449 specimens collected from gillnet-cum-longline landings at the Cochin fisheries harbour during 2013–2014. Sex ratios of sampled specimens were biased to males in pelagic thresher, bigeye thresher, tiger shark and blue shark, while females dominated in the specimens of oceanic whitetip shark. Females matured at greater lengths than males in all species except oceanic whitetip shark. Lengths at maturity for males were in the range of 189.05–286.56 cm, whereas those of females were in the range of 187.74–310.69 cm. Litter sizes of both the thresher shark species were always two, while in oceanic whitetip shark, litter size was 3–9 and 22–51 in tiger shark. Seasonal reproduction was noticed in oceanic whitetip shark and tiger shark. Pregnant females were not found in the blue shark, shortfin and longfin makos sampled during the study period. Reproductive aspects of pelagic thresher, bigeye thresher, oceanic whitetip shark, tiger shark, shortfin mako, longfin mako and blue sharks in the eastern Arabian Sea are generally consistent with earlier reports from other regions of the world's oceans. These preliminary findings should be useful to identify suitable management measures for the above shark species.
9
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.
10
Jordaan, Gareth L., Jorge Santos, and Johan C. Groeneveld. "Effects of inconsistent reporting, regulation changes and market demand on abundance indices of sharks caught by pelagic longliners off southern Africa." PeerJ 6 (October 24, 2018): e5726. http://dx.doi.org/10.7717/peerj.5726.
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The assumption of a proportional relationship between catch-per-unit-effort (CPUE) and the abundance of sharks caught by pelagic longliners is tenuous when based on fisher logbooks that report only retained specimens. Nevertheless, commercial logbooks and landings statistics are often the only data available for stock status assessments. Logbook data collected from local and foreign pelagic longline vessels operating in four areas off southern Africa between 2000 and 2015 were used to construct standardized CPUE indices for blue sharks Prionace glauca and shortfin makos Isurus oxyrinchus. Generalized linear mixed models were used to explore the effects of year, month, vessel, fleet and presence of an observer on blue shark and shortfin mako variability. Landing statistics and auxiliary information on the history of the fishery, regulation changes, and market factors were superimposed on the CPUE indices, to test hypotheses that they would influence CPUE trends. Indices in the West and Southwest (Atlantic) areas were elevated for both species, compared to the South and East (Indian Ocean). The scale of year-on-year CPUE increments, up to an order of magnitude for blue sharks, reflected occasional targeting and retention, interspersed with periods where blue sharks were not caught, or discarded and not reported. Increments were smaller for higher value shortfin makos, suggesting that indices were less affected by unreported discarding. CPUE indices and landings of both shark species have increased in recent years, suggesting increased importance as target species. Analysis of logbook data resulted in unreliable indicators of shark abundance, but when trends were interpreted in conjunction with landings data, disaggregated by area and month, and with hindsight of market demand and regulation changes, anomalies could be explained.
11
Berrow, S. D. "Incidental capture of elasmobranchs in the bottom-set gill-net fishery off the south coast of Ireland." Journal of the Marine Biological Association of the United Kingdom 74, no. 4 (November 1994): 837–47. http://dx.doi.org/10.1017/s0025315400090081.
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The incidental capture of sharks in the bottom-set gill-net fishery off the south coast of Ireland was quantified by placing observers on commercial gill-netters for the duration of a fishing trip. Forty fishing trips were sampled resulting in 1,167 km and 19,760 km h of observed fishing effort. Sixty individual sharks of seven species were reported entangled in the fishing gear. Tope, porbeagle and six-gilled sharks were the most frequently caught species, with black-mouthed dogfish, blue shark, basking shark and starry smooth hound also recorded. Total fishing effort along the south coast was calculated and total capture extrapolated from observed catch rates. An estimated 6,000 sharks were caught in this fishery during the study period.
12
Francis, Malcolm P., Lynda H. Griggs, and Susan Jane Baird. "Pelagic shark bycatch in the New Zealand tuna longline fishery." Marine and Freshwater Research 52, no. 2 (2001): 165. http://dx.doi.org/10.1071/mf00086.
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Tuna longline effort declined from 23—26 million hooks per year in 1979mdash;82 to 2mdash;4 million hooks per year in 1995mdash;98. Scientific observer coverage averaged 7.5%since 1988mdash;89, but increased in 1992mdash;93 (mean 23%). Observed catch per unit effort (CPUE) and the numbers of hooks set were used to estimate shark catches. Between 1988mdash;89 and 1997mdash;98,about 450 000 blue sharks (Prionace glauca), 65 000 porbeagles (Lamna nasus ) and 25 000 shortfin makos (Isurus oxyrinchus) were caught. In 1997mdash;98,about 45 000 blue sharks, 4000 porbeagles and 3000 makos were caught. Corresponding weight estimates were 1400 t, 150 t and 200 t. CPUE varied between foreign and domestic vessels, between north and south regions and among years, but there were no consistent temporal trends. Most males and females were immature, and most sharks were alive when recovered. Most sharks were processed, but usually only the fins were retained. The New Zealand tuna longline fishery is probably not seriously affecting pelagic shark stocks, but adequate assessment is not currently feasible. Accurate monitoring of Pacific Ocean catches is an important first step towards ensuring sustainability of their populations.
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PANAYIOTOU, NIKOLAS, SEBASTIΑN BITON PORSMOGUER, DIMITRIOS Κ. MOUTOPOULOS, and JOSEP LLORET. "Offshore recreational fisheries of large vulnerable sharks and teleost fish in the Mediterranean Sea: first information on the species caught." Mediterranean Marine Science 21, no. 1 (April 30, 2020): 222. http://dx.doi.org/10.12681/mms.21938.
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Large-sized pelagic sharks and teleost fish are vulnerable to overexploitation by professional fisheries but little is known about the species caught by recreational fishing. This study presents for the first time in the Mediterranean an evaluation of the catch of pelagic sharks and teleost fish being caught by recreational fishermen by analyzing publicly available videos posted on social media. The analysis reveals that several vulnerable species, including the blue shark Prionace glauca, the shortfin mako Isurus oxyrinchus, the thresher shark Alopias vulpinus, the sixgill shark Hexanchus griseus, the swordfish Xiphias gladius, and the Mediterranean spearfish Tetrapturus belone are caught by offshore recreational fishermen, with the blue shark and the swordfish being the most commonly caught species. The majority of individuals caught are juveniles that are mostly released back to sea, issues that are in agreement with field studies. New measures related to handling practices are proposed to protect these species.
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Kai, Mikihiko, and Hiroki Yokoi. "Evaluation of harvest strategies for pelagic sharks taking ecological characteristics into consideration: an example for North Pacific blue shark." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 6 (June 2017): 933–47. http://dx.doi.org/10.1139/cjfas-2016-0170.
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We have developed a population dynamics model that considers the spatial segregation by sex and ontogenetic stages of pelagic sharks. The model was used to evaluate the performance of harvest strategies based on ecological characteristics. We proposed five harvest strategies for longline fisheries based on the ecological characteristics of blue shark (Prionace glauca) in the North Pacific. Management objectives for depleted populations are to increase yield to the level that provides maximum sustainable yield through increases in biomass without collapsing the fishery. Deterministic and stochastic analyses were undertaken. We determined that the harvest of male sharks was robust to uncertainty of environmental changes, reducing the likelihood of fishery collapse and stabilizing yield and mean biomass. The harvest of male sharks was also robust to the uncertainties of biological parameters such as natural mortality and steepness. These results suggested that if there was no sperm limitation or impact on the mating behavior of the species, the harvest of males would be the most appropriate harvest strategy for blue shark in the North Pacific.
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queiroz, nuno, fernando p. lima, anabela maia, pedro a. ribeiro, joão p. correia, and antónio m. santos. "movement of blue shark, prionace glauca, in the north-east atlantic based on mark–recapture data." Journal of the Marine Biological Association of the United Kingdom 85, no. 5 (October 2005): 1107–12. http://dx.doi.org/10.1017/s0025315405012154.
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a shark tagging programme along the portuguese coast was initiated in 2001 in collaboration with the national marine fisheries service. from a total of 168 blue sharks (prionace glauca) tagged, 34 sharks were recaptured (20% return rate) providing important information on this species' movement patterns for the area. a total of 28 sharks travelled less than 1000 km while at liberty for time periods ranging from 22 to 1294 days. the remaining fish travelled long distances to north-west africa, central atlantic and the bay of biscay. only one shark made a transatlantic migration, being recaptured 3187 km from the tagging site. north–south movements seem to be related to seasonal sea-surface temperature variation in the north-east atlantic. seasonal segregation of different life stages also occurs.
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Carvalho, Felipe C., Debra J. Murie, Fábio H. V. Hazin, Humberto G. Hazin, Bruno Leite-Mourato, and George H. Burgess. "Spatial predictions of blue shark (Prionace glauca) catch rate and catch probability of juveniles in the Southwest Atlantic." ICES Journal of Marine Science 68, no. 5 (May 1, 2011): 890–900. http://dx.doi.org/10.1093/icesjms/fsr047.
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Abstract Carvalho, F. C., Murie, D. J., Hazin, F. H. V., Hazin, H. G., Leite-Mourato, B., and Burgess, G. H. 2011. Spatial predictions of blue shark (Prionace glauca) catch rate and catch probability of juveniles in the Southwest Atlantic. – ICES Journal of Marine Science, 68: 890–900. Generalized regression analysis and spatial prediction was applied to catch per unit effort (cpue) data for blue shark (Prionace glauca) caught by the Brazilian tuna longline fleet between 1997 and 2008 (43 546 longline sets) to predict the effect of environmental, spatial, and temporal factors on catch distribution. In addition, the size distribution of blue sharks measured by on-board observers during the years 2006–2008 was used to model the proportion of juvenile blue sharks in the catches from a spatial perspective. Latitude was the most important factor influencing blue shark cpue in the Southwest Atlantic, with cpue spatial predictions suggesting two areas of higher catch probabilities. Latitude was also the most important factor influencing the proportion of juveniles in the catches. The spatial prediction map showed that juveniles were more frequently caught south of 35°S (∼38°S). This information can assist in the design of management strategies either to exploit this predictable spatial distribution of the catch or to manage the fisheries in a spatially explicit manner if one component (i.e. juveniles) requires protective measures.
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Choy, Christina Pei Pei, and Benjamin J. Wainwright. "What Is in Your Shark Fin Soup? Probably an Endangered Shark Species and a Bit of Mercury." Animals 12, no. 7 (March 22, 2022): 802. http://dx.doi.org/10.3390/ani12070802.
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Shark fin soup, consumed by Asian communities throughout the world, is one of the principal drivers of the demand of shark fins. This near USD 1 billion global industry has contributed to a shark population declines of up to 70%. In an effort to arrest these declines, the trade in several species of sharks is regulated under the auspices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Despite this legal framework, the dried fins of trade-regulated sharks are frequently sold in markets and consumed in shark fin soup. Shark fins found in soups break down into a fibrous mass of ceratotrichia, meaning that identifying the species of sharks in the soup becomes impossible by visual methods. In this paper, we use DNA barcoding to identify the species of sharks found in bowls of shark fin soup collected in Singapore. The most common species identified in our samples was the blue shark (Prionace glauca), a species listed as Near Threatened on the International Union for Conservation of Nature (IUCN) Red List with a decreasing population, on which scientific data suggests catch limits should be imposed. We identified four other shark species that are listed on CITES Appendix II, and in total ten species that are assessed as Critically Endangered, Endangered or Vulnerable under the IUCN Red List of Threatened Species. Globally, the blue shark has been shown to contain levels of mercury that frequently exceed safe dose limits. Given the prevalence of this species in the examined soups and the global nature of the fin trade, it is extremely likely that consumers of shark fin soup will be exposed to unsafe levels of this neurotoxin.
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Li, Weiwen, Xiaojie Dai, Kevin W. Staples, Bin Chen, Hao Huang, and Siquan Tian. "Blue Shark (Prionace glauca) Distribution in the Pacific Ocean: A Look at Continuity and Size Differences." Water 15, no. 7 (March 28, 2023): 1324. http://dx.doi.org/10.3390/w15071324.
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Blue shark (Prionace glauca) is a major bycatch species in the long-line and gill-net Pacific Ocean tuna fisheries, and the population structure is critical for fishery management. We employed generalized additive models to analyze the fork lengths of blue sharks and biological data (i.e., feeding level, sex, and genetic data), as well as environmental and spatial variables (i.e., sea surface temperature, month, longitude, and latitude) collected from 2011 to 2014 by the Chinese Thunnus alalunga long-line tuna fishery observer program. Fork length was significantly affected (p < 0.05) with location (latitude and longitude) and sex, and positively effected with sea surface temperature. No relationships were found between fork length and feeding level, month, and genetic data. We detected fork length differences among blue sharks over the range of the observed data, but the genetic data implied a panmictic population. Thus, we hypothesize that the genetic similarity was so close that it could not be well separated. Based on the precautionary principle, we recommend that the blue shark in the Pacific Ocean should be managed as two independent populations to ensure its sustainable use.
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Amri Komarudin, Nurul, Fahrunnisa Fahrunnisa, and Yuni Yolanda. "Community-Based Whale Sharks Conservation to Strengthen Ma-rine Tourism Management in Sumbawa." International Journal of Geotourism Science and Development 2, no. 2 (October 30, 2022): 25–31. http://dx.doi.org/10.58856/ijgsd.v2i2.20.
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Sumbawa is famous for its marine tourism, apart from the beauty of its beaches, Sumbawa also has marine fauna that attracts the attention of tourists, namely whale sharks. It is recorded that there are around 99 species of Whale Sharks located in Saleh Bay, Sumbawa. Thus, making Saleh Bay the location with the second largest whale shark population in Indonesia and UNESCO designated Saleh Bay as part of the SAMOTA biosphere reserve. Currently, whale sharks have protected fauna according to the decree of the Minister of Marine Affairs and Fisheries No. 18 of 2013. This is due to the pollution of whale shark habitats by pollutants including garbage and microplastics. In addition, the Overexploitation of whale sharks is some of the causes of the significant decline in whale shark populations. Marine ecotourism activities in the form of exhibiting Whale Sharks to tourists can be an alternative way of sustainable use because it has minimal impact on individual Whale Sharks, in addition, marine ecotourism activities can also provide economic benefits to the Sumbawa community and regional development including supporting efforts to protect and preserve the whale shark fauna. The Study "Community-Based Whale Shark Conservation to Strengthen Marine Tourism Management in Sumbawa “aims to present a blue economy model for coastal communities in Sumbawa and increase community participation in conservation activities, as well as improve the welfare of coastal communities in Sumbawa.
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Damalas, Dimitrios, and Persefoni Megalofonou. "Environmental effects on blue shark (Prionace glauca) and oilfish (Ruvettus pretiosus) distribution based on fishery-dependent data from the eastern Mediterranean Sea." Journal of the Marine Biological Association of the United Kingdom 90, no. 3 (April 26, 2010): 467–80. http://dx.doi.org/10.1017/s0025315409991214.
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Blue sharks (Prionace glauca) and oilfish (Ruvettus pretiosus) are frequently caught incidentally in the swordfish surface drifting longline fishery of the eastern Mediterranean Sea. An information theoretic generalized additive model approach, modelling separately: (1) the probability of making a catch; and (2) the positive catch rates, suggested the presence of intra-annual variations in their abundance and revealed interesting associations with some environmental features. Blue sharks were more frequently encountered during late summer in cool water masses. However, the likelihood of making a larger catch peaked in warmer waters through late spring in the vicinity of land. Occurrences of blue sharks were more frequent to the south-west (Ionian Sea), while positive catch rates were higher in the eastern-most regions (Levantine). Oilfish occurrences, as well as catch rates, were always above average to the east. Intra-annual variation was analogous to that of blue sharks. The species showed a preference for cooler water bodies and its distribution was strongly dictated by the lunar cycle. Annual time series showed a decreasing trend of blue sharks abundance. Catch rates for both species depended on fishing gear configuration. Deeper settings (>20 m), more resilient lines and use of fish attractant light-sticks increased the probability of capturing a fish.
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Ćetković, Ilija, Ana Pešić, Aleksandar Joksimović, Jovana Tomanić, and Stefan Ralević. "Morphometric measurements of newborn blue shark Prionace glauca (Linnaeus, 1758) and characteristics of its potential parturition areas in coastal waters of Montenegro (Southeastern Adriatic)." Acta Adriatica 60, no. 1 (July 22, 2019): 61–67. http://dx.doi.org/10.32582/aa.60.1.6.
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The blue shark belongs to the group of the most widespread pelagic sharks in the world. It inha-bits the pelagic zone of almost all warm and temperate seas and oceans. As it is one of the most abundant shark species, it is frequently caught in different types of fishing gear operated in the pela-gic zone. This study provides the first data on the reproduction of this species in Montenegrin waters (in the Southeastern Adriatic Sea). Six newborn blue sharks were found during our field excursions. For three of them, detailed morphometric measurements are presented. Alongside the newborns, a gravid female was also recorded. The data was collected in the period from April to October 2017. According to the published literature and the data presented in this paper, species reproduction is likely to be seasonal. A review of the areas where the specimens were recorded was carried out in order to infer if the adult females choose them specifically as their parturition grounds
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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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Dolfo, Violaine, Emilie Boissin, Matthieu Lapinski, and Serge Planes. "New insights into population structure, demographic history, and effective population size of the critically endangered blue shark Prionace glauca in the Mediterranean Sea." PLOS ONE 19, no. 6 (June 17, 2024): e0305608. http://dx.doi.org/10.1371/journal.pone.0305608.
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The blue shark, Prionace glauca, is the most abundant pelagic shark in the open ocean but its vulnerability remains poorly understood while being one of the most fecund sharks. In the Mediterranean Sea, the blue shark is listed as Critically Endangered (CR) by the International Union for Conservation of Nature. The species is facing a strong decline due to fishing, and scientific data regarding its genetic structure and vulnerability are still lacking. Here, we investigated the genetic diversity, demographic history, and population structure of the blue shark within the Mediterranean Sea, from samples of the Gulf of Lion and Malta, using sequences of the mtDNA control region and 22 microsatellite markers. We also compared our mitochondrial data to previous studies to examine the Atlantic-Mediterranean population structure. We assessed the blue shark’s genetic vulnerability in the Mediterranean basin by modelling its effective population size. Our results showed a genetic differentiation between the Atlantic and the Mediterranean basins, with limited gene flow between the two areas, and distinct demographic histories making the Mediterranean population an independent management unit. Within the Mediterranean Sea, no sign of population structure was detected, suggesting a single population across the Western and Central parts of the sea. The estimated effective population size was low and highlighted the high vulnerability of the Mediterranean blue shark population, as the estimated size we calculated might not be sufficient to ensure the long-term persistence of the population. Our data also provide additional evidence that the Gulf of Lion area acts as a nursery for P. glauca, where protection is essential for the conservation strategy of the species in the Mediterranean.
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Klimley, A. Peter. "A Sensor Designed to Record Underwater Irradiance with Concern for a Shark’s Spectral Sensitivity." Biosensors 11, no. 4 (April 3, 2021): 105. http://dx.doi.org/10.3390/bios11040105.
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To ascertain how scalloped hammerhead sharks make nightly migrations to their feeding grounds as many as 20 km from their daytime abode, a seamount, a sensor was developed that measured irradiance intensity within the spectral range and sensitivity of the vision of the species. Could the sharks guide their movements by sensing the polarity of irradiation energy radiated from the sun or moon that penetrated into the oceanic depths? Two sensory receptors, cones and rods, are present in the retina of sharks to enable them to see both during daytime and nighttime. The peak sensitivity of the cones is red-shifted due to the presence of these wavelengths during the former period, while their response is linear under the range of the high light levels also present at this time; the peak sensitivity of rods is blue-shifted due to the presence of these wavelengths during dawn, dusk, and nighttime and is linear over the complementary range of low light levels. Spectral response curves for these two receptors were determined for sharks, and an attempt was made to match those of the sensors to the shark’s wavelength perception. The first sensor was matched to the photopic range using a photocell covered with a red-shifted gel filter; the second was matched to the scotopic range using a blue-shifted gel filter.
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Hernández-Aguilar, Sandra Berenice, Ofelia Escobar-Sánchez, Felipe Galván-Magaña, and Leonardo Andrés Abitia-Cárdenas. "Trophic ecology of the blue shark (Prionace glauca) based on stable isotopes (δ13C and δ15N) and stomach content." Journal of the Marine Biological Association of the United Kingdom 96, no. 7 (September 8, 2015): 1403–10. http://dx.doi.org/10.1017/s0025315415001393.
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Occupying the upper levels of trophic webs and thus regulating prey at lower levels, sharks play an important role in the trophic structure and energy dynamics of marine ecosystems. In recent years, the removal of these individuals from upper trophic levels as a result of overfishing has negatively affected ecosystems. We analysed the diet of blue sharks (Prionace glauca) caught off the west coast of Baja California Sur, Mexico, during the months of February–June in 2001, 2005 and 2006. We employed both stomach content and stable isotope analyses as each method provides distinct yet important information regarding the role of blue sharks in marine food webs, allowing us to estimate the relative contribution of different prey items to this predator's diet. Of the 368 stomachs analysed, 210 contained food (57%) and 158 (43%) were empty. Based on stomach contents and the index of relative importance (IRI), the pelagic red crab (Pleuroncodes planipes) was the most important prey, followed by the squids Gonatus californiensis (34.1%) and Ancistrocheirus lesueurii (10.4%). The mean (±SD) values for δ15N (16.48 ± 0.94‰) and δ13C (−18.48 ± 0.63‰) suggest that blue sharks prefer feeding in oceanic waters. The trophic level based on stomach content analysis was 4.05, while that based on the stable isotope analysis was 3.8, making blue sharks top consumers in the marine ecosystem of Baja California Sur, Mexico.
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Leone, Agostino, Ilenia Urso, Dimitrios Damalas, Jann Martinsohn, Antonella Zanzi, Stefano Mariani, Emilio Sperone, et al. "Genetic differentiation and phylogeography of Mediterranean-North Eastern Atlantic blue shark (Prionace glauca, L. 1758) using mitochondrial DNA: panmixia or complex stock structure?" PeerJ 5 (December 6, 2017): e4112. http://dx.doi.org/10.7717/peerj.4112.
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BackgroundThe blue shark (Prionace glauca, Linnaeus 1758) is one of the most abundant epipelagic shark inhabiting all the oceans except the poles, including the Mediterranean Sea, but its genetic structure has not been confirmed at basin and interoceanic distances. Past tagging programs in the Atlantic Ocean failed to find evidence of migration of blue sharks between the Mediterranean and the adjacent Atlantic, despite the extreme vagility of the species. Although the high rate of by-catch in the Mediterranean basin, to date no genetic study on Mediterranean blue shark was carried out, which constitutes a significant knowledge gap, considering that this population is classified as “Critically Endangered”, unlike its open-ocean counterpart.MethodsBlue shark phylogeography and demography in the Mediterranean Sea and North-Eastern Atlantic Ocean were inferred using two mitochondrial genes (Cytb and control region) amplified from 207 and 170 individuals respectively, collected from six localities across the Mediterranean and two from the North-Eastern Atlantic.ResultsAlthough no obvious pattern of geographical differentiation was apparent from the haplotype network, Φst analyses indicated significant genetic structure among four geographical groups. Demographic analyses suggest that these populations have experienced a constant population expansion in the last 0.4–0.1 million of years.DiscussionThe weak, but significant, differences in Mediterranean and adjacent North-eastern Atlantic blue sharks revealed a complex phylogeographic structure, which appears to reject the assumption of panmixia across the study area, but also supports a certain degree of population connectivity across the Strait of Gibraltar, despite the lack of evidence of migratory movements observed by tagging data. Analyses of spatial genetic structure in relation to sex-ratio and size could indicate some level of sex/stage biased migratory behaviour.
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Aires-da-Silva, Alexandre M., Mark N. Maunder, Vincent F. Gallucci, Nancy E. Kohler, and John J. Hoey. "A spatially structured tagging model to estimate movement and fishing mortality rates for the blue shark (Prionace glauca) in the North Atlantic Ocean." Marine and Freshwater Research 60, no. 10 (2009): 1029. http://dx.doi.org/10.1071/mf08235.
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Large numbers of blue sharks are caught as bycatch, and have even become the target species in pelagic longline fisheries in the North Atlantic Ocean. The status of the stock is ambiguous due to the limitations of the fishery-dependent data. This study presents a spatially structured tagging model to estimate blue shark movement and fishing mortality rates in the North Atlantic Ocean. The model uses the blue shark tag-recovery data collected by the United States National Marine Fisheries Service Cooperative Shark Tagging Program (1965–2004). Four major geographical regions (two on each side of the ocean) are assumed. The blue shark fishing mortality rates (F) were found to be heterogeneous across the four regions. While the estimates of F obtained for the western North Atlantic Ocean were historically lower than 0.1 year–1, the F estimates over the most recent decade (1990s) in the eastern side of the ocean are rapidly approaching 0.2 year–1. Because of the particular life-history of the blue shark, these results suggest careful monitoring of the fishery as the juvenile and pregnant female segments of the stock are highly vulnerable to exploitation in the eastern North Atlantic Ocean.
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Sitorus, Yuni Debora Prasicilia, Pande Gde Sasmita Julyantoro, and Ayu Putu Wiweka Krisna Dewi. "Identification of Dominant Shark Fins Landed at The Port of Benoa, Bali Based on CO1 Gene." Journal of Marine and Aquatic Sciences 8, no. 2 (February 1, 2023): 221. http://dx.doi.org/10.24843/jmas.2022.v08.i02.p07.
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Indonesia is one of the world's most shark-catching countries. One of the fishery ports that has a by-product of sharks is the Port of Benoa. The purpose of this study was to determine the species and phylogenetic relationship of sharks from dominant fin samples landed at the Port of Benoa, Bali based on the results of morphological identification and DNA barcoding techniques. The study was conducted from January to February 2018 at the Pengawasan Sumberdaya Kelautan dan Perikanan Base (PSDKP) Benoa. This research uses exploration method with survey technique. The data used in this research is primary data of dominant shark fin samples in research location area and secondary data of location where shark caught by fisherman based on PSDKP database. The results showed that by-catch sharks from dominant fin samples at the Port of Benoa, Bali based on morphological identification and DNA barcoding technique were Prionace glauca (Blue Shark) species. The results of phylogenetic analysis of by-catch shark species from dominant fin samples landed at the Port of Benoa, Bali have close relation with Carcharhinidae family. Prionace glauca shark species have an amplified nucleotide base length of 600 pb with similarity reaching 99 values with species present in GenBank.
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Baremore, Ivy E., Rachel T. Graham, George H. Burgess, and Daniel W. Castellanos. "Movements and residency of Caribbean reef sharks at a remote atoll in Belize, Central America." Royal Society Open Science 8, no. 8 (August 2021): 201036. http://dx.doi.org/10.1098/rsos.201036.
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We investigated spatial use patterns of 77 Caribbean reef sharks ( Carcharhinus perezi ) at Lighthouse Reef Atoll, Belize over 7 years using residency patterns, kernel density (KD) estimation and network analysis. We found a high degree individual variation in spatial use of the atoll, but there were significant differences in residency and activity space between sexes, with females being overall more resident. Ontogenetic shifts in movement and residency were largely limited to females, as the residency index increased and activity space estimates decreased as females matured, while for males there was no relationship between space use or residency and size. KD analysis revealed many mature females were highly resident to discrete locations, and average activity space of the intermediate-sized sharks was significantly larger than that of the adults, but not the smallest sharks. Markov chain analyses indicated that the southwestern portion of the atoll was the most important movement corridor for all sharks. Both the Blue Hole and Half Moon Caye Natural Monuments provide some protection for larger Caribbean reef sharks; however, a gear ban on longlines on the southwestern forereef between Long Caye and the channel entrance to the Blue Hole would maximize the benefits for all sharks.
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Vaske Júnior, Teodoro, Rosangela Paula Lessa, and Otto Bismarck Fazzano Gadig. "Feeding habits of the blue shark (Prionace glauca) off the coast of Brazil." Biota Neotropica 9, no. 3 (September 2009): 55–60. http://dx.doi.org/10.1590/s1676-06032009000300004.
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Stomachs from 222 blue sharks collected along the Brazilian coast were analyzed - 116 from the northeastern region and 106 from the southern region. A total of 51 prey taxa were identified. The most important prey items in the southern region were Mysticeti whales, teleosteans, the gempylid Ruvettus pretiosus and the nomeid Arioma bondi. Cephalopods were more diverse, with dominance of vertical migrants Histioteuthis spp., Cranchiidae and the epipelagic octopus Ocythoe tuberculata. In the northeastern region, blue sharks consumed mainly teleosteans, including the alepisaurid Alepisaurus ferox and the gempylid Gempylus serpens. Among cephalopods, Histioteuthis spp. and the epipelagic octopus Tremoctopus violaceus were the dominant items. Predation upon schooling prey was occasional, as observed on Arioma bondi. Birds also were consumed in both regions; Puffinus gravis was the fifth most frequent item in the northeastern region. During the reproductive migration cycle, blue sharks likely prey in the thermocline, which is deeper in the northeastern region and closer to the surface in the southern region.
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Elliott, Riley, Jingjing Zhang, Todd Dennis, John Montgomery, and Craig Radford. "Evaluating Behavioural Modelling Predictions in the Blue Shark (Prionace glauca) Enables Greater Insight on Habitat Use from Location only Argos Data." Research in Ecology 5, no. 4 (October 31, 2023): 31–48. http://dx.doi.org/10.30564/re.v5i4.5894.
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The relationship between habitat and behaviour provides important information for species management. For large, free roaming, marine animals satellite tags provide high resolution information on movement, but such datasets are restricted due to cost. Extracting additional biologically important information from these data would increase utilisation and value. Several modelling approaches have been developed to identify behavioural states in tracking data. The objective of this study was to evaluate a behavioural state prediction model for blue shark (Prionace glauca) ARGOS surface location-only data. The novel nature of the six SPLASH satellite tags used enabled behavioural events to be identified in blue shark dive data and accurately mapped spatio-temporally along respective surface location-only tracks. Behavioural states modelled along the six surface location-only tracks were then tested against observed behavioural events to evaluate the model's accuracy. Results showed that the Behavioural Change Point Analysis (BCPA) model augmented with K means clustering analysis performed well for predicting foraging behaviour (correct 86% of the time). Prediction accuracy was lower for searching (52%) and travelling (63%) behaviour, likely related to the numerical dominance of foraging events in dive data. The model's validation for predicting foraging behaviour justified its application to nine additional surface location-only (SPOT tag) tracks, substantially increasing the utilisation of expensive and rare data. Results enabled the critical behavioural state of foraging, to be mapped throughout the entire home range of blue sharks, allowing drivers of critical habitat to be investigated. This validation strengthens the use of such modelling to interpret historic and future datasets, for blue sharks but also other species, contributing to conservational management.
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Elliott, Riley, Jingjing Zhang, Todd Dennis, John Montgomery, and Craig Radford. "Evaluating Behavioural Modelling Predictions in the Blue Shark (Prionace glauca) Enables Greater Insight on Habitat Use from Location only Argos Data." Research in Ecology 5, no. 3 (October 31, 2023): 31–48. http://dx.doi.org/10.30564/re.v5i3.5894.
Full textAbstract:
The relationship between habitat and behaviour provides important information for species management. For large, free roaming, marine animals satellite tags provide high resolution information on movement, but such datasets are restricted due to cost. Extracting additional biologically important information from these data would increase utilisation and value. Several modelling approaches have been developed to identify behavioural states in tracking data. The objective of this study was to evaluate a behavioural state prediction model for blue shark (Prionace glauca) ARGOS surface location-only data. The novel nature of the six SPLASH satellite tags used enabled behavioural events to be identified in blue shark dive data and accurately mapped spatio-temporally along respective surface location-only tracks. Behavioural states modelled along the six surface location-only tracks were then tested against observed behavioural events to evaluate the model's accuracy. Results showed that the Behavioural Change Point Analysis (BCPA) model augmented with K means clustering analysis performed well for predicting foraging behaviour (correct 86% of the time). Prediction accuracy was lower for searching (52%) and travelling (63%) behaviour, likely related to the numerical dominance of foraging events in dive data. The model's validation for predicting foraging behaviour justified its application to nine additional surface location-only (SPOT tag) tracks, substantially increasing the utilisation of expensive and rare data. Results enabled the critical behavioural state of foraging, to be mapped throughout the entire home range of blue sharks, allowing drivers of critical habitat to be investigated. This validation strengthens the use of such modelling to interpret historic and future datasets, for blue sharks but also other species, contributing to conservational management.
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Mitchell, Christian Danielle, and Michael F. Criscitiello. "Code Blue: Nurse Cells Can Resuscitate Lymphocyte Receptors in Nurse Shark Thymus by Secondary Rearrangement." Journal of Immunology 204, no. 1_Supplement (May 1, 2020): 92.30. http://dx.doi.org/10.4049/jimmunol.204.supp.92.30.
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Abstract The thymus is the most conserved primary lymphoid organ present, in some form, in mammals to all the way back in lamprey. It is composed of a densely-packed outer cortex and an exiguous inner medulla. The thymus functions to provide a microenvironment conducive to T lymphocyte maturation and receptor repertoire formation. Sharks are situated at a pivotal location in evolutionary immunology. They are the oldest vertebrates to have similar adaptive immune characteristics to mammals. Shark lymphocyte antigen receptors are diversified by V(D)J recombination via RAG and heavy chain class switch recombination catalyzed by AID. Somatic hypermutation occurs in both B and T cell antigen receptors of shark, mediated by AID as well. Shark T cell receptors also employ antibody-like NARTCR and IgHV components. Looking at the oldest lymphoid tissue in the oldest vertebrate ancestor with adaptive characteristics similar to mammals will yield important information on the evolution of the adaptive immune response as it relates to T lymphocytes. Nurse cells are cortical thymic epithelial cells that play an important role in selection of functional T cells during the maturation process. Nurse cells have been shown, in mice, to surround non-functional T cells in order to allow them to reconfigure their receptors and attempt selection another time via RAG and/or AID. Through the use of immunohistochemistry and in situ hybridization, we will investigate whether nurse cells provide a microenvironment for shark thymocyte receptor revision in sharks as in mammals.
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Aguilera, Orangel, Zoneibe Luz, Jorge D. Carrillo-Briceño, László Kocsis, Torsten W. Vennemann, Peter Mann de Toledo, Afonso Nogueira, et al. "Neogene sharks and rays from the Brazilian ‘Blue Amazon’." PLOS ONE 12, no. 8 (August 23, 2017): e0182740. http://dx.doi.org/10.1371/journal.pone.0182740.
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Castro, JA, and J. Mejuto. "Reproductive parameters of blue shark, Prionace glauca, and other sharks in the Gulf of Guinea." Marine and Freshwater Research 46, no. 6 (1995): 967. http://dx.doi.org/10.1071/mf9950967.
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In total, 1967 pelagic sharks of eight different species were sampled in waters of the Gulf of Guinea between June and August 1993 by commercial longline gear. Catches of Prionace glauca and Sphyma zygaena included a large number of pregnant females, making it possible to calculate some of their reproductive parameters. In total, 419 gravid females of P. glauca were caught, ranging in size from 170 to 260 cm fork length. The size at which 50% of females have embryos was determined to be 180 cm FL. Examination of the uteri from 128 of these females showed a higher number of embryos (59-60%) in the right uterus. The mean number of embryos was 37. Data on embryo size suggests that P. glauca may have a west-east migration to give birth along the Atlantic equatorial line. The embryonic sex ratio was 1 : 1. In the same catch there were 21 gravid females of S. zygaena. No difference in the number of embryos between uteri was found in this species. Mean embryo number was 33.5 and embryonic sex ratio was 1 : 1.
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Taguchi, Mioko, Jacquelynne R. King, Michael Wetklo, Ruth E. Withler, and Kotaro Yokawa. "Population genetic structure and demographic history of Pacific blue sharks (Prionace glauca) inferred from mitochondrial DNA analysis." Marine and Freshwater Research 66, no. 3 (2015): 267. http://dx.doi.org/10.1071/mf14075.
Full textAbstract:
Cosmopolitan pelagic species often show shallow genetic divergence and weak, or no, genetic structure across a species’ range. However, there have been few such genetic studies for pelagic sharks. The pelagic blue shark (Prionace glauca) has a broad circumglobal distribution in tropical and temperate oceans. To investigate the population genetic structure and demographic history of this species, we analysed variation in the mitochondrial cytochrome b sequence for a total of 404 specimens collected from 10 locations across the Indo-Pacific region. The observed genetic diversities were comparable among sampling locations (h=0.77–0.87; π=0.17–0.23%). Spatial analysis of molecular variance (SAMOVA), pairwise ΦST and conventional FST estimates, and analysis of isolation with migration indicated weak or no genetic differentiation of this species across the Indo-Pacific region. The results of three phylogeographic analyses (i.e. mismatch distribution and parsimony haplotype network analyses and a neutrality test) suggested that the Pacific blue shark had historically experienced a sudden population expansion. These results, coupled with the biological properties of this species, imply that historical climate fluctuation has had only a minor effect on the genetic structuring of the blue shark.
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Sentosa, Agus Arifin, Umi Chodrijah, and Irwan Jatmiko. "SEBARAN UKURAN DAN BEBERAPA PARAMETER POPULASI HIU KARET (Prionace glauca Linnaeus, 1758) YANG TERTANGKAP DI PERAIRAN SELATAN NUSA TENGGARA." Jurnal Penelitian Perikanan Indonesia 23, no. 2 (November 14, 2017): 67. http://dx.doi.org/10.15578/jppi.23.2.2017.67-76.
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Hiu karet (Prionace glauca) adalah hiu pelagis yang menjadi target tangkapan nelayan artisanal Tanjung Luar dan umumnya tertangkap di Samudera Hindia Selatan Nusa Tenggara. Penelitian ini bertujuan untuk mengetahui sebaran ukuran dan beberapa parameter populasi hiu karet (Prionace glauca) yang tertangkap di perairan selatan Nusa Tenggara. Analisis dilakukan terhadap 1.414 ekor hiu karet yang tertangkap rawai hanyut di selatan Nusa Tenggara dan didaratkan di Tanjung Luar, Lombok Timur selama periode 2014 – 2016. Analisis data dilakukan secara deskriptif dan beberapa parameter populasi diduga menurut rumus empiris Froese & Binohlan (2000). Hasil penelitian menunjukkan sebaran ukuran panjang total hiu karet berkisar antara 95 – 383 cm (jantan) dan 113 – 333 cm (betina) dengan rerata ukuran yang tertangkap tidak berbeda nyata. Nisbah kelamin didominasi oleh hiu karet jantan dan telah matang kelamin. Dugaan terhadap beberapa parameter adalah: nilai L∞ antara 333,02 - 385,59 cm dengan Lm jantan antara 187,21 – 215 cm dan betina 139,82 – 159,34 cm. Sebanyak 39,96 – 44,71% hiu karet tertangkap pada panjang optimumnya sehingga ada kecenderungan tangkap lebih.The blue shark (Prionace glauca) is targeted pelagic shark of artisanal fishermen of Tanjung Luar and commonly caught from the southern part of Nusa Tenggara water. The research aims to determine the size distribution and some population parameters of blue shark (Prionace glauca) caught in the Southern part of Nusa Tenggara water. The analysis was performed on 1,414 blue sharks caught by drifting longlines in the Southern part of Nusa Tenggara water and landed at Tanjung Luar, East Lombok during the period 2014 - 2016. The data were analyzed descriptively and some parameters of the population were calculated by the empirical formula from Froese & Binohlan (2000). The results showed that the length total size distribution of blue sharks ranged between 95-383 cm (male) and 113-333 cm (females). The sex ratio was dominated by male shark. The estimation of population parameters of shark were L∞ ranged between 333.02 - 385.59 cm, Lm estimated ranged between 187.21 to 215 cm (male) and from 139.82 to 159.34 cm (female). About 39.96 to 44.71% of total sample was caught at its optimum length, so it tends to be over exploitation.
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PENADÉS-SUAY, J., J. TOMÁS, and F. J. AZNAR. "Deadly impalement of a blue shark Prionace glauca by a swordfish Xiphias gladius." Mediterranean Marine Science 18, no. 2 (July 26, 2017): 340. http://dx.doi.org/10.12681/mms.1959.
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In September, 2016, an adult female blue shark (Prionace glauca) 247 cm long stranded alive on the coast of Valencia (Spain, Western Mediterranean) but died shortly afterwards. The necropsy revealed ongoing pregnancy, with 65 embryos in early stage of development, and a healthy condition with no signs of starvation. Two fishing hooks surrounded by scarred tissue were detected in the mandible, indicating past interaction with fisheries. In addition, a fragment of the tip of a swordfish (Xiphias gladius) rostrum (length: 18 cm long, width: 0.5 cm (distal) and 3 cm (proximal)) was removed from the animal. The fragment had pierced the head producing an incision of 3.5 cm close to the left eye, crossing the head anterior to the pre-orbital process. No apparent damage was observed in the olfactory capsule or the eye, but the fragment had penetrated both sides of the skull causing extensive lesions in the brain, which were inferred to be the cause of death. Allometric analysis suggested that the swordfish was ca. 110 cm long, corresponding to a juvenile 1-2 yrs old. Swordfish had previously been reported driving their rostrum into pelagic sharks, allegedly as a defensive strategy. However, this is the first report of impalement as the direct cause of death in blue sharks.
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Gonzalez-Pestana, Adriana, Carlos Kouri J., and Ximena Velez-Zuazo. "Shark fisheries in the Southeast Pacific: A 61-year analysis from Peru." F1000Research 3 (July 21, 2014): 164. http://dx.doi.org/10.12688/f1000research.4412.1.
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Peruvian waters exhibit high conservation value for sharks. This contrasts with a lag in initiatives for their management and a lack of studies about their biology, ecology and fishery. We investigated the dynamics of Peruvian shark fishery and its legal framework identifying information gaps for recommending actions to improve management. Further, we investigated the importance of the Peruvian shark fishery from a regional perspective. From 1950 to 2010, 372,015 tons of sharks were landed in Peru. From 1950 to 1969, we detected a significant increase in landings; but from 2000 to 2011 there was a significant decrease in landings, estimated at 3.5% per year. Six species represented 94% of landings: blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), smooth hammerhead (Sphyrna zygaena), common thresher (Alopias vulpinus), smooth-hound (Mustelus whitneyi) and angel shark (Squatina californica). Of these, the angel shark exhibits a strong and significant decrease in landings: 18.9% per year from 2000 to 2010. Peru reports the highest accumulated historical landings in the Pacific Ocean; but its contribution to annual landings has decreased since 1968. Still, Peru is among the top 12 countries exporting shark fins to the Hong Kong market. Although the government collects total weight by species, the number of specimens landed as well as population parameters (e.g. sex, size and weight) are not reported. Further, for some genera, species-level identification is deficient and so overestimates the biomass landed by species and underestimates the species diversity. Recently, regional efforts to regulate shark fishery have been implemented to support the conservation of sharks but in Peru work remains to be done
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Gonzalez-Pestana, Adriana, Carlos Kouri J., and Ximena Velez-Zuazo. "Shark fisheries in the Southeast Pacific: A 61-year analysis from Peru." F1000Research 3 (April 12, 2016): 164. http://dx.doi.org/10.12688/f1000research.4412.2.
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Peruvian waters exhibit high conservation value for sharks. This contrasts with a lag in initiatives for their management and a lack of studies about their biology, ecology and fishery. We investigated the dynamics of Peruvian shark fishery and its legal framework identifying information gaps for recommending actions to improve management. Further, we investigated the importance of the Peruvian shark fishery from a regional perspective. From 1950 to 2010, 372,015 tons of sharks were landed in Peru. From 1950 to 1969, we detected a significant increase in landings; but from 2000 to 2011 there was a significant decrease in landings, estimated at 3.5% per year. Six species represented 94% of landings: blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), smooth hammerhead (Sphyrna zygaena), common thresher (Alopias vulpinus), smooth-hound (Mustelus whitneyi) and angel shark (Squatina californica). Of these, the angel shark exhibits a strong and significant decrease in landings: 18.9% per year from 2000 to 2010. Peru reports the highest accumulated historical landings in the Pacific Ocean; but its contribution to annual landings has decreased since 1968. Still, Peru is among the top 12 countries exporting shark fins to the Hong Kong market. Although the government collects total weight by species, the number of specimens landed as well as population parameters (e.g. sex, size and weight) are not reported. Further, for some genera, species-level identification is deficient and so overestimates the biomass landed by species and underestimates the species diversity. Recently, regional efforts to regulate shark fishery have been implemented to support the conservation of sharks but in Peru work remains to be done.
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Vandeperre, Frederic, Alexandre Aires-da-Silva, Jorge Fontes, Marco Santos, Ricardo Serrão Santos, and Pedro Afonso. "Movements of Blue Sharks (Prionace glauca) across Their Life History." PLoS ONE 9, no. 8 (August 13, 2014): e103538. http://dx.doi.org/10.1371/journal.pone.0103538.
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Carey, F. G., J. V. Scharold, and Ad J. Kalmijn. "Movements of blue sharks (Prionace glauca) in depth and course." Marine Biology 106, no. 3 (October 1990): 329–42. http://dx.doi.org/10.1007/bf01344309.
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Sulaiman, Priyo Suharsono, Mufti Petala Patria, and Rauf Achmad Sue. "The shark by-catch of tuna longline fisheries in Southern Indian Ocean of Java, Indonesia." E3S Web of Conferences 74 (2018): 02004. http://dx.doi.org/10.1051/e3sconf/20187402004.
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In relation to the achievement of the target SDG’s No. 14, the sustainable shark fisheries management need to implement. As a part of the tuna fisheries by-catch, a high number of shark resources have been caught in the Indian Ocean waters. One of the main vessels of tuna catchers in the Southern Indian Ocean of Java is the tuna longline from Cilacap. This paper aims to analyze the shark by-catch of tuna longline in the Indian Ocean in the south Java that landed in Cilacap. The research data was obtained from daily recording activities of fishing vessel loading activities by Cilacap Ocean Fisheries Port staff during the period of 2013-2017. The analysis was done through data tabulation, graphical approaches, and data trend analysis through the availability of time series data. The data analyzed include fleet development, fishing ground, catch composition and CPUE value. The results of the analysis show that there are about eight species of sharks that are by-catch of tuna longline from Cilacap. The highest shark by-catch occurred in April with CPUE averaging 9 kg/day/vessel. The blue shark (Prionace glauca) is the dominant shark catch which reaches 66% of the total sharks catch.
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Mohan, John A., Nathan R. Miller, Sharon Z. Herzka, Oscar Sosa-Nishizaki, Suzanne Kohin, Heidi Dewar, Michael Kinney, Owyn Snodgrass, and R. J. David Wells. "Elements of time and place: manganese and barium in shark vertebrae reflect age and upwelling histories." Proceedings of the Royal Society B: Biological Sciences 285, no. 1890 (November 7, 2018): 20181760. http://dx.doi.org/10.1098/rspb.2018.1760.
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As upper-level predators, sharks are important for maintaining marine food web structure, but populations are threatened by fishery exploitation. Sustainable management of shark populations requires improved understanding of migration patterns and population demographics, which has traditionally been sought through physical and/or electronic tagging studies. The application of natural tags such as elemental variations in mineralized band pairs of elasmobranch vertebrae cartilage could also reveal endogenous and exogenous processes experienced by sharks throughout their life histories. Here, elemental profiles were characterized in vertebrae encompassing complete life histories (birth-to-death) of shortfin mako ( Isurus oxyrinchus ), common thresher ( Alopias vulpinus ) and blue shark ( Prionace glauca ) of known tag and recapture locations in the eastern North Pacific Ocean. All sharks were injected with oxytetracycline at initial capture, released and subsequently recaptured, with individual liberty times ranging from 215 days to 6 years. Vertebral band pairs forming over the liberty intervals were verified by counting the number of band pairs deposited since the oxytetracycline band. Regular oscillations in vertebrae manganese (Mn) content corresponded well with the number of validated band pairs, suggesting that Mn variation could be used to age sharks. Increases in vertebrae barium concentration were correlated with times when individuals occupied areas with high coastal upwelling indices, the timing and spatial intensity of which varied from year to year. Interspecific relationships were probably influenced by behavioural differences in horizontal and vertical habitat use, feeding habits and thermoregulatory physiology. These results indicate that vertebral sclerochronology has the potential to advance our knowledge of elasmobranch life history including age and growth estimation and environmental reconstruction.
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Markaida, Unai, and Oscar Sosa-Nishizaki. "Food and feeding habits of the blue shark Prionace glauca caught off Ensenada, Baja California, Mexico, with a review on its feeding." Journal of the Marine Biological Association of the United Kingdom 90, no. 5 (February 12, 2010): 977–94. http://dx.doi.org/10.1017/s0025315409991597.
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Stomach contents of 893 blue shark (Prionace glauca) caught off Ensenada, Todos Santos Bay, Baja California, from 1995 to 1997 were analysed. 614 had identifiable food remains. A large variety of pelagic cephalopods occurred in 55.5% of all stomachs and accounted for 46.2% of all prey and 84% by estimated weight of stomach contents. The most abundant (17%) and frequent (32%) was Histioteuthis heteropsis and the most important by estimated weight (22%) was ‘Gonatus californiensis’. Argonauta spp. and Vampyroteuthis infernalis were also abundant prey. A pair of beaks of giant squid Architeuthis sp. constitutes the first record for Mexican waters. Feeding habits and the probability of scavenging on mesopelagic cephalopods is discussed. The single most abundant prey was the pelagic, red crab Pleuroncodes planipes (41.7%). Other prey included teleost fish, amniotes and floating items. Diet varied greatly between months with no clear seasonal pattern. Tiny diet differences due to shark size or sex were inconclusive. A thorough review of studies on blue sharks stomach contents analysis is given. Blue shark feed on a large variety of passive pelagic prey, mainly mesopelagic cephalopods, that could be preyed upon as well as scavenged. Depletion of this predator due to overfishing may be leading to unknown cascading top-down effects in the mesopelagic realm.
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Preti, Antonella, Ken MacKenzie, Kate A. Spivey, Leslie R. Noble, Catherine S. Jones, Ralph G. Appy, and Graham J. Pierce. "Spiral valve parasites of blue and common thresher sharks as indicators of shark feeding behaviour and ecology." Journal of Fish Biology 97, no. 2 (June 21, 2020): 354–61. http://dx.doi.org/10.1111/jfb.14363.
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Thompson, Christopher D. H., and Jessica J. Meeuwig. "Sharks are the preferred scraping surface for large pelagic fishes: Possible implications for parasite removal and fitness in a changing ocean." PLOS ONE 17, no. 10 (October 19, 2022): e0275458. http://dx.doi.org/10.1371/journal.pone.0275458.
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Mutualistic and commensal interactions can have significant positive impacts on animal fitness and survival. However, behavioural interactions between pelagic animals living in offshore oceanic environments are little studied. Parasites can negatively effect the fitness of their hosts by draining resources and diverting energy from growth, reproduction, and other bodily functions. Pelagic fishes are hosts to a diverse array of parasites, however their environment provides few options for removal. Here we provide records of scraping behaviour of several pelagic teleost species, a behaviour that is likely used for parasite removal. These records span three ocean basins and, to the best of our knowledge, include the first records of scraping interactions involving tunas, blue sharks, and mako sharks as well as the first records of intraspecific scraping. We found that scrapers preferred scraping their head, eyes, gill cover, and lateral surfaces, areas where parasites are commonly found and where damage would likely have a substantial impact on fitness. Scraper species varied in their scraping preferences with tunas scraping mostly on the posterior caudal margins of sharks and occasionally conspecifics, while rainbow runner scraped in more varied locations on both sharks and conspecifics. Lengths of scrapers and scrapees were positively correlated and fish scraping on sharks were larger than those scraping on conspecifics, suggesting that risk of predation may be a limiting factor. We show that pelagic teleosts prefer to scrape on sharks rather than conspecifics or other teleosts and suggest that this behaviour may have a positive impact on teleost fitness by reducing parasite loads. The decline of shark populations in the global ocean and the reduction in mean size of many species may limit these interactions, eroding possible fitness benefits associated with this behaviour, and consequently placing more pressure on already highly targeted and vulnerable species.
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Pastén-Marambio, Víctor, Valentina Hevia-Hormazábal, Enzo Acuña, and Alonso Vega. "A case of tetrophthalmia with unilateral synophthalmia in an unborn fetus of blue shark Prionace glauca (Carcharhiniformes, Carcharhinidae)." Revista de Biología Marina y Oceanografía 53 (August 1, 2018): 25. http://dx.doi.org/10.22370/rbmo.2018.53.0.1251.
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This study describes and classifies a case of multiple malformations in an unborn blue shark Prionace glauca fetus, which was extracted from a gravid female captured during a research campaign addressed to the biological study of sharks in northern and central Chile. The analyzed specimen shows tetrophthalmia with unilateral synophthalmia, anomaly characterized by the existence of 4 ocular globes, two of which are partially fused. In addition, the axial skeleton of the fetus shows thoracic lordosis and helical torsion in the abdominal-caudal portion. This is the first world report of tetrophthalmia with unilateral synophthalmia in chondrichthyans.
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Abel, D. C., W. R. Lowell, J. B. Graham, and R. Shabetai. "Elasmobranch pericardial function 2. The influence of pericardial pressure on cardiac stroke volume in horn sharks and blue sharks." Fish Physiology and Biochemistry 4, no. 1 (July 1987): 5–14. http://dx.doi.org/10.1007/bf02073861.
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Prat-Varela, Alejandro, Agusti Torres, Daniel Cervantes, Marc Aquino-Baleytó, Ana-Maria Abril, and Eric E. G. Clua. "Improved Baited Remote Underwater Video (BRUV) for 24 h Real-Time Monitoring of Pelagic and Demersal Marine Species from the Epipelagic Zone." Journal of Marine Science and Engineering 11, no. 6 (June 6, 2023): 1182. http://dx.doi.org/10.3390/jmse11061182.
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Bait-based remote underwater video (BRUV) systems are effective devices for remotely observing fish and other marine organisms in challenging environments. The development of a long duration (24 h) surface BRUV observation surveys allowed the monitoring of scarce and elusive pelagic sharks and the direct impact on non-targeted species of longline fishing in the Western Mediterranean. Technological limitations, such as the limited storage capacity and a single surface camera, were improved by (i) adding a deep camera equipped with light (below 80 m depth) and (ii) replacing Gopros with a multi-camera video surveillance system (surface and depth) with a storage capacity of several days and access to real-time observation. Based on a deployment effort of 1884 h video data, we identified 11 blue sharks (Prionace glauca) and one bluntnose sixgill shark (Hexanchus griseus), a deep-sea species that scarcely swims at the surface. The real-time observation capability was a powerful tool for reducing logistical costs and for raising environmental awareness in educational and outreach programmes.