Get big fast! Patterns of first-year growth in seven species of minnows (Leuciscidae) from south-central Ontario

Abstract

Common patterns of growth are presented for the young-of-year of seven species of minnows (Leuciscidae) based on analysis of daily growth increments in the microstructure of otoliths. All seven species show a period of growth during May–September and reach approximately the same size (~4.3 cm) entering their first winter. The first annulus appears to develop in May. The most striking feature, observed in all seven species, is a sudden and marked increase in rate of growth at ~25 days post-hatch. The first 21 days of this surge in growth account for 29% of the first-year’s growth. The growth surge may result from reaching a developmental milestone, such as the ossification of fin rays or flexion of the notochord that allows for greater mobility and capture of invertebrate prey. Given that small size is negatively associated with survival in juvenile fishes, achieving the growth surge in early life is likely important for survival. These results may be broadly applicable to leuciscids, an ecologically important and understudied group of fish.