Man-induced Environmental Factors in Relation to Fertility Changes in Pinnipeds

Reijnders, P.J.H.

doi:10.1017/s0376892900013503

Cited by 22 publications

(4 citation statements)

References 13 publications

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“…The probability of beluga presence decreased closer to both coastal cities and oil rigs. This finding may reflect the fact that human communities and oil development areas are associated with higher boat traffic (Allen et al 1984), air traffic (Moore et al 2000), and pollution (Reijnders 1984). However, these results should be interpreted with caution, as most of the human communities are located on the east coast of the lower inlet, and oil platforms are located well south of the Susitna Delta where belugas are commonly seen in the summer.…”

Section: Discussionmentioning

confidence: 97%

Identifying essential summer habitat of the endangered beluga whale Delphinapterus leucas in Cook Inlet, Alaska

Goetz¹,

Montgomery

Hoef³

et al. 2012

Endang. Species. Res.

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In response to the critically low numbers of beluga whales Delphinapterus leucas in Cook Inlet, Alaska, USA, the US federal government listed this isolated population as endangered in 2008. Despite the curtailment of subsistence hunting in 1999, the abundance of Cook Inlet belugas has remained low (< 400 whales), with no obvious signs of recovery. As habitat is a critical component of population viability, our goal was to identify habitat selected by beluga whales. We developed predictive habitat models from the distribution and group size of beluga whales observed between 1994 and 2008. We fit a 2-part hurdle model to describe the physical and anthropogenic factors that influence (1) beluga presence (mixed model logistic regression) and (2) beluga count data (mixed model Poisson regression). Beluga presence was negatively associated with sources of anthropogenic disturbance and positively associated with fish availability and access to tidal flats and sandy substrate. Beluga group size was positively associated with tidal flats and proxies for seasonally available fish. We produced habitat maps for beluga presence, group size, and the expected number of belugas in each 1 km 2 cell of Cook Inlet. These maps distinguish suitable habitat which could prove integral to the sustainability and recovery of the Cook Inlet beluga whale population.

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Section: Discussionmentioning

confidence: 97%

Identifying essential summer habitat of the endangered beluga whale Delphinapterus leucas in Cook Inlet, Alaska

Goetz¹,

Montgomery

Hoef³

et al. 2012

Endang. Species. Res.

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“…The bioaccumulation of contaminants, particularly poly-chlorinated biphenyls (PCBs) and other organo-halogens, is a serious conservation concern for apex predators in Arctic and sub-Arctic regions due to atmospheric cycling that causes this region to be a worldwide sink for airborne pollutants (Norstrom and Muir 1994, Borrell and Reijnders 1999, Aguilar et al 2002. Organo-halogens act as endocrine disrupters and are known to impair reproduction in pinnipeds (Reijnders 1984, 1986, Aguilar et al 2002, Barron et al 2003. Data on PCB levels in Steller sea lions are limited.…”

Section: Discussionmentioning

confidence: 99%

Age‐structured Modeling Reveals Long‐term Declines in the Natality of Western Steller Sea Lions

Holmes

Fritz

York³

et al. 2007

Ecological Applications

113

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Since the mid-1970s, the western Steller sea lion (Eumetopias jubatus), inhabiting Alaskan waters from Prince William Sound west through the Aleutian Islands, has declined by over 80%. Changing oceanographic conditions, competition from fishing operations, direct human-related mortality, and predators have been suggested as factors driving the decline, but the indirect and interactive nature of their effects on sea lions have made it difficult to attribute changes in abundance to specific factors. In part, this is because only changes in abundance, not changes in vital rates, are known. To determine how vital rates of the western Steller sea lion have changed during its 28-year decline, we first estimated the changes in Steller sea lion age structure using measurements of animals in aerial photographs taken during population surveys since 1985 in the central Gulf of Alaska (CGOA). We then fit an age-structured model with temporally varying vital rates to the age-structure data and to total population and pup counts. The model fits indicate that birth rate in the CGOA steadily declined from 1976 to 2004. Over the same period, survivorship first dropped severely in the early 1980s, when the population collapsed, and then survivorship steadily recovered. The best-fitting model indicates that in 2004, the birth rate in the central Gulf of Alaska was 36% lower than in the 1970s, while adult and juvenile survivorship were close to or slightly above 1970s levels. These predictions and other model predictions concerning population structure match independent field data from mark-recapture studies and photometric analyses. The dominant eigenvalue for the estimated 2004 Leslie matrix is 1.0014, indicating a stable population. The stability, however, depends on very high adult survival, and the shift in vital rates results in a population that is more sensitive to changes in adult survivorship. Although our modeling analysis focused exclusively on the central Gulf of Alaska, the western Gulf of Alaska and eastern Aleutians show a similar pattern of declining pup fraction with no increase in the juvenile, or pre-breeding, fraction. This suggests that declining birth rate may be a problem for western Steller sea lions across the Gulf of Alaska and into the Aleutian Islands.

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“…This result seems logical, as human populations are associated with foot traffic (Kenyon 1972, Moss 1992, car traffic, boat traffic (Allen et al 1984, Watts 1996, air traffic (Moore et al 2000) and pollution (Reijnders 1984). Anthropogenic disturbance can lead seals to avoid or completely abandon haul-out areas (Sullivan 1980, da Silva & Terhune 1988).…”

Section: Discussionmentioning

confidence: 99%

Spatial modeling of haul-out site use by harbor seals in Cook Inlet, Alaska

Montgomery¹,

Hoef²,

Boveng³

2007

Mar. Ecol. Prog. Ser.

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Harbor seals Phoca vitulina haul out on land to give birth to and rear their pups, rest, escape aquatic predation and molt. The choice of a haul-out site is therefore fundamental to survival and reproduction. Aerial surveys of harbor seals were conducted in Cook Inlet, Alaska, to investigate the seals' selection of various environmental characteristics of haul-out sites. Eight surveys from April, June, August and October were performed to understand how haul-out site use varies seasonally. A GIS database describing all potential haul-out habitats in the study area was created by acquiring separate data sets on bathymetry, sea-bed type, proximity to sources of anthropogenic disturbance, prey availability, biological wave exposure and substrate type. Because harbor seal abundance and several environmental features varied temporally, 4 separate models were developed to account for conditions specific to each survey month. Spatial regression analyses, which allowed data to be spatially autocorrelated, were used to identify the relationships between harbor seal abundance and environmental variables associated with haul-out sites. Harbor seals were found to haul out near available prey and to avoid areas high in anthropogenic disturbance. The seals also selected haul-out sites of rock substrate and those that were near deep water.

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Man-induced Environmental Factors in Relation to Fertility Changes in Pinnipeds

Cited by 22 publications

References 13 publications

Identifying essential summer habitat of the endangered beluga whale Delphinapterus leucas in Cook Inlet, Alaska

Identifying essential summer habitat of the endangered beluga whale Delphinapterus leucas in Cook Inlet, Alaska

Age‐structured Modeling Reveals Long‐term Declines in the Natality of Western Steller Sea Lions

Spatial modeling of haul-out site use by harbor seals in Cook Inlet, Alaska

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