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.
Mummichog (Fundulus heteroclitus) is native to the Atlantic coast of the United States and Canada. The species is typically found in estuarine habitats, but does have populations in freshwater sections of coastal rivers. It can survive well in freshwater, where it has been introduced for mosquito control or as bait. Bait bucket introductions have likely led to established populations in inland United States, outside of the species’ native range, and F. heteroclitus has been reported in the Detroit River in the Great Lakes as well as in many places in Pennsylvania. It was also reported as introduced to Hawaii in the early 1900s. This species has been introduced and has spread along the southern coast of the Iberian Peninsula. It was also recently reported to be introduced and established in northeast Morocco. This species is reported to hybridize with Fundulus diaphanous, another species of killifish native to the United States. The history of invasiveness is Data Deficient. There are reports of impacts to native species in the Iberian Peninsula, particularly reductions in abundance, potentially to the point of endangering the existence of a population. However, many of those statements were framed as potential impacts, impacts in conjunction with other introduced species, or the information those statements were derived from could not be found. The climate match for the contiguous United States is high with most of the eastern United States and parts of the Gulf Coast having a high match. Much of the Midwest and West had medium to low matches except for much of California, which had high matches. The certainty of assessment is low due to the lack of detailed information available regarding the species impacts of introductions. The overall risk category for this species is Uncertain.
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Uncertain Risk
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