Evolution of Grand Canyon Science: Mike Yard 3

Well, um, let's, let's approach it like the timeline.

And it's important to identify that there are so many different researchers and collaborators on so many independent studies.

But the focus of our conversation principally today is going to be about both humpback chub and rainbow trout, and what we've learned about both of those species as well as the interactions with those species at different densities.

Uh, and so it- it'll be kinda nice to talk about that timeline and what we knew at the time and what we have learned since and how certain study programs expanded as well as contracted through time.

But we kind of, during our last podcast, talked about the near shoreline ecology study, which was, in a lot of ways, uh, a proof of concept of whether or not we could not only estimate abundance of juvenile chub, not adults, but juvenile chub in the main stem as well as their vital rates.

And based on their findings, allowed us to then approach the larger question of establishing a good monitoring program down below the LCR for juvenile chub, which we called the juvenile chub monitoring, and also in the LCR, so we could track how the, uh, small chub were responding to flows as well as part of their life history.

In turn, we combined this with an effort that you and I were involved with, the Natal Origin Study, which was trying to better understand where the providence of trout in and around the LCR were associated with.

Were they locally reproducing in the area or just slightly upstream, or was their source all the way up in Lee's Ferry? And what were the environmental factors at the time that were driving this? And so part of the Natal Origin Study was really to understand trout dynamics and understand also...

And so we'd-- It's almost like we'd put on two different hats, if you remember.

Oh, absolutely.

Yeah.

We...

And besides huge amount of sleep deprivation that we would do, we would sample our way from Lee's Ferry down through Marble Canyon, and then throw our chub hats on and start, uh, catching not only trout, but chub, to get an understanding of their abundance and vital rates.

Uh, and that program, uh- Lasted all the way to about 2015.

And we learned an inordinate amount based on that study and a concurrent study going on in the middle of the summer, kinda, uh, just right at the cusp of the monsoons happening.

Matter of fact, Tanner Carruthers was one of the techs on that study, uh, and it was run by Charles Ukulik and Maria Jewell.

And, uh, they were just like we were doing, uh, in the main stem, uh, catching young juvenile chub and marking them with these visual implant elastomer tags that I talked about last time that would give us an idea of their size and their location.

So they would mark them with a different color than what we'd see and use in the main stem.

So we could look at the effect of monsoons and the higher discharge and the displacement or active movement of these young fish into the main stem.

And so we could track not only that pulse of a change in abundance, but their vital rates.

Do they grow faster? Do they survive better or vice versa? And so, uh, a really neat study came out by, uh, Ukulik in 2014 on looking at all the dynamics that are going on, not only for the juvenile fish, but also the adults, and, uh, identified that a combination of there's a shared breeding of adults in both LCR and main stem, but there is a resident population in the LCR.

And those adults in the main stem tend to skip spawn, in that they don't run up into the LCR every year.

They're garnering resources to develop eggs.

You know, Randy males, you know, a bucket of sperm is, you know, a dime a dozen, but the eggs trying to grow of a certain size and produce enough gametes that they could reproduce in the LCR.

Alternatively, the LCR adults are growing better.