New Zealand Journal of Marine and Freshwater Research abstracts
M00003Received 13 January 2000; accepted 18 May 2000
Revised estimates of natural mortality for the Foveaux Strait oyster
(Ostrea chilensis)
ALISTAIR DUNN
H. JOHN CRANFIELD
IAN J. DOONAN
KEITH P. MICHAEL
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 14 901, Kilbirnie
Wellington, New Zealand
email: a.dunn@niwa.cri.nz
Abstract We present revised estimates of the instantaneous
natural mortality rate of recruited (legal sized) Foveaux Strait dredge oysters
(
Ostrea chilensis, Philippi, 1845) for the years 1974-86. A
mark-return experiment was analysed, assuming constant rate of fishing (and
hence sampling) over 6 months of the year (i.e., the period of the fishing
season). The natural mortality between 1974 and 1986 of recruited oysters
increased from 0.02 to 0.19 year
-1 for a sample of oysters released
in 1974, and from 0.01 to 0.20 year
-1 for those released in 1973. We
explored possible causes for the observed increases including the impact of
indirect fishing mortality, rising disease mortality ahead of the
Bonamia sp. epidemic of 1986, and systematic misreporting in returns of
living and dead tagged oysters. We find no direct evidence for any of these,
and hence speculate that the observed increase in natural mortality of the
tagged individuals is associated with senescence.
Keywords Ostrea chilensis; dredge oyster;
natural mortality; senescence; tagging; mark-recapture
New Zealand Journal of Marine and Freshwater Research, 2000, Vol. 34:
669-680
0028-8330/00/3404-0669 $7.00 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (501K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
