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1.
Mary p. O'Malley Kathy A. Townsend Paul Hilton Shawn Heinrichs Joshua D. Stewart 《水产资源保护:海洋与淡水生态系统》2017,27(2):394-413
- Dried gill plates from manta and devil rays, some of the world's most biologically vulnerable fishes, have become a valued commodity in Asian dried‐seafood and traditional Chinese medicine markets. This trade is a primary driver of fisheries, which have led to declines in many mobulid populations.
- With no reliable trade statistics and scarce data on mobulid fisheries, this study estimates the number and species of mobulids required to supply this trade, and investigates the consumers and suppliers involved and drivers of demand. Following preliminary market research, 525 trader surveys were conducted in Hong Kong, Singapore, Macau, Taiwan, and southern China.
- Guangzhou, China was identified as the centre of the trade accounting for 99% of total estimated market volume of 60.5 tons of dried gill plates in 2011, increasing to 120.5 tons by 2013. The estimated number of mobulids converted from tons of gill plates more than doubled over the period to 130 000, comprising 96% devil rays, Mobula japanica, Mobula thurstoni, and Mobula tarapacana, and 4% Manta spp. By 2015 the Guangzhou market had declined sharply, reportedly due to conservation campaigns and government policies. However Hong Kong's gill plate sales increased dramatically between 2011 and 2015.
- China, Indonesia, Vietnam, Sri Lanka, and India were reported most frequently as gill plate sources.
- Vendors recommend gill plates (trade name pengyusai) for ailments ranging from acne to cancer and as a general health tonic. While pengyusai is a new addition to traditional Chinese medicine literature and is rarely prescribed by traditional medicine practitioners, it is readily available over the counter and aggressively marketed by vendors.
- Working in concert with consumer demand reduction efforts, increased measures to restrict mobulid fisheries and trade are recommended to prevent further population declines of these highly vulnerable species.
2.
Yvonne Sadovy de Mitcheson Susanti R. Suharti Patrick L. Colin 《水产资源保护:海洋与淡水生态系统》2019,29(8):1285-1301
- The Napoleon wrasse, an endangered fish (Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II, 2004), is a valuable component of the Chinese live reef fish trade. Only Indonesia legally exports up to 2000 Napoleon fish annually, with each fish weighing between 1 and 3 kg.
- Information on natural abundance and fish sizes was required to determine sustainable export quotas. Hence, an underwater visual survey method, using GPS‐based multi‐kilometre transects, was tailored for this uncommon wide‐ranging fish. Transects totalling 430 km were run between 2005 and 2016 at nine locations. Six locations were resurveyed between six and nine years later, which was long enough to allow for recruitment and maturation.
- Fish density and sizes across locations were inversely related to fishing intensity, and densities increased significantly between surveys. Low density (0.04‐0.86 fish hectare‐1) and few adult‐sized fish were in heavily fished locations. Higher densities occurred (0.86‐4.0 fish hectare‐1) in lightly/unfished locations, where evidence of recruitment was also seen. Nowhere were many male-sized (>1 m long) fish present. At Karas Is., where fishing ceased between surveys, clear sign of recovery was seen after 9 years.
- Comparison of survey data from 11 Indo‐Pacific countries indicated that in Indonesia adult densities were lower at comparable levels of fishing pressure than elsewhere. Densities of 5 fish hectare?1 or more are more typical of lightly fished or unfished areas across the Pacific, which is greater than the highest density of 4 fish hectare?1 noted in this study at Banda Islands. Low densities of the species, despite the presence of adult‐sized fish, in Bunaken Marine Park probably reflects the continuance of fishing both within and adjacent to the park.
- Conservation options include improved implementation of CITES regulations by Indonesia, through tighter export controls and the tagging of legally exported fish, the activation of the National Plan of Action, a temporary moratorium to restore reproductive capacity, and more marine protected areas.
3.
- South Florida has a significant number of recreational anglers, and some shore-based fishing sites overlap with habitat for juvenile manta rays. Although manta rays are prohibited from harvest in Florida, they are frequently seen foul-hooked or entangled in fishing line.
- Recreational anglers (n = 198) were surveyed at piers and inlet jetties in Palm Beach County, Florida, USA to assess their knowledge of and actions and attitudes towards manta rays.
- Analysis of the responses revealed that while most anglers could identify a manta ray (66.7%) and expressed no interest in casting at (93.4%) or catching a manta ray (95.5%), they lacked knowledge about threats to mantas, as well as their conservation and protected status. Surveyed anglers overwhelmingly supported manta ray conservation (82.3%) and environmental protection (98.0%).
- Results indicate pier and inlet anglers are not using tackle strong enough to land a large ray to remove fishing gear, therefore it is recommended that outreach focuses on preventing recreational fishery interactions with manta rays, encouraging use of environmentally friendly tackle, and fostering engagement with anglers as citizen scientists.
- These results can inform the design of outreach materials aimed at closing knowledge gaps and encouraging best practices. Positive attitudes towards the environment and existing neutral behaviours towards manta rays indicate an opportunity to shift the behaviour of shore-based anglers in this area in support of manta ray conservation.
4.
- Pelagic longline fisheries for relatively fecund tuna and tuna‐like species can have large adverse effects on incidentally caught species with low‐fecundity, including elasmobranchs.
- Analyses of observer programme data from the Fiji longline fishery from 2011 to 2014 were conducted to characterize the shark and ray catch composition and identify factors that significantly explained standardized catch rates. Catch data were fitted to generalized linear models to identify potentially significant explanatory variables.
- With a nominal catch rate of 0.610 elasmobranchs per 1000 hooks, a total of 27 species of elasmobranchs were captured, 48% of which are categorized as Threatened under the IUCN Red List. Sharks and rays made up 2.4% and 1.4%, respectively, of total fish catch. Blue sharks and pelagic stingrays accounted for 51% and 99% of caught sharks and rays, respectively.
- There was near elimination of ‘shark lines’, branchlines set at or near the sea surface via attachment directly to floats, after 2011.
- Of caught elasmobranchs, 35% were finned, 11% had the entire carcass retained, and the remainder was released alive or discarded dead. Finning of elasmobranchs listed in CITES Appendix II was not observed in 2014.
- There were significantly higher standardized shark and ray catch rates on narrower J‐shaped hooks than on wider circle hooks. Based on findings from previous studies on single factor effects of hook width and shape, the smaller minimum width of the J‐shaped hooks may have caused the higher shark and ray catch rates. For sharks, the effect of hook width may have exceeded the effect of hook shape, where small increases in shark catch rates have been observed on circle vs J‐shaped hooks.
- Shark and ray standardized catch rates were lowest in the latter half of the year. Focusing effort during the second half of the year could reduce elasmobranch catch rates.
5.
Jonathan J. Smart Alastair V. Harry Andrew J. Tobin Colin A. Simpfendorfer 《水产资源保护:海洋与淡水生态系统》2013,23(1):124-134
- Many sharks are listed as data deficient in assessment and management reports owing to a lack of basic life history data, making decisions about conservation management difficult. As such, the collection of these data is a priority. However, rare or threatened species with populations that are already small can be difficult to sample. Thus there is a need for techniques that permit the use of small sample sizes to provide preliminary information on life history parameters such as age and growth.
- In this study, growth curves were fitted to length‐at‐age data for five rare or difficult to sample sharks from north‐eastern Australia: Carcharhinus coatesi (n = 56), Carcharhinus fitzroyensis (n = 39), Carcharhinus macloti (n = 37), Eusphyra blochii (n = 14) and Hemipristis elongata (n = 14) to provide the first estimates of growth for these species. Vertebral centra from field collections were aged to obtain length‐at‐age data, and partial age adjustments were used to increase the precision of age estimates. In addition, back calculation techniques were applied to add interpolated data to fill gaps in the growth curves caused by missing length classes.
- Back calculation techniques did not substantially alter the growth curves of the species, which had an even spread of data across size classes (C. fitzroyensis, E. blochii and H. elongata). However, the back calculation techniques considerably improved the growth curves for C. coatesi and C. macloti where juveniles were missing from the samples.
- Small sample sizes often provide a barrier to conducting growth studies because of the perception that growth estimates can only be obtained from ‘large’ sample sizes. However, by including individuals across all of the species length classes and maximizing the use of all available exogenous information using back calculation and partial age adjustments, as well as through judicious choice of growth models, it is possible to obtain practical estimates of growth, even when sample sizes are extremely limited. Copyright © 2012 John Wiley & Sons, Ltd.
6.
Ryan Daly Denham Parker Geremy Cliff Gareth L. Jordaan Nkabi Nomfundo Rhett H. Bennett Bruce Q. Mann 《水产资源保护:海洋与淡水生态系统》2021,31(4):777-788
- The white-spotted wedgefish (Rhynchobatus djiddensis) is a Critically Endangered shark-like ray in the family Rhinidae. Throughout its Western Indian Ocean distribution, it is targeted for its valuable meat and fins and is reported to have undergone major population declines. However, there remains a need for species specific time-series data to accurately assess localized population declines.
- This study used two independent long-term (37 and 40 years) time-series catch data from competitive shore angling and shark nets to investigate the size composition and catch per unit effort (CPUE) and conduct a risk assessment for the population on the east coast of South Africa.
- From 1977 to 2017 the competitive shore fishery captured 7,703 individual R. djiddensis, whilst shark nets in the same region captured 2,856 individuals from 1981 to 2017. Individuals captured in the nets had a sex ratio of 1.8:1 females to males, and were larger than those caught by the anglers. Although the mean annual sizes of net-caught individuals were above the size of reported sexual maturity, there was little evidence to suggest that any individuals captured were reproductively active.
- Both the competitive shore fishery and shark net catches exhibited strong seasonal trends with the majority of R. djiddensis catches occurring from October to May peaking in austral summer. Standardized CPUE from the competitive shore fishery declined substantially between 1977 and 2017 and shark net catches exhibited a significant (p < 0.05) fourfold decline in annual nominal CPUE from 1981 to 2017.
- Ultimately, a risk assessment showed a 65.1% decline in abundance over a period of three generation lengths, which indicates that the sampled population of R. djiddensis in South Africa should be classified as Endangered according to the IUCN Red List using criterion A2b. The conservation implications of this are discussed.
7.
Donald A. Croll Heidi Dewar Nicholas K. Dulvy Daniel Fernando Malcolm P. Francis Felipe Galván‐Magaña Martin Hall Shawn Heinrichs Andrea Marshall Douglas Mccauley Kelly M. Newton Giuseppe Notarbartolo‐Di‐Sciara Mary O'Malley John O'Sullivan Marloes Poortvliet Marlon Roman Guy Stevens Bernie R. Tershy William T. White 《水产资源保护:海洋与淡水生态系统》2016,26(3):562-575
- Manta and devil rays of the subfamily Mobulinae (mobulids) are rarely studied, large, pelagic elasmobranchs, with all eight of well‐evaluated species listed on the IUCN Red List as threatened or near threatened.
- Mobulids have life history characteristics (matrotrophic reproduction, extremely low fecundity, and delayed age of first reproduction) that make them exceptionally susceptible to overexploitation.
- Targeted and bycatch mortality from fisheries is a globally important and increasing threat, and targeted fisheries are incentivized by the high value of the global trade in mobulid gill plates.
- Fisheries bycatch of mobulids is substantial in tuna purse seine fisheries.
- Thirteen fisheries in 12 countries specifically targeting mobulids, and 30 fisheries in 23 countries with mobulid bycatch were identified.
- Aside from a few recently enacted national restrictions on capture, there is no comprehensive monitoring, assessment or control of mobulid fisheries or bycatch. Recent listing through the Convention on the International Trade in Endangered Species (CITES) may benefit mobulids of the genus Manta (manta rays), but none of the mobulids in the genus Mobula (devil rays) are protected.
- The relative economic costs of catch mitigation are minimal, particularly compared with a broad range of other, more complicated, marine conservation issues.
8.
Jeff M. Whitty Nicole M. Phillips Dean C. Thorburn Colin A. Simpfendorfer Iain Field Stirling C. Peverell David L. Morgan 《水产资源保护:海洋与淡水生态系统》2014,24(6):791-804
- Effective management of critically endangered sawfishes can be a difficult task, in part due to interspecies misidentification. Current methods for identifying sawfishes can be impractical as they are based on morphological features that are often unobservable. Further exploration is required to develop a more reliable means of identification.
- This study explored the utility of sawfish rostra in determining the species, size and sex of sawfishes, as rostra are commonly the only feature of a sawfish observed by fishers or present in public and private collections.
- A morphometric and meristic database consisting of over 1100 narrow sawfish (Anoxypristis cuspidata), dwarf sawfish (Pristis clavata), largetooth (or freshwater) sawfish (Pristis pristis; formerly Pristis microdon) and green sawfish (Pristis zijsron) rostra from Australian waters, was statistically analysed.
- Identification of sawfishes was found to be possible through the use of the variables: inter‐tooth spacing, standard rostrum width/standard rostrum length, standard rostrum length/total rostrum length, rostrum tip width/standard rostrum length, and/or rostral tooth count range, although the distinguishing variables were species‐dependent.
- The relationship between standard rostrum length and total length was also observed to vary substantially between most species. Models for estimating total length from standard rostrum length are provided.
- This study has provided a tool that can be used to identify accurately the species and size of sawfishes by their rostra, and therefore can assist in clarifying historical and contemporary sawfish records, nomenclature and distributions. A better understanding of these issues should allow sawfish conservation strategies to become more focused, and thus more effective.
9.
- The purpose of this study was to investigate the effects of a circle hook ring on catch rates of target fish species and bycatch rates of sea turtles, elasmobranchs, and non‐commercial fish in a shallow‐set Italian swordfish longline fishery.
- Results were compared from 65 sets from six commercial fishing vessels totalling 50 800 hooks in which ringed and non‐ringed 16/0 circle hooks with a 10° offset were alternated along the length of the longline. In total, 464 individuals were caught in the 4 years of experiment, with swordfish (Xiphias gladius) comprising 83% of the total number of animals captured. Catch rates of targeted swordfish were significantly higher on ringed hooks (CPUEringed hooks = 8.465, CPUEnon‐ringed hooks = 6.654).
- Results indicate that ringed circle hooks captured significantly more small‐sized swordfish than non‐ringed circle hooks (27.7% vs. 19.5%, respectively).
- For species with sufficient sample sizes, the odds ratio (OR) of a capture was in favour of ringed hooks; significantly for swordfish (OR = 1.27 95%CI 1.04–1.57), and not significantly for bluefin tuna (Thunnus thynnus) (OR = 1.50, 95%CI 0.68–3.42) nor for pelagic stingray (Pteroplatytrigon violacea) (OR = 1.13, 95%CI 0.54–2.36). All six loggerhead turtles (Caretta caretta) and three of the four blue sharks (Prionace glauca) were captured on ringed hooks, however, the small sample sizes prevented meaningful statistical analysis.
- In summary, results from this study suggest that the addition of a ring to 16/0 circle hooks confers higher catchability for small‐sized commercial swordfish, and does not significantly reduce catch rate of bycatch species and protected species in a Mediterranean shallow pelagic longline fishery.
- These findings should motivate fisheries managers to consider factors in addition to hook shape when aiming to promote sustainable fishing practices. The presence of a ring has the potential to negate some conservation benefits.
10.
- Northern abalone (Haliotis kamtschatkana) in British Columbia, Canada, are listed as endangered and are protected from fishing, yet their populations continue to decline. It is suspected that supplementation of wild populations with hatchery‐reared abalone will be necessary for the recovery of this species. This study examines the magnitude, timing, and causes of post‐outplanting mortality of hatchery‐reared late‐juvenile northern abalone.
- Abalone survivorship declined precipitously following outplanting, with 83% of abalone surviving 24 h after release and only 34% surviving 2 weeks in the wild.
- Handling, tagging, and temperature variations experienced during the outplanting procedure did not cause mortality. The majority of the abalone mortality in this study was attributable to predators. Additional factors accounted for only 1–2% mortality over 7 d.
- A 1‐week acclimatization period within predator exclosures did not improve subsequent survival of outplants.
- These results demonstrate that the ouplanting of hatchery‐reared abalone as a method of restoring wild populations of this endangered species is primarily constrained by high mortality during the first few days after outplanting, and that almost all of this early mortality is caused by predation. Predation mortality will therefore have to be overcome if outplanting of hatchery‐reared juvenile abalone is to be an effective restoration strategy.
11.
Md Anwar Hossain Benjamin S. Thompson Gawsia Wahidunnessa ChowdHury Samiul Mohsanin Zubair H. Fahad Heather J. Koldewey Md Anwarul Islam 《水产资源保护:海洋与淡水生态系统》2015,25(6):781-799
- Sawfish are among the world's most threatened and understudied marine fishes. There are few studies on sawfish from outside Australian and USA waters ‐ a significant knowledge gap considering their circumtropical distribution and migratory nature.
- This paper presents the first assessment of sawfish exploitation and status in Bangladesh: a country that is subject to extensive fishing efforts, and home to the largest mangrove forest on Earth – an ecosystem that provides critical nursery habitat for juvenile sawfish.
- A countrywide rapid assessment was undertaken between December 2011 and November 2012, using an interdisciplinary methodology. Fish landing stations, dry fish markets, and fishing villages were visited and a sawfish medicine maker was found and interviewed. In addition, interviews with national specialists at academic and fisheries institutions were undertaken. In total, 203 questionnaire surveys were conducted with fishers and traders in order to understand the extent of decline, potential drivers of declines, and local perceptions and uses of sawfish. Eighteen rostra were documented from museum archives and private collections, and unpublished data were sourced.
- Two sawfish species, Pristis pristis and Anoxypristis cuspidata were confirmed to be present in Bangladesh. General population declines were revealed. The average annual sawfish encounter rate (observations and catches) declined from 3.7 individuals using lifetime recall data (~22‐year), to 1.5 using 5‐year recall data, and further to 0.7 using 1‐year recall data.
- The consensus from social research methods was that sawfish were caught as bycatch, with drift gill nets being cited as the most damaging gear type. Every respondent perceived sawfish as a useful animal – typically for medicinal or cultural values. Conservation measures are proposed, including a local education and outreach programme to seek behavioural changes – primarily to release live sawfish.
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13.
Harriet L. Allen Bryce D. Stewart Colin J. McClean James Hancock Richard Rees 《水产资源保护:海洋与淡水生态系统》2021,31(6):1429-1442
- Whale sharks collect in predictable seasonal aggregations across the tropics. South Ari Atoll in the Maldives is one of a few aggregation sites where whale sharks can be encountered year-round. Here, areas with high levels of tourism-related boating traffic overlap with the whale shark hotspot, increasing the probability of anthropogenic injury. Whale sharks have been reported to remain faithful to this aggregation site following injury, despite the costs of injury and the risk of re-injury. However, the impacts of injury on site fidelity and residency behaviour are not fully understood.
- Encounter data on individual sharks from the Maldives Whale Shark Research Programme database (2006–2018) were analysed to assess the relationship between injury and site fidelity in whale sharks. There was no difference in geographic site use, with injured and non-injured individuals being encountered in the same areas. However, there were differences in residency timings: injured resident whale sharks (individuals repeatedly encountered over 6 months or longer) spent significantly more time at the atoll and less time absent, and were seen more consistently than non-injured residents. Increased residency duration, return rate and number of residency periods correlated with increasing injury number.
- These differences in behaviour imply a cost to injury, with whale sharks potentially remaining at this site to recover. With boat traffic being concentrated at the aggregation site, injured sharks may be more vulnerable to further injury. Alternatively, these individuals may remain at the atoll despite injury because the benefits gained from this area outweigh the potential costs, with more resident individuals facing greater exposure to anthropogenic threats. These findings highlight the importance of this location and emphasize the need for improved management of anthropogenic activities, particularly boating traffic, at aggregation hotspots to reduce injury rates and any subsequent impacts on behaviour and fitness.
14.
David L. Morgan Karissa O. Lear Emma Dobinson Adrian C. Gleiss Travis Fazeldean Richard D. Pillans Stephen J. Beatty Jeff M. Whitty 《水产资源保护:海洋与淡水生态系统》2021,31(8):2164-2177
- Sawfishes (Family: Pristidae) are one of the most imperilled fish families worldwide. There is an increasingly urgent need to better understand the biology, ecology, and population status of the five sawfish species to develop more effective conservation measures. The dwarf sawfish, Pristis clavata, is one of the least researched members of the pristids, with literature limited to analysing disparate datasets or collations of rare encounters in northern Australia.
- This study examined the spatial ecology of dwarf sawfish using targeted surveys and acoustic telemetry to determine its habitat use in a macrotidal estuary in northern Australia. Seventeen dwarf sawfish were tagged with acoustic transmitters and monitored in the Fitzroy River estuary and adjacent King Sound (Kimberley, Western Australia) between August 2015 and November 2017.
- Dwarf sawfish observed within the Fitzroy River estuary and King Sound were juveniles, ranging between 740 and 2,540 mm in total length. Catch per unit effort of dwarf sawfish in the late dry season was relatively high in the estuary, with the catch rate in 2015 being one of the highest reported for any sawfish species.
- Acoustic detections revealed a distinct seasonal pattern in the use of different parts of the estuary and King Sound, which was found to be driven by salinity. Dwarf sawfish predominately occupied a single large pool near the terminus of the tidal limit in the late dry season (August–November), before transitioning to regions in closer proximity to the river mouth or in King Sound in the wet and early dry seasons (December–July).
- Given the high abundance and residency of dwarf sawfish in the Fitzroy River estuary, this area is an important nursery for the species during the late dry season and should be formally recognized as a habitat protection area for the species.
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16.
Caitlin K. Frankish Andrea Manica Joan Navarro Richard A. Phillips 《水产资源保护:海洋与淡水生态系统》2021,31(7):1715-1729
- Many seabirds dive to forage, and the ability to use this hunting technique varies according to such factors as morphology, physiology, prey availability, and ambient light levels. Proficient divers are more able to seize sinking baits deployed by longline fishing vessels and may return them to the surface, increasing exposure of other species. Hence, diving ability has major implications for mitigating incidental mortality (bycatch) in fisheries.
- Here, the diving behaviour and activity patterns of the most bycaught seabird species worldwide, the white-chinned petrel (Procellaria aequinoctialis), tracked from Bird Island (South Georgia), are analysed. Three data sources (dives, spatial movements, and immersion events) are combined to examine diverse aspects of at-sea foraging behaviour, and their implications for alternative approaches to bycatch mitigation are considered.
- The tracked white-chinned petrels (n = 14) mostly performed shallow dives (<3 m deep) of very short duration (<5 s), predominantly during darkness, but only 7 and 10% of landings in daylight and darkness, respectively, involved diving, suggesting that surface-seizing is the preferred foraging technique. Nonetheless, individuals were able to dive to considerable depth (max = 14.5 m) and at speed (max = 2.0 m·s−1), underlining the importance of using heavy line-weighting to maximize hook sink rates, and bird-scaring lines (Tori lines) that extend for long distances behind vessels to protect hooks until beyond diving depths.
17.
Leanne K. Faulks Adam Kerezsy Peter J. Unmack Jerald B. Johnson Jane M. Hughes 《水产资源保护:海洋与淡水生态系统》2017,27(1):39-50
- Artesian springs are particularly sensitive freshwater ecosystems, characterized by specialized flora and fauna which, owing to their isolation, are often endemic. Thus, protection of spring habitats and endemic spring biota is important for biodiversity conservation, particularly because human impacts such as invasive species, habitat destruction, and fragmentation can have such devastating effects.
- This study investigated the mitochondrial DNA (mtDNA) genetic diversity and structure of two critically endangered (IUCN) freshwater fish species: red‐finned blue‐eye Scaturiginichthys vermeilipinnis, and Edgbaston goby Chlamydogobius squamigenus, with the aim of assisting management agencies to establish relocated populations that conserve the genetic integrity and evolutionary potential of both species.
- 2862 bp from multiple mtDNA genes were amplified from 111 red‐finned blue‐eye individuals (17 from the 1990s and 94 from 2010), and a 660 bp segment of mtDNA cytochrome b was amplified from 111 Edgbaston goby individuals (from 2010). In total, 14 concatenated mtDNA haplotypes were identified in red‐finned blue‐eye and three cytb haplotypes were identified in Edgbaston goby.
- Overall assessment of the genetic diversity and structure of the endemic fish fauna from the Edgbaston springs revealed low levels of diversity in both species and a loss of haplotypes in red‐finned blue‐eye over time. In addition, both species displayed significant genetic structure: at the spring scale for red‐finned blue‐eye and at the spring group scale for Edgbaston goby. It is concluded that without the appropriate management of relocated populations, such as considering genetic structure and diversity and selecting high quality habitats, these species are at a severe risk of losing evolutionary potential and becoming extinct. This study provides a valuable example for conservation managers of the contribution that population genetic studies can make regarding the adaptive management of endangered species.
18.
John D. Waters Rui Coelho Joana Fernandez‐Carvalho Amy A. Timmers Tonya Wiley Jason C. Seitz Matthew T. Mcdavitt George H. Burgess Gregg R. Poulakis 《水产资源保护:海洋与淡水生态系统》2014,24(6):760-776
- Sawfishes are among the most threatened fish species globally, with only the smalltooth sawfish (Pristis pectinata) currently regularly observed in the western Atlantic. The National Sawfish Encounter Database (NSED) documents reported encounters with sawfishes in the western Atlantic and contains 4945 reports of 8773 individual P. pectinata (1782–2011).
- Statistical modelling (generalized linear models and generalized additive models) and kernel density analyses were used to (1) identify spatio‐temporal patterns among encounter reports, including range reduction in the western Atlantic; (2) determine current distribution to identify areas and time periods where conservation and recovery efforts could be focused; and (3) identify and describe spatio‐temporal distribution patterns of large juveniles and adults.
- Pristis pectinata were found to be year‐round residents of Florida but showed relatively consistent spatial and temporal trends by life stage throughout the year. Although the historical range in the western Atlantic included coastal waters from North Carolina to Brazil, the current geographic range of the species was limited to Florida from 2001 through 2011, with occasional reports in neighbouring states, the Bahamas, and Cuba.
- Seasonally, encounters of all life stages peaked from March through July and annual recruitment of juveniles was apparent during the study period. Spatial hotspots based on increased numbers of encounters of large juveniles (201–340 cm) and adults (>340 cm) were identified in southern Charlotte Harbor, the Ten Thousand Islands, Florida Bay, the Atlantic side of the Florida Keys, and off St. Lucie in south‐east Florida. The analyses presented herein provide evidence of range reduction in the western Atlantic, provide an important tool for resource managers to focus research, monitoring, and conservation efforts, and may provide a framework to model and predict habitat use of other species.
19.
Jean‐Baptiste Thiebot Karine Delord Christophe Barbraud Cédric Marteau Henri Weimerskirch 《水产资源保护:海洋与淡水生态系统》2016,26(4):674-688
1. Industrial fisheries represent one of the most serious threats worldwide to seabird conservation. Death of birds in fishing operations (i.e. bycatch) has especially adverse effects on populations of albatrosses, which have extremely low fecundity. 2. The single population worldwide of Amsterdam albatross (Diomedea amsterdamensis) comprises only 167 individuals and risks considerable decline over the mid‐term from additional mortality levels potentially induced by fisheries. The priority actions listed in the current conservation plan for this species included characterizing the longline fisheries operating within its range, dynamically analysing the overlap between albatrosses and these fisheries, and providing fisheries management authorities with potential impact estimates of longline fisheries on the Amsterdam albatross. 3. During all life‐cycle stages and year quarters the birds overlapped extensively with fishing effort in the southern Indian and Atlantic oceans. Fishing effort, and consequently overlap score (calculated as the product of fishing effort and time spent by the birds in a spatial unit) was highest in July–September (45% of the hooks annually deployed). Just three fleets (Taiwanese, Japanese and Spanish) contributed to >98% of the overlap scores for each stage (72% from the Taiwanese fleet alone, on average). Daily overlap scores were higher for the non‐breeding versus the breeding stages (3‐fold factor on average). 4. Based on previous bycatch rates for other albatross species, this study estimated that longline fisheries currently have the potential to remove ~2–16 individuals (i.e. ~5%) each year from the total Amsterdam albatross population, depending on whether bycatch mitigation measures were or were not systematically employed during the fishing operations. 5. Recent bycatch mitigation measures may be instrumental in the conservation of the Amsterdam albatross. This study suggests three further key recommendations: (1) to focus conservation efforts on the austral winter; (2) to require all operating vessels to report ring recoveries; and (3) to allocate special regulation of fishing operations in the areas of peak bycatch risk for the Amsterdam albatrosses. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
Eva K. M. Meyers Fernando Tuya Joanna Barker David Jiménez Alvarado José Juan Castro‐Hernández Ricardo Haroun Dennis Rödder 《水产资源保护:海洋与淡水生态系统》2017,27(6):1133-1144
- Angel sharks are among the most threatened fish worldwide, facing regional and global extinction. In Europe, populations of the three Critically Endangered angel sharks (Squatina aculeata, Squatina oculata and Squatina squatina) have been severely depleted.
- Taking advantage of the last global ‘hotspot’ of the angelshark, Squatina squatina, this study gathered data through a citizen science programme to describe the occurrence of this shark in the coastal waters of the Canary Islands. Specifically, this study described (1) the population structure, and (2) habitat use of this species, which was used in a Species Distribution Model to (3) examine realized and potential distribution patterns, and to (4) determine the relative importance of environmental predictors on the occurrence of S. squatina.
- Over the 12 months sampling period (April 2014 – March 2015), 678 sightings were reported. Individuals ranged from 20 to 200 cm (total length). Larger sightings of both females and neonates occurred mostly in April to July, i.e. during the pupping season. Males were significantly more frequent in November to January, i.e. during the mating season. Angelsharks were encountered at depths from <1 m to a maximum of 45 m. Small‐sized individuals (i.e. neonates) exclusively occurred in shallow water (0–25 m). Most sharks occurred on sandy bottoms adjacent to reefs.
- Even though sightings were recorded at all seven islands in the archipelago, there were fewer encounters in the western than the eastern islands.
- The Species Distribution Model indicated that the probability of occurrence mainly correlated with sea surface temperature, chlorophyll, salinity and depth. Areas with the greatest habitat suitability were in shallow water.
- The angelshark displayed spatial (vertical and horizontal) and temporal segregation by size and sex. This information is vital to inform conservation of this Critically Endangered shark in its last stronghold.