Blackstripe Topminnow

The blackstripe topminnow (Fundulus notatus) is a small freshwater fish of the family Fundulidae found across the central and eastern United States, largely within the Mississippi River basin and Great Lakes tributaries. It is one of several look-alike "striped" topminnow species and is best recognized by the bold, solid black lateral stripe that runs the length of its body. It inhabits quiet pools and slow-flowing sections of small to medium streams, often near cover such as logs or overhanging vegetation. The species is common and widespread, making it a frequently encountered surface-dwelling fish in stream surveys across its range.

Blackstripe topminnows are slender fish, usually 5-8 cm long.

• Body: elongated, translucent olive to tan, slightly flattened on top with an upturned mouth
• Key mark: a single, solid black horizontal stripe running from the snout through the eye to the base of the tail
• Fins: rounded, lightly speckled dorsal and anal fins set well back on the body
• Sexes: similar in pattern, though males may show a darker overall tone during breeding

The unbroken, solid black stripe distinguishes it from the closely related blackspotted topminnow, which instead shows rows of dark spots rather than a continuous line.

This species occupies quiet pools, backwaters, and slow-flowing reaches of small to medium streams and rivers across the central and eastern United States, with its core range in the Mississippi River basin. It prefers clear to slightly turbid, warm freshwater with soft substrate and nearby cover such as fallen wood, undercut banks, or overhanging vegetation. Blackstripe topminnows typically stay near the surface in calm water, avoiding fast current, and are often found schooling loosely along shaded stream margins. They generally avoid deep, open channels, instead concentrating along vegetated banks and quiet side pools where surface insects collect.

Blackstripe topminnows swim near the surface in loose aggregations, feeding on insects, insect larvae, and other small invertebrates picked from the water's surface and among vegetation. They are generally non-aggressive and tolerate close proximity to other individuals, though males may spar briefly during the breeding season. Spawning occurs over an extended warm-season period, with adhesive eggs deposited among submerged plants or debris and left without parental care. The species is an important prey item for larger fish and serves as a useful bioindicator of healthy, well-vegetated stream habitat.