Ecological Risk Screening Summary - Bleak (Alburnus alburnus) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.

Bleak (Alburnus alburnus) is a freshwater and brackish water fish native to parts of Europe and western Asia. The fish primarily consumes invertebrates and is a forage species for larger, predatory fish. This species can form high-density shoals. The history of invasiveness is high. This species has established populations in several countries outside of its native range including Spain, Italy, and Cyprus. The spread of this species has been facilitated by stream modifications and by intentional transportation to new areas for use as bait or forage fish for sport fish. In some areas this species is reported to compete with native fish for resources, directly causing a decline in a native fish. The study underlying that report has not been peer-reviewed. Other impacts reported include changes in water quality and interfering in the genetic integrity of endemic species through hybridization. The climate match to the contiguous United States is high. There are many areas of high match stretching from southern New England to the Pacific Coast. The certainty of assessment is medium. Information on documented impacts of introduction is lacking peer-review. The overall risk assessment category is high.