Conservation Fisheries, Inc.

Newsletter #6 May 15, 2001

What’s happening around the hatchery….an update.

Percina aurolineata

Goldline Darter

The only other species of Percina we are working with this year is the rare pearl darter, P. aurora. We were fortunate to obtain three specimens (a male and two females) from Rick Mayden. Rick managed to collect these in the Leaf River on the way to the ASB meeting in New Orleans this spring. We arranged to get the specimens from Rick and back to Knoxville alive.

Several years ago we were contracted to develop techniques for spawning these fish using a close relative, the channel darter, P. copelandi,as a surrogate. We had reasonable success with these (for a Percina!) and waited patiently for someone to turn up some pearl darters for us.

After settling in we managed to collect a few fertilized eggs from the trio. Past experience suggested that these fish would spawn better in a group. Guess we’ll have to wait a bit longer for this! We managed to incubate and hatch several of these eggs (we never were able to collect more than five live eggs). We saw larvae for a few days and these were feeding. At the time of this writing, however, we no longer seem to have lost the larvae and the trio does not appear to still be spawning. We suspect that the fish were nearly spent when we received them. Maybe next year!

Spring has sprung at the CFI hatchery! I had intended to write several articles before getting into this update, but so much is going on right now that a short catch-up article is in order.

Romance is in the air…..at least where the fish are concerned. Several species are spawning earlier than usual this year. We assume this is due in part to the early warm weather we had this spring.

Some of the earliest spawners around our place are darters of the genus Percina. This year is no exception. Goldline darters, P.aurolineata, have been spawning for over a month now. We have collected more eggs than ever before this year. Our breeders, which consist in part of fishes spawned at CFI are larger this year. This coupled with heavy conditioning probably accounts for the increased egg output.

Despite this, we are still working to improve survivorship. Any of you that might have attempted to rear Percina know that the larvae are very demanding! They are pelagic, very small, and require a constant supply of appropriately sized foods. We are working with several powdered foods along with Brachionus rotifers and greenwater cultures. All of this coupled with the fact that they need to be fed almost constantly translates into a very labor-intensive fish! Add to this, just about everything that could go wrong, did…. From rotifer cultures crashing to Hydra in the larval tanks! It’s been a learning experience.

We are managing to raise a few and production is increasing. At this point, spawning has slowed down a bit. I hope to devote a future article to their spawning behavior. We spawn these in rather large groups (20+fish). Some of the male-male interactions are truly remarkable!

Our yearling duskytail darters, Etheostoma percnurum,have been spawning for several weeks now. We placed about 15 fish in a large, shallow trough with a fine natural sand (almost silty!) substrate. Numerous spawning structures were supplied, including natural slab-rocks and 6x6 ceramic tiles (duskytail eggs on slate) . At the time of this writing, we have collected over 16 nests from this set-up! These are some of the best spawning results we have ever had with this fish. Most of the fish chose the 6x6 slates on which to deposit their eggs. Most nests are in the size range of around 50 eggs, suggesting most are the result of a single female. If left in the tank longer, we have seen several females contribute to a nest.

The eggs are doing well and mortality is very low. We have quite a few larvae as of right now. Fortunately, these larvae are much simpler to deal with than the Percina! We will be collecting a few wild nests from Citico Creek to supplement the gene pool this year, but as a result of the good spawning success, will not have to rely as heavily on wild collected nests.

Etheostoma percnurum

Duskytail Darter

Duskytail Darter eggs

Relict Darter

Etheostoma chienense

Boulder Darter

Etheostoma wapiti

Our relict darters, E. chienense, are also spawning. This is another relatively easy one. Like the duskytail darters, the relicts spawn on the under-surface of some structure in the tank. We use primarily ceramic tiles because of the ease of handling. These larval darters readily feed on brine shrimp nauplii and are usually relatively easy to rear.

The boulder darters, E. wapiti, are spawning well at this time. Their larvae are, like the Percina, pelagic and require intensive feedings with small, live foods. We have found that we have our best success with these larvae when we transfer them directly from a hatching tray into a 20 gallon “long” tank soon after they hatch. We use air stones to create a gentle current throughout the tank. This helps keep the larvae and food suspended in the water column. This is the same technique we have begun using with the goldline darters.

We are gearing up for production of several additional species that should start spawning in the next month. Barrens topminnows, Fundulus julisia have already started. Cape Fear shiners, Notropis mekistocholas are just beginning to spawn and, as we finish with the goldline darters, we will move Cahaba shiners, N. cahabae into their stream tank.

We are also very hopeful about our chances of spawning more madtoms this year. Already, we have had a spawning of the Smoky madtom, Noturus baileyi. This is the first natural spawning we have had of this species. It is also the first time we have had fertile eggs produced! We will be setting up pairs and spawning groups of numerous other madtom species over the next week or so. I hope to be able to report on these future spawnings over the next couple of months.

J. R. Shute

May 15, 2001