Population

An major part of our activities is to ensure the long term monitoring of seabird and sea mammal populations at the 4 localities of the French Antarctic and Southern Territories (TAAF).

Our aim is to determine long and medium term trends of the marine predators population sizes.
 

For that, every year, and since 50 years, we count colonies of seabirds and sea mammals. This population monitoring is in line with international programmes animated by the SCAR  (Scientific Committee on Antarctic Research) and the CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources). During the past 50 years, the numbers have changed in different ways. Concerning some species such as the King Penguin or the Fur Seal, the populations have increased very rapidly.

Nevertheless, a larger number of species actually suffer a severe decline, among which all species of Albatrosses, the Emperor Penguin and the Rockhopper Penguin.

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Monitoring of the individual demographic performance-Populations dynamics

Since 1960, 120 000 individuals of 27 different species of seabirds and sea mammals have been ringed or marked.   The successive recapture/resighting of individuals in study colonies allowed to estimate the demographic parameters (survival, recruitment rate in the population, breeding frequency and breeding success, offspring quality, age of sexual maturity ) of the population from one year to another (transversal monitoring). It also allowed to estimate the variation of individual performances (longitudinal monitoring), such as how these parameters change with the age.

The information is centralized in the Centre d’Etudes Biologiques de Chizé (CNRS) in a demographic data base among the most important in the world because of the number of species studied and the duration of the monitoring. This data base constitute an precious source of information for more fundamental studies in evolutionary ecology or for studies in conservation biology.

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The simultaneous analysis of long term monitoring of population sizes and of demographic parameters permit to understand the demographic causes of population changes.
Seabirds are long-lived animals and the abrupt drop of populations are in general due to the increase of adult mortality.
 

The connection with environmental parameters or quantified human activities allow us to understand why the population sizes vary.

Our analyses clearly demonstrated that wandering albatrosses at Crozet have decreased because of an increase of female mortality during the 1970s, due to an increase in the fishing activities in the Indian Ocean (Weimerskirch et al. 1997). The global warming, particularly pronouced in the Southern Ocean, was followed by a decrease in number of several species such as the Emperor Penguin (Barbraud & Weimerskirch 2001).

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