Zoological Studies

Vol. 37 No. 4, 1998

Microhabitat Use by Formosan Landlocked Salmon, Oncorhynchus masou formosanus

Eric Hsienshao Tsao1,*, Yao-Sung Lin1, Robert J. Behnke2 and Eric P. Berqerserr2

1Department of Zoology, National Taiwan University, Taipei, Taiwan 106
2Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO 80523, USA

Eric Hsienshao Tsao, Yao-Sung Lin, Robert J. Behnke and Eric P. Bergersen (1998) Microhabitat requirements of the Formosan landlocked salmon (Oncorhynchus masou formosanus) were studied in four 85-m-long sections of the Chichiawan Stream. Underwater observations to locate the salmon, followed by measurements of physical habitat variables, were conducted along transects established at 5-m intervals. Available and occupied habitat units were compared to quantify water depth, current velocity, instream cover, and substrate type of suitable microhabitat. Data were pooled to represent salmon habitat use during 2 water temperature periods. Newly emerged fry extensively used habitats with nearly no current velocity and abundant instream cover. More than 50% of the salmon from 5 to 9 cm moved into deeper water having moderate current (0.1 to 0.86 m/sec) and less instream cover. Adult salmon used slower (less than 0.2 m/sec), shallower sites with abundant instream cover for resting, and fast velocity (0.6 to 1.1 m/sec), deeper sites with less instream cover for feeding. Spawning salmon preferred shallower waters (0.1 to 0.39 m), slower currents (0 to 0.3 m/sec), and small to moderate substrate sizes 25.6 cm). Microhabitat selection by Formosan landlocked salmon is related to fish size, water temperature, and life history activities.

Key words: Salmon, Microhabitat, Selection, Underwater observation.

*Correspondence: Current address: Department of Collection, Taipei Zoo, 30, Sec. 2, Hsinkung Rd., Taipei, Taiwan 116, R.O.C. Tel: 886-2-29382300 ext. 204. Fax: 886-2-29382316. E-mail: dwx07@mail.zoo.gov.tw