Recent publication on harp seals (fwd)

From: Pita Admininstrator (pita@whale.wheelock.edu)
Date: Fri Apr 19 2002 - 11:49:57 EDT


here is the abstract of our recent publication:

Chabot, D. & Stenson, G. B. 2002. Growth and seasonal fluctuations in size
and condition of male northwest Atlantic harp seals (Phoca groenlandica): an
analysis using sequential growth curves. Marine Ecology Progress Series 227,
25-42.

The cycle of energy accumulation before breeding and energy losses during
reproduction and molt, common in pinnipeds, is not well described in male
harp seals (Phoca groenlandica). Between 1979 and 1995, 3167 Northwest
Atlantic male harp seals were sampled. The part of the yearly cycle covered
in this study (November­May) was divided into short periods usually lasting
3 weeks (range 1-4). For each period, a growth curve was calculated for body
mass, sculp mass, core mass and standard length. These sequential growth
curves were used to calculate changes in size-at-age between periods. In
addition, seasonal changes in condition were analyzed using locally weighted
regressions. In November, male harp seals arrived in the study area heavier
and in better condition than when they left the previous spring. However,
maxima in length, mass and condition were not observed until the period of
February 12 to March 4, or in the case of seals younger than 5 yr, March 5
to 25. Mass losses associated with the rut began in the period of March 5 to
25, and were most pronounced in seals older than 10 yr. We estimated that
males lost 39.4 kg during the rut (1.16 kg d-1 or 0.78% of initial mass d-1,
44% from the sculp and 56% from the core) and incurred energy expenditures
of 840 MJ (24.7 MJ d-1). This corresponds to twice the standard metabolic
rate (SMR), and suggests that males are feeding during the rut. All males
lost mass in April, and again in May. They began to molt in the period of
April 16 to 22, but fewer than half the seals had completed the shedding of
old hair when the study ended, in the period of April 30 to May 20. Rates of
mass loss during the molt varied from 1 to 1.8 kg d-1, depending on the age
of the seals. Minima of length, mass and condition were observed in May.
Molting appears to be a period of high energy expenditures (3 to 5 SMR)
despite the low levels of activity observed at this time. This study
revealed that length also changes seasonally: fat seals in February were
longer than lean seals of the same age in late April.

Sincerely,

Denis Chabot
<chabotd@dfo-mpo.gc.ca>

-- 
Denis Chabot, Ph. D.
Chercheur en bioenergetique
Institut Maurice-Lamontagne
850 route de la Mer, B.P. 1000
Mont-Joli, QC G5H 3Z4
Canada



This archive was generated by hypermail 2b30 : Mon Aug 05 2002 - 20:12:25 EDT