When are historical data sufficient for making watershed-level stream fish management and conservation decisions?

Area of Science:

• Ecology
• Ichthyology
• Conservation Biology

Background:

• Landscape-level threats necessitate watershed-level species inventories for effective stream fish management.
• Watershed-level ichthyofaunal surveys can be prohibitively expensive, making historical data a potential alternative.
• Existing species lists compiled from historical data may contain biases and limitations crucial for managers to consider.

Purpose of the Study:

• To assess the suitability of species lists compiled from existing data sources for watershed-level fish management and conservation.
• To compare species lists derived from historical data with those from intensive field surveys in the Great Lakes watersheds.

Main Methods:

• Compiled existing species lists from federal, state, and museum fish survey data for nine Great Lakes watersheds.
• Conducted intensive field surveys in 2002 to create current species lists for the same watersheds.
• Compared the size and species composition of existing lists against current lists.

Main Results:

• Existing data sources commonly missed species found in 2002 field surveys (5-21 species per watershed).
• Multiyear/seasonal historical data improved list completeness but are rarely available.
• Older surveys (pre-1984) showed inaccuracies and misidentifications, not reflecting current species composition.
• Migratory and introduced species were frequently omitted from existing lists, though game species were usually included.

Conclusions:

• Existing species lists derived from historical data have significant limitations for watershed-level fish management and conservation.
• Managers should critically evaluate the completeness, accuracy, and temporal relevance of historical datasets.
• Recommendations are provided for the judicious use of existing data in conservation planning.