It was the least I could do…
The Least Brook Lamprey, that is!
This is a fish story – perhaps unlike any other fish story that you have heard and I’m sure that you have heard some doozies. This story starts in March of 2005, soon after my family moved into our neighborhood in rural Johnston County. Chris, my then 14-year-old son, saw some long skinny fish in the stream behind our house and asked what they were. I dipped one up with a net and expected it to be an American Eel (Anguilla rostrata). I immediately knew it was not and recognized the lamprey-like appearance. A quick phone conversation with Wayne Starnes, then Curator of Fishes at the Museum, revealed that it was the Least Brook Lamprey (Lampetra aepyptera). This is a small (4-7 inches), non-migratory and non-parasitic freshwater lamprey unlike the Sea Lamprey you may be more familiar with. There were so few records of them from the state that Wayne was glad to get a few specimens for the research collection.
The stream where we found them is so small that you can step across it in most places. It is a clear running stream with an average depth of only about 6 inches on a gravel and sand bed. The stream originates in the mixed wooded area behind my house and is probably spring fed. Most people would not give the stream a second thought and probably would lump it in the category of a “drainage ditch”. But for the Least Brook Lamprey (and who knows what else) this little stream and others like it is their whole world. They live here, feed here, reproduce here and die here! So these little streams are not just special to them—they are essential.
The Least Brook Lamprey belongs to the family Petromyzontidae, which includes about 20 species of freshwater brook lampreys plus the Sea Lamprey in North America. The Least Brook Lamprey is one of three brook lampreys found in North Carolina. In North Carolina it is only known from a few locations in the Neuse and Tar River basins. The species may be more widespread in these two river systems, but they are very hard to detect except during their short spawning season. The two-three week spawning season is the culmination of a very interesting life cycle.
These lampreys start in a larval fish form, called ammocoetes, hatched from the eggs produced during spawning. As ammocoetes, the lampreys live in the stream sediment and filter feed on algae and other organic material. The ammocoetes do not even have eyes in this form. They live for 3 to 7 years in this stage (Fritz Rohde et. al. 1976) feeding in the stream bed and generally hidden from sight. Only when the lampreys transform to the adult form and emerge to spawn do they become easy to see. And what a show they put on!
The adult lampreys work in small groups (3-10 +) creating nest depressions in the sand and gravel substrate of the stream. Working in shallow water with a steady current, they are almost always swimming upstream and using their sucker-like mouth to move rocks from the depression. They also anchor to larger rocks and vigorously undulate their body churning sand and smaller rocks out of the depression. They rest by anchoring to a rock, floating just under the stream surface.
Intervals of spawning occur the nest building activity. The female anchors to a larger rock and then a male will attach with his mouth on top of the female’s head. He then curls the posterior of his body around the female and both vigorously wriggle. Eggs and sperm are being released at this time. The sticky eggs fall and stick to the sand and gravel substrate. Hatching is presumed to happen within a few days. And thus the ammocoete phase of their life begins.
The adult lampreys do not feed at all and die soon after the spawning season. Since the larval lampreys take at least several years to mature, it is presumed that each year’s group of spawning adults are from the brood of one or two year’s spawning a few years ago. So it would be expected that the number of adults observed will vary from year to year based on reproductive effort in a previous year and on stream conditions in the intervening years before maturity that would have affected the growth and survival of the larval lampreys.
I began systematically documenting the lampreys spawning effort in 2015 by surveying the section of stream immediately behind my house every day during the two-three week spawning season. In 2015, my highest daily count was 14 lampreys. In 2016, my highest count was 43 lampreys.
It is a short show, but it is a fascinating thing to watch when the lampreys are spawning. Towards the end of the spawning season, the few remaining lampreys just hang out in or near the nest attached to a rock and limply swaying with the current as their life comes to an end. It is a little sad, but this is the way of their life on earth.
The small streams that they need for their life on earth are also a dying “breed”. These small clear running streams don’t fare too well with nearby construction of commercial and residential projects. It would only take one faulty siltation fence or retention pond from a nearby construction project to fail resulting in the smothering of such a stream under a blanket of mud and silt. The lampreys and all the other inhabitants of the stream would suffer greatly.
So relish those small streams. Spend some time in them to discover the wonderful diversity of life they support. And keep an eye on them to make sure they don’t suffer from any construction projects that might be nearby. Once lost, it is hard to get them and all the life that once was there back. The Least Brook Lamprey may not be the prettiest animal you will ever see. But they certainly are one of the more interesting animals that live here. Ensuring their continued survival in our world is the least that we can do!