Wednesday, Nov. 7, 2018
Editor's note: As of Nov. 12, Rice Rivers Center researchers' count of baby sturgeon found in the James River this fall has climbed to 148.
For the past eight years, Matt Balazik, Ph.D., and other researchers from the Rice Rivers Center at Virginia Commonwealth University have conducted trawl surveys in the James River in hopes of finding Atlantic sturgeon, the once-plentiful ancient fish that was listed as an endangered species in 2012.
During that time, Balazik and his peers have identified more than 600 different adult sturgeon. Among the hundreds of thousands of fish they found on their research trips, however, not once did they ever spot any baby sturgeon — and only twice did they find any juveniles of the species.
Then, last week, baby sturgeon started showing up in researchers’ nets. In the course of a week, Balazik and his fellow researchers identified 24 baby sturgeon during a series of especially productive trips on the river.
“We’re really excited,” Balazik said. “It’s been very encouraging. After going out all those times and catching nothing, it’s been rewarding to start to see these fish at this stage.”
The Rice Rivers Center is at the center of the Virginia Sturgeon Restoration Team’s effort to restore the sturgeon to its native range and historical stature within state waters. The center’s work receives support from the National Oceanic and Atmospheric Administration and the Virginia Department of Game and Inland Fisheries. In 2012, Balazik documented fall spawning by the James River’s sturgeon, overturning a longstanding assumption that the fish spawned only in the spring.
The imbalance between researchers’ findings of adult fish and younger fish has been a source of concern, because it indicates possible issues preventing survival at a rate to sustain the population in the James. Sturgeon leave the Chesapeake Bay tributaries while immature and mature in the ocean, returning multiple times to spawn in the tributaries.
During the past week, Balazik and other Rice Rivers Center researchers have been documenting the baby sturgeon they find, attempting to identify their drifting patterns, among other key details.
Balazik answered questions from VCU News about the baby sturgeon and the importance of their appearance in the James.
Rice Rivers Center researchers locate baby sturgeon in James River
In 2016, you caught two juvenile sturgeon in a gill net in the James. These were the first juveniles of that species found in the James in more than a decade. How are this year’s discoveries different?
Those were age-1 fish, and these are actually age-0 fish. These are fish that were just hatched in mid-September. Because we've been doing these trawl surveys one way or another for eight years and never caught any sturgeon this young, we’re trying to figure out what’s going on this year. Is it a good bumper year because of all the river flow from the heavy rains and there was a lot of good spawning habitat this year? We’re not sure.
How significant are these findings for the sturgeon population in the James River?
It's exciting, but we knew that this was going on. We knew that there were fish at this age and size class, because the fish are spawning. But the fact that we're catching so many this year when we haven’t caught any in previous years makes me really hopeful that this will be a bumper crop year and we’ll get a bunch of 1-year-olds next year.
In the James, we’ve been having problems catching 1-year-olds when researchers at other rivers with much lower abundances of adult sturgeon spawning have caught a lot more than us. And we’ve brought in people from other rivers to work with us who have been catching them in their rivers and we’ve tried all kinds of methods, but we just do not catch age-1 fish. It’s nice to see these fish, though they still have a long way to go and a lot to deal with in natural mortality, mostly through predation, but what we’re really hoping is that we see them again next year.
Once they’re a 1-year-old, they’re pretty big and they’ve made it through the bigger threat of predation. Next year if we’re catching a bunch of age-1 fish, that’s when I’ll really start popping the champagne. So this is great and it’s giving us a lot of hope, but it’s really next year when we’ll see if this is really a bumper crop or we just happened to get lucky this year.
What do you think is the likely reason you’re seeing sturgeon this young this year?
I think it’s really the heavy flow in the river this year because we have gotten so much rain. The river flows were high and the ground was saturated and then we had some significant rain events right in the peak of the spawning season — that couldn’t have been timed any better. I think either the sturgeon spawned a little further downstream or they could get to better spawning habitat closer to where we trawl. We had a lot of fish that were hanging around the rapids this year and that’s a good spawning habitat. Those heavy flows may have cleaned out some sediment that has built up in a lot of spawning habitat and made that nice and clean. There are lots of possibilities, but we will probably never know what the trigger was. One possibility is that the sturgeon have bad or modest recruitment year after year and then they just wait for these bumper years to really build the population. We don’t know, but hopefully we’ll be able to track it over time.
What are the big takeaways for ongoing research into the sturgeon in the James River?
A fish technically isn’t recruited to the population until it’s actually reproducing itself. For sturgeon in general, their natural mortality is very high in their early few months to maybe half a year. Once they get some size to them — maybe like a foot long or maybe even a little bit longer, when they’re about 1 year old — they have very low natural mortality, so it’s kind of safe to say that once fish get to age 1, age 2, that most likely they will survive to recruit to the spawning population. For the James River, a male isn’t mature until they're around 10 years of age and a female around 15. But once they get to age 1, age 2, most likely they will make it to maturity and start to reproduce themselves and be recruited to the sturgeon population of the James. That’s why we're hoping to see a bunch of 1-year-olds next year this time. That would be a great sign for the future of the sturgeon in the James.