Age structure and growth of shells of the Pacific basket-cockle,
Clinocardium nuttallii in Netarts Bay, Oregon, were investigated with
special emphasis on the differences between subtidal and intertidal
populations. The cockle was chosen for study because its growth is
highly sensitive to physical factors in the environment. Evidence is
presented which suggests that stresses of the physical environment
and biological factors result in oldest individuals being in the subtidal,
and that growth of shells is correlated with the amount of
tidal submergence. A short-term tagging study was done at two
sites and most of yearly growth occurred in the Spring months.
Collections were made from July, 1975, through September,
1976, from six sites to study synchronism of gonadal development
and fecundity of populations by histological examination of gonads.
Synchronism of gonadal development to the ripe stage occurs among
intertidal and subtidal populations in the same area, while populations
from different areas of the bay do not reach the ripe condition
at the same time. There is evidence of protandric spawning
behavior, and the hermaphroditic nature of C. nuttallii is compared
to that of the Family Tridacnidae. The fecundity of the subtidal
populations, in terms of percentages of the populations producing
ripe gonads, was greater than fecundity of the intertidal populations.
The subtidal environment is suggested to serve as 'refugia' for
adult breeding populations. / Graduation date: 1978
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26993 |
| Date | 21 July 1977 |
| Creators | Ratti, Frank Douglas |
| Contributors | McCauley, James E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Relation | North Coast Explorer |
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