Title
Fish diversity, microhabitat use, and behavior in secondary channels of the Bitterroot River, Montana
Abstract
The central Bitterroot River floodplain is characterized by a complex secondary channel network that provides a range of aquatic environments for native and nonnative fish. To better understand fish communities using these aquatic habitats, I used snorkeling and electrofishing to evaluate habitat variation, fish community diversity and microhabitat use in six secondary channels between August 1998 and September 1999. Secondary channels provide a range of habitats and microhabitats influenced by secondary channel proximity to the Bitterroot River, upwelling groundwater, and inchannel habitat complexity created by woody debris. Secondary channel morphologies remained stable over the year, while secondary channel water chemistry varied seasonally and in relation to the mainstem Bitterroot River. Fish community diversity was greatest in complex channel reaches and tended to decrease with distance from the mainstem. Of the eight fish species commonly encountered, microhabitat use and day-night fish behavior patterns were apparent. Among young-of-year and juvenile age classes of different species, microhabitat use overlapped and day-night behaviors were similar. During the day, young fish generally selected microhabitats associated with dense cover, while at night these fish moved into less protected, low water velocity microhabitats. Adult fish of larger species used microhabitats that differed from those used by young-of-year and juveniles of the same species. Adult fish occupied deeper microhabitats or those associated with large woody debris or overhead bank cover. However, these results were species-specific in many cases and were influenced by site-to-site differences in microhabitat availability. Bitterroot River secondary channels provide a variety of habitats occupied by numerous fish species and age classes. Protection of the Bitterroot River floodplain from inappropriate development is critical to maintaining the region’s habitat and fish diversity.
Start Date
14-4-2000 12:00 AM
End Date
14-4-2000 12:00 AM
Document Type
Poster
Fish diversity, microhabitat use, and behavior in secondary channels of the Bitterroot River, Montana
The central Bitterroot River floodplain is characterized by a complex secondary channel network that provides a range of aquatic environments for native and nonnative fish. To better understand fish communities using these aquatic habitats, I used snorkeling and electrofishing to evaluate habitat variation, fish community diversity and microhabitat use in six secondary channels between August 1998 and September 1999. Secondary channels provide a range of habitats and microhabitats influenced by secondary channel proximity to the Bitterroot River, upwelling groundwater, and inchannel habitat complexity created by woody debris. Secondary channel morphologies remained stable over the year, while secondary channel water chemistry varied seasonally and in relation to the mainstem Bitterroot River. Fish community diversity was greatest in complex channel reaches and tended to decrease with distance from the mainstem. Of the eight fish species commonly encountered, microhabitat use and day-night fish behavior patterns were apparent. Among young-of-year and juvenile age classes of different species, microhabitat use overlapped and day-night behaviors were similar. During the day, young fish generally selected microhabitats associated with dense cover, while at night these fish moved into less protected, low water velocity microhabitats. Adult fish of larger species used microhabitats that differed from those used by young-of-year and juveniles of the same species. Adult fish occupied deeper microhabitats or those associated with large woody debris or overhead bank cover. However, these results were species-specific in many cases and were influenced by site-to-site differences in microhabitat availability. Bitterroot River secondary channels provide a variety of habitats occupied by numerous fish species and age classes. Protection of the Bitterroot River floodplain from inappropriate development is critical to maintaining the region’s habitat and fish diversity.