Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.
The fourspine stickleback (Apeltes quadracus) is a small fish native to the Atlantic Coastal areas in northeast North America. This species can survive in fresh, brackish, and marine waters. The climate match for this ERSS is valid for only fresh and brackish water areas. The history of invasiveness is none documented. There have been introductions outside the native range of the fish and at least one introduction resulted in an established population. No records of actual, observed impacts were found but there are indications that it may be displacing native sticklebacks. Introductions are likely via the ballast water of ships, including intra-lake ballast, and possibly through mixing with fish sold as bait. The overall climate match was high for the contiguous United States. The Northeast region to the Midwest region of the United States had a high climate match, as well as the Gulf Coast. The climate match decreased heading west. Part of the high climate match was in the species’ native range. The certainty of assessment is low. The overall risk assessment category is uncertain.
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Uncertain Risk
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