New Zealand Journal of Marine and Freshwater Research abstracts

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Diel feeding periodicity of torrentfish (Cheimarrichthys fosteri) in two braided rivers of Canterbury, New Zealand

G. J. GLOVA

P. M. SAGAR

C. R. DOCHERTY

Freshwater Fisheries Centre Ministry of Agriculture and Fisheries P.O. Box 8324, Riccarton Christchurch, New Zealand

Abstract Torrentfish Cheimarrichthys fosteri Haast were collected at 4-hour intervals over a full day in winter and summer, 1984-85, from the Ashley and Rakaia Rivers in Canterbury, New Zealand, to determine their diel feeding periodicity. Both populations fed, almost exclusively, from dusk to dawn in both seasons, with the quantity of food in their stomachs accumulating to peak levels by early morning. However, Ashley females had significantly less food in their stomachs than did males in summer, the season with a high incidence (91%) of females in spawning condition. Aquatic stages of Deleatidium spp. (Ephemeroptera: Leptophle-biidae) and Chironomidae constituted from 85 to 98% by number and 63 to 80% by dry weight of all foods eaten. Chironomids (small prey) comprised up to 85% of the total foods eaten by number but only 17% by dry weight, while Deleatidium (large prey) comprised up to 69% of the prey by number and 63% by dry weight. Numerically, chironomids were an important component in the torrentfish diet in both seasons in the Rakaia (71 to 75%), but only so in winter in the Ashley (85%). The reported daily feeding cycle is consistent with observations in a simulated stream, that torrentfish largely remain inactive during the day and come out to feed at night.

Keywords Ashley River; Rakaia River; noctur-nally active; benthic prey; diet; bottom-dwelling fish; stream invertebrates; riffle habitat

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 555-561 0028-8330/87/2104-0555$2.50/0 © Crown copyright 1987 Received 5 August 1986; accepted 12 January 1987

PDF file of entire paper: medium quality (515K); (scanned from paper original: notes about this process)

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