Age and Growth of the Longfin Dace, Agosia Chrysogaster Girard

This is the first study to determine the age and growth of the longfin dace, Agosia chrsogaster Girard. During March, June, and October, 1961, 8,568 dace were collected from the Mimbres, San Francisco River and one of the Mimbres River indicate that Agosia lives just over one year. Estimates of age based on the examination of scales from a stratified subsample of 255 fish appear to agree with length-frequency estimates. The position of a check near the outer margin of scales established the formation of a winter check in March. Two or more checks appear to be formed each year. Linear-regression formulae of body-scale relationships for both sexes indicate that changes may occur in these relationships as gonadal development begins and again just prior to spawning. Length-frequency data suggest that Agosia spawns at least twice between March and October. Both sexes appear to mature and spawn as it fish. Maximum fork length found was just over 90mm. Males and females were found to grow at the same rate until they reach 44mm fork length. thereafter, females grew at a faster rate and attained a greater maximum size. Mortality was found to be greater in males than females throughout life. Linear-regression formulae were calculated to show the relationships among standard length, fork length, and total length for each sex. Nearly perfect linear relationships were demonstrated among the three lengths