Last November, the Barrens Topminnow “lab” exhibit in Rivery Journey was replaced by the small fish-focused Tiny, But Mighty Important exhibit. Vestiges of the old exhibit remain, however, including two stacks of tanks containing endangered Barrens Topminnows (Fundulus julisia) at various stages of their life cycle.
On April 16, Adam Johnson, the Aquarium’s Barrens Topminnow Research Assistant, found hatched eggs in the exhibit that were produced by genetically distinct groups of Barrens Topminnows. These baby fish will be used to stock and eventually to breed new Barrens Topminnows next year.
Nearly-microscopic baby Barrens Topminnows swim in a protective mesh pouch at the Tennessee Aquarium
The baby fish are visible, if barely, within a mesh screen-enclosed container they’re in called a palpin located in one of the tanks. At full size, the Barrens Topminnow tops out at about three inches, and these newly hatched fish are less than a centimeter (0.4 inches) long, making them especially hard to see.
Since the Aquarium’s efforts with the Barrens Topminnow began, it and its partner organizations have released more than 44,000 fish propagated in human care back into their natural habitat.
Representatives from the Tennessee Aquarium Conservation Institute and U.S. Fish and Wildlife use drag nets to look for Barrens Topminnows in a creek in Middle Tennessee
These new baby Barrens will remain on exhibit until they grow too large to stay in the palpin, which will take about three more weeks. At that point, Johnson says, they’ll be relocated to the Tennessee Aquarium Conservation Institute freshwater science center to finish growing. They’ll remain there and will, eventually, contribute to the Aquarium’s future breeding efforts with this species.
“By the time they outgrow the palpin, they’ll be up to 20 Millimeters (about three-quarters of an inch) long,” Johnson says. “We’ll have more cycling in, so I’ll have to keep them constantly size-sorted so they don’t compete with each other.”
A scientist from the Tennessee Aquarium Conservation Institute holds an adult Barrens Topminnow collected in a net