Exposure of wild Caspian seals (Pusa caspica) to parasites, bacterial and viral pathogens, evaluated via molecular and serological assays

Disease surveillance of marine mammal populations is essential to understand the causes of strandings, identify potential threats to animal health, and to support development of conservation strategies. Here we report the first large multi-pathogen screening of prevalence for viruses, bacteria and parasites in a sample of 177 live, healthy, wild Caspian seals (Pusa caspica), captured and released during satellite telemetry studies 2007-2017. Employing molecular and serological assays we assess prevalence of pathogens known to be of significance for marine mammal health worldwide, and evaluate the results in relation to Caspian seal health and conservation. RT-PCR, and PCR assays find evidence for infection by Canine Distemper Virus (CDV), Phocine herpes virus, phocine adenovirus and Influenza A at prevalences of 5%, 6.4%, 21.7%, and 4% respectively. The genomes of CDV isolates collected in 2008 showed 99.59% identity with the 2000 Caspian seal CDV epizootic strain. A partial coding sequence for the Us2 gene from the Caspian seal herpes virus was identical to PhHV-1 isolate PB84, previously reported from a harbor seal (Phoca vitulina), while amplicon sequences for the adenovirus polymerase gene indicated a novel strain. ELISA assays detected exposure to Influenza A (55% of tested samples), adenovirus (25%), coronavirus (6%), CDV (8%), herpes virus (94%), Toxoplasma gondii (2.6%) and heartworm (1%). Hemagglutination inhibition (HI) tests detected exposure to Influenza B at a prevalence of 20%, and Leptospira microscopic agglutination tests detected suspected exposure to Leptospira serovars in 9% of tested samples. Overall, the risks, profile and prevalence of pathogens in Caspian seals appear comparable to other wild phocid seal populations. Our results suggest Caspian seals have exposure pathways to pathogens with epizootic potential or ability to cause significant morbidity, and that disease impacts could reduce the resilience of the population to other conservation threats. Caspian seals are listed as Endangered by the International Union for Conservation of Nature (IUCN), and we recommend that resources are invested to support further surveillance programs and to understand how anthropogenic pressures may influence future disease risks. A translated version of this abstract is available in Russian and Kazakh in the Supplementary Material (Presentation 1 and Presentation 2

Assessment of impacts and potential mitigation for icebreaking vessels transiting pupping areas of an ice-breeding seal

Icebreaker operations in the Arctic and other areas are increasing rapidly to support new industrial activities and shipping routes, but the impact on pinnipeds in these habitats is poorly explored. We present the first quantitative study of icebreakers transiting ice-breeding habitat of a phocid seal and recommendations for mitigation. Impacts were recorded from the vessel bridge during seven ice seasons 2006–2013, for Caspian seals (Pusa caspica) breeding on the winter ice-field of the Caspian Sea. Impacts included displacement and separation of mothers and pups, breakage of birth or nursery sites and vessel-seal collisions. The flight distance of mothers with pups ahead was < 100 m, but measurable disturbance occurred at distances exceeding 200 m. Separation distances of pups from mothers were greatest for seals < 10 m to the side of the vessel, and declined with increasing distance from the vessel. The relative risk of separation by ≥ 20 m was greatest for distances < 50 m from the vessel path. Seals on flat ice were more likely to be separated or displaced by ≥ 20 m than seals in an ice rubble field. The relative risk of vessel collisions with mothers or pups was significantly greater at night when breaking new channels (12.6 times), with vessel speeds ≥ 4 kn (7.8 times). A mitigation hierarchy is recommended for the Caspian Sea which could be applied to Arctic pinnipeds, including reducing icebreaker transits during critical periods, and using data from aerial surveys to plan routes to minimise encounters with seals. Where pre-emptive avoidance is not possible, recommendations include maintaining a safe separation from breeding seals at least 50 m beyond the distance at which measurable disturbance occurs, speed limits, use of thermal imaging at night, dedicated on-board Seal Observers, and training of vessel officers to take effective reactive measures

Data associated with 'Assessment of impacts and potential mitigation for icebreaking vessels transiting pupping areas of an ice-breeding seal. Biological Conservation (2017), http://dx.doi.org/10.1016/j.biocon.2017.05.028'

A zip file archive - Original data for the above paper comprising i) a text file in ‘.csv’ format organised by columns and rows, with context and behavioural data relating to individual vessel-seal encounters; ii) A PDF giving text definitions of variables and column contents

Assessment of Caspian Seal By-Catch in an Illegal Fishery Using an Interview-Based Approach.

The Caspian seal (Pusa caspica) has declined by more than 90% since 1900 and is listed as endangered by IUCN. We made the first quantitative assessment of Caspian seal by-catch mortality in fisheries in the north Caspian Sea by conducting semi-structured interviews in fishing communities along the coasts of Russia (Kalmykia, Dagestan), Kazakhstan and Turkmenistan. We recorded a documented minimum by-catch of 1,215 seals in the survey sample, for the 2008-2009 fishing season, 93% of which occurred in illegal sturgeon fisheries. Due to the illegal nature of the fishery, accurately quantifying total fishing effort is problematic and the survey sample could reflect less than 10% of poaching activity in the north Caspian Sea. Therefore total annual by-catch may be significantly greater than the minimum documented by the survey. The presence of high by-catch rates was supported independently by evidence of net entanglement from seal carcasses, during a mass stranding on the Kazakh coast in May 2009, where 30 of 312 carcasses were entangled in large mesh sturgeon net remnants. The documented minimum by-catch may account for 5 to 19% of annual pup production. Sturgeon poaching therefore not only represents a serious threat to Caspian sturgeon populations, but may also be having broader impacts on the Caspian Sea ecosystem by contributing to a decline in one of the ecosystem's key predators. This study demonstrates the utility of interview-based approaches in providing rapid assessments of by-catch in illegal small-scale fisheries, which are not amenable to study by other methods

Vital rates for Caspian seals during the periods 1930–1964 and 1965–2005.

<p>Three pup survival rates, i.e. 0.8<i>p</i>_p, <i>p</i>_p, or 1.2<i>p</i>_p, are used to attain a realistic span for population size in 1867.</p

Collapse of a Marine Mammal Species Driven by Human Impacts

<div><p>Understanding historical roles of species in ecosystems can be crucial for assessing long term human impacts on environments, providing context for management or restoration objectives, and making conservation evaluations of species status. In most cases limited historical abundance data impedes quantitative investigations, but harvested species may have long-term data accessible from hunting records. Here we make use of annual hunting records for Caspian seals (<em>Pusa caspica</em>) dating back to the mid-19^th century, and current census data from aerial surveys, to reconstruct historical abundance using a hind-casting model. We estimate the minimum numbers of seals in 1867 to have been 1–1.6 million, but the population declined by at least 90% to around 100,000 individuals by 2005, primarily due to unsustainable hunting throughout the 20^th century. This collapse is part of a broader picture of catastrophic ecological change in the Caspian over the 20^th Century. Our results combined with fisheries data show that the current biomass of top predators in the Caspian is much reduced compared to historical conditions. The potential for the Caspian and other similar perturbed ecosystems to sustain natural resources of much greater biological and economic value than at present depends on the extent to which a number of anthropogenic impacts can be harnessed.</p> </div

Estimated minimum total female population size (solid line) and the number adult females (dashed line) in the Caspian for the period 1867–2005 as based on historical hunting records (<b>Fig. 1</b>).

<p>The hunt during the 1960s led to a rapid decline in population size.</p

Total registered harvest of Caspian seals (solid line) and the number of pups (dashed line) for the period 1867–2005.

<p>Based on published hunting records <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043130#pone.0043130-Sklabinskij1" target="_blank">[14]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043130#pone.0043130-Dorofeev1" target="_blank">[15]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043130#pone.0043130-Badamshin1" target="_blank">[16]</a>. Data for recent years are derived from Russian Federal Fisheries Agency reports <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043130#pone.0043130-Russian1" target="_blank">[29]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043130#pone.0043130-Russian2" target="_blank">[30]</a>.</p

The population growth rate of the Caspian seal population from 1867 to 2006 has fluctuated significantly because of the variable hunting pressure.

<p>The population growth rate of the Caspian seal population from 1867 to 2006 has fluctuated significantly because of the variable hunting pressure.</p