NCCN Monitoring Fish Assemblages

Brenkman, Sam; Crain, Patrick

Determine seasonal and annual trends in fish assemblages in 10 rivers of Olympic National Park. Specific objectives of the river protocol are to determine trends in: 1) juvenile and adult fish species composition; 2) timing of migration; 3) relative abundance with an emphasis on key species that have ecological, cultural, or harvest significance; 4) fish growth; and 5) extent of non-native and hatchery salmonids in park waters. The protocol ultimately will track trends in all but the very rare species in each river. Purpose: Rivers and streams that drain from the Olympic National Park are among the most protected corridors in the lower 48 States, and represent some of the largest tracts of contiguous, undisturbed habitat throughout the range of several key fish species of the Pacific Northwest. These watersheds are of high regional importance as freshwater habitat sanctuaries for native fish, where habitat conditions are characterized as having little to no disturbance from development, channelization, impervious surfaces, roads, diversions, or hydroelectric projects. Fishery resources are of high ecological and cultural importance in Pacific Northwest National Parks, and significantly contribute to economically important recreational, commercial, and tribal fisheries. Fish assemblages link freshwater, marine, and terrestrial ecosystems. They also serve as focal resources of national parks and are excellent indicators of ecological conditions of rivers and streams. Objectives: This monitoring data allows managers to detect increases and decreases in abundance of priority management species, and occurrence of non-native, hatchery, and federally listed fish. The detection of trends in fish assemblages allows for specific management actions that may include: implementation of more appropriate fishing regulations, evaluation of existing hatchery releases, control of non-native fish species, and prioritization of habitat restoration projects. River surveys are conducted by doing day snorkel counts every 7–10 days from June to September, with as many as ten surveys per river per year. Water visibility and flow conditions, along with general weather conditions are noted. REGARDING items excluded from data collection: Safety and visibility considerations limit snorkeling activity to daylight hours in June, July, August, and September. Day snorkel surveys are not effective at enumerating species typically observed at night (for example, juvenile bull trout) or species associated with the benthos such as sculpin spp. Seasonality of snorkeling activity and the inability to snorkel in low-visibility conditions means that we do not obtain data on many key anadromous species. The snorkel surveys only record fish that are greater than 15 cm in length. Because of the difficulty in distinguishing between cutthroat trout and rainbow trout underwater, counts of these two species are combined as cutthroat/rainbow trout. All fish are identified to species except: sculpin and lamprey to genus; and rainbow trout and cutthroat trout under 60 mm are recorded as “trout”.

NCCN Monitoring Fish Assemblages

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