Conservation Fisheries, Inc.

Newsletter #26 February 2005

Spawning the goldstripe darter

Spawning Goldstripe Darters, Etheostoma parvipinne

In the last newsletter (#25, December 2004), we told about collecting goldstripe darters in West Tennessee . These are indeed an interesting fish! As many of you know, we’ve had an unusual winter here in the southeastern US! Early January was warm by almost any standards! We had temperatures approaching 70F for days on end! Since we rely on outside temperatures to cool our hatchery, our water temperatures crept into the upper 50s, then into the low 60s! At this point, we were seeing behavior in the goldstripe darters that was obviously romantically motivated. The males darkened considerably and developed an almost metallic blue cast. The females were very gravid.  

Soon, we were seeing males pursuing and occasionally mounting the females. The tanks were supplied with nylon yarn mops, the same ones we use with our topminnows. On 01/14/05 , several mops were removed and checked for eggs. Numerous small (~1mm) eggs were found loosely adhering to the mops. We found that the eggs were easily dislodged from the mops by swirling them (the mops) in plastic shoeboxes filled with tank water. Using a light table, the eggs were removed from the shoebox and placed in small, plastic containers and floated in the tanks for temperature control. We removed 20-30 eggs in this first collection attempt.  

Within a day or two of this, the temperature outside began to fall back to temperatures you would expect for January. By the 19^th, the water temperature had fallen to 50F. However, the eggs still looked fine and the adults were still determined to continue spawning!  

Ten days later, the water temperature was 48F and the eggs still had not hatched. The embryos were well pigmented and could be seen moving within the chorion. The first egg hatched on the 25^th, eleven days after they were collected (probably 12 days after spawning). The larvae were tiny, approximately 3mm in length. After about a day, they were very mobile and tended to spend the majority of their time swimming up from the bottom. Within a couple of days, they were clearly spending most of the time up in the water column.  

We are rearing them in the black rubber tubs that we have used for most of our pelagic darters. One of these is pictured in CFI Newsletter #23. Now came the task of figuring out what to feed such  small larvae! We were just starting our live food cultures up for the spawning season. These guys took us by surprise by starting so early!  

We started by “greening-up” the tub with Instant Algae (Nanochloropsis). This is a wonderful concentrated algae solution that we dilute with filtered water. It can be stored in the refrigerator or frozen. It has eliminated our headaches associated with culturing large amounts of “greenwater”. In the past, we have found that, for whatever reason, many of these tiny larvae do better when their culture containers are kept slightly green. We supplemented the algae feedings with powdered foods (primarily O.S.I. APR formula). In addition, we filter out the neonates from our Ceriodaphnia cultures. These are somewhat smaller than brine shrimp nauplii. We have a mixed Rotifer culture that we use to feed these and other small larvae. (The Instant Algae has proven to be great for feeding our rotifers and cladocerans.) Finally, we have been supplementing this with micro worm (Nematodes) feedings. This is the first year we have used micro worms and are interested in seeing how they work out. I suspect they will be better for larvae that are more benthic.  

In any case, something in this mix has worked and the larvae have done well for us! As of this writing, we have transferred approximately 90 larvae into the tub and can count more than 40 swimming around in there. There are probably quite a few more as they are difficult to see against the dark background of the tub.  

The earliest larvae are still pelagic at this time! We did not expect this to be the case with these fish. One observation we have made in the past is that darter larvae that are pelagic tend to be virtually unpigmented. Larvae that are well pigmented tend to be more benthic. This, of course, makes sense……a clear larva is more difficult to see in the water column. But, these guys didn’t fit into our theory at all! But, this probably makes sense too. Goldstripe darters are found in heavily vegetated, often dark stained waters. A darkly pigmented larva might be more invisible under these conditions. Indeed, like I said, against the black background of the rearing tub, these guys are extremely difficult to spot. Sometimes, we just have to adjust our thinking to fit the circumstances!  

This project was undertaken to develop spawning and rearing protocols for the extremely rare and imperiled rush darter, Etheostoma phytophilum. We hope to begin propagation of these over the next couple of years.  

Thanks for the continued interest. As always, feel free to contact me with questions or comments!

J. R. Shute