Conservation Fisheries, Inc.

Newsletter #22 April 2004

Springtime Spawnings!

Well, as the days get longer and the water warms in our tanks, some of the fish start thinking about romance! This year, our first spawners are the Warrior darters, Etheostoma bellator.

This beautiful little snubnose darter has a limited distribution in central Alabama's Black Warrior river system. We are propagating warrior darters in an effort to develop techniques for propagating the critically rare vermilion darter, E chermocki, found in only a small stretch of one stream tributary of the Locust Fork, also in central Alabama. Population monitoring is underway in Alabama to determine the current status of the vermilion darter. Once completed, we hope to bring these imperiled fish into propagation. 

Warrior darters presented us with a unique propagation challenge. Like other snubnose darters, these fish deposit their eggs singly over a wide area. Some have likened this to an Easter egg hunt strategy (appropriate for this time of year!) What that means for us is that there is no one piece of substrate to be removed where the eggs are deposited. We have approached this from several different directions. We wanted to experiment with two set-ups to start with. In one, we offered an assortment of substrate items that the fish would (hopefully) deposit eggs on. We used several different kinds of rocks, ceramic tiles and PVC scraps. The second set-up provided the fish with a coarse pebble substrate along with another selection of rocks and other items. In the first set-up, we intended to let the fish spawn for a few days, then remove the substrate into hatching containers for incubation. In the second instance, we intended to allow the fish to spawn for a few days, to perhaps a week, remove the fish and let the eggs hatch in the tank. We would then figure a way to extract the larvae, or simply allow them to grow in that tank. 

Tanks were stocked with several different assortments of the darters. Some had a single male and several females. Some had multiple males along with several females. 

The first eggs were discovered on March 1st. These were seen on the sponge filter that was part of the system set-up. Although the filters were not intended to be part of the spawning substrates, the fish seemed to prefer these! At this point, the system temperatures had been running in the mid 50sF. We removed this first sponge filter and transferred it to a hatching tray. At these cool temperatures, the eggs took about a week to hatch. Larvae were small and remained on the floor of the tray for perhaps a day. After this, they became more mobile. These first larvae were always gone within about another day! At this point, with water temperatures still in the low to middle 50sF (we had just experienced a cold spell in the weather), and we were assuming that the cool temperatures might be the reason for the lack of larval survivorship. 

In the second set-up, after we started seeing eggs hatch in the trays, we removed the spawning adults and began watching for larvae in those tanks. We would occasionally see several and these were removed to rearing trays. Again, these died or disappeared within a day or so. 

Finally, water temperatures reached 60F and stayed there. After this, spawning activity increased dramatically and so did our larval survival! We found that removing substrate from the tanks was cumbersome. We ended up just moving adults after about a week in the spawning tank. Afterward, we would look for larvae several times throughout the day. Larvae were removed from the tank using a pipette and transferred to circular rearing tubs.

With the warmer water temperatures, we started getting great survival of the larvae. They are small, requiring fine powdered and live (early instar Cereodaphnia) foods. They are are also still pelagic at this point (at least a week). 

With so much spawning going on, we have had the chance to experiment some with these. Most recently, we decided to remove spawning adults from a tank and took the overflow strainer off of the bulkhead drain. The hose from that drain was directed into our rearing tub (see above). As larvae started hatching, they flowed from the spawning tank into the rearing tub. This saves us the effort or removing each larval fish by hand! After the first night, our tub was full of larvae! 

We will update how the larvae progress in future newsletters! 

Tangerine Darters

Our tangerine darters are starting to show some interest in each other! There's some interesting behavior going on and the males have really become intensely colored! We're keeping our fingers crossed and have romantic music and candles going all around their tank! This is another one we'll keep you posted on.

Thanks for your continued interest! 

J. R. Shute