Harbor Seals Phoca Vitulina Richardsi Research Articles

Skin histology and its role in heat dissipation in three pinniped species.

BackgroundPinnipeds have a thick blubber layer and may have difficulty maintaining their body temperature during hot weather when on land. The skin is the main thermoregulatory conduit which emits excessive body heat.MethodsThorough evaluation of the skin histology in three pinniped species; the California sea lion-Zalophus californianus, the Pacific harbor seal-Phoca vitulina richardsi, and the Northern elephant seal-Mirounga angustirostris, was conducted to identify the presence, location and distribution of skin structures which contribute to thermoregulation. These structures included hair, adipose tissue, sweat glands, vasculature, and arteriovenous anastomoses (AVA). Thermal imaging was performed on live animals of the same species to correlate histological findings with thermal emission of the skin.ResultsThe presence and distribution of skin structures directly relates to emissivity of the skin in all three species. Emissivity of skin in phocids (Pacific harbor and Northern elephant seals) follows a different pattern than skin in otariids (California sea lions). The flipper skin in phocids tends to be the most emissive region during hot weather and least emissive during cold weather. On the contrary in otariids, skin of the entire body has a tendency to be emissive during both hot and cold weather.ConclusionHeat dissipation of the skin directly relates to the presence and distribution of skin structures in all three species. Different skin thermal dissipation patterns were observed in phocid versus otariid seals. Observed thermal patterns can be used for proper understanding of optimum thermal needs of seals housed in research facilities, rescue centers and zoo exhibits.

Persistent decline in abundance of harbor seals Phoca vitulina richardsi over three decades in Aialik Bay, an Alaskan tidewater glacial fjord

Glacial ice calved from tidewater glaciers in Alaska provides an important haulout habi- tat for harbor seals Phoca vitulina richardsi, and its extent and ecological influence is being reduced by climate change. The number of harbor seals using glacial ice adjacent to Aialik Glacier, central Gulf of Alaska, declined by 93% from 1979 to 2009. During this time, seals demonstrated variability in their selection of haulout locations, particularly during the molt. Near Pedersen Glacier, 6 km south of Aialik Glacier, the number of seals doubled from 2005 to 2007; this was followed by an equivalent loss from 2007 to 2009. This influx, which occurred during a period of cold marine conditions, was associated with the arrival of seals from locations outside Aialik Bay, rather than from movements of seals from Aialik Glacier. Nearly all pups were born near Aialik Glacier. Pup production, which was stable from 1979 to 1983, subsequently declined by 12.4% yr -1 through 1994. Although the rate of decline abated, the numbers of pups continued to decline by 4.6% annually from 1994 to 2009. The persistent decline of harbor seals in Aialik Bay is similar to that observed in Glacier Bay, southeast Alaska, but contrasts with trends at nonglacial sites in the Gulf of Alaska and southeast Alaska where populations have been increasing since the mid-1990s. Results indicate flexibility in selection of haul- out location and potentially the proportion of time seals are present on the ice. The persistent decline in pup production, however, raises concern over the future of harbor seals in previously important glacial pupping habitats and the integrity of unique glacial fjord ecosystems.

Evaluation of an Electric Gradient to Deter Seal Predation on Salmon Caught in Gill‐Net Test Fisheries

AbstractAn electric deterrent system was tested as an effective and safe method of deterring predation by Pacific harbor seals Phoca vitulina richardsi on sockeye salmon Oncorhynchus nerka and pink salmon Oncorhynchus gorbuscha caught in a Fraser River gill‐net test fishery. Seals were deterred from foraging in a test fishing gill net in the Fraser River by using a pulsed, low‐voltage DC electric gradient. Salmon catch per unit effort (CPUE) was significantly greater for the treated (electric) section of the gill net than for the nontreated section (marginal mean CPUE = 4.0/1,000 m · min versus 1.0/1,000 m · min), and there was no overlap in the 95% confidence intervals for the two treatments. There were no apparent injuries to any animals during the study. This previously undocumented nonlethal technology demonstrates the potential to reduce pinniped predation on salmon, with meaningful implications for fisheries management agencies that rely on gill‐net test fisheries in freshwater rivers frequented by pinnipeds.

Descriptive account of long-term health and behavior of two satellite-tagged captive harbor seals Phoca vitulina

The use of satellite tags to monitor pinnipeds in their natural habitats has become a common practice. However, near-continuous long-term observations of the behavior of tagged ani- mals, the process of tag detachment, and regular close examination of the tagging site to detect any development of tag-induced lesions have not been reported. The present study investigated these issues. Dummy satellite tags were glued to two captive male Pacific harbor seals Phoca vitulina richardsi using mesh or no mesh attachment. Tag attachment and animal health and behavior were monitored during the 8 mo attachment period. No tag-associated changes in animal health or behav- ior were noted until the tags started to loosen a few days before detachment. We found no differences in the strength or length of attachment associated with mesh or no mesh attachment. There was a small area of superficial skin irritation associated with the mesh attachment due to cracked epoxy rubbing against the seal. Although this was a small pilot study, we concluded that the satellite tag attachment and detachment processes were without significant adverse effect, that the tagged seals' behavior was not significantly altered, and that it is likely that these findings will hold true for other small phocid seals.

Evidence of bottom-up control of diet driven by top-down processes in a declining harbor seal Phoca vitulina richardsi population

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 374:287-300 (2009) - DOI: https://doi.org/10.3354/meps07719 Evidence of bottom-up control of diet driven by top-down processes in a declining harbor seal Phoca vitulina richardsi population Jason K. Herreman1,*, Gail M. Blundell2, Merav Ben-David1 1Department of Zoology and Physiology, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, USA 2Alaska Department of Fish and Game, Division of Wildlife Conservation, PO Box 110024, Juneau, Alaska 99811-0024, USA *Email: jkherreman@hotmail.com ABSTRACT: Two mechanisms of population control dominate most biological systems: bottom-up and top-down regulation. It is possible, however, that top-down mediation may lead to bottom-up control of a population if predators simultaneously compete for the same prey. Harbor seal Phoca vitulina richardsi populations in Glacier Bay (GB) and Prince William Sound (PWS), Alaska, have declined drastically since the 1970s, with PWS recently stabilizing and GB continuing to decline. Hypotheses for the declines include both bottom-up and top-down processes. We hypothesized that increased competition and predation risk are causing harbor seals in GB to forage on lower quality prey. We combined analyses of prey remains in scat and stable carbon and nitrogen isotope ratios in blood and hair to compare seal diets in these areas. Seal diets in GB and PWS varied spatially and temporally due to changes in resource availability and sexual segregation. Adults showed clear divergence in diet during specific times of the year in both areas. Sexual segregation of diet in GB was most prevalent during spring and fall, while in PWS segregation was greatest during late summer. Diet of seals in PWS showed annual variation not found in GB, likely following prey cycles. In GB during summer, all seals switched to a diet with a lower fat content, including more intertidal/demersal species such as rockfish and sculpin. This switch coincided with an increase in competitors and predators entering GB. The change in diet, combined with higher emigration of harbor seals out of GB, suggest that increased competition and risk of predation may contribute to overall population declines. KEY WORDS: Population decline · Phoca vitulina richardsi · Feces · Pinnipeds · Prey remains · Sexual segregation · Stable isotopes Full text in pdf format PreviousNextCite this article as: Herreman JK, Blundell GM, Ben-David M (2009) Evidence of bottom-up control of diet driven by top-down processes in a declining harbor seal Phoca vitulina richardsi population. Mar Ecol Prog Ser 374:287-300. https://doi.org/10.3354/meps07719 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 374. Online publication date: January 13, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Fatty acid signatures reveal fine scale structure of foraging distribution of harbor seals and their prey in Prince William Sound, Alaska

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 151:255-271 (1997) - doi:10.3354/meps151255 Fatty acid signatures reveal fine scale structure of foraging distribution of harbor seals and their prey in Prince William Sound, Alaska Iverson SJ, Frost KJ, Lowry LF Fatty acid signature analysis was used to investigate the diet and the spatial scales of foraging in harbor seals Phoca vitulinarichardsi in Prince William Sound (PWS) and elsewhere in the Gulf of Alaska. Blubber samples collected in 1994 and 1995 from 104 harbor seals from PWS, Kodiak Island, and southeast Alaska were analyzed for fatty acid composition. A total of 163 potential prey samples representing 10 taxa were collected and individually analyzed for total fat content and fatty acid composition. Approximately 70 fatty acids and isomers were found in both harbor seals and their prey. Classification and regression tree analysis was used to classify seals and prey according to their fatty acid signatures. Large differences were found in the fatty acid composition of blubber from seals sampled at Kodiak, southeast Alaska and PWS, over a broad geographical scale of 400 to 800 km. Additionally, fatty acid signatures distinguished seals from different regions within PWS, as well as on fine-scale resolutions of specific haulout sites within 9 to 15 km of one another. These findings suggest that seals forage site-specifically. These conclusions are supported by prey fatty acid patterns, which also differed on similarly small spatial scales within PWS. Not only could prey species such as herring Clupea pallasi and pollock Theragra chalcogramma be differentiated from one another using fatty acid signatures, but they could also be distinguished by size-class and location within PWS, reflecting differences in diet with age and as well as with fine-scale habitat. Results from this study are consistent with both satellite data from tagged harbor seals and stomach content analyses of forage fish species in PWS. Although preliminary, analyses suggest that large herring and pollock, as well as flatfish, may have dominated the diet of seals in southern PWS, whereas diets of seals in northern and eastern PWS may have been comprised more of small size classes of herring and pollock, and perhaps other items such as cephalopods, sandlance Ammodyteshexapterus, cod Gadus macrocephalus, and shrimp. We conclude that fatty acid signature analysis will be an important contribution to understanding marine food webs in estuarine and other marine environments. Foraging ecology · Fatty acid signatures · Harbor seals · Fish · Spatial scales Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 151. Publication date: May 22, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Coronary blood flow and myocardial segment dimensions during simulated dives in seals.

Three harbor seals Phoca vitulina richardsi and five spotted seals Phoca vitulina largha were used in studies of acute episodes of local myocardial ischemia in open-chest, anesthetized animals and of coronary blood flow and regional function as indicated by left ventricular segment dimensions during experimentally simulated dives of conscious, instrumented animals. We observed that seal myocardium, in which there are few coronary anastomoses, responded to brief local occlusion with prompt local dysfunction and systolic bulging; coronary flow in the nondiving seal oscillated irregularly and declined with spontaneous apnea and related falling heart rate; flow continued to oscillate but was much reduced during dives, frequently ceasing entirely for periods as long as 45 s; ventricular segment dimension shortening was reduced intermittently during dives; and elevated heart rate induced during dives by cardiac pacing or by administration of atropine diminished or eliminated the reductions in coronary blood flow. Responses of seal heart reflect the reduction in cardiac metabolic demand during diving and the seal's myocardial adaptation for enhanced anaerobic glycolysis. The seal heart can maintain mechanical function during dives with minimal coronary perfusion, despite the progressive and ultimately profound hypoxia, hypercapnia, and acidosis. Reduced cardiac metabolism, copious glycolytic reserves, and metabolite washout by intermittent brief bursts of coronary blood flow are apparently sufficient to support continued cardiac function, even though the seal heart has little tolerance for acute localized ischemia.