Verification of the scale method for ageing (Age determination) the cyprinid, Mirogrex terraesanctae terraesanctae (Steinitz, 1952) in Lake Kinneret (Israel)
1986
Davidoff, E.B. (District Fisheries Office, Tiberias (Israel). Lake Kinneret Fisheries Research Lab.)
A critical examination was made of the validity of scale annuli for determining the age and growth of the cyprinid, Mirogrex terraesanctae terraesanctae (Steinitz, 1952). General features of Mirogrex scales are described. There was a regular appearance of annuli, and the relative position of respective annuli was consistent among scales. The number of annuli were observed to increase systematically as growth proceeded. Modes of small fish in the length-frequency distribution of catch coincided with the modal lengths of corresponding age-groups based on scale readings. Annulus formation occurred in late March or during the month of April, when water temperatures increased after the winter minimum. Lengths at the time of annulus formation, calculated from scale measurements, agreed well with corresponding empirical lengths of younger age-groups whose ages had been determined by scale reading. Annuli found on scales of Mirogrex were shown to be valid year marks for estimating the age and growth of this species in Lake Kinneret. Mirogrex aged 1-4 years at the time of annulus formation ranged in size from 95-176mm. Their greatest gain in weight occurred between ages two and three
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