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Diego Bernal Joseph P. Reid Julie M. Roessig Shinsyu Matsumoto Chugey A. Sepulveda Joseph J. CechJr. Jeffrey B. Graham 《Fish physiology and biochemistry》2018,44(3):949-967
In fish, regional endothermy (i.e., the capacity to significantly elevate tissue temperatures above ambient via vascular heat exchangers) in the red swimming muscles (RM) has evolved only in a few marine groups (e.g., sharks: Lamnidae, Alopiidae, and teleosts Scombridae). Within these taxa, several species have also been shown to share similar physiological adaptations to enhance oxygen delivery to the working tissues. Although the hemoglobin (Hb) of most fish has a decreased affinity for oxygen with an increase in temperature, some regionally endothermic teleosts (e.g., tunas) have evolved Hbs that have a very low or even an increased affinity for oxygen with an increase in temperature. For sharks, however, blood oxygen affinities remain largely unknown. We examined the effects of temperature on the blood oxygen affinity in two pelagic species (the regionally endothermic shortfin mako shark and the ectothermic blue shark) at 15, 20, and 25 °C, and two coastal ectothermic species (the leopard shark and brown smooth-hound shark) at 10, 15, and 20 °C. Relative to the effects of temperature on the blood oxygen affinity of ectothermic sharks (e.g., blue shark), shortfin mako shark blood was less affected by an increase in temperature, a scenario similar to that documented in some of the tunas. In the shortfin mako shark, this may act to prevent premature oxygen dissociation from Hb as the blood is warmed during its passage through vascular heat exchangers. Even though the shortfin mako shark and blue shark occupy a similar niche, the effects of temperature on blood oxygen affinity in the latter more closely resembled that of the blood in the two coastal shark species examined in this study. The only exception was a small, reverse temperature effect (an increase in blood oxygen affinity with temperature) observed during the warming of the leopard shark blood under simulated arterial conditions, a finding that is likely related to the estuarine ecology of this species. Taken together, we found species-specific differences in how temperature affects blood oxygen affinity in sharks, with some similarities between the regionally endothermic sharks and several regionally endothermic teleost fishes. 相似文献
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热带大西洋金枪鱼延绳钓兼捕鲨鱼种类组成和渔获率及其与表温的关系 总被引：1，自引：0，他引：1
根据2007年12月~2008年3月采集的热带大西洋(05°37′~12°01′N、29°00′~36°51′W)金枪鱼延绳钓渔获物数据,分析了金枪鱼延绳钓兼捕鲨鱼的种类组成、渔获量、渔获率及其与表温的关系。本次调查共捕获鲨鱼8种,隶属3目7科7属,总渔获尾数为633 ind,总渔获量达26 837.4 kg,其中大青鲨为主要兼捕种类。各种鲨鱼渔获率平均值在0.003~1.524 ind/1 000 hooks之间,其中大青鲨最高,其值为1.524 ind/1 000 hooks,大眼砂锥齿鲨最低,其值为0.003 ind/1 000 hooks。各种鲨鱼渔获率月变化不明显(ANOVA,P=0.901)。鲨鱼总渔获率和大青鲨渔获率与表温都呈显著性负相关。大青鲨主要出现渔场的表温范围为24.6~25.8℃。 相似文献
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The primary gear type used to harvest coastal sharks in the U.S. Atlantic shark fishery is bottom longline. Recent stock assessments have found several species of coastal sharks in U.S. Atlantic Ocean waters have declined from 60% to 80% of virgin levels. To aid in stock rebuilding, alternative gear restriction measures such as reduced soak time, restrictions on the length of gear, and fishing depth restrictions have been considered but not implemented. In order to evaluate the effectiveness of some of these management measures, controlled experiments were performed using hook timers and time depth recorders, assessing the factors affecting mortality during longline capture for the four most abundant species that incurred at-vessel mortality: sandbar (Carcharhinus plumbeus), blacktip (Carcharhinus limbatus), bull (Carcharhinus leucas), and blacknose (Carcharhinus acronotus). Our results indicate that as hook time and shark size increased mortality rates for the sandbar and blacktip sharks increased. Predicted models indicated mortality rates increased steadily for the three species but appeared to increase the most after 10, 6, and 1 h on the hook for sandbar, blacktip and blacknose shark, respectively. Sandbar sharks larger than approximately 170 cm FL are more susceptible to hooking mortality. Blacknose shark mortality rates increased as hook time increased but bull shark mortality rates were not affected by any factor. The probability of a hook being bitten increased the most between 5 and 12 h after the fishing gear had been set and the mean amount of time hooks were in the water prior to being bitten was 4, 5 and 9 h for sandbar and blacknose sharks, blacktip, and bull sharks, respectively. A significant difference was found between these means for sandbar and bull sharks and between blacknose and bull sharks. Shark species were commonly caught at different temperature and depth ranges. These results could be used by fisheries management to implement restrictions of fishing depth and soak time to aid in the recovery of coastal sharks species. 相似文献
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Rick D. Tate Brendan P. Kelaher Craig P. Brand Brian R. Cullis Christopher R. Gallen Stephen D.A. Smith Paul A. Butcher 《Fisheries Management and Ecology》2021,28(5):496-506
White (Carcharodon carcharias L.), bull (Carcharhinus leucas, Müller & Henle) and tiger (Galeocerdo cuvier, Péron & Lesueur) sharks are the primary species responsible for unprovoked shark bites. Historically, management practices were based on culling “target” shark species (i.e. white, bull and tiger sharks), which resulted in high levels of bycatch and mortality. Shark-Management-Alert-in-Real-Time (SMART) drumlines were trialled in New South Wales, Australia, aiming to optimise the capture of target shark species while minimising bycatch and mortality. Target shark species accounted for 70% of the total catch, with white sharks contributing 298 of the 350 sharks that were caught. Four animals died, and bycatch consisted of 13 species including two threatened species. Generalised linear mixed models (GLMMs) revealed a significant spatial, temporal, environmental and gear influence on white shark catch rates. SMART drumlines are a useful tool for catching target shark species with low bycatch and mortality relative to historical bather protection methods. 相似文献
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Abstract Healthy lemon sharks, Negaprion brevirostris (Poey), were inoculated with Vibrio carchariae and V. damsela , two vibrios known to cause disease in other shark species. Vibrio damsela was not recovered from the inoculated sharks; V. carchariae infected the healthy lemon sharks, but did not produce clinically observable disease. However, histological evaluation revealed active splenic and hepatic disease with Gram-negative bacteria found in association with mononuclear cells. When the experiment was repeated with a physiologically compromised lemon shark, V. carchariae was lethal for the test animal, but V. damsela was again cleared. Vibrio carchariae was also isolated from skin lesions of a lemon shark infested with monogeneans ( Dermophthirius nigrellii ). Histological evidence indicated that this shark died of protozoan infection. Thus, lemon sharks are susceptible to infection with V. carchariae which can cause subclinical disease in otherwise healthy specimens. We suggest that D. nigrellii may act as a vector of V. carchariae and that stress plays a role in the clinical manifestation of this disease. 相似文献
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Abstract Many US states have recreational and commercial fisheries that occur in nursery areas occupied by subadult sharks and can potentially affect their survival. Georgia is one of few US states without a directed commercial shark fishery, but the state has a large, nearshore penaeid shrimp trawl fishery in which small sharks occur as bycatch. During our 1995–1998 investigation of bycatch in fishery‐dependent sampling events, 34% of 127 trawls contained sharks. This bycatch totalled 217 individuals from six species, with Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson), the most common and finetooth shark, Carcharhinus isodon (Müller & Henle) and spinner shark, Carcharhinus brevipinna (Müller & Henle), the least common. The highest catch rates for sharks occurred during June and July and coincided with the peak months of the pupping season for many species. Trawl tow speed and tow time did not significantly influence catch rates for shark species. Gear configurations [net type, turtle excluder device (TED), bycatch reduction device] affected catch rates for shark species. Results of this study indicate gear restrictions, a delayed season opening, or reduced bar spacing on TEDs may reduce shark bycatch in this fishery. 相似文献
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据1994—2001年4个航次在金枪鱼延绳钓渔船对热带大洋性中上层鲨鱼资源进行调查，并分析国际大西洋金枪鱼资源保护委员会提供的关于中上层鲨鱼的渔业数据。结果表明：延绳钓渔业共兼捕13种鲨鱼，其中，尖吻鲭鲨和大青鲨是优势种类。尖吻鲭鲨在第1、第2和第4航次的CPUE分别为每千钩0．3502、0．1754和0．0642尾，呈下降趋势。大青鲨在第1～3航次的的CPUE达到每千钩5～7尾，而在第4航次下降为每千钩0．8尾。研究报告了中国金枪鱼船队自1993年开始在大西洋兼捕尖吻鲭鲨和大青鲨的渔获量，并根据捕捞死亡系数和大西洋总渔获量数据，初步探讨了尖吻鲭鲨和大青鲨年平均资源量，影响CPUE的因素和大西洋中上层资源状况。 相似文献
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Sharks fisheries have declined globally due to over‐ and unregulated fishing. As with many collapsed and unmonitored coastal fisheries, information is difficult to obtain, yet it is important to understand the historical changes determining population trends and evaluate the current status of sharks in order to conserve these vulnerable species. Here, we document for the first time the history and general condition of the shark fisheries of Southern China, specifically Hong Kong, and Guangdong, Fujian and Hainan Provinces. This study shows, through the use of historical literature and anecdotal accounts, including fisher interviews, that all known shark fisheries in the region collapsed between the 1970s and the 1990s. Of the 109 species present historically in the South China Sea, only 18 species were recorded in current market surveys, of which all were landed as bycatch and 65% were below the size of sexual maturity. Markets are dominated by smaller species, including the spadenose shark (Scoliodon laticaudus) and the whitespotted bambooshark (Chiloscyllium plagiosum). Marketed large shark species are almost all below the size of sexual maturation, evidence of growth overfishing and a factor in recruitment overfishing. Some species, like the whale (Rhincodon typus) and basking sharks (Cetorhinus maximus), are clearly vulnerable to local extinction without intervention. Given the inherent vulnerability of sharks and the overfished states of many sharks, there is clearly an urgent need to formulate impacting conservation and management plans for these rapidly declining species in a region that has the highest demand for shark products globally. 相似文献
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- The Mediterranean Sea represents an area of elevated risk of extinction for sharks, where data deficiency is a pervasive problem.
- To compensate for such a paucity of information, this study investigated the use of social media content as a complementary approach to evaluate the distribution and habitat use of the Critically Endangered blue shark Prionace glauca in coastal waters, as well as public perceptions of the sharks.
- Through social media data mining a total of 146 records, comprising 158 individual blue sharks approaching Italian coastal waters, have been recorded from 2011 to 2020.
- This study revealed that, over the past decade, blue sharks regularly visited Italian coastal habitats for extended periods of time. Differences in the temporal distribution of blue sharks by sex and size appear to be linked to reproductive activity. The higher number of adult females approaching the shore in spring and the increase in young-of-the-year (YOY) sightings in the following months possibly indicate parturition in coastal waters. Spatial analyses also showed that certain Italian coastal areas, such as those in Calabria and Puglia, were preferred coastal habitats for this species.
- Results also indicate that social media platforms can be considered an ever-growing source of data on wildlife, which can shed light on the occurrence and distribution of endangered shark species in poorly known habitats. Furthermore, social media platforms should be used for awareness campaigns to educate the public, as this study showed that negative reactions to shark encounters remain widespread.
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- 1. Worldwide, there are concerns about the potential impact of a growing tourism industry on the behaviour and ecology of sharks. Several shark species are key attractions in the scuba diving industry in both the Galápagos Marine Reserve (Ecuador) and the Sanctuary of Fauna and Flora Malpelo (Colombia).
- 2. In this study, the reactions of five species of shark to the behaviour of scuba divers were investigated in the Galápagos and Malpelo.
- 3. Four discrete categories of shark reaction (evasion, spontaneous approach, alert and no reaction) were identified and analysed against five categories of diver behaviour (direct approach, camera flash, sudden movement, noise and simple presence), two categories of observation strategy (still and movement) and the distance of the focal diver group to the sharks.
- 4. The type of reaction in the sharks was determined by the behaviour of the divers, their distance to the fish and, especially, by their observation strategy. Shark reactions varied between species and locations and divers acted more intrusively towards those species they were not afraid of, and which they could access more easily due to the conditions of their environment.
- 5. ‘Direct approach’, ‘sudden movement’, the observation strategy ‘moving’ and distances closer than 4 m between divers and sharks elicited stronger behavioural responses by the species targeted. Recommendations are given for the preferred actions divers should employ in order to diminish the effects on the target species analysed in this study. Copyright © 2011 John Wiley & Sons, Ltd.
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The Arabian Seas Region plays an important role in the global landings and trade of sharks and rays. The United Arab Emirates (UAE) and Yemen, two countries with stark socio‐economic differences, serve as major regional trade hubs for shark and ray products and four countries (Oman, Pakistan, UAE and Yemen) supply nearly 11% of dried fin exports to Hong Kong. Yet, little information is available on the characteristics of this trade and the fisheries contributing to it. Here, we review the fisheries characteristics, trade, utilization and distribution chain of sharks and rays in 15 countries of the Arabian Seas Region based on published and grey literature, landing surveys, field observations and interviews with fishermen and traders. Although regional shark fisheries remain mostly artisanal, reported shark and ray landings represent 28% of the regional total fish production, reaching 56,074 mt in 2012 (7.3% of total world catches), with Iran, Oman, Pakistan and Yemen ranking as the primary catchers. Utilization and distribution patterns are complex, vary between landing sites and countries, and remain unmonitored. Based on widespread over‐exploitation of most teleost fisheries, current exploitation levels for most sharks and rays are potentially unsustainable. The situation is exacerbated by limited research and political will to support policy development, the incomplete nature of fisheries data, as well as insufficient regulations and enforcement. A better understanding of shark and ray fisheries will be key for regulating trade, promoting conservation and developing management initiatives to secure food security, livelihoods and biodiversity conservation in the region. 相似文献
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Distribution,body length,and abundance of blue shark and shortfin mako offshore of northeastern Japan,as determined from observed pelagic longline data, 2000–2014 
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下载免费PDF全文 Seiji Ohshimo Yuki Fujinami Ko Shiozaki Mikihiko Kai Yasuko Semba Nobuhiro Katsumata Daisuke Ochi Hiroaki Matsunaga Hiroshi Minami Masashi Kiyota Kotaro Yokawa 《Fisheries Oceanography》2016,25(3):259-276
Longline surveys have been conducted in the Northwest Pacific Ocean from 2000 to 2014 using chartered commercial longline vessels. Each year, two cruises were conducted offshore of northeastern Japan from mid‐April to mid‐June. For each longline set during the surveys, onboard scientists collected detailed biological information about the species caught, such as the size and sex, and recorded the catch numbers for all species. Blue shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus) have eurythermal distributions, but the application of a generalized additive model (GAM) showed that the sea surface temperatures (SSTs) at catch sites positive for shortfin mako were warmer than those for blue shark. On the basis of the GAM, the probabilities of occurrence of both sharks differed by size category: small sharks had a narrower SST range than that of large sharks. Most catches of both sharks were juveniles, and the nominal catch rate of blue shark was more than 10 times that of shortfin mako. The standardized catch per unit effort (CPUE) for both species was calculated using a generalized linear model (GLM) with negative binomial errors, or a delta‐lognormal GLM. The standardized CPUE for blue shark in the second quarter of the year peaked in the mid‐2000s and then decreased, but it has been increasing since 2012. The CPUE for shortfin mako in the second quarter generally increased, with fluctuations. 相似文献
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C. Cattano G. Turco M. Di Lorenzo M. Gristina G. Visconti M. Milazzo 《水产资源保护:海洋与淡水生态系统》2021,31(6):1420-1428
- An aggregation of sandbar sharks Carcharhinus plumbeus occurs every summer around the remote uninhabited islet of Lampione (Pelagie Islands Marine Protected Area, south-western Mediterranean Sea), attracting an increasing number of tourists for a shark watching experience.
- Despite the ecological and socio-economic importance of this rare occurrence in Mediterranean waters, there is a lack of scientific data and lack of information as to the potential impact of tourist activities on the presence and behaviour of this shark species.
- Using baited underwater videos, this study provides the first assessment of this shark aggregation, as well as a preliminary evaluation of the potential effects that boating and diving activities may have on sandbar sharks during two different periods within the tourism season (July and September 2019).
- Overall, 241 sandbar shark sightings (with up to five individuals together) were recorded in July, whereas there were only six sightings in September. The average MaxN was 1.18 hr−1 (±0.21 hr−1 SE) and 0.22 hr−1 (±0.10 hr−1 SE) individuals in July and September respectively. Higher frequentation levels of divers and boats significantly reduced the number of shark sightings at the aggregation site.
- This study emphasizes the need for further investigations on Mediterranean shark aggregations and the implementation of specific conservation measures, such as an increase of protection level in Lampione and better enforcement, aside from strategies that promote sustainable tourism, including restrictions on the number of boats and divers’ visits per day. In the meantime, a precautionary approach aimed at regulating the interactions between tourists and sharks should be implemented through the application of a self-regulatory code of conduct for divers when sharks aggregate around the island.
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Johann Mourier Marc Soria Antonin Blaison Monique Simier Grégoire Certain Angélique Demichelis Tarek Hattab 《水产资源保护:海洋与淡水生态系统》2021,31(10):2926-2937
- Knowledge about spatial and temporal variability in the distribution and abundance of predators is necessary to adapt measures to mitigate human–wildlife interactions.
- Acoustic telemetry and network analyses were used to investigate the spatial ecology of bull sharks, the species responsible for most shark bites in Reunion Island, one of the world's shark bite hotspots.
- The west coast of the island was not used uniformly by every individual, with size predicting the movements of sharks along the coast.
- Node-based metrics – closeness, node strength, and cumulated continuous residency times – derived from up to 181 monthly movement networks from 20 individuals, revealed that smaller sharks (<250 cm total length) primarily used the south-west coast while larger individuals spent most of their time in the northern region with regular visits to multiple areas along the coast.
- This study provides essential knowledge on bull shark behaviour and central areas used at different periods of the year, which correlates well with the dynamics of observed shark bites. Our approach provides a non-invasive alternative to help predicting and anticipating human–shark conflicts and avoid shark culling programmes detrimental to the conservation of large predators such as sharks.
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Simon J. Pierce Adriana Méndez‐Jiménez Kym Collins Marcela Rosero‐Caicedo Ara monadjem 《水产资源保护:海洋与淡水生态系统》2010,20(7):782-788
- 1. The whale shark (Rhincodon typus) is a popular focal species within the global marine tourism industry. Although this has contributed to increased protection being granted to the species in several countries, tourism itself can be detrimental to the sharks in the absence of appropriate management. Potential impacts can be mitigated, at least in the short term, by adherence to well‐designed interaction guidelines.
- 2. A burgeoning marine tourism industry based on swimming with whale sharks has developed at Tofo Beach in Mozambique. However, no formal management is currently in place at this site.
- 3. The behaviour of whale sharks during interactions with boats and swimmers were recorded during 137 commercial snorkelling trips run from Tofo Beach over a 20 month period. Whale sharks were encountered on 87% of trips, which operated year‐round.
- 4. Boat proximity and shark size were significant predictors of avoidance behaviour. No avoidance responses were recorded at >20 m boat distance.
- 5. The mean in‐water interaction time between sharks and swimmers was 8 min 48 s overall. There was a significant decrease in interaction times during encounters where sharks expressed avoidance behaviours, and also in cases where sharks had expressed boat avoidance behaviour before swimmers entered the water.
- 6. It is suggested that mean encounter times can be extended through adherence to a basic Code of Conduct for operators and swimmers that enforces minimum distances between the sharks, boats and swimmers. Using encounter time as a measure of the ‘success’ of interactions holds promise, as longer encounters appear to be indicative of lower impacts on sharks while also providing higher customer satisfaction for swimmers. Copyright © 2010 John Wiley & Sons, Ltd.