When attempting to breed rare fish, embrace ‘too much of a good thing’

Sometimes, things don’t go as planned. And occasionally, that’s good.

A few of the Chesapeake logperch collected by partners in March to seed a captive-rearing effort. Credit: Crystal Rubble/Conservation Fisheries Inc.

In late March, scientists from Pennsylvania Fish and Boat Commission, Penn State University, Maryland Department of Natural Resources, and the Susquehanna River Basin Commission delivered 28 wild-caught Chesapeake logperch to a nonprofit aquaculture company in Knoxville, Tennessee. The aquaculturists planned to pilot techniques for propagating this rare fish in captivity, in hopes of someday reintroducing it to the parts of its historic range in the Chesapeake Bay watershed where it’s no longer found.

“Someday” may come much sooner than expected, because success sure has.

“We almost have more success than we can handle,” laughed J.R. Shute, co-director of the nonprofit, Conservation Fisheries Inc. (CFI).

Over the course of a month, CFI produced more than 1,500 baby Chesapeake logperch — so many that they had to stop the fish from spawning for fear of running out of space to care for their offspring.

Just a few of the Chesapeake logperch successfully propagated in a lab in Tennessee as part of a multi-year effort to recover these fish in their namesake watershed. Credit: J.R. Shute/Conservation Fisheries Inc.

It is an unexpected head start for a multi-year conservation initiative with an ambitious end goal: keep the Chesapeake logperch from the endangered species list by demonstrating that if partners take the right actions, in the right places, the fish can make a comeback. The U.S. Fish and Wildlife Service will be reviewing the logperch’s status in 2023 to determine whether or not it needs federal protection.

With funding from a state wildlife grant, the Fish and Boat Commission is leading the project to recover the Chesapeake logperch in the Susquehanna River in Pennsylvania and to develop a conservation plan in Maryland, in collaboration with the Susquehanna River Basin Commission, Maryland Department of Natural Resources, Penn State, CFI, and the Service.

Partners have been working in the field and in the lab to better understand the Chesapeake logperch, including through a collaborative population genetics assessment with the U.S. Fish and Wildlife Service’s Northeast Fishery Center and Pennsylvania Field Office. Credit: Geoff Smith/Pennsylvania Fish and Boat Commission

“For the first two years of the project, we planned to focus on collecting data to understand the life history and habitat requirements of this fish,” said Doug Fischer, a nongame fisheries biologist for Pennsylvania. “Then we would develop a reintroduction strategy based on what we learned.”

Now they have about 1,500 new research assistants to help them with data collection. By this fall, scientists will have a plan for releasing the propagated logperch into carefully selected places so they can learn from how the fish respond.

“If you put a thousand fish in the middle of the Susquehanna River, they may never find each other,” Fischer said. “We need to strategize, and release them in streams that are small enough that they will be able to find each other when it’s time to spawn.”

In addition to being the right size, the streams need to offer the right conditions, in terms of water quality, substrate composition, flow, and maybe other attributes. Scientists don’t yet know exactly what sweet spots look like for this species, and it’s possible they need different kinds of habitat at different times of the year.

“These fish are relatively unknown to science,” Fischer explained. In fact, Chesapeake logperch was only distinguished as a unique species, Percina bimaculata, in 2008. It was first described in the 1800s, but lumped in with the more common Logperch, Percina caprodes.

Chesapeake logperch is a bottom-dwelling, or “benthic,” species of fish, and lays its eggs in sandy stream bottoms. To facilitate breeding in the aquaculture facility, the wild-caught adults are placed in tanks featuring sand and gravel, makeshift shelters, and pumps to generate flow similar to a stream current. Credit: Conservation Fisheries Inc.

While both fish are around seven inches long, with a greenish gold body featuring numerous dark lateral bars akin to tiger stripes, there are subtle differences between them. The Chesapeake logperch has no more than 11 stripes, and an orange-yellow band in the first dorsal fin, while the common logperch has more stripes, and no orange-yellow band at all. “We always knew they were different,” Fischer said, and genetic testing confirmed it.

Fortunately, these two logperch species do have something important in common. “They have very similar reproductive techniques,” Shute said. “They are essentially no different in that respect.”

That commonality gave the aquaculturists an advantage in their propagation experiment because they already had experience raising logperch for another project.

Although adult Chesapeake logperch are benthic as adults, their larvae swim near the surface. At CFI, the aquaculturists simulate a slow, circular flow in the larger feeding containers so the young can school together and swim into the current. Credit: Crystal Rubble/Conservation Fisheries Incorporated

While tending to the fish over the last two months, Shute has noticed that they share another behavior common to species in the logperch group. “The fun thing about logperch is that they use their snouts to flip rocks over when they are foraging,” he said.

The common name for logperch, “caprodes,” means “like a pig” — a reference to its snout, not its manners. “Even when they are small like the ones in our tanks, you’ll see them flipping over tiny pieces of gravel; they take to that behavior early on,” Shute said.

This spring and summer, researchers will go into the water in boats and snorkels to observe other behaviors of Chesapeake logperch in the places where they have persisted, in hopes of learning why they prefer to live where they do, and what they need to thrive.

Because this fall, there will be lots of juveniles ready to join them.