Erin Lyons, Evan DAlessandro, Manoj Shivlani, Clayton Pollock, Kristen Ewen
ABSTRACT: The hawksbill sea turtle is listed as Critically Endangered under the IUCN Red List and has been slow to recover in the Caribbean due to historical exploitation and ongoing anthropogenic threats. In turtles, sex and reproductive success are determined by incubation temperatures, whereby lower temperatures produce male hatchlings and higher temperatures produce female hatchlings. As incubation temperatures increase due to climate change, nests are predicted to produce predominantly female hatchlings, threatening sex ratios, reproductive success, and species persistence. One of the largest remaining nesting hawksbill populations within the USA nests on Buck Island. This study aimed to (1) assess the factors driving incubation temperatures and (2) identify the relationship between hatch success and the proportion of time exposed to increasing incubation temperatures. Nest incubation temperatures, beach sector, habitat type, deposition month, percent soil composition, hatch success, and emergence success data were collected from 2019 to 2021. Differences in incubation temperatures across these factors confirmed that the absence of vegetative cover is increasing incubation temperatures on Buck Island, leading to reduced hatchling survival. Results from this study indicate that declines in hatch success may be driven by long-term exposure to temperatures that were previously considered in the literature to be non-lethal to embryos. These findings emphasize the continued need for conservation interventions to protect the future of hawksbills.
{"title":"Factors regulating incubation temperature and thermal stress in hawksbills in St. Croix, USVI","authors":"Erin Lyons, Evan DAlessandro, Manoj Shivlani, Clayton Pollock, Kristen Ewen","doi":"10.3354/esr01303","DOIUrl":"https://doi.org/10.3354/esr01303","url":null,"abstract":"ABSTRACT: The hawksbill sea turtle is listed as Critically Endangered under the IUCN Red List and has been slow to recover in the Caribbean due to historical exploitation and ongoing anthropogenic threats. In turtles, sex and reproductive success are determined by incubation temperatures, whereby lower temperatures produce male hatchlings and higher temperatures produce female hatchlings. As incubation temperatures increase due to climate change, nests are predicted to produce predominantly female hatchlings, threatening sex ratios, reproductive success, and species persistence. One of the largest remaining nesting hawksbill populations within the USA nests on Buck Island. This study aimed to (1) assess the factors driving incubation temperatures and (2) identify the relationship between hatch success and the proportion of time exposed to increasing incubation temperatures. Nest incubation temperatures, beach sector, habitat type, deposition month, percent soil composition, hatch success, and emergence success data were collected from 2019 to 2021. Differences in incubation temperatures across these factors confirmed that the absence of vegetative cover is increasing incubation temperatures on Buck Island, leading to reduced hatchling survival. Results from this study indicate that declines in hatch success may be driven by long-term exposure to temperatures that were previously considered in the literature to be non-lethal to embryos. These findings emphasize the continued need for conservation interventions to protect the future of hawksbills.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140010244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT: The short-tailed albatross Phoebastria albatrus, a globally Vulnerable species recovering from near-extinction, breeds mainly on 2 island groups in the north-western Pacific: Torishima and Senkaku Islands. Recently, it became clear that this is a species complex, composed of 2 populations (‘Torishima’ and ‘Senkaku’ types) that are distinct from both genetic and morphological perspectives, and which mate assortatively on Torishima. We tested the hypothesis of premating isolation as a possible mechanism for genetic differentiation and shifted breeding date in short-tailed albatrosses. Using light-based geolocation and molecular analysis, we examined whether adults from the 2 populations breeding on Torishima differed in their at-sea distribution during the nonbreeding period (June-September) and in their return dates. From 22 bird tracks collected from 12 birds over 4 yr, we identified 2 distinct nonbreeding areas: around the Aleutian Islands in the Bering Sea and near the Kuril Islands in the Okhotsk Sea. All 6 tracks of Torishima-type birds migrated directly to the Bering Sea in all years. In contrast, most of the Senkaku-type birds migrated along northeast Japan to the Okhotsk Sea (9 tracks), with the others moving to the Bering Sea (7 tracks). There was no clear difference in the dates of return to Torishima between the 2 bird types. Overall, no absolute pre-mating isolation in space or time was observed in short-tailed albatrosses, but we highlighted notable divergences in the nonbreeding distribution of both types. This result suggests that Torishima- and Senkaku-type populations should be treated as separate management units.
{"title":"Incomplete isolation in the nonbreeding areas of two genetically separated but sympatric short-tailed albatross populations","authors":"Naoki Tomita, Fumio Sato, Jean-Baptiste Thiebot, Bungo Nishizawa, Masaki Eda, Hiroe Izumi, Satoshi Konno, Miwa Konno, Yutaka Watanuki","doi":"10.3354/esr01302","DOIUrl":"https://doi.org/10.3354/esr01302","url":null,"abstract":"ABSTRACT: The short-tailed albatross <i>Phoebastria albatrus</i>, a globally Vulnerable species recovering from near-extinction, breeds mainly on 2 island groups in the north-western Pacific: Torishima and Senkaku Islands. Recently, it became clear that this is a species complex, composed of 2 populations (‘Torishima’ and ‘Senkaku’ types) that are distinct from both genetic and morphological perspectives, and which mate assortatively on Torishima. We tested the hypothesis of premating isolation as a possible mechanism for genetic differentiation and shifted breeding date in short-tailed albatrosses. Using light-based geolocation and molecular analysis, we examined whether adults from the 2 populations breeding on Torishima differed in their at-sea distribution during the nonbreeding period (June-September) and in their return dates. From 22 bird tracks collected from 12 birds over 4 yr, we identified 2 distinct nonbreeding areas: around the Aleutian Islands in the Bering Sea and near the Kuril Islands in the Okhotsk Sea. All 6 tracks of Torishima-type birds migrated directly to the Bering Sea in all years. In contrast, most of the Senkaku-type birds migrated along northeast Japan to the Okhotsk Sea (9 tracks), with the others moving to the Bering Sea (7 tracks). There was no clear difference in the dates of return to Torishima between the 2 bird types. Overall, no absolute pre-mating isolation in space or time was observed in short-tailed albatrosses, but we highlighted notable divergences in the nonbreeding distribution of both types. This result suggests that Torishima- and Senkaku-type populations should be treated as separate management units.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140010238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Abrantes, N. Wildermann, I. B. Miller, M. Hamann, C. J. Limpus, C. A. Madden Hof, I. Bell, M. Sheaves, A. Barnett
ABSTRACT: Identifying migration routes and key habitats is critical for the management and conservation of migratory species. Tracking and stable isotope analysis (SIA), particularly of carbon (δ13C) and nitrogen (δ15N), are often used to study animal movements, with SIA particularly useful when animals move through isotopic gradients. Marine turtles are typically highly migratory, moving between nesting and foraging grounds often located 100s-1000s km apart. The flatback turtle Natator depressus is endemic to the Australian continental shelf. Satellite tracking (n = 44) and SIA (n = 33) of females nesting in eastern Queensland, Australia, were used to identify main foraging areas, describe intraspecific variation in the location of foraging areas, and determine if δ13C and/or δ15N values can be used to identify foraging regions. Although foraging grounds were widely dispersed, tracking identified 3 main foraging regions. SIA agreed with tracking, indicating foraging site fidelity. Generalized linear models and linear discriminant analysis (LDA) were used to estimate how well δ13C/δ15N and nesting sites can perform as indicators of broad foraging regions and to predict foraging regions for turtles with no tracking data. δ15N was a strong predictor of the foraging region. LDA correctly classified the foraging region of 94% of individuals and was suitable to predict foraging regions of untracked individuals. A strong negative linear relationship between turtle δ15N and foraging latitude indicates the presence of a δ15N isoscape along the eastern Queensland coast. This is the first demonstration of an isoscape for the region, which should be useful for studying and monitoring the habitat use of flatback turtles and other migratory species.
{"title":"Intraspecific variability in flatback turtle habitat use: δ15N as an indicator of foraging locations","authors":"K. Abrantes, N. Wildermann, I. B. Miller, M. Hamann, C. J. Limpus, C. A. Madden Hof, I. Bell, M. Sheaves, A. Barnett","doi":"10.3354/esr01293","DOIUrl":"https://doi.org/10.3354/esr01293","url":null,"abstract":"ABSTRACT: Identifying migration routes and key habitats is critical for the management and conservation of migratory species. Tracking and stable isotope analysis (SIA), particularly of carbon (δ<sup>13</sup>C) and nitrogen (δ<sup>15</sup>N), are often used to study animal movements, with SIA particularly useful when animals move through isotopic gradients. Marine turtles are typically highly migratory, moving between nesting and foraging grounds often located 100s-1000s km apart. The flatback turtle <i>Natator depressus</i> is endemic to the Australian continental shelf. Satellite tracking (n = 44) and SIA (n = 33) of females nesting in eastern Queensland, Australia, were used to identify main foraging areas, describe intraspecific variation in the location of foraging areas, and determine if δ<sup>13</sup>C and/or δ<sup>15</sup>N values can be used to identify foraging regions. Although foraging grounds were widely dispersed, tracking identified 3 main foraging regions. SIA agreed with tracking, indicating foraging site fidelity. Generalized linear models and linear discriminant analysis (LDA) were used to estimate how well δ<sup>13</sup>C/δ<sup>15</sup>N and nesting sites can perform as indicators of broad foraging regions and to predict foraging regions for turtles with no tracking data. δ<sup>15</sup>N was a strong predictor of the foraging region. LDA correctly classified the foraging region of 94% of individuals and was suitable to predict foraging regions of untracked individuals. A strong negative linear relationship between turtle δ<sup>15</sup>N and foraging latitude indicates the presence of a δ<sup>15</sup>N isoscape along the eastern Queensland coast. This is the first demonstration of an isoscape for the region, which should be useful for studying and monitoring the habitat use of flatback turtles and other migratory species.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139758648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ravi Kumar Singh, Jailabdeen AjjiM, Jeffrey W. Lang, Harika Segu, Harisharan Ramesh, Karthikeyan Vasudevan
ABSTRACT: The gharial Gavialis gangeticus is a Critically Endangered crocodylian endemic to the Indian subcontinent. The species has experienced a 95% population decline over the past 2 centuries. The largest self-sustaining population inhabits the protected National Chambal Sanctuary (NCS) in north India and represents >80% of extant gharials globally. We developed de novo a panel of polymorphic gharial-specific microsatellites, using whole genome information and microsatellite search tools. These 15 new markers have multiple numbers of polymorphic alleles that are more informative than those obtained from previous studies. Analyses of 93 scute samples collected across age classes from wild gharials residing in the NCS facilitated accurate assessments of genetic diversity and inbreeding coefficient and identified a historical bottleneck event. Estimates of the observed and expected heterozygosities were lower than those reported earlier. The inbreeding coefficient was low, and the population did not deviate significantly from Hardy-Weinberg equilibrium. The calculated M ratio and 2 heterozygosity tests detected a genetic bottleneck, which is consistent with historic sharp declines in population size, followed by recent recovery. These new gharial microsatellite markers are statistically robust and provide an improved means to assess the population genetics of the largest self-sustaining wild gharial population. This study will facilitate additional investigations on the genetic diversity of other extant gharial populations—not only the few remaining wild populations but also those in zoos and rearing facilities. Additional genetic studies of gharial in the NCS are warranted to inform management strategies.
{"title":"Population genetics of gharial Gavialis gangeticus in the Chambal River, India, using novel polymorphic microsatellite markers","authors":"Ravi Kumar Singh, Jailabdeen AjjiM, Jeffrey W. Lang, Harika Segu, Harisharan Ramesh, Karthikeyan Vasudevan","doi":"10.3354/esr01297","DOIUrl":"https://doi.org/10.3354/esr01297","url":null,"abstract":"ABSTRACT: The gharial <i>Gavialis gangeticus</i> is a Critically Endangered crocodylian endemic to the Indian subcontinent. The species has experienced a 95% population decline over the past 2 centuries. The largest self-sustaining population inhabits the protected National Chambal Sanctuary (NCS) in north India and represents >80% of extant gharials globally. We developed de novo a panel of polymorphic gharial-specific microsatellites, using whole genome information and microsatellite search tools. These 15 new markers have multiple numbers of polymorphic alleles that are more informative than those obtained from previous studies. Analyses of 93 scute samples collected across age classes from wild gharials residing in the NCS facilitated accurate assessments of genetic diversity and inbreeding coefficient and identified a historical bottleneck event. Estimates of the observed and expected heterozygosities were lower than those reported earlier. The inbreeding coefficient was low, and the population did not deviate significantly from Hardy-Weinberg equilibrium. The calculated <i>M</i> ratio and 2 heterozygosity tests detected a genetic bottleneck, which is consistent with historic sharp declines in population size, followed by recent recovery. These new gharial microsatellite markers are statistically robust and provide an improved means to assess the population genetics of the largest self-sustaining wild gharial population. This study will facilitate additional investigations on the genetic diversity of other extant gharial populations—not only the few remaining wild populations but also those in zoos and rearing facilities. Additional genetic studies of gharial in the NCS are warranted to inform management strategies.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139758537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Marcos Gorresen, Paul Cryan, Megan Parker, Frank Alig, Melia Nafus, Eben H. Paxton
ABSTRACT: The yǻyaguak (Mariana swiftlet; Aerodramus bartschi) is an endangered cave-nesting species historically found on Guam and the southern Mariana Islands, Micronesia. The population on Guam has been severely affected by the introduction of the brown treesnake Boiga irregularis. Population status assessments have, however, been challenging due to the limitations of traditional counting methods, which rely on visual observations at cave entrances and are prone to inaccuracies. To improve count accuracy, we estimated yǻyaguak population size and relative nesting activity using thermal and near-infrared videography. The population on Guam was surveyed at the island’s 3 known occupied caves (Mahlac, Maemong, and Fachi) between 2019 and 2023. Mahlac Cave harbored the largest colony, which ranged from 506 to 665 birds; Maemong Cave held 144 to 196 birds; and Fachi Cave, which is sometimes flooded, had 28 (in 2019) and 35 birds (in 2023). Our estimates indicate a slight decline in the yǻyaguak population over the study period. This study demonstrates the potential of thermal and near-infrared videography for improved monitoring of yǻyaguak colonies and nesting activity, which will contribute to our understanding of population dynamics and the effectiveness of management strategies such as brown treesnake control.
{"title":"Videographic monitoring at caves to estimate population size of the endangered yǻyaguak (Mariana swiftlet) on Guam","authors":"P. Marcos Gorresen, Paul Cryan, Megan Parker, Frank Alig, Melia Nafus, Eben H. Paxton","doi":"10.3354/esr01296","DOIUrl":"https://doi.org/10.3354/esr01296","url":null,"abstract":"ABSTRACT: The yǻyaguak (Mariana swiftlet; <i>Aerodramus bartschi</i>) is an endangered cave-nesting species historically found on Guam and the southern Mariana Islands, Micronesia. The population on Guam has been severely affected by the introduction of the brown treesnake <i>Boiga irregularis</i>. Population status assessments have, however, been challenging due to the limitations of traditional counting methods, which rely on visual observations at cave entrances and are prone to inaccuracies. To improve count accuracy, we estimated yǻyaguak population size and relative nesting activity using thermal and near-infrared videography. The population on Guam was surveyed at the island’s 3 known occupied caves (Mahlac, Maemong, and Fachi) between 2019 and 2023. Mahlac Cave harbored the largest colony, which ranged from 506 to 665 birds; Maemong Cave held 144 to 196 birds; and Fachi Cave, which is sometimes flooded, had 28 (in 2019) and 35 birds (in 2023). Our estimates indicate a slight decline in the yǻyaguak population over the study period. This study demonstrates the potential of thermal and near-infrared videography for improved monitoring of yǻyaguak colonies and nesting activity, which will contribute to our understanding of population dynamics and the effectiveness of management strategies such as brown treesnake control.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139758647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Erina J. Young, Kristin S. Warren, Scott D. Whiting, Nahiid S. Stephens, Mieghan Bruce, Rebecca Donaldson, Bethany Jackson, Lian Yeap, Rebecca Vaughan-Higgins
ABSTRACT: Blood reference intervals (RIs) provide an indication of systemic health and are central to any baseline health survey. RIs are available for all sea turtle species, except for the flatback turtle Natator depressus. We developed the first nesting and foraging flatback turtle RIs from a healthy reference population of 211 individuals. We found flatback turtle RIs were generally similar to other published sea turtle RIs. For flatback turtles, we detected significant differences in blood reference values (RVs) by life stage (nesting vs. foraging), sex, and location, as well as by measurement technique (laboratory vs. field). Clinically significant differences justified the establishment of separate RIs for nesting and foraging flatback turtles and for laboratory and field techniques. Clinical application of these blood RIs for individuals in rehabilitation includes disease diagnosis, health monitoring, and the development of prognostic indicators. As sea turtles are regarded as sentinels of environmental health, flatback turtle baseline health data will also be useful for population health monitoring and as a reference for future studies where changes in RIs may indicate an environment in decline.
{"title":"Haematologic and plasma biochemical reference intervals for flatback turtles Natator depressus","authors":"Erina J. Young, Kristin S. Warren, Scott D. Whiting, Nahiid S. Stephens, Mieghan Bruce, Rebecca Donaldson, Bethany Jackson, Lian Yeap, Rebecca Vaughan-Higgins","doi":"10.3354/esr01299","DOIUrl":"https://doi.org/10.3354/esr01299","url":null,"abstract":"ABSTRACT: Blood reference intervals (RIs) provide an indication of systemic health and are central to any baseline health survey. RIs are available for all sea turtle species, except for the flatback turtle <i>Natator depressus</i>. We developed the first nesting and foraging flatback turtle RIs from a healthy reference population of 211 individuals. We found flatback turtle RIs were generally similar to other published sea turtle RIs. For flatback turtles, we detected significant differences in blood reference values (RVs) by life stage (nesting vs. foraging), sex, and location, as well as by measurement technique (laboratory vs. field). Clinically significant differences justified the establishment of separate RIs for nesting and foraging flatback turtles and for laboratory and field techniques. Clinical application of these blood RIs for individuals in rehabilitation includes disease diagnosis, health monitoring, and the development of prognostic indicators. As sea turtles are regarded as sentinels of environmental health, flatback turtle baseline health data will also be useful for population health monitoring and as a reference for future studies where changes in RIs may indicate an environment in decline.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139758593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shamsa Al Hameli, Stephan Bruns, Aaron C. Henderson
ABSTRACT: The Pakistan whipray Maculabatis arabica and the halavi guitarfish Glaucostegus halavi are Critically Endangered elasmobranch species that are endemic to areas of the northern Indian Ocean. An unexpectedly high abundance of both species in a shallow, nearshore area of Abu Dhabi, United Arab Emirates, is described here. Both species were found to utilise this area year-round, although seasonal fluctuations in abundance were evident. Male and female G. halavi were encountered at sizes that suggest a mix of immature and mature individuals; however, all except 1 M. arabica were female, indicating sexual segregation in this species. Further studies are required to learn more about the importance of the study area in the life history of these Critically Endangered species, but it is a matter of considerable concern that the wider Khor Faridah area is currently undergoing intensive coastal development.
摘要：巴基斯坦鞭鱼（Maculabatis arabica）和哈拉维吉他鱼（Glaucostegus halavi）是印度洋北部地区特有的极度濒危鞘鳃类物种。本文描述了这两个物种在阿拉伯联合酋长国阿布扎比近岸浅海区域出人意料的高丰度。尽管丰度的季节性波动很明显，但发现这两个物种全年都在这一区域活动。雄性和雌性 G. halavi 的个体大小表明，未成熟个体和成熟个体混杂在一起；然而，除 1 条 M. arabica 外，其余均为雌性，这表明该物种存在性分离现象。要进一步了解研究区域在这些极度濒危物种生活史中的重要性，还需要进一步的研究，但令人相当担忧的是，更广泛的霍尔法里达地区目前正在进行密集的沿海开发。
{"title":"Notable abundance of two Critically Endangered elasmobranch fishes near an area of intensive coastal development in the Arabian Gulf","authors":"Shamsa Al Hameli, Stephan Bruns, Aaron C. Henderson","doi":"10.3354/esr01290","DOIUrl":"https://doi.org/10.3354/esr01290","url":null,"abstract":"ABSTRACT: The Pakistan whipray <i>Maculabatis arabica</i> and the halavi guitarfish <i>Glaucostegus halavi</i> are Critically Endangered elasmobranch species that are endemic to areas of the northern Indian Ocean. An unexpectedly high abundance of both species in a shallow, nearshore area of Abu Dhabi, United Arab Emirates, is described here. Both species were found to utilise this area year-round, although seasonal fluctuations in abundance were evident. Male and female <i>G. halavi</i> were encountered at sizes that suggest a mix of immature and mature individuals; however, all except 1 <i>M. arabica</i> were female, indicating sexual segregation in this species. Further studies are required to learn more about the importance of the study area in the life history of these Critically Endangered species, but it is a matter of considerable concern that the wider Khor Faridah area is currently undergoing intensive coastal development.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139656065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruth H. Leeney, Alexanra Bagarinao-Regalado, Diana Verdote, Carla Drury Salgado
ABSTRACT: Globally, sawfishes are amongst the most threatened of all sharks and rays, but a paucity of current data on their presence and status has limited conservation action in many countries. Whilst 2 sawfish species, Pristis pristis and P. zijsron, were historically present in the Philippines, a lack of recent reports suggests that they may have become extremely rare. To determine the current status of sawfishes in the Philippines, interviews were conducted with 106 fishers, fish brokers and fisheries officers at 31 sites in 2016. Interviewees confirmed that sawfishes had inhabited Laguna de Bay and the Agusan and Cagayan Rivers in the past, but the majority of interviewees had last seen a sawfish several decades ago. The most recent observations of a sawfish reported during interviews were in 2014, at the estuary of the Tamontaka River, Mindanao, and at Mercedes fish port, Bicol. After the study, photographic evidence of the landing in 2015 of a largetooth sawfish in Zamboanga Peninsula was published on social media. The considerable degradation and modification of freshwater ecosystems, mangrove loss, coastal degradation, fishing pressure and widespread bottom trawling since the 1940s have all likely contributed to sawfish declines. This study confirms that sawfishes, previously abundant in the Philippines, are now extremely rare or locally extinct. Bottlenose wedgefish Rhynchobatus australiae were observed at Mercedes port during the study and interviewees stated that they are landed regularly. Given the Critically Endangered status of this species, this fishery likely needs immediate management.
{"title":"A rapid assessment of the status of sawfishes in the Philippines","authors":"Ruth H. Leeney, Alexanra Bagarinao-Regalado, Diana Verdote, Carla Drury Salgado","doi":"10.3354/esr01295","DOIUrl":"https://doi.org/10.3354/esr01295","url":null,"abstract":"ABSTRACT: Globally, sawfishes are amongst the most threatened of all sharks and rays, but a paucity of current data on their presence and status has limited conservation action in many countries. Whilst 2 sawfish species, <i>Pristis pristis</i> and <i>P. zijsron</i>, were historically present in the Philippines, a lack of recent reports suggests that they may have become extremely rare. To determine the current status of sawfishes in the Philippines, interviews were conducted with 106 fishers, fish brokers and fisheries officers at 31 sites in 2016. Interviewees confirmed that sawfishes had inhabited Laguna de Bay and the Agusan and Cagayan Rivers in the past, but the majority of interviewees had last seen a sawfish several decades ago. The most recent observations of a sawfish reported during interviews were in 2014, at the estuary of the Tamontaka River, Mindanao, and at Mercedes fish port, Bicol. After the study, photographic evidence of the landing in 2015 of a largetooth sawfish in Zamboanga Peninsula was published on social media. The considerable degradation and modification of freshwater ecosystems, mangrove loss, coastal degradation, fishing pressure and widespread bottom trawling since the 1940s have all likely contributed to sawfish declines. This study confirms that sawfishes, previously abundant in the Philippines, are now extremely rare or locally extinct. Bottlenose wedgefish <i>Rhynchobatus australiae</i> were observed at Mercedes port during the study and interviewees stated that they are landed regularly. Given the Critically Endangered status of this species, this fishery likely needs immediate management.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139656280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alastair V. Harry, Corey B. Wakefield, Stephen J. Newman, J. Matias Braccini
ABSTRACT: Northwestern Australia is thought to have some of the world’s last remaining viable sawfish populations, although little quantitative data exists on their status or trends. This study examined 17 years of logbook bycatch records (n = 815) for green sawfish Pristis zijsron and narrow sawfish Anoxypristis cuspidata from a trawl fishery operating on the Australian North West Shelf. Incidental sawfish captures by the fishery are rare, occurring approximately once every 75 trawls (~199 trawl hours). To standardize catch rates and account for excess zeros in the data, we employed generalized additive models for location, scale, and shape (GAMLSSs) using a zero-inflated Poisson distribution. For green sawfish, catch rates approximately doubled over the study period, while an oscillating trend was observed for narrow sawfish catch rates. Reported captures occurred throughout the management boundaries of the fishery, which operates in mid-shelf waters from 48 to 121 m. A weak seasonal signal in catch rates was detected for both species, with the highest capture numbers occurring during autumn-winter, consistent with an expected inshore migration for parturition during spring-summer. Logbook trends were partly corroborated by independently verified data collected in a subset of years, which also showed an increasing proportion of green sawfish in the catch. Our findings emphasize the importance of sawfish populations in northwestern Australia within the context of global conservation efforts for this taxon.
{"title":"Trends in catch rates of sawfish on the Australian North West Shelf","authors":"Alastair V. Harry, Corey B. Wakefield, Stephen J. Newman, J. Matias Braccini","doi":"10.3354/esr01289","DOIUrl":"https://doi.org/10.3354/esr01289","url":null,"abstract":"ABSTRACT: Northwestern Australia is thought to have some of the world’s last remaining viable sawfish populations, although little quantitative data exists on their status or trends. This study examined 17 years of logbook bycatch records (n = 815) for green sawfish <i>Pristis zijsron</i> and narrow sawfish <i>Anoxypristis cuspidata</i> from a trawl fishery operating on the Australian North West Shelf. Incidental sawfish captures by the fishery are rare, occurring approximately once every 75 trawls (~199 trawl hours). To standardize catch rates and account for excess zeros in the data, we employed generalized additive models for location, scale, and shape (GAMLSSs) using a zero-inflated Poisson distribution. For green sawfish, catch rates approximately doubled over the study period, while an oscillating trend was observed for narrow sawfish catch rates. Reported captures occurred throughout the management boundaries of the fishery, which operates in mid-shelf waters from 48 to 121 m. A weak seasonal signal in catch rates was detected for both species, with the highest capture numbers occurring during autumn-winter, consistent with an expected inshore migration for parturition during spring-summer. Logbook trends were partly corroborated by independently verified data collected in a subset of years, which also showed an increasing proportion of green sawfish in the catch. Our findings emphasize the importance of sawfish populations in northwestern Australia within the context of global conservation efforts for this taxon.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139656299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
KM Stafford, G Boussarie, M Caputo, L Irvine, S Laing, E Nancy, H Pearson, JJ Kiszka
Historically, the Seychelles archipelago was an opportunistic whaling ground for fleets en route to and from the Antarctic. Soviet whalers illegally killed 500 blue whales near the Seychelles in the 1960s. Since then, no dedicated research has occurred to understand the ecological importance of this region for blue whales. Based on opportunistic sightings, we undertook 2 expeditions to assess the occurrence of blue whales. The overall goals were to determine blue whale distribution, obtain photo-identification data and collect the first acoustic data on this species in this region using a hydrophone deployed for a year. The expeditions consisted of vessel-based visual surveys that focused on the slope habitat (500-2000 m) off the northern portion of the Mahé Plateau. Over the 2 expeditions, a total of 5 sightings of up to 10 animals were seen. The results of our acoustic monitoring off Seychelles demonstrate that blue whales occur there regularly, primarily from December to April, and that the acoustic population identity matches that from near Sri Lanka. Published records and the results of our work suggest that blue whales from the northwestern Indian Ocean are seasonally present in the western equatorial Indian Ocean.
{"title":"Acoustic detections and sightings of blue whales (Balaenoptera musculus) in the Seychelles, western tropical Indian Ocean (2020-2022)","authors":"KM Stafford, G Boussarie, M Caputo, L Irvine, S Laing, E Nancy, H Pearson, JJ Kiszka","doi":"10.3354/esr01277","DOIUrl":"https://doi.org/10.3354/esr01277","url":null,"abstract":"Historically, the Seychelles archipelago was an opportunistic whaling ground for fleets en route to and from the Antarctic. Soviet whalers illegally killed 500 blue whales near the Seychelles in the 1960s. Since then, no dedicated research has occurred to understand the ecological importance of this region for blue whales. Based on opportunistic sightings, we undertook 2 expeditions to assess the occurrence of blue whales. The overall goals were to determine blue whale distribution, obtain photo-identification data and collect the first acoustic data on this species in this region using a hydrophone deployed for a year. The expeditions consisted of vessel-based visual surveys that focused on the slope habitat (500-2000 m) off the northern portion of the Mahé Plateau. Over the 2 expeditions, a total of 5 sightings of up to 10 animals were seen. The results of our acoustic monitoring off Seychelles demonstrate that blue whales occur there regularly, primarily from December to April, and that the acoustic population identity matches that from near Sri Lanka. Published records and the results of our work suggest that blue whales from the northwestern Indian Ocean are seasonally present in the western equatorial Indian Ocean.","PeriodicalId":48746,"journal":{"name":"Endangered Species Research","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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