California Sea Lions Zalophus Californianus Research Articles

Revision of Corynosoma australe Johnston, 1937 (Acanthocephala: Polymorphidae) from a North American population using novel SEM images, Energy Dispersive X-ray Analysis, and molecular analysis.

We describe a population of the acanthocephalan Corynosoma australe Johnston, 1937 (Polymorphidae) from a California sea lion Zalophus californianus (Lesson, 1828) in California using novel scanning electron microscopy (SEM) images, Energy Dispersive x-ray analysis (EDXA), and molecular analysis for the first time. The taxonomic history of C. australe is replete with accounts using only line drawings some of which proved erroneous. The distribution of ventral spines on the female trunk has been the primary distinction between C. australe and Corynosoma obtuscens Lincicome, 1943, its junior synonym; being continuous in the latter but discontinuous posteriorly in the former species. The distribution of ventral spines is invariably discontinuous in males. Our redescription and SEM images help to resolve this issue further validating the synonymy. Morphological variability has been documented between our California population and others from various host species in California, South Australia, South Shetlands, and the Argentinian coast. Our SEM images document features not previously detectable in line drawings, erroneously reported or missed in previous accounts. The EDXA spectra show high levels of calcium and phosphorous and low levels of sulfur characteristic of C. australe. EDXA for other species of Corynosoma Lühe, 1904 provide support for the diagnostic distinction of C. australe. EDXA spectra were shown to be species specific and have diagnostic value in the taxonomy of the Acanthocephala. Our molecular analysis used amplification of 18S of ribosomal DNA and cytochrome c oxidase 1 (Cox1) gene. Phylogenetic analyses for Cox1 gene revealed a close relationship between Corynosoma hannae Zdzitowiecki, 1984 and C. australe. The phylogenetic trees confirmed that the isolates belonged to C. australe. The haplotype network inferred by Cox1 with C. australe sequences revealed that haplotypes clearly separated from each other and formed clusters related to samples from the Northern Hemisphere (the USA and Mexico), and the second from the Southern Hemisphere (Argentina, Brazil and Peru).

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 4

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 4

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 3

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 3

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 2

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 2

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 1

Consumption of Pacific salmon (Oncorhynchus spp.) by California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus) in northwest Washington during 2010–2013: supplementary table 1

Temporary Hearing Threshold Shift in California Sea Lions (Zalophus californianus) Due to One-Sixth-Octave Noise Bands Centered at 0.6 and 1 kHz

To determine the frequency-dependent susceptibility of California sea lions (Zalophus californianus) to noise-induced temporary hearing threshold shift (TTS), one of two subjects were exposed for 60 minutes to two continuous one-sixth-octave noise bands (NBs) as fatiguing sounds: one centered at 0.6 kHz, at sound pressure levels (SPLs) of 168 to 174 dB re 1 µPa (sound exposure levels [SELs] of 204 to 210 dB re 1 µPa2s), or one centered at 1 kHz, at SPLs of 144 to 159 dB re 1 µPa (SELs of 180 to 195 dB re 1 µPa2s). Using a psychoacoustic technique, TTSs were quantified at 0.6, 0.85, 1, 1.2, 1.4, and 2 kHz (at the center frequency of each NB, half an octave higher, and one octave higher). When significant TTS occurred, higher SELs resulted in greater TTSs. In the sea lion that was tested 1 to 4 minutes after exposure to the fatiguing sounds, the largest TTSs occurred when the hearing test frequency was half an octave higher than the center frequency of the two fatiguing sounds. The highest TTS levels elicited were 8.7 dB at 0.85 kHz and 9.6 dB at 1.4 kHz. When their hearing was tested at the same time after the fatiguing sounds stopped, initial TTSs and hearing recovery patterns were similar in both sea lions. These findings will contribute to the protection of hearing of species in the Otariidae family from anthropogenic noise by facilitating the development of an evidence-based underwater sound weighting function.

Temporary Hearing Threshold Shift in California Sea Lions (Zalophus californianus) Due to One-Sixth-Octave Noise Bands Centered at 8 and 16 kHz: Effect of Duty Cycle and Testing the Equal-Energy Hypothesis

To determine the frequency-dependent susceptibility of California sea lions (Zalophus californianus) to noise-induced temporary hearing threshold shift (TTS), two subjects were exposed for 60 min to two fatiguing sounds: continuous one-sixth-octave noise bands (NBs) centered at 8 kHz (at sound exposure levels [SELs] of 166 to 190 dB re 1 µPa2s) and at 16 kHz (at SELs of 183 to 207 dB re 1 µPa2s). Using a psychoacoustic technique, TTSs were quantified at 8, 11.3, 16, 22.4, and 32 kHz (at the center frequency of each NB, half an octave higher, and one octave higher). For both NBs, higher SELs resulted in greater TTSs. In the SEL ranges that were tested, the largest TTSs occurred when the hearing test frequency was half an octave higher than the frequency of the fatiguing sound. When their hearing was tested at the same time after the fatiguing sounds stopped, initial TTSs and hearing recovery patterns were similar in both sea lions. The effect of fatiguing sound duty cycle on TTS was investigated with the 8 kHz NB, using 1,600 ms signals at a mean sound pressure level (SPL) of 154 dB re 1 µPa. Duty cycle reduction from 100 to 90% resulted in a large decrease in TTS; no TTS was observed at duty cycles ≤ 30%. The equal-energy hypothesis was tested with the 8 kHz NB and found to hold true: five combinations of SPL and exposure duration all resulting in a 182 dB SEL produced similar initial TTSs in both sea lions. These findings will contribute to the protection of otariid hearing from anthropogenic noise by facilitating the development of evidence-based underwater sound weighting functions. Our results also show that the introduction of short inter-pulse intervals to underwater sounds aids in the protection of otariid hearing by allowing recovery to take place.

Spatio-temporal diet variability of the California sea lion Zalophus californianus in the southern California Current Ecosystem

Characterizing predator diets is essential to understanding food web dynamics. We investigated the dietary breadth and variation of the California sea lion (CSL) Zalophus californianus at 3 of the California Channel Islands from 1981-2015. Prey species were identified from hard parts and soft-tissue remains of pyrosomes recovered from fecal samples, revealing a diverse diet of fish and cephalopods. Percent frequency of occurrence and percent split-sample frequency of occurrence were used to describe long-term trends, correlations between prey taxa, diet diversity, and diet similarity. The most common of 142 prey taxa identified to species were market squid Doryteuthis opalescens, northern anchovy Engraulis mordax, shortbelly rockfish Sebastes jordani, jack mackerel Trachurus symmetricus, Pacific sardine Sardinops sagax, Pacific hake Merluccius productus, and Pacific mackerel Scomber japonicus. Dietary differences were observed between male and female sea lions, and between animals from different islands and seasons. Intra-island diets at 2 locations were more similar than inter-island diets. Important inter-annual and decadal changes in diet were identified. CSL diet shifted from an anchovy-based diet in the 1980s to a market squid based-diet in the 1990s and 2000s, with other prey taxa being consumed more frequently when consumption of those 2 main prey declined. Prey-switching likely provides flexibility needed in the dynamic California Current Ecosystem, and may allow CSLs to adapt to changes in food supply and availability driven by climate change.

Nasopulmonary mites (Halarachnidae) of coastal Californian pinnipeds: Identity, prevalence, and molecular characterization

Mites from the family Halarachnidae Oudemans 1906 are obligate endoparasites that colonize the respiratory tracts of free-living and captive marine mammals. Infestations can range from mild to severe and result in respiratory tract irritation or impairment. Nasopulmonary acariasis was determined to be a contributing cause of death among several southern sea otters Enhydra lutris nereis Merriam 1904 in a longitudinal study of otter mortality, and proximity to Pacific harbor seals Phoca vitulina richardii Gray 1864 was a significant risk factor for sea otter infestation. Beyond scattered opportunistic reports, each halarachnid mite species' affinity for particular hosts and the extent of mite transmission between host species is poorly understood. We investigated the identity and prevalence of nasopulmonary mites from Pacific harbor seals, California sea lions Zalophus californianus Lesson 1828, northern elephant seals Mirounga angustirostris Gill 1866, northern fur seals Callorhinus ursinus Linnaeus 1758, and Guadalupe fur seals Arctocephalus philippii townsendi Merriam 1897 to complement published nasopulmonary mite findings from sympatric southern sea otters during a comparable timeframe. Halarachnid mite infestation was common among California sea lions (74.1%), northern fur seals (73.3%), and northern elephant seals (46.6%), but was less common among harbor seals (18.7%) and Guadalupe fur seals (8.8%). Observed host-mite relationships suggest a distinct host specificity, with genus Orthohalarachne infesting otariids, and genus Halarachne infesting phocids and lutrinids along the California coast. Harbor seals and southern sea otters were the primary hosts of H. halichoeri, but one nothern elephant seal was infested with both H. miroungae and a single H. halichoeri. We also present the first high-resolution SEM images for H. miroungae and O. attenuata and possible evidence for a new host record for H. halichoeri.

Diphyllobothrium sprakeri n. sp. (Cestoda: Diphyllobothriidae): a hidden broad tapeworm from sea lions off North and South America

BackgroundThe systematic of several marine diphyllobothriid tapeworms of pinnipeds has been revised in recent years. However, 20 species of Diphyllobothrium from phocids and otariids are still recognized as incertae sedis. We describe a new species of Diphyllobothrium from the intestine of California sea lions Zalophus californianus (Lesson) (type-host) and South American sea lions Otaria flavescens (Shaw).MethodsZalophus californianus from the Pacific coast of the USA and O. flavescens from Peru and Argentina were screened for parasites. Partial fragments of the large ribosomal subunit gene (lsrDNA) and the cytochrome c oxidase subunit 1 (cox1) mitochondrial gene were amplified for 22 isolates. Properly fixed material from California sea lions was examined using light and scanning electron microscopy.ResultsA total of four lsrDNA and 21 cox1 sequences were generated and aligned with published sequences of other diphyllobothriid taxa. Based on cox1 sequences, four diphyllobothriid tapeworms from O. flavescens in Peru were found to be conspecific with Adenocephalus pacificus Nybelin, 1931. The other newly generated sequences fall into a well-supported clade with sequences of a putative new species previously identified as Diphyllobothrium sp. 1. from Z. californianus and O. flavescens. A new species, Diphyllobothrium sprakeri n. sp., is proposed for tapeworms of this clade.ConclusionsDiphyllobothrium sprakeri n. sp. is the first diphyllobothriid species described from Z. californianus from the Pacific coast of North America, but O. flavescens from Argentina, Chile and Peru was confirmed as an additional host. The present study molecularly confirmed the first coinfection of two diphyllobothriid species in sea lions from the Southern Hemisphere.Graphical

Campylobacter pinnipediorum subsp. caledonicus and C. pinnipediorum subsp. pinnipediorum recovered from abscesses in pinnipeds.

Campylobacter pinnipediorum was described recently for isolates recovered from pinnipeds. The novel species was further split into 2 subspecies based on host and geography, with C. pinnipediorum subsp. pinnipediorum recovered from otariid seals in California (USA) and C. pinnipediorum subsp. caledonicus recovered from phocid seals in Scotland. We report details of the infections of 7 pinnipeds from which C. pinnipediorum was isolated: C. pinnipediorum subsp. caledonicus was isolated from 2 harbour seals Phoca vitulina and a single grey seal Halichoerus grypus, and C. pinnipediorum subsp. pinnipediorum was isolated from California sea lions Zalophus californianus. Six of the isolates were recovered from samples collected at post-mortem investigation. In 2 of the Scottish seals and in 3 of the California seals, C. pinnipediorum was the sole bacterial isolate recovered from abscesses present and suggests they may have resulted from conspecific or intraspecific bite wounds.

Estimating population‐specific predation effects on Chinook salmon via data integration

Abstract Recent success in the conservation of many marine mammals has resulted in new management challenges due to increasing conflict with fisheries. Increasing predation by pinnipeds on threatened salmon is of particular concern. Seemingly, pinniped conservation is now in conflict with the recovery of threatened salmon, creating a dilemma for managers. We use the Lower Columbia River as a case study for examining the relationship between seasonal California sea lion Zalophus californianus abundance and survival of threatened salmon. To quantify mortality associated with increasing sea lion abundance, we examined the effect of seasonal sea lion abundance on adult Chinook salmon Oncorhynchus tshawytscha survival during migrations through the Lower Columbia River. We integrated data on survival with data on population‐specific migration timing, allowing quantification of the relationship between sea lion abundance and survival in 18 populations of spring–summer Chinook salmon listed as Threatened or Endangered under the U.S. Endangered Species Act. Of the 18 populations examined, earlier migrating populations experienced lower survival in association with increased exposure to higher sea lion abundance. We estimated that in years with high sea lion abundance, the nine earliest‐migrating populations experienced an additional 21.1% (95% CI = 16.3–26.1) mortality compared to years with baseline sea lion abundance, while the nine latest migrating populations experienced an additional 10.1% (7.5–13.0). Synthesis and applications. Integrating datasets on seasonal survival and migration timing made it possible for us to estimate population‐specific mortality associated with increased sea lion abundance in the Lower Columbia River. This information could not be produced from any one dataset, highlighting the utility of data integration approaches. The mortality experienced by early migrating Chinook salmon suggests the potential for demographic and evolutionary consequences. Management actions such as hazing, relocating, or removing individuals that are frequent predators on salmon have been proposed. Identifying the management actions that will allow for socially and legally acceptable trade‐offs between multiple conservation and other social values will be facilitated by development of explicit multi‐species management frameworks. Continued monitoring will help to reduce the substantial uncertainty about the effect of pinnipeds on salmon and the predicted outcomes of alternative management actions.

Evidence of a ‘dinner bell’ effect from acoustic transmitters in adult Chinook salmon

The ‘dinner bell’ hypothesis posits that marine mammals hear or otherwise sense soundwaves produced by acoustic transmitters and use the signal to selectively prey on fish carrying them. A dual tagging study conducted during 2010 and 2011 supports this hypothesis. Results from this study revealed a significant difference in the survival of fish marked with passive integrated transponder (PIT) tags and those marked with active acoustic transmitters. Our objective had been to use both types of tags to study behavior and survival of migrating adult spring Chinook salmon Oncorhynchus tshawytscha at 2 different spatial scales. We tagged fish as they entered the Columbia River, USA, and monitored their survival and progress over a 193 km reach to Bonneville Dam (river km 234), its lowest impoundment. In 2010, estimated survival was 0.74 (95% CI, 0.62-0.86) for PIT-tagged fish but only 0.30 (0.15-0.45) for acoustic-tagged fish. Therefore, in 2011, we included archival tags and a sham acoustic transmitter group to help identify causes of the survival discrepancy. Survival was 0.75 (0.54-0.97) for sham transmitter fish and 0.73 (0.60-0.86) for PIT fish, but only 0.10 (0.00-0.24) for active acoustic transmitter fish. Our study area was replete with harbor seals Phoca vitulina, California sea lions Zalophus californianus, and Steller sea lions Eumetopias jubatus during both years. We suspect the most likely cause of survival differences between tag treatment groups was pinniped predation. Using temperature data from archival tags, we found evidence of such predation and support for a ‘dinner bell’ effect from acoustic transmitter tags.

Morphological and molecular evidence for synonymy of Corynosoma obtuscens Lincicome, 1943 with Corynosoma australe Johnston, 1937 (Acanthocephala: Polymorphidae).

Corynosoma obtuscens Lincicome, 1943 (Acanthocephala: Polymorphidae) is synonymised with Corynosoma australe Johnston, 1937 based on combined morphological and molecular evidence. Morphological comparison of C. obtuscens (24 males and 27 females) collected from a California sea lion Zalophus californianus (Lesson) in California, USA, with the type-specimens of C. obtuscens and C. australe, and with published data on C. australe collected from different hosts and regions showed no significant differences. The levels of genetic divergence in the cox1 sequences obtained from C. obtuscens from a California sea lion in the present study and C. australe from otariid seals from Argentina and penguins from Brazil ranged between 1.4-1.6% and was considered to represent intraspecific variability. Additionally, cox1 sequences were generated for Andracantha phalacrocoracis (Yamaguti, 1939), Corynosoma semerme (Forssell, 1904), C. strumosum (Rudolphi, 1802), C. validum Van Cleave, 1953 and C. villosum Van Cleave, 1953. Our results revealed inconsistency in the identification of material used as a source of the previously published sequence data for C. obtuscens and C. magdaleni Montreuil, 1958.

Vibrissa growth rate in California sea lions based on environmental and isotopic oscillations.

Pinniped vibrissae provide information on changes in diet at seasonal and annual scales; however, species-specific growth patterns must first be determined in order to interpret these data. In this study, a simple linear model was used to estimate the growth rate of vibrissae from adult female California sea lions (Zalophus californianus) from San Esteban Island in the Gulf of California, Mexico. The δ15N and δ13C values do not display a marked oscillatory pattern that would permit direct determination of the time period contained in each vibrissa; thus, time (age) was calculated in two ways: 1) based on the correlation between the observed number of peaks (Fourier series) in the δ15N profile and the length of each vibrissa, and 2) through direct comparison with the observed number of peaks in the δ15N profile. Cross-correlation confirmed that the two peaks in the δ15N profile reflected the two peaks in the chlorophyll-a concentration recorded annually around the island. The mean growth rate obtained from the correlation was 0.08 ± 0.01 mm d-1, while that calculated based on the observed number of peaks was 0.10 ± 0.05 mm d-1. Both are consistent with the rates reported for adult females of other otariid species (0.07 to 0.11 mm d-1). Vibrissa growth rates vary by individual, age, sex, and species; moreover, small differences in the growth rate can result in significant differences over the time periods represented by the isotopic signal. Thus, it is important to assess this parameter on a species-by-species basis.

Metazoan parasites of California sea lions (Zalophus californianus): A new data and review.

The population of California sea lion Zalophus californianus (CSL) has steadily increased during the last several decades. Despite extensive research addressing CSL biology and ecology performed during the last decades, there has been a minimal number of published papers documenting their parasite fauna. Our objective was to analyze the actual list of the metazoan parasites reported from CSLs and add new data on the age-related differences in the prevalence and biodiversity of the parasite community. There have been 33 species recorded but this study considers only 24 of them valid. Among them, 11 species are specific parasites of CSLs and 13 species are not specific. Additional species represent accidental infections or misidentifications. In total, 6653 helminths and 847 mites were collected and identified from 34 CSLs for this study. Six species of nematodes, Anisakis simplex sensu lato s. l. (prevalence 41%; intensity 7.6), Contracaecum ogmorhini s. l. (38%; 269.6), Pseudoterranova decipiens s. l. (29%; 33), P. azarazi (9%; 2.7), Acanthocheilonema odendhali (15%; 3.5) and Parafilaroides decorus were found. Two species of cestodes, Diphyllobothrium sp. (38%; 8.5) and Anophryocephalus sp. (15%; 14.6) represent novel undescribed species. Two species of trematodes, Apophallus zalophi (18%; 19.7) and Zalophotrema hepaticum (12%; 39.2), and five species of acanthocephalans, Corynosoma obtuscens (68%; 100.8), C. strumosum (53%; 4.6), Andracantha phalacrocoracis (3%; 1), Andracantha sp. (9%; 4.3) and Profilicollis altmani (6%; 8.5) were found. Mites Orthohalarchne attenuata (prevalence 85%) were found in the nasal cavity, while O. diminuata (21%) parasitized in the trachea and bronchi. The highest levels of infection with nematodes and trematodes were found in adult CSLs (3–16 years old), whereas the highest level of infection with acanthocephalans was found in young CSLs (pups and yearlings).

A multi-model approach to understanding the role of Pacific sardine in the California Current food web

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 617-618:307-321 (2019) - DOI: https://doi.org/10.3354/meps12504 A multi-model approach to understanding the role of Pacific sardine in the California Current food web Isaac C. Kaplan1,*, Tessa B. Francis2, André E. Punt3, Laura E. Koehn3, Enrique Curchitser4, Felipe Hurtado-Ferro3, Kelli F. Johnson3, Salvador E. Lluch-Cota5, William J. Sydeman6, Timothy E. Essington3, Nathan Taylor7, Kirstin Holsman8, Alec D. MacCall6, Phillip S. Levin9 1Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, 2725 Montlake Blvd E, Seattle, WA 98112, USA 2University of Washington Tacoma, Puget Sound Institute, Tacoma, WA 98421, USA 3School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195-5020, USA 4Department of Environmental Sciences, Rutgers University, 14 College Farm Road, Room 243, New Brunswick, NJ 08901, USA 5Centro de Investigaciones Biológicas del Noroeste, S.C., 23096 La Paz, BCS, Mexico 6Farallon Institute, 101 H Street, Suite Q, Petaluma, CA 94952, USA 7Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Rd, Nanaimo, BC V9T 6N7, Canada 8Alaska Fisheries Science Center, NOAA Fisheries, 7600 Sand Point Way NE, Building 4, Seattle, WA 98115, USA 9School of Environmental & Forest Sciences, University of Washington, Box 351200, Seattle, WA 98195, USA *Corresponding author: isaac.kaplan@noaa.govAdvance View available online April 17, 2018 ABSTRACT: We develop a multi-model approach to explore how abundance of a forage fish (Pacific sardine Sardinops sagax) impacts the ecosystem and predators in the California Current, a region where sardine and anchovy Engraulis mordax have recently declined to less than 10% of contemporary peak abundances. We developed or improved applications of 3 ecosystem modeling approaches: Ecopath, Model of Intermediate Complexity for Ecosystem assessment (MICE), and Atlantis. We also used Ecopath diets to predict impacts to predators using a statistical generalization of the dynamic Ecosim model (Predator Response to the Exploitation of Prey [PREP]). Models that included brown pelican Pelecanus occidentalis at the species level (MICE and Ecopath/PREP) both predict moderate to high vulnerability of brown pelicans to low sardine abundance. This vulnerability arises because sardine comprises a large fraction of their diet, and because other important prey (anchovy) also exhibit large population fluctuations. Two of the ecosystem models (MICE and Atlantis) suggest that California sea lions Zalophus californianus exhibit relatively minor responses to sardine depletion, due to having broader diets and lower reliance on another fluctuating species, anchovy. On the other hand, Ecopath/PREP suggests that sardine declines will have a stronger impact on California sea lions. This discrepancy may in part reflect structural differences in the models: Atlantis and MICE explicitly represent density dependence and age-structure, which can mitigate effects of prey depletion in these models. Future work should identify fisheries management strategies that are robust to uncertainties within and among models, rather than relying on single models to assess ecosystem impacts of management and forage fish abundance. KEY WORDS: Forage fish · Pacific sardine · California Current · Ecosystem model · California sea lion · Brown pelican · Multi-model approach Full text in pdf format Supplementary material PreviousNextCite this article as: Kaplan IC, Francis TB, Punt AE, Koehn LE and others (2019) A multi-model approach to understanding the role of Pacific sardine in the California Current food web. Mar Ecol Prog Ser 617-618:307-321. https://doi.org/10.3354/meps12504 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 617-618. Online publication date: May 16, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Dirofilaria immitis in pinnipeds and a\xa0new host record

BackgroundDirofilaria immitis is a mosquito-borne pathogen that is spreading worldwide, and the associated infection (i.e. dirofilariosis) is becoming a threat to animals and humans living in endemic areas. Little is known about the occurrence and risk of infection of D. immitis in pinnipeds. Here we report dirofilariosis by D. immitis in several pinniped species kept in captivity in Portugal.MethodsAnimals were housed in an oceanographic park located in Algarve, southern Portugal, a geographical area endemic for canine dirofilariosis. To assess the occurrence of D. immitis, blood was collected from the park’s resident pinniped population, which consisted of 16 animals (5 common seals Phoca vitulina, 2 grey seals Halichoerus grypus, 3 California sea lions Zalophus californianus and 6 South African fur seals Arctocephalus pusillus pusillus). Dirofilaria immitis nematodes were detected by real-time PCR and by the presence of circulating antigens. In addition, modified Knott’s technique was performed to detect circulating microfilariae. Necropsies and histopathological examination of two animals which died during the study were also conducted.ResultsOut of the 16 pinnipeds housed at the park, seven (43.8%) were positive for D. immitis by real-time PCR (3 P. vitulina, 2 Z. californianus and 2 A. p. pusillus), two of which (P. vitulina) were also positive for the nematode’s antigen. Additionally, D. immitis microfilariae were detected in one A. p. pusillus. Furthermore, several D. immitis specimens were retrieved from the right ventricle and pulmonary arteries at the necropsy of one P. vitulina and one A. p. pusillus.ConclusionsThis study provides new epidemiological data on D. immitis infection in pinnipeds diagnosed through clinical, molecular and pathological findings. Additionally, the South African fur seal is herein reported as a new host for this zoonotic filarioid. The situation herein described could also occur in other parks located in areas where canine dirofilariosis is endemic. Active surveillance and preventive measures of dirofilariosis in pinnipeds on a local and global scale are therefore vital to improve the early diagnosis and control of dirofilariosis.

Can fear conditioning repel California sea lions from fishing activities?

AbstractMarine mammal interactions with fisheries create conflicts that can threaten human safety, economic interests and marine mammal survival. A deterrent that capitalizes on learning mechanisms, like fear conditioning, may enhance success while simultaneously balancing welfare concerns and reduce noise pollution. During fear conditioning, individuals learn the cues that precede the dangerous stimuli, and respond by avoiding the painful situations. We tested the efficacy of fear conditioning using acoustic stimuli for reducing California sea lion Zalophus californianus interactions from two fishing contexts in California, USA; bait barges and recreational fishing vessels. We performed conditioning trials on 24 individual sea lions interacting with bait barges. We tested for acquisition of conditioned fear by pairing a neutral tone with a startle stimulus. Avoidance was strongest in response to the startle stimulus alone, but low when paired with a neutral tone. From actively fishing vessels, we tested for fear conditioning by exposing sea lions to a neutral tone followed by a startle pulse, a startle pulse alone or a no sound control. We conducted playbacks from 146 (including 48 no sound control) stops over two summer fishing seasons (2013, 2014). The startle stimulus decreased surfacing frequency, reduced bait foraging and increased surfacing distance from the vessel while the conditioned stimulus only caused a mild reduction in surfacing frequency with no other behavioral change. Exposing animals to a pair of a conditioned stimulus with a startle pulse did not achieve the intended management outcome. Rather, it generated evidence (in two study contexts) of immediate learning that led to the reduction of the unconditioned response. Taken together, our results suggest that for fear conditioning to be applied as a non‐lethal deterrent, careful consideration has to be given to individual behavior, the unconditioned/conditioned responses and the overall management goals.

Examining the metabolic cost of otariid foraging under varying conditions

In order to understand the effects of changing prey availability on dive behavior and energetic costs, behavior and metabolism must be measured simultaneously. Video dive analysis and open-flow respirometry were used to assess changes in dive behavior and energetics of two captive trained California sea lions (Zalophus californianus) in response to high and low prey densities and increased cost of swimming. Differences in dive duration, foraging duration, dive efficiency and foraging efficiency were examined between high and low prey encounter rates, and between standard and cost-increased dives. Changes in foraging metabolic rate (FVO2) and foraging carbon dioxide elimination (FVCO2) were also assessed across all four conditions. Both animals had longer dive durations, greater dive efficiency and lower FVO2 and FVCO2 levels at high prey encounter rates. Foraging metabolic rate and FVCO2 showed a slight increasing trend in cost-increased bouts for both animals, and surface interval durations were shorter. The results suggest that at high prey encounter rates animals minimize their metabolic rate to extend dive duration. These results also suggest that although FVCO2 decreases under high prey encounter rates, increasing the cost of transport keeps VCO2 levels elevated and increases the animal's oxygen debt. The authors hypothesize that as the level of work increases, the ability of the body to sequester CO2 into bicarbonate diminishes due to an inability of the proton buffering process within the blood and muscles to keep pace with increasing CO2 production. Therefore, CO2 may be a more sensitive physiological marker than O2 when examining the metabolic cost of foraging.