scholarly journals Elevated accumulation of the toxic metal mercury in the Critically Endangered oceanic whitetip shark Carcharhinus longimanus from the northwestern Atlantic Ocean

2020 ◽  
Vol 43 ◽  
pp. 267-279 ◽  
Author(s):  
J Gelsleichter ◽  
G Sparkman ◽  
LA Howey ◽  
EJ Brooks ◽  
ON Shipley
Keyword(s):  
Toxic Metal ◽  
Anthropogenic Pollution ◽  
Strong Relationship ◽  
Critically Endangered ◽  
Shark Species ◽  
Environmental Toxicants ◽  
Population Declines ◽  
The Bahamas ◽  
Blood Cell And Plasma ◽  
Special Risk

The oceanic whitetip shark Carcharhinus longimanus is a widely distributed large pelagic shark species once considered abundant in tropical and warm temperate waters, but recently listed as Critically Endangered by the IUCN due to drastic population declines associated with overfishing. In addition to risks posed to its populations due to overexploitation, oceanic whitetip sharks are also capable of accumulating elevated quantities of harmful environmental toxicants, placing them at special risk from anthropogenic pollution. Herein, we provide the first data on accumulation of the toxic, non-essential metal mercury (Hg) in northwest Atlantic (NWA) oceanic whitetip sharks, focusing on aggregations occurring at Cat Island, The Bahamas. Total Hg (THg) concentrations were measured in muscle of 26 oceanic whitetip sharks and compared with animal length and muscle δ15N to evaluate potential drivers of Hg accumulation. THg concentrations were also measured in fin and blood subcomponents (red blood cells and plasma) to determine their value as surrogates for assessing Hg burden. Muscle THg concentrations were among the highest ever reported for a shark species and correlated significantly with animal length, but not muscle δ15N. Fin, red blood cell, and plasma THg concentrations were significantly correlated with muscle THg. Fin THg content was best suited for use as a surrogate for estimating internal Hg burden because of its strong relationship with muscle THg levels, whereas blood THg levels may be better suited for characterizing recent Hg exposure. We conclude that Hg poses health risks to NWA oceanic whitetip sharks and human consumers of this species.

Resilience in the aftermath of hurricanes: Fluctuations in a Critically Endangered population of West Indian Woodpeckers Melanerpes superciliaris nyeanus over two decades

2020 ◽  
pp. 1-21
Author(s):  
MICHAEL E. AKRESH ◽  
ROBERT A. ASKINS ◽  
DAVID I. KING ◽  
FLOYD E. HAYES ◽  
PATRICIA E. BARRY ◽  
...  
Keyword(s):  
Population Size ◽  
Bird Species ◽  
West Indian ◽  
Iucn Red List ◽  
Critically Endangered ◽  
Small Island ◽  
Population Declines ◽  
The Bahamas ◽  
San Salvador ◽  
Bird Populations

Summary Cyclonic storms (often called hurricanes, typhoons, or cyclones) often cause population declines in vulnerable bird species, and the intensity of these storms appears to be increasing due to climate change. Prior studies have reported short-term impacts of hurricanes on avifauna, but few have examined long-term impacts. Over two decades (1993–2018), we periodically surveyed a subspecies of West Indian Woodpecker Melanerpes superciliaris nyeanus on San Salvador, a small island in The Bahamas, to determine its distribution on the island, habitat use, and effects of hurricanes on abundance and population size. We conducted passive and playback surveys, supplemented with mist-netting. Woodpeckers were found only in the northern part of San Salvador, despite extensive surveys throughout other accessible areas of the island. Birds occupied areas with taller coppice adjacent to sabal palm Sabal palmetto groves, which were used for nesting. After hurricanes with >160 kph winds passed over San Salvador, woodpecker densities declined to 35–40% of pre-hurricane densities, but generally recovered back to pre-hurricane densities within 2–3 years. Based on an estimated density of woodpeckers within a ~1,400 ha occupied area, we calculated a population size of approximately 240 individuals (CI = 68-408). However, the population declined to far lower numbers immediately following hurricanes. Under IUCN Red List criteria, M. s. nyeanus classifies as ‘Critically Endangered’, and could be especially sensitive to future hurricanes if they occur at a high enough frequency or intensity to prevent the population from rebounding. Given the small size, isolation, and vulnerability of this population, we recommend preservation of the core habitat, continued monitoring, and further research. Our study shows that small, threatened bird populations can be resilient to the effects of hurricanes, but increased intensity of hurricanes, in combination with other threats, may limit this resilience in the future.

Validating the occurrence of Caribbean reef sharks, Carcharhinus perezi (Poey), (Chondrichthyes: Carcharhiniformes) in the northern Gulf of Mexico, with a key for sharks of the family Carcharhinidae inhabiting the region

Zootaxa ◽  
2011 ◽  
Vol 2933 (1) ◽  
pp. 65 ◽  
Author(s):  
WILLIAM B. DRIGGERS III ◽  
ERIC R. HOFFMAYER ◽  
EMMA L. HICKERSON ◽  
TIMOTHY L. MARTIN ◽  
CHRISTOPHER T. GLEDHILL
Keyword(s):  
Gulf Of Mexico ◽  
North Atlantic ◽  
Mississippi River ◽  
North Atlantic Ocean ◽  
Shark Species ◽  
Mississippi River Delta ◽  
The Bahamas ◽  
Northern Gulf Of Mexico ◽  
The Family ◽  
Reef Sharks

Among the sharks inhabiting the continental shelf waters of the western North Atlantic Ocean, those within the genus Carcharhinus are the most speciose (Castro 2011). Authoritative sources agree on the presence of twelve species of carcharhinids in the northern Gulf of Mexico; however, they disagree on the presence of a thirteenth species, C. perezi (Poey), in the region (Compagno 1984, Compagno 2002, McEachran & Fechhelm 1998, Castro 2011). While the range of C. perezi is well-documented to extend from the southeastern coast of Florida and the Bahamas to Brazil (Castro 2011), published records of C. perezi occurring in the northern Gulf of Mexico are limited to two sources. In their description of Eulamia springeri, a junior synonym of C. perezi, Bigelow & Schroeder (1944) place the species in the northern Gulf of Mexico based on “a somewhat shrivelled skin with head” from a specimen collected off the west coast of Florida that was reported by the authors to be “probably of this species.” Later, Springer (1960) reported the capture of a single specimen off the Mississippi River Delta in 1947; however, no detail of the capture was provided other than it being listed within a table summarizing shark species collected during exploratory fishing operations.

scholarly journals Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes

2016 ◽  
Vol 283 (1840) ◽  
pp. 20161853 ◽  
Author(s):  
James T. Thorson ◽  
Anna Rindorf ◽  
Jin Gao ◽  
Dana H. Hanselman ◽  
Henning Winker
Keyword(s):  
Ideal Free Distribution ◽  
Spatial Dynamics ◽  
Negative Relationship ◽  
Strong Relationship ◽  
Effective Area ◽  
Marine Fishes ◽  
Population Declines ◽  
Density Dependent ◽  
Sea Bottom ◽  
Mixed Support

The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution theory) or the basin model (BM; positive abundance–area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance–area relationship as well as variability among taxa and regions. The average relationship is weak but significant (0.6% increase in area for a 10% increase in abundance), whereas only a small proportion of species–region combinations show a negative relationship (i.e. shrinking area when abundance increases). Approximately one-third of combinations (34.6%) are predicted to increase in area more than 1% for every 10% increase in abundance. We therefore infer that population density generally changes faster than effective area occupied during abundance changes. Gadiformes have the strongest estimated relationship (average 1.0% area increase for every 10% abundance increase) followed by Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a strong relationship between abundance and area occupied relative to other regions. We conclude that the BM explains a small but important portion of spatial dynamics for sea-bottom-associated fishes, and that many individual populations merit cautious management during population declines, because a compressed range may increase the efficiency of harvest.

Variation in behavioural responses of sub-tropical marine fishes to experimental longline capture

2020 ◽  
Author(s):  
Brendan S Talwar ◽  
Ian A Bouyoucos ◽  
Edward J Brooks ◽  
Jacob W Brownscombe ◽  
Cory D Suski ◽  
...  
Keyword(s):  
Physiological Stress ◽  
Behavioural Response ◽  
Shark Species ◽  
The Bahamas ◽  
Behavioural Responses ◽  
Capture Event ◽  
Physiological Stress Response ◽  
Elasmobranch Species ◽  
Quadratic Response ◽  
Nurse Sharks

Abstract Fishes are often caught as bycatch on longlines and subsequently discarded. The behavioural response of fishes to longline capture is poorly understood, although it may be linked to the magnitude of the physiological stress response, and, ultimately, contribute to stress-induced mortality. We used accelerometers, video cameras, and hook timers to analyse the behavioural response of 13 subtropical teleost and elasmobranch species to experimental longline capture in The Bahamas. We found that, across all species and species groups, fight intensity during a capture event was best described by a negative linear and positive quadratic response. Nurse sharks and tiger sharks had lower fight intensity values and exhibited less steepness in their quadratic response during the first 10 min of capture than other species, particularly blacktip and Caribbean reef sharks. Nurse sharks also exhibited the most consistent fight intensity during the entire capture event compared to other shark species, particularly the blacknose shark. Generally, obligate ram ventilators and mixed ventilators exhibited higher steepness in fight intensity trajectories than buccal/spiracular pumpers, which had more consistent, lower fight intensity values. Behavioural responses to longline capture are species specific but may be linked to distinct evolutionary traits such as respiratory mode.

scholarly journals Wild gut microbiomes reveal individuals, species, and location as drivers of variation in two critically endangered tropical birds

2021 ◽  
Author(s):  
Maria Sara Costantini ◽  
Matthew C I Medeiros ◽  
Lisa H Crampton ◽  
Floyd A. Reed
Keyword(s):  
Endangered Species ◽  
Gut Microbiome ◽  
Environmental Changes ◽  
Critically Endangered ◽  
Sampling Location ◽  
Human Populations ◽  
Rrna Gene ◽  
Population Declines ◽  
Important Species ◽  
Hawaiian Honeycreepers

The gut microbiome of an animal has a strong influence on the health, fitness, and behavior of its host, and is thus a critical component of the animal itself. Most research in the microbiome field has focused on human populations and commercially important species. However, researchers are now considering the link between endangered species conservation and the microbiome. In Hawaiʻi, several threats have caused widespread population declines of Hawaiian honeycreepers (subfamily Carduelinae). These threats, and the environmental changes that result, can have a significant effect on the avian gut microbiome and may even lead to disruption of microbial function. However, no previous study has explored the natural patterns of the gut microbiome of a honeycreeper species in the wild. This project used amplicon-based sequencing of the 16S rRNA gene to characterize the gut microbiome of two critically endangered species of Hawaiian honeycreepers. The two species differed significantly in both alpha and beta diversity. Intraspecific variation of the gut microbiome among individual birds was a major factor. However, small but significant differences also exist between sampling location and sexes. This baseline knowledge will help inform management decisions for these honeycreeper species both in their native habitats and in captivity.

scholarly journals Have population declines in Egyptian Vulture and Red-headed Vulture in India slowed since the 2006 ban on veterinary diclofenac?

2014 ◽  
Vol 24 (3) ◽  
pp. 272-281 ◽  
Author(s):  
TOBY H. GALLIGAN ◽  
TATSUYA AMANO ◽  
VIBHU M. PRAKASH ◽  
MANDAR KULKARNI ◽  
ROHAN SHRINGARPURE ◽  
...  
Keyword(s):  
Protected Areas ◽  
Indian Subcontinent ◽  
Critically Endangered ◽  
Population Declines ◽  
Inflammatory Drug ◽  
Egyptian Vulture ◽  
Neophron Percnopterus ◽  
Anti Inflammatory

SummaryPopulations of three vulture species of the genus Gyps, the Egyptian Vulture Neophron percnopterus and Red-headed Vulture Sarcogyps calvus have declined markedly on the Indian subcontinent since the mid-1990s and all are now Critically Endangered or Endangered. Gyps vultures have been killed by the widely used non-steroidal anti-inflammatory drug diclofenac, ingested when they feed on carcasses of domesticated ungulates treated with the drug shortly before death. However, it is not known whether Egyptian Vulture and Red-headed Vulture are also sensitive to diclofenac. Veterinary use of diclofenac was banned in India in 2006. Since then, the prevalence and concentration of diclofenac in domesticated ungulates carcasses has decreased and population declines of Gyps vultures have slowed or reversed. Here, we examine counts of Egyptian and Red-headed Vultures obtained on road transects in and near protected areas between 1992 and 2011. We found indications that the declines in both species appear to have slowed and possibly increased after the ban was introduced, though the small numbers of birds counted make this conclusion less robust than that for the Gyps species. These results suggest that both species may have been adversely impacted by diclofenac and that government bans on this drug, which are beginning to take effect, may benefit a wider range of vulture species in the Indian subcontinent than was previously thought.

scholarly journals Satellite telemetry reveals higher fishing mortality rates than previously estimated, suggesting overfishing of an apex marine predator

2017 ◽  
Vol 284 (1860) ◽  
pp. 20170658 ◽  
Author(s):  
Michael E. Byrne ◽  
Enric Cortés ◽  
Jeremy J. Vaudo ◽  
Guy C. McN. Harvey ◽  
Mark Sampson ◽  
...  
Keyword(s):  
North Atlantic Ocean ◽  
Satellite Telemetry ◽  
Mortality Rates ◽  
Maximum Sustainable Yield ◽  
Conservation Strategies ◽  
Shark Species ◽  
Fishing Mortality ◽  
Population Declines ◽  
Marine Predator ◽  
Shortfin Mako

Overfishing is a primary cause of population declines for many shark species of conservation concern. However, means of obtaining information on fishery interactions and mortality, necessary for the development of successful conservation strategies, are often fisheries-dependent and of questionable quality for many species of commercially exploited pelagic sharks. We used satellite telemetry as a fisheries-independent tool to document fisheries interactions, and quantify fishing mortality of the highly migratory shortfin mako shark ( Isurus oxyrinchus ) in the western North Atlantic Ocean. Forty satellite-tagged shortfin mako sharks tracked over 3 years entered the Exclusive Economic Zones of 19 countries and were harvested in fisheries of five countries, with 30% of tagged sharks harvested. Our tagging-derived estimates of instantaneous fishing mortality rates ( F = 0.19–0.56) were 10-fold higher than previous estimates from fisheries-dependent data (approx. 0.015–0.024), suggesting data used in stock assessments may considerably underestimate fishing mortality. Additionally, our estimates of F were greater than those associated with maximum sustainable yield, suggesting a state of overfishing. This information has direct application to evaluations of stock status and for effective management of populations, and thus satellite tagging studies have potential to provide more accurate estimates of fishing mortality and survival than traditional fisheries-dependent methodology.

scholarly journals Positive association between rat abundance and breeding success of the Critically Endangered Mariana Crow Corvus kubaryi

2013 ◽  
Vol 24 (2) ◽  
pp. 192-200 ◽  
Author(s):  
ARJUN AMAR ◽  
JACOB A. ESSELSTYN
Keyword(s):  
Breeding Success ◽  
Nest Predation ◽  
Wild Population ◽  
Positive Association ◽  
Critically Endangered ◽  
Mariana Islands ◽  
Population Declines ◽  
Nest Sites ◽  
Plausible Hypothesis ◽  
Shared Predator

SummaryDiagnosing the causes of population declines of highly endangered species is vital to ensure that appropriate conservation measures are undertaken. Although experiments can provide critical information on potential causes, these can be time consuming and costly, and so it is important to determine the most plausible hypothesis for such tests. The last wild population of the Critically Endangered Mariana Crow Corvus kubaryi has been declining rapidly on Rota in the Mariana Islands. Because nest predation by introduced rats Rattus spp. has been implicated in the declines of other Pacific island birds, we tested for a correlation between breeding success of Mariana Crows and abundance of rats R. diardii surrounding their nest sites. If rats are a contributing factor in this species’s decline, we predicted that breeding success would be lower in areas where rats were more abundant. In complete contrast to this prediction, we found that breeding success was significantly higher where rats were most abundant, suggesting that rats are unlikely to be a major driving force behind the decline in this species. The positive association between crow breeding success and rat abundance suggests these species may be responding to similar habitat needs or a shared predator. This study illustrates the importance of gathering sufficient knowledge on the ecology of a species prior to undertaking costly, logistically difficult and time consuming experiments.

scholarly journals Effects of anthropogenic mortality on Critically Endangered red wolf Canis rufus breeding pairs: implications for red wolf recovery

Oryx ◽  
2015 ◽  
Vol 51 (1) ◽  
pp. 174-181 ◽  
Author(s):  
Joseph W. Hinton ◽  
Kristin E. Brzeski ◽  
David R. Rabon ◽  
Michael J. Chamberlain
Keyword(s):  
North Carolina ◽  
Critically Endangered ◽  
Population Declines ◽  
Canis Rufus ◽  
Red Wolf ◽  
Management Actions ◽  
Control Programmes ◽  
Negative Effect ◽  
Eastern North Carolina ◽  
Red Wolves

AbstractFollowing precipitous population declines as a result of intensive hunting and 20th century predator-control programmes, hybridization of the Critically Endangered red wolf Canis rufus with coyotes Canis latrans posed a significant challenge for red wolf recovery efforts. Anthropogenic mortality and hybridization continue to pose challenges; the increasing number of wolf deaths caused by humans has limited wolf population growth, facilitated the encroachment of coyotes into eastern North Carolina, and affected the formation and disbandment of breeding pairs. We assessed the effects of anthropogenic mortality on Canis breeding units during a 22-year period (1991–2013). Our results show that deaths caused by people accounted for 40.6% of breeding pair disbandment, and gunshots were the primary cause of mortality. Red wolves replaced congeneric breeding pairs > 75% of the time when pairs disbanded under natural conditions or as a result of management actions. Since the mid 2000s anthropogenic mortality has caused annual preservation rates of red wolf breeding pairs to decline by 34%, and replacement of Canis breeders by red wolves to decline by 30%. Our results demonstrate that human-caused mortality, specifically by gunshots, had a strong negative effect on the longevity of red wolf pairs, which may benefit coyotes indirectly by removing their primary competitor. Coyotes are exacerbating the decline of red wolves by pair-bonding with resident wolves whose mates have been killed.

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