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White Sturgeon Spawning Habitat in an Unregulated River: Fraser River, Canada
Author(s) -
Perrin Chris J.,
Rempel Laura L.,
Rosenau Marvin L.
Publication year - 2003
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(2003)132<0154:wsshia>2.0.co;2
Subject(s) - sturgeon , habitat , turbidity , fishery , channel (broadcasting) , shoal , hydrology (agriculture) , environmental science , lake sturgeon , ecology , acipenser , geology , oceanography , biology , fish <actinopterygii> , geotechnical engineering , electrical engineering , engineering
Spawning habitat used by white sturgeon Acipenser transmontanus in the lower Fraser River, British Columbia, is described based on field sampling in 1998 and 1999. Fraser River flow is unregulated and, within our study area, its channel morphology is largely unaltered by land use activities. The study area consisted of (1) the wandering reach (river km 98–143), which had side channels, wooded islands, and gravel bars; and (2) the confined reach (river km 145–181), which was naturally restricted by mountains, producing a single‐thread and simple channel. Six spawning sites were identified in the study area, five in side channels of the wandering reach and one in the main channel of the confined reach. Within the wandering reach, eggs and larvae were collected only from side channels despite sampling efforts in main‐channel areas. Multiple lines of evidence, including radio‐tracking of prespawning adults and visual observations, substantiated the use of side channels by white sturgeon for spawning. A total of 3 unfertilized and 80 fertilized eggs were captured at water velocities averaging 1.8 m/s, whereas 101 larvae were found in velocities averaging 1.0 m/s. Water depths averaged 2.9 m at capture locations for all life stages and were shallow compared with depths of egg and larval captures reported from most regulated rivers. Turbidity, which averaged 42 nephelometric turbidity units during the spawning period, was notably higher than in regulated rivers. We hypothesize that reduced light attenuation due to turbidity may substantially influence habitat suitability for spawning within the range of available water depths and velocities. Our observations of white sturgeon spawning activity outside of main‐channel habitats are unique, and we have demonstrated that spawning may occur over a wider range of habitat conditions than previously reported. Our observations of white sturgeon spawning in an unregulated river in which fluvial processes and channel morphology are relatively unaltered, albeit increasingly threatened by river engineering, are also unique.