A hunted population in recovery: Effective population size for South American sea lions from Patagonia

2012 ◽  
Vol 62 (4) ◽  
pp. 433-450 ◽  
Author(s):  
M. Florencia Grandi ◽  
Larissa R. de Oliveira ◽  
Silvana L. Dans ◽  
Enrique A. Crespo
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Evolutionary Biology ◽  
South American ◽  
Adult Males ◽  
Effective Population ◽  
Sea Lions ◽  
Management Plans ◽  
Viable Population ◽  
Patagonian Coast

Effective population size () is a parameter of central importance in evolutionary biology and conservation. Factors such as unequal sex ratios of breeding individuals, periodic fluctuation in population size and variance in reproductive success can affect the in general. At present, South American sea lions, Otaria flavescens, from northern Patagonia, Argentina, belongs to one of the several populations that are recovering from overhunting which occurred in the early 20th century. Here, we present the estimate of for this population that takes into account the effects of their polygynous mating system and variation in population size through time. The resultant overall ’s were 4171 ± 2450 or 4745 ± 2681 breeding animals depending on the inclusion of peripheral adult males. The estimated ’s are not critical, because they are close to the average mean minimum viable population for vertebrates (5000 breeding adults). Even though the northern Patagonian population of O. flavescens is increasing its abundance is still far below its historical numbers. The estimated should be considered the minimum range to be maintained, especially in light of bycatch related to fishery interactions along the Patagonian coast. We emphasise the importance of estimating for future management plans of the species within different populations.

scholarly journals Historical population size of the threatened New Zealand sea lion Phocarctos hookeri

2015 ◽  
Vol 97 (2) ◽  
pp. 436-443 ◽  
Author(s):  
Catherine J. Collins ◽  
B. Louise Chilvers ◽  
Matthew Taylor ◽  
Bruce C. Robertson
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Effective Population Size ◽  
Carrying Capacity ◽  
Effective Population ◽  
Sea Lion ◽  
Sea Lions ◽  
Target Values ◽  
Phocarctos Hookeri

Abstract Marine mammal species were exploited worldwide during periods of commercial sealing in the 18th and 19th centuries. For many of these species, an estimate of the pre-exploitation abundance of the species is lacking, as historical catch records are generally scarce and inaccurate. Genetic estimates of long-term effective population size provide a means to estimate the pre-exploitation abundance. Here, we apply genetic methods to estimate the long-term effective population size of the subantarctic lineage of the New Zealand sea lion (NZ sea lion), Phocarctos hookeri . This species is predominantly restricted to the subantarctic islands, south of mainland New Zealand, following commercial sealing in the 19th century. Today, the population consists of ~9,880 animals and population growth is slow. Auckland Island breeding colonies of NZ sea lion are currently impacted by commercial trawl fisheries via regular sea lion deaths as bycatch. In order to estimate sustainable levels of bycatch, an estimate of the population’s carrying capacity ( K ) is required. We apply the genetically estimated long-term effective population size of NZ sea lions as a proxy for the estimated historical carrying capacity of the subantarctic population. The historical abundance of subantarctic NZ sea lions was significantly higher than the target values of K employed by the contemporary management. The current management strategy may allow unsustainable bycatch levels, thereby limiting the recovery of the NZ sea lion population toward historical carrying capacity.

scholarly journals Management of genetic diversity using gene dropping method based on pedigree information

2013 ◽  
Vol 56 (1) ◽  
pp. 518-526
Author(s):  
M. Khaldari ◽  
A. N. Javaremi ◽  
A. Pakdel ◽  
H. M. Yeganeh ◽  
P. Berg
Keyword(s):  
Genetic Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
Low Frequency ◽  
Pedigree Analysis ◽  
Simulation Software ◽  
Pedigree Information ◽  
Genetic Contribution ◽  
Effective Population ◽  
Management Plans

Abstract. Preservation of genetic diversity in populations is an important task to ensure a possible longterm response to selection in animal breeding. The purpose of this study was to consider how pedigree analysis and gene dropping method could be used for management plans in order to maintain genetic variation in a population under selection of Japanese quail. Therefore, the distributions of alleles frequencies originated from founders were estimated on an actual pedigree using gene dropping simulation software. Then, genetic contribution of founders to the current population, components such as the F-statistics and effective population size were estimated. The results show that from 156 founders there are only 64 of them (22 males and 42 females) in the last generation. The average genetic contribution of a founder male and female contributing to the last generation were 1.87 and 1.40 %, respectively. A total of 87 and 95 % of the genome in the last generation were constituted by 34 and 42 founders, respectively. The effective population size decreased as inbreeding increases. The allele frequency averaged over replicates agreed with the genetic contribution. Some useful information regarding the management of genetic diversity such as the probability of allele extinction, the probability of alleles surviving at a critically low frequency and risk of future allele extinction were derived by using these distributions. Results show that pedigree analysis and gene dropping are valuable tools in optimizing decisions to preserve genetic variability.

scholarly journals The role of behavior in tern conservation

2014 ◽  
Vol 60 (4) ◽  
pp. 500-514 ◽  
Author(s):  
Brian G. Palestis
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Habitat Management ◽  
Habitat Modification ◽  
Effective Population ◽  
Nest Sites ◽  
Stopover Sites ◽  
Management Plans ◽  
Census Population Size

Abstract Behavioral research has long had an important role in the conservation of terns (Aves: Sternidae). Habitat management and restoration of breeding colony sites depends on knowledge of the cues used to select colony and nest sites. For example, conspecific attraction with playback and decoys is commonly used to bring terns to suitable colony sites and habitat modification is often used to increase the availability of suitable nest sites. Tern colonies are interconnected by dispersal, and a metapopulation approach is needed for effective management. Population dynamics are therefore affected by behaviors that influence the frequency of movement among colony sites: site fidelity, natal and breeding dispersal, and group adherence. The monogamous breeding system of terns should keep effective population size similar to census population size, but variation in sex ratios (likely resulting from sex differences in behavior) and in parental quality can result in a smaller than expected effective population size. In addition to the behavior of terns, knowledge of the behavior of predators on terns contributes to management plans, because predator behavior can sometimes be manipulated and predation is often performed by only a few specialized individuals. Other examples of links between tern behavior and conservation are also briefly reviewed, such as behavioral toxicology research and studies of behavioral responses to human disturbance and manmade structures. More work is needed on the behavior of migratory terns at staging sites, stopover sites and wintering grounds, and on the behavior of less well-studied species and species in less well-studied geographic regions [Current Zoology 60 (4): 500–514, 2014].

Effective population size for South American sea lions along the Peruvian coast: the survivors of the strongest El Niño event in history

2012 ◽  
Vol 92 (8) ◽  
pp. 1835-1841 ◽  
Author(s):  
Larissa Rosa de Oliveira ◽  
Lúcia Darsie Fraga ◽  
Patricia Majluf
Keyword(s):  
Population Size ◽  
El Niño ◽  
El Nino ◽  
South American ◽  
Effective Population ◽  
Sea Lions ◽  
El Niño Event ◽  
Peruvian Coast ◽  
El Niño Events ◽  
El Nino Events

The South American sea lion, Otaria flavescens, has been considered vulnerable and under the threat of extinction in Peru due to the drastic demographic changes as a result of the impact of low food availability and the unusual timing of the severe El Niño event of 1997–1998. We present the first estimate of effective population size (Ne) for the species that takes into account the effects of mating system and variation in population size in different generations caused by the severe El Niño event of 1997–1998. The resulting Ne was 7715 specimens. We believe that the estimated Ne for the Peruvian population is not a critical value, because it is higher than the mean minimum viable population generally accepted for vertebrates (ca. 5000 breeding adults). However, the viability of O. flavescens on the Peruvian coast may depend primarily on local availability of food resources. Climatic change models predict stronger and more frequent El Niño events. In this sense, the Ne of 7715 should be considered as a value to be maintained in order to keep the population large enough to avoid inbreeding or to retain adaptive genetic variation to survive to future El Niño events. Moreover, this Ne estimate is important data in discussions about resuming culling activities, based on the statement of an increasing competition between fishery activity and sea lions during El Niño events. Thus, this Ne should be taken into account in future management plans to ensure the conservation of the species on the Peruvian coast.

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