New Podcast: All the Fish in the World with Dr. Dave Neely

[Zach Matthews]

Dr. Dave Neely is the Indiana Jones of fish. A research scientist with the Tennessee Aquarium Research Institute in Chattanooga, Dave has traveled the world capturing almost every species of fish imaginable–including most of the members of the taimen family.

[Dave N.]

Zach Matthews wrote:

Dr. Dave Neely is the Indiana Jones of fish…

Except uglier, with no lasso, and with a hat that’s way less cool.

I misspoke — the fifth taimen is in the Tumen River drainage, which forms the border between <China> and North Korea (which is still pretty heavily militarized!). My bad. Maybe I shouldn’t have cracked that second IPA during the interview…

Also, if I would have realized that you’d already done a podcast with Joe Tomelleri, I would have given him full props — none of the Mexican work would have happened without him and the rest of the gang!

[Tim Angeli]

Nice podcast Zach and Dave – I finally got around to listening to it. Really interesting stuff.

Dave, do you know how the relatively new ‘Native Trout Conservation’ regulations in Yellowstone are playing out? Among other changes, they implemented a mandatory kill policy for all rainbow and brook trout in the Lamar River drainage, and I’m wondering if any of the effects of that policy change have begun to manifest yet.

Thanks!

[Dave N.]

Hi Tim,

Sorry for the delayed response. It’s been a crazy couple weeks.

The regulation has only been in place for a year, so probably not long enough to have much of an effect. It’s going to be nearly impossible to eliminate non-natives (particularly while trying to retain natural connectivity among Yellowstone cutthroat populations), but reducing them in that watershed is a reasonable goal — and at least for rainbows, may be achievable. Hopefully most anglers will actually follow the regulations and not just go fish elsewhere. There certainly could have been more outreach on the part of the Park justifying the change, but there’s likely a subset of anglers who aren’t going to be happy no matter what management actions are taken! It will certainly be interesting to watch over the next few years…

[Tim Angeli]

Thanks for the insight Dave. I’m very interested to see how it plays out in the coming years. The Lamar drainage is a great fishery, and I’m interested to see how the new conservation efforts affect it.

Can you comment on the extent to which fish / species move and redistribute within a river system, and how that may impact the efforts to minimize the rainbow population in the Lamar? The Lamar is obviously part of the Yellowstone drainage, which has a healthy population of rainbows. There are no obstacles, that I know of, that would inhibit those fish in the Yellowstone from moving up into the Lamar drainage, even pushing into the headwaters of the system like Slough and Soda Butte creeks. Can you speculate as to what extent such redistribution of the rainbow population might occur in the Lamar? I suppose the fisheries biologists that work for Yellowstone must think that the rainbows will be killed faster than they repopulate.

Thanks,
Tim

[Dave N.]

Stream fish, even those things that we think of as being relatively sedentary like darters and sculpins, have an amazing ability to move when they get the opportunity. This isn’t just larval drift or downstream dispersal of juveniles — this is active movement upstream as well. I actually just ran some numbers on post-glacial dispersal rates for mottled scupin, largescale stonerollers, and central stonerollers — fish for which I have some genetic data available and can track dispersal patterns from refugia. For all three, the minimum post-glacial dispersal rate over the last 18,000 years is around 30km/yr. This is probably on the low side, as the initial conditions were probably highly turbid with fine glacial silts, which isn’t particularly great habitat for most fishes. For sculpins, which are often said to move <50m in their lifetime, this is remarkable! Keep in mind, however, that this is northward dispersal into previously glaciated areas as the glacial front receded, so there’s no fish fauna there to have to compete with. Interestingly, if you look at dispersal rates for introduced populations of a couple species of darters in the mid-Atlantic region, both exhibit dispersal rates ~35km/yr downstream and ~30km/yr upstream. This is a situation where there’s no similar darter species occupying that niche, allowing rapid (unfettered?) colonization. If this is the case, why do so many fishes down here in the southeast have such small geographic ranges? It’s not all isolation by geographic, habitat, or thermal barriers… I suspect that invasion rates are tied to structure and ecological interactions with the existing fauna, and that it’s more difficult for new species to establish and disperse in communities that already are packed with similar species — unless they have some novel trick or otherwise minimize niche overlap. This is actually something I’m looking at in a bit more detail…

Long story short, if populations of cutthroats can be maintained at a relatively high density, it may reduce the frequency of rainbows migrating up into the system. If you combine that with a mandatory kill policy and high angler effort, it might be enough to keep rainbows at a very low level. The big question is whether this will be enough to compromise reproduction? Recruitment? Will the lower frequency of rainbows actually increase incidence of hybridization with cutts (as seen elsewhere where one species is present at very low densities)? I don’t know, but the alternative strategy of doing nothing will almost certainly lead to near-replacement of cutts by rainbows in the system.

The bigger issue is with brook trout. I’m not sure there’s enough angler pressure on tiny headwater trickles to knock them down low enough to either reduce recruitment or allow cutts to reestablish… but it will sure be interesting to watch!

[Tim Angeli]

Awesome, thanks Dave. Very interesting data for the dispersal rates of the sculpin, stonerollers, and darters – 30km/yr is much farther than I would have imagined. Like you said, the inter-population dynamics in a system like the Lamar, where there are multiple established species, will likely be much different. It will be interesting to follow over the coming years as data becomes available. In my opinion, any action to conserve the cutthroats is far better than sitting back and watching them become extinct.

Thanks again for the insights, very interesting.

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