ISSN:
1095-8649
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
This study describes a pattern of circulus spacing on the scales of sockeye salmon, Oncorhynchus nerka, which has not been reported previously. The average distance between circuli formed during the second year of ocean growth is much less than that of first year or in subsequent years. This pattern was persistent for fishes of two river systems, six year–classes and two age groups (2.2 and 2.3) and was due to summer growth. Statistical analyses were conducted only on age 2.2 fish because of small sample sizes in four of the six years for age 2.3 fish. There were significant (p 〈 0.05) differences in the distance between circuli formed in the summer and in the two stocks for various years at sea. No significant variation in average spacing between circuli was explained by oceanic temperatures.Annuli were formed between November and January. However, oceanic temperatures were declining at this time and do not reach minima until April. Thus, annuli are formed about the time of the equinox and during a declining temperature regime. We hypothesize that the pattern of circuli spacing and annulus formation are responses to photoperiod and food availability which the fish experience during their existence at sea.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1095-8649.1988.tb05357.x
