The Opercular Bone as an Indicator of Age and Growth of the Carp, Cyprinus Carpio Linnaeus

Abstract

As part of an investigation of the non-game fish resources of Utah, a study of the age and growth rate of the carp was instituted. A preliminary investigation indicated that the opercular method was superior to several other methods of determining age and growth. Age and growth were calculated from the opercular bones of 330 carp collected at Ogden Bay Refuge in 1950–51. Distances to annuli were measured directly. The relationship between the posterior radius of the opercular bone and the standard length of the carp was curvilinear. Past growth was calculated with a logarithmic nomograph. Expected number of annuli on opercular bones of known age carp, agreement of ages assessed by length frequency modes and those assessed from opercular bones of the same fish, agreement of ages assessed by empirical length frequency modes with modes formed by pooled calculated lengths, agreement between ages assessed by scales and opercular bones, and increase in age with increase in size were accepted as evidence of the validity of the opercular method. Decrease in growth rate at any year of life for successive age groups is attributed to a gradual change of the environment.