Age and Growth of the Silverjaw Minnow, Ericymba buccata Cope, in Kentucky

Abstract

Age and growth studies of the silverjaw minnow were based on 2324 specimens from Plum Creek and 1609 from other streams in Kentucky. The length-frequency method was employed in aging all fish and the scale method was used to verify the ages of fish from Plum Creek. The normal life span of the minnow is 3 years with a few indi- viduals living into the 4th year. The greatest rate of growth in length of silverjaw minnows occurred in the first 2 years of life and the greatest rate of growth in weight occurred in the 2nd and 3rd years. The length-weight equation W = aLn, or its logarithmic form W log a + n log TL, was used to express the relationship between total length (TL) and total weight (W) of minnows from Plum Creek and other streams in Kentucky, and between males and females from Plum Creek. That same equation was used to show the relationship between total lengths and total weight less the gonads for fish from Stations I and II on Plum Creek, between males and females, and among speci- mens from Plum Creek taken during three different seasons. Silverjaw minnows from Plum Creek had a higher average coefficient W X 105 of condition (K = ) than those from other streams in Ken- TL3 tucky. Females had higher K values than males when gonads were in- cluded in the body weight, but males had higher condition values when the gonads were excluded. Fish from Station I and those collected during the spawning season had higher coefficients of condition than those col- lected at Station II and during other periods of the year, respectively. Scales first appeared along the midlateral region of the caudal pedun- cle when the fish was about 13 mm long. Scalation was complete at a total length of approximately 27 mm. Development of fins was initiated before hatching and completed by a total length of 14 mm. The first fin to complete development was the caudal fin and the last was the pelvic. Differential growth rates of several morphometric characters were compared between different length groups of minnows. Head length and length of the pectoral and pelvic fins increased at a greater rate in smaller fish than in larger fish. Length of the caudal peduncle and total length increased at approximately the same rate in all length groups.