Estimating the demographic effective population size of the Saimaa ringed seal (Phoca hispida saimensis Nordq.)

Kokko, Hanna; Lindström, Jan; Ranta, Esa; Sipilä, Tero; Koskela, Jouni

doi:10.1017/s1367943098001061

Cited by 10 publications

(14 citation statements)

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“…Branching process models have not been widely used in conservation demography yet provide a useful means of assessing probability of population persistence (e.g. Kokko et al 1998). In such models, individuals survive and reproduce independently, with the life cycle of each individual characterized by the annual probabilities of survival, reproduction, changing age/ social classes, and by the probability distribution of litter size for each reproduction event.…”

Section: O D E L L I N G a P P R O A C Hmentioning

confidence: 99%

The impact on tigers of poaching versus prey depletion

Chapron

Miquelle

Lambert

et al. 2008

Journal of Applied Ecology

156

127

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Summary 1.There exists a continuing dilemma in prioritizing conservation actions for large carnivores. Habitat loss, poaching, and prey depletion have often been cited as the three primary threats, but there is debate over the relative importance of each. 2. We assess the relative importance of poaching and prey depletion rates, and use existing information in the literature and multi-type branching process and deterministic felid population models to address four lines of evidence used to infer that tiger populations are inherently resilient to high mortality rates. 3. Our results suggest that tigers, more so than leopards or cougars, require large populations to persist, are quite susceptible to modest increases in mortality, and less likely to recover quickly after population declines. Demographic responses that would ensure population persistence with mortality rates that are sustainable for cougars or leopards are biologically unrealistic for tigers. 4. We propose alternative interpretations of evidence used to suggest that tigers are inherently resilient to high mortality rates. In contrast to other solitary felids, tigers breed later and their inter-birth interval is larger, making them less resilient to poaching. A model used to support the contention that prey depletion has greater impact on population persistence than poaching appears to be based on false premises. Camera-trapping data that suggest positive population growth despite low survival rate cannot differentiate mortality from emigration, and does not differentiate the impact of varying survival rate on different sex-age classes; for example, low survival rate of dispersers is tolerable if survival rate of adult breeding females is high. 5. Synthesis and applications. While high prey numbers are essential to sustain tiger populations, our results suggest prey recovery efforts will not be sufficient if mortality rates reach 15%. Extrapolating demographic responses from other, even closely related species to develop conservation strategies can be misleading. Reduction of human-caused mortality, especially of resident breeding females, appears to be the most essential short-term conservation effort that must be made. Since mortality rates are usually unknown and generally stochastic in nature, any management policy that might reduce survival rates should be firmly avoided.

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Section: O D E L L I N G a P P R O A C Hmentioning

confidence: 99%

The impact on tigers of poaching versus prey depletion

Chapron

Miquelle

Lambert

et al. 2008

Journal of Applied Ecology

156

127

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“…The proportion of males participating in the reproduction is less well known, but males have underwater territories (Van Parijs et al 2000), and alfa males may outcompete subordinate males in the presence of mature females during the breeding season (e.g., Harkonen et al 1999, Van Parijs et al 2000. This would result in a female-biased sex ratio, and lower the effective population size correspondingly (Kokko et al 1998). However, using genetic estimates of paternity, Coltman et al (1998) concluded that the variance in male reproductive success was rather low, suggesting most males contribute to the mating.…”

Section: ( 4 )mentioning

confidence: 99%

“…However, this population has always been dispersed at several localities, and data from contemporary populations show that individuals exhibit strong site fidelity (e.g., Harkonen and Harding 2001). The resulting spatial structure of populations (Harkonen and Harding 2001) implies that the demographic effective population sizes were considerably smaller as compared with panmictic populations (Kokko et al 1998). Thus, isolation of a population of the size indicated by data presented in this study, would explain both the observed, and even larger, losses of genetic variation over a time span of 8,000 yr.…”

Section: Genetic Variation In the East Balticmentioning

confidence: 99%

Colonization History of the Baltic Harbor Seals: Integrating Archaeological, Behavioral, and Genetic Data

Härkönen¹,

Hårding

Goodman

et al. 2005

Marine Mammal Sci

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Detailed knowledge about the history of colonization, population dynamics and behavior greatly enhance evaluation of genetic models of population units and migration rates in spatially structured populations. Here, the genetic uniqueness of harbor seals (Phoca vitulinia) in the eastern Baltic is evaluated in the light of new information on the distribution and abundance of Baltic and eastern North Sea populations during the last 11,000 yr, recent hunting statistics, and population counts. Archaeological records reveal that the Baltic population of harbor seals was founded about 8,000 yr ago. Adjacent populations in the North Sea areas were either small, or went extinct, and became significant only during the last 300 yr. This information generates the hypothesis that the Baltic population has been isolated during the last 8,000 yr, despite the lack of geographical barriers. We show that stochastic effects, isolation, and a documented recent population bottleneck can account for the low observed genetic variation in Baltic harbor seals.

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“…The subspecies is currently designated as critically endangered in the Red List of Finnish species (Rassi et al 2010), and also by the IUCN (Kovacs et al 2011), and is categorized as a species which needs “special conservation areas” and strict protection under the European Union's Habitat Directive (Council Directive 92/43/EEC, Annexes II and IV). The most common cause of death among Saimaa ringed seal pups that have been examined during the last 30 yr is bycatching, especially entanglement in gill nets (Sipilä et al 1990, Ranta et al 1996, Kokko et al 1998, Sipilä 2003). Juvenile survival is a critical factor for the growth of the population (Kokko et al 1998), a fact which emphasizes the importance of determining the temporal and spatial habitat usage of the pups.…”

mentioning

confidence: 99%

“…The most common cause of death among Saimaa ringed seal pups that have been examined during the last 30 yr is bycatching, especially entanglement in gill nets (Sipilä et al 1990, Ranta et al 1996, Kokko et al 1998, Sipilä 2003). Juvenile survival is a critical factor for the growth of the population (Kokko et al 1998), a fact which emphasizes the importance of determining the temporal and spatial habitat usage of the pups.…”

mentioning

confidence: 99%

Home range, survival, and dispersal of endangered Saimaa ringed seal pups: Implications for conservation

Niemi

Auttila

Viljanen

et al. 2011

Marine Mammal Science

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Lake Saimaa in eastern Finland is inhabited by a critically endangered ringed seal subspecies Pusa hispida saimensis. Since accidental mortality in gill nets, resulting in reduced pup survival, is considered to be the main factor contributing to the decline in its population, fishing restriction areas have been established. In this study, 10 pups were located daily using very high frequency (VHF) telemetry to estimate their home ranges, movements, and survival. The pups dispersed after weaning at the age of ca. 3 mo and moved up to 15 km a day between consecutive locations and up to 25 km away from their birth sites. The home ranges of the pups at the age of 3-4 mo were variable in size, from 3 to 162 km 2 . The pups preferred the same shallow water areas (<6 m) that were used for gill net fishing. The annual fishing restrictions covered an average of 83% of the pups' home ranges. Four of the pups were nevertheless killed in fishing gear. The results have implications for Saimaa ringed seal management and conservation. For instance, large home ranges of pups and the long distances movements should be taken into account when zoning shore use and imposing fishing restrictions.

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Estimating the demographic effective population size of the Saimaa ringed seal (Phoca hispida saimensis Nordq.)

Cited by 10 publications

References 0 publications

The impact on tigers of poaching versus prey depletion

The impact on tigers of poaching versus prey depletion

Colonization History of the Baltic Harbor Seals: Integrating Archaeological, Behavioral, and Genetic Data

Home range, survival, and dispersal of endangered Saimaa ringed seal pups: Implications for conservation

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