Is it a Steelhead or a Rainbow? With Katie Kobayashi

Tom Rosenbauer (00:01): My guest today is Katie Kobayashi and I met Katie at at Patagonia Baker Lodge this past December. She was there with with her dad and with a bunch of friends of theirs. It was a quite a lively week. We had a lot of fun. We were we were filming. I was there with the new Fly Fisher crew. We were filming, but we had dinner with these guys. And Katie impressed me because she was

Katie Kobayashi (00:17): You

Tom Rosenbauer (00:30): I think she was the only one that went out in the most miserable rainy day I can ever remember with a guide to try to catch a big brown trout on a streamer. The rest of us stayed back in the lodge and stayed comfortable. And ⁓ also, as I remember most days you caught a big brown trout when you were there, Katie. So.

Katie Kobayashi (00:36): You Yeah, that rainy day was on the list of probably coldest days of my life. I was pretty soggy.

Tom Rosenbauer (00:58): Yeah. Yeah. And it was summer in Patagonia, right? Anyway, Katie is, is a fish biologist and Katie's done some research that I think will be of interest to podcast listeners. So Katie, why don't you first tell people how you got where you where you are today. And then we can talk about talk about some of your research.

Katie Kobayashi (01:22): Sure. Boy, how did I get here? ⁓ I have been fascinated by fish for as long as I can remember. You mentioned that you met me on a fishing trip with my dad and that's really how it all started. Even as a kid, we would go out on lakes and go on fishing trips and catching critters and being outdoors has always been a huge part of my life. ⁓ So when I got to ⁓

Tom Rosenbauer (01:47): Mm-hmm.

Katie Kobayashi (01:54): ⁓ College, I quickly found that it turns out you can make a career out of that. ⁓ So I studied biology ⁓ and then went and got a PhD in ecology and evolutionary biology. And I'm now a fisheries biologist with Stillwater Sciences where I work with resource managers and... ⁓

Tom Rosenbauer (02:01): Yeah.

Katie Kobayashi (02:21): different conservation organizations on water issues surrounding fish. And in particular, I work with a lot of salmonid species. So salmon and trout here on the Pacific coast.

Tom Rosenbauer (02:34): And you work for the government for a while too, right?

Katie Kobayashi (02:37): I did, yeah. So during my PhD, I collaborated quite closely with ⁓ federal fisheries biologists at NOAA Fisheries and worked with them on a number of conservation projects, research projects down in the Santa Cruz, Monterey Bay area, ⁓ looking at migratory patterns in steelhead, effects of wildfire. ⁓

Tom Rosenbauer (02:59): Mm-hmm.

Katie Kobayashi (03:06): among a number of other issues that are near and dear to our hearts here in California.

Tom Rosenbauer (03:11): Yeah. So ⁓ so let's talk about what you what you have discovered about ⁓ steelheads, steelhead and rainbows, which which may be stuff that's not in the, know, in the in the popular. ⁓ Lexicon, Lexicon, I don't know. Anyway, it hasn't been available to us civilians yet, right?

Katie Kobayashi (03:31): Ha Yeah, well I think what is starting to become, ⁓ at least among us anglers, is what we know is that steelhead and rainbow trout are the same species, two different life history forms of the same species. And ⁓ specifically steelhead is typically used to refer to trout ⁓ that migrate to the ocean and return to spawn similar to the life cycle of ⁓ the other salmon species. ⁓ Whereas rainbow trout spend their entire life cycle in freshwater. This is something that as scientists we've known for a while, anglers who are fish nerds have realized that folks like my dad, know, sometimes it takes them a little while to for that little bit to click. ⁓

Tom Rosenbauer (04:30): ⁓

Katie Kobayashi (04:33): But I know. ⁓

Tom Rosenbauer (04:33): you're in trouble with your dad now.

Katie Kobayashi (04:39): But what we've been studying more recently is what the real genetic underpinnings of that difference between these life histories are. And what we've found is that... ⁓

Tom Rosenbauer (04:50): Mm-hmm.

Katie Kobayashi (04:54): especially in populations within central California, those major life history differences of going out to the ocean, becoming a steelhead and returning to spawn versus staying a little rainbow in a creek for your entire life ⁓ can be attributed to essentially a single ⁓ region of their genome, a single, what we call a super gene. ⁓ And just like studying basic genetics in school, you'll remember the examples of if you have brown hair and blonde hair, you have one gene for each. And depending on which versions of those genes you have, it's going to tell if you're going to have brown hair. We see a very similar thing in trout, which is there's an anadromous gene or a migratory gene. ⁓ is the less jargony term for it, and a resident gene. And you get one from mom, you get one from dad. And depending on what combination of those genes you get will predict to a very ⁓ predictable level whether or not an individual fish is going to migrate.

Tom Rosenbauer (06:10): Now this is new stuff because because I know in the popular literature you will read that steelhead and rainbows have exactly the same DNA right. And so this is this is news. This is news that there is there is a real there's a steelhead gene super gene.

Katie Kobayashi (06:21): Yes. there's a steelhead super gene. That's a great way of putting it. Now, the same DNA component comes into play in the sense that these are still biologically the same species, right? So steelhead and rainbow trout can reproduce with one another and offspring of a single pair of steelhead or rainbow trout can...

Tom Rosenbauer (06:33): Yeah.

Katie Kobayashi (06:55): become one or the other. So you can have a steelhead and a rainbow, they spawn together and produce a mixed batch, right? You can have two steelhead if they both have just the migratory genes are gonna produce mostly to all steelhead. ⁓ So the same DNA often refers to the fact that these two species can reproduce with one another.

Tom Rosenbauer (06:56): Mm-hmm. Right?

Katie Kobayashi (07:22): They are the same species, but this gene, so just like ⁓ we have genes for eye color and hair color, there's a gene that codes this whether or not you're gonna migrate piece. The steelhead super gene, I like that term for it.

Tom Rosenbauer (07:39): Well, that's just it was your term. Right. I'm just parroting back.

Katie Kobayashi (07:41): But adding the steel head, it makes it catchy.

Tom Rosenbauer (07:47): Yeah, yeah. So so that means that if in a given red in a given nest in a stream, the fry hatch, and some of them are gonna are predetermined that they're going to go to the ocean and some of them are just going to stay put if

Katie Kobayashi (08:04): Yeah, that's exactly right. ⁓ So especially in central California, where I've done a lot of my research, we have very mixed populations or what we call partially migratory populations, which means ⁓ in the same beats that we're fishing or doing research, we see both life history types in the same habitat, sharing the same habitat. ⁓

Tom Rosenbauer (08:18): Yeah.

Katie Kobayashi (08:31): which means there's a lot more variation in this gene. ⁓ And so what happens is you may have two steelheads bonding together. What's particularly common is male steelhead are particularly prone to this stay-coated gene. ⁓ And so you'll get these tiny little males that we call sneaker males that will

Tom Rosenbauer (08:55): Mmm.

Katie Kobayashi (09:01): ⁓ you know,

Tom Rosenbauer (09:02): Sneaker.

Katie Kobayashi (09:03): do exactly what it sounds like. They'll jump in and spawn with the steelhead and then you get even more variation in which, you know, which of these gene ⁓ ecotypes are being added to the eggs in the basket, so to say. ⁓ And so a lot of my research has then looked at the juveniles that come from these ⁓

Tom Rosenbauer (09:05): Yeah. Ugh.

Katie Kobayashi (09:31): these cohorts. I go out in the summer when they're still ⁓ fried and fingerlings ⁓ and tag them with RFID tags. So same technology we have in our credit cards, our library books, it's all over the place now. ⁓ And we set up antennas in the stream ⁓ that fish will swim past. And when they swim past, we get a ping indicating which individual, which tag just passed the antenna.

Tom Rosenbauer (10:00): Hmm

Katie Kobayashi (10:00): We also take a fin clip and a genetic sample of each of these fish when we tag them. And so we're able to pair up on an individual level which version of the gene each of these little fry has and whether or not we saw it migrate out to the ocean. So we have a series of antennas all through the river that we can track their movement. And like you said, we see a mixed bag.

Tom Rosenbauer (10:17): Wow.

Katie Kobayashi (10:28): especially in these anadromous spawning areas with partial migration. Some fish stay, some fish go. The mechanisms behind that are a little, there are a couple different things that kind of influence the likelihood. But yeah, it's really quite fun to track them.

Tom Rosenbauer (10:50): What kind of things influence the likelihood? Do know? Or do you suspect?

Katie Kobayashi (10:54): ⁓ There's a lot of, ⁓ we've found a lot of correlations, ⁓ but the exact mechanisms are still a bit of a black box. We know that ⁓ growth is an important component. ⁓ So one hypothesis is that ⁓ the way this gene works is ⁓ the trigger

Tom Rosenbauer (11:07): Mm-hmm.

Katie Kobayashi (11:23): to leave is somehow dependent on whether or not fish hit a certain size, grow to a certain size by a certain point in time. ⁓ And part of this comes from kind of the evolutionary ⁓ theory that survival in the ocean, which is a big scary place with lots of scary predators, ⁓ is very dependent on body size. So, ⁓

Tom Rosenbauer (11:49): Mm.

Katie Kobayashi (11:51): If fish grow fast enough to increase the likelihood of survival in the ocean, it might be beneficial to migrate ⁓ to the ocean where you can get big. ⁓ You can then reproduce more ⁓ or produce more offspring ⁓ versus ⁓ fish in streams where Growth is very slow, there's not a lot of feeding opportunities. You never get that big that quick. For example, we see this a lot in some of the more southern populations. ⁓ Survival is gonna be really low if you go to the ocean. So. ⁓ you never quite hit that threshold to trigger you to migrate. ⁓ Some of the other important factors, sex is really important. So females are more likely to migrate than males. ⁓ And that's because ⁓ egg production is tightly correlated with body size. ⁓ And so the payoff,

Tom Rosenbauer (12:51): Mm. Mm-hmm, yeah.

Katie Kobayashi (13:02): as a female to get big and produce far more eggs is a lot bigger ⁓ difference than, you know, I mentioned to these sneaker males earlier. The cost of getting big for males is much smaller. So we see a difference where this gene actually, if you have one of each gene, one migratory and one ⁓ resident gene,

Tom Rosenbauer (13:14): Yeah.

Katie Kobayashi (13:31): So you're heterozygous. ⁓ If you're female, you're more likely to go. And if you're male, you're more likely to stay. So there are a lot of these kind of factors that interact with whether or not you have a certain copy of this gene that then come into play.

Tom Rosenbauer (13:49): I got a couple I got a couple questions that I'm thinking of. One is, these are these are excuse my ignorance, because I also studied fisheries in college, but I never became a fish biologist. but in in for any given female that lays eggs in a red, ⁓ there can be multiple males that fertilize those eggs, right? So can be so it can be a mixed genetic bag. OK.

Katie Kobayashi (14:09): Mm-hmm. Yeah, absolutely. Yep. Yep. And that's exactly what we see with these sneaker strategies, especially as you'll have, you know, multiple, you know, one female lays a bunch of eggs, some and some go to the steelhead and some go to these sneaker males. ⁓ But even so, there can be multiple, multiple male steelhead fertilizing the same red. ⁓ Absolutely. Yep.

Tom Rosenbauer (14:29): Yeah. Mm-hmm. Mm hmm. Yeah, okay. And my other question is, originally, were rainbows slash steel had an anadromous and rainbows became landlocked or were rainbows originally landlocked and became an anadromous? You know, do we do we know? Okay, tell me, tell me, tell me.

Katie Kobayashi (15:00): That's a great question. I do know, we do know, yeah. ⁓ The ancestral form of the steelhead rainbow trout life history spectrum ⁓ is the anadromous migratory form. that's the rainbow trout, sorry, rainbow trout and steelhead, the species is closely related to the other Pacific salmon species. So coho, king, ⁓

Tom Rosenbauer (15:17): Okay. Mm-hmm.

Katie Kobayashi (15:30): know whole gamut of Pacific salmon ⁓ and so and the closest relatives fun fact are coho. ⁓ So originally we had an adromous steelhead that were migrating ⁓ into streams to spawn just like the other salmon species and this resident life history evolved largely when populations ⁓

Tom Rosenbauer (15:32): Right. Right. Hmm, interesting.

Katie Kobayashi (16:02): became landlocked or otherwise ⁓ were no longer able to migrate. So you get these populations that are isolated, can't migrate anymore. ⁓ And basically in parallel across a number of populations, we see again and again that this resident life history evolves quite rapidly. ⁓ As... due to the selection pressure of no longer being able to migrate. In fact, this is a great jumping off point, Tom, is ⁓ we actually still see that quite regularly today. So a lot of my work looks at ⁓ places where, for example, steelhead were taken 100 years ago in a bucket upstream above a big waterfall ⁓ by loggers who wanted angling opportunities.

Tom Rosenbauer (16:53): huh, yeah. Right.

Katie Kobayashi (16:57): ⁓ drop them off above a waterfall and within a matter of a hundred years you can have a fully resident population that is self supporting upstream of these waterfalls. And so a lot of what I've done is actually looked at these places where we have steelhead down below waterfalls, rainbow trout above, and actually figure out the timing and difference in their ⁓ gene frequencies and

Tom Rosenbauer (17:05): Mm.

Katie Kobayashi (17:27): origin, whether or not they came from the same population or were planted from, you know, the McLeod or some hatchery. ⁓ And so we can actually see where these resident populations upstream, we like to call them perched populations now because they're perched above a, you know, anadromous population down below. We can see whether or not they originated from the same downstream population ⁓ were introduced, you know, by

Tom Rosenbauer (17:43): Mm-hmm. Right. Yeah.

Katie Kobayashi (17:56): CDF &W or some sort of agency program, we can actually trace back where those individual populations came from.

Tom Rosenbauer (18:04): So are these perch populations still throwing off ⁓ steelhead that go down over the waterfalls and never get back?

Katie Kobayashi (18:13): They do. It depends. So some of my research actually showed that... So I used to work in a watershed that had two kind of primary tributaries that there was barriers on each. ⁓ Below those barriers on both tributaries, was a pretty ⁓ strong steelhead population. We still see... decent returns, lot of true migratory fish that are coming back after several years getting big. And those fish were introduced above both barriers in both tributaries. ⁓ roughly 100 years ago. ⁓ And so I went up and tagged fish up above these waterfalls too, which was quite a recon mission. ⁓ We got up above these waterfalls, tagged fish up there too, and had those antennas set up that I mentioned earlier. And what we found is that ⁓ the gene frequencies of that anadromous versus ⁓ resident gene were different.

Tom Rosenbauer (19:09): Mm-hmm. Right?

Katie Kobayashi (19:28): in those two upstream populations, one was far further down the evolve to residency ⁓ path than the other. And in that population that still had a little bit of that anadromous gene left over in it, we saw fish migrating down over a waterfall and out to the ocean. And this is like a 200 foot waterfall. Like this is no like tiny barrier. Fish are not getting back up this. ⁓

Tom Rosenbauer (19:49): Mmm. Hmm. Yeah. Uh-huh.

Katie Kobayashi (19:57): when they come back. ⁓ But ⁓ impressive little subset of them finds a way to bounce down a 200 foot waterfall and make it past our antennas and to the ocean still to this day.

Tom Rosenbauer (20:11): Hmm. So one one population was different in the percentage of ⁓ downstream migrants. And do think that's just from random random variation? Or do you think there was some environmental factor? Because they were stocked at the same time, right? They're stocked about the same time.

Katie Kobayashi (20:19): Yeah, exactly. Probably a combination of both. They were stalked about the same time, ⁓ but the rate at which they evolve seemed to be different. ⁓ And that could be due to a number of things, and we don't know for sure. ⁓ But that could be due to selection pressure. That could be due to one of the barriers being

Tom Rosenbauer (20:34): Yeah. Mm-hmm.

Katie Kobayashi (20:56): smaller than the other and so there's more genetic mixing happening ⁓ in certain times. ⁓ There could have been additional introduction events, ⁓ but basically these two populations have evolved completely independent independently of each other. So ⁓ the selective pressures, the environmental pressures telling fish to migrate are going to be independent of each other as well.

Tom Rosenbauer (20:58): Uh-huh. Mm-hmm. Yep. Hmm. That's fascinating. I have. Yeah, you know, I have a little wild trout stream in my backyard and I have wild rainbows and Browns and certain times a year the rainbows disappear. They just they're just gone. And I don't know if they've got some migratory gene in him, but of course they can't get to the ocean.

Katie Kobayashi (21:28): Yeah, it's pretty fun. Yeah.

Tom Rosenbauer (21:53): they get to the Champlain Canal, which isn't gonna do them any good, they're gonna die. ⁓ But I, you know, I often wonder why they, you know, why they move around so much, why they disappear.

Katie Kobayashi (22:04): Yeah, so researchers have actually gone out and tried to see whether or not this trend, ⁓ know, rainbow trout have been introduced all over the place in all sorts of different systems now. ⁓ And this gene exists in all of them. And so one of the big questions has been ⁓ what happens to these populations that

Tom Rosenbauer (22:15): Mm-hmm, yeah. Yeah.

Katie Kobayashi (22:27): don't have access to the ocean, but perhaps they have access to a really large, productive lake or some sort of exactly feeding habitat that serves as a proxy for that productive marine environment versus staying in the creek. And as you may be guessing, we see that gene for migration versus stay. ⁓

Tom Rosenbauer (22:35): Like, like the Great Lakes. Yep. Yeah.

Katie Kobayashi (22:56): can hold true in those sorts of systems too. So completely landlocked ⁓ where that gene still predicts whether or not a fish is going to stay in their tributary, so perhaps the creek in your backyard, ⁓ versus migrate to better feeding grounds. ⁓ It's not the ocean, but it serves a very similar ecological purpose. And so if they have that opportunity, that anadromous migratory gene can still ⁓ be maintained in the population.

Tom Rosenbauer (23:30): huh. Okay. So I have to ask you, I have to ask you the million dollar question that is, that is going to, that is no matter how you answer this, it's going to provoke a reaction. Okay. So if there is a, if there is a steelhead gene, right. Or super gene are the migratory fish in the great lakes, steelhead.

Katie Kobayashi (23:51): huh. huh. Hahaha

Tom Rosenbauer (24:01): And you, and you got to say yes or no. You can't, you can't waffle. You can't waffle on this one. can't be a biologist.

Katie Kobayashi (24:05): It's gotta be yes or no. Ugh, I'm gonna say no. I know, no. I totally, you know, knowing what I know about the, no I did. Knowing what I know about the gene, could pick either side and make an argument for them. But my hot take is going to be no, because they're not migrating to a marine environment.

Tom Rosenbauer (24:13): You didn't know I was gonna put you on the spot, did you? ⁓ You didn't expect this one? Yeah. OK, give me give me that give me.

Katie Kobayashi (24:41): and I like to use the term steelhead exclusively for fish that are migrating to the ocean, whereas migratory fish in the Great Lakes are migratory, but not truly anadromous.

Tom Rosenbauer (24:41): Okay. Spoken like a true West coaster. So OK, so you gave us you gave us one side of the argument. You said it could be argued the other way. So how would someone defend a lake eerie fish as being a steelhead?

Katie Kobayashi (25:16): Sure, well, ⁓ you know, the gene that's making them migrate like a steelhead is the same in a Lake Erie steelhead as it is for a Central Coast steelhead, right? So if it's the same gene and the same pattern, why wouldn't it get the same name?

Tom Rosenbauer (25:17): you Right. Okay. So it can be looked at either way. Yeah, I told you you were supposed to waffle but you did give me a definitive answer. did say, yeah, you did say.

Katie Kobayashi (25:37): It can be looked at either way. I gave my definitive answer, which was based on how I define an anadromy, more so than how I define, know, steelhead are an incredibly flexible species. So even though we like to categorize them into these two bins of rainbow trout steelhead and one stays and one goes, there have been, there are papers that have documented as many as

Tom Rosenbauer (25:47): Okay. Mm hmm. Yeah. Yeah. Right. Yeah.

Katie Kobayashi (26:06): 50 some different life history strategies that span the whole spectrum from full-blown salmon, goes to the ocean, comes back at four years, spawns once and dies to steal a ⁓ rainbow trout that stay forever. But in between there are some that go some years, stay over summer in the creek other years. There are... ⁓

Tom Rosenbauer (26:09): Mm. Mm-hmm.

Katie Kobayashi (26:33): individuals that spawn multiple times, that may survive even if migratory opportunities in a particular water year are limited. ⁓ some just go to lagoons, so these coastal productive estuary systems that we see on the west coast, so some will migrate to the lagoon, these big estuary areas where they can grow and get big without ever actually making it truly to the ocean. ⁓ Exactly, so those are migratory residents technically.

Tom Rosenbauer (27:03): So those aren't steelhead, right? I'm curious, are there populations of steelhead that die after spawning? I mean, some of them always die because there's a lot of rigor there, but are there some populations where all or most of them, most of the steelhead die after spawning?

Katie Kobayashi (27:30): ⁓ There are populations where migratory fish a large ⁓ most of them die after spawning but it's not coded in them the way it is in the other pacific salmon species so those populations are mostly dying simply because

Tom Rosenbauer (27:36): Mm. Yeah. ⁓

Katie Kobayashi (27:46): migrating and spawning is a very energetically costly process. So even if you are biologically able to migrate again, reproduce again, just the burden of migrating, having limited feeding opportunities, holding in cold, fast water. ⁓

Tom Rosenbauer (27:50): Yeah.

Katie Kobayashi (28:09): And then, you know, digging reds and spawning is just such a taxing process that a high percentage of them die ⁓ simply because of that energetic burden.

Tom Rosenbauer (28:22): Yeah, yeah, even in even in, you know, inland trout stream, some of the fish die after spawning because it's tough. It's a lot of work and a lot of fight, a lot of fighting, a lot of migrating.

Katie Kobayashi (28:27): Yeah. Yeah. Yeah. You go to some of these salmon systems and during spawning season and you see how beat up they get digging reds, you know, digging, digging around in rocks with a slimy little tail. It's it's hard on a hard on a fish.

Tom Rosenbauer (28:40): Mm-hmm. Yeah. Yeah, really. ⁓ Are there any Pacific salmon that like individuals that that don't die after spawning? Does that ever happen?

Katie Kobayashi (29:00): Oof, I think he asked me this question at the lodge. maybe it was Mark. ⁓

Tom Rosenbauer (29:04): No, it wasn't me. I don't think it was. Maybe it was me.

Katie Kobayashi (29:12): As far as I know, no.

Tom Rosenbauer (29:14): Okay. Yeah.

Katie Kobayashi (29:16): ⁓ The Pacific salmon species are all considered, the term is simulparis, which means they automatically die after spawning.

Tom Rosenbauer (29:29): I remember seeing.

Katie Kobayashi (29:30): whether or not they're anecdotal accounts suggesting otherwise, I am not aware.

Tom Rosenbauer (29:36): Yeah, I remember seeing in Alaska, I remember seeing ⁓ very small young ⁓ male salmon, they called him jacks. And I was wondering if if they die as well, because they're, you know, they're like, not really ready to do their thing. But they're trying.

Katie Kobayashi (29:45): Mm-hmm. Yeah, yeah. Jacks are ⁓ a common life history in a few of the salmon species and those are fish that return prematurely, but they are sexually mature so they will still reproduce and die ⁓ the same as, you know, the older bigger fish that waited a little longer.

Tom Rosenbauer (30:00): Yeah. ⁓ okay. Okay. Okay. Okay. All right. What else? Anything else? I your research is fascinating. Anything else that you've discovered about, about cell monads that we may not, we may not know about yet that you can tell us?

Katie Kobayashi (30:32): gosh. ⁓ Well, some of the cool stuff coming out of the research lab that I'm affiliated with down in Santa Cruz ⁓ and is starting to look at this gene. ⁓ mentioned a little bit that it maybe holds true in other places where steelhead have been introduced. ⁓ So one place that we're now starting to look to see whether or not this this pattern holds is New Zealand. So ⁓ some of these more remote introduced fisheries, New Zealand, Patagonia, ⁓ places that happen to also be

Tom Rosenbauer (31:08): Hmm

Katie Kobayashi (31:19): great locations for sampling. Oh darn. We don't have a really good sense of what the relative rates of migration and this migratory gene are.

Tom Rosenbauer (31:23): Yeah, we know that. Mm-hmm.

Katie Kobayashi (31:37): spent plenty of time down in Chile now and have seen that some of those rainbow trout get really, really big, but we don't really see those same really chromed up, sea run, anadromous rainbow trout in the systems that we fish in down there. And the same is true in a lot of places in New Zealand. So ⁓ one of the things we're kind of exploring is...

Tom Rosenbauer (31:51): No. Yeah. huh.

Katie Kobayashi (32:03): whether that has to do with the gene frequencies ⁓ or the environmental conditions that are occurring in some of those other introduced populations. I'll say we haven't quite come to an answer yet. More sampling is needed. Yeah.

Tom Rosenbauer (32:14): That's it. I think more sampling is needed in ⁓ Patagonia. I'll help you out. You know, I was reading recently about some Pacific, no, Atlantic drainage rainbow trout streams in Argentina that do have runs of steelhead. ⁓ But on the Chilean side, mean, well, take the Simpson River that you fish. ⁓ King salmon. go to the ocean and they come back and they spawn and they're fine. The rainbows apparently don't because you don't see you mean you see big rainbows but you don't see steelhead looking rainbows in the Simpsons. So they have access.

Katie Kobayashi (32:57): Yeah, even when I've gone down and fished the ice in and some of those lower, bigger pockets of water, you catch big rainbows down there, but they're not that chromed up steelhead type. Another factor that plays into whether or not fish migrate or whether or not this gene is really a good... ⁓

Tom Rosenbauer (33:12): No, no, I wonder why.

Katie Kobayashi (33:27): It comes back to how this gene works. I mentioned a little earlier that growth is likely a big... ⁓ of the mechanism that this gene uses to trigger migration. ⁓ And another place where you see this, where this has been studied a little more, is ⁓ in some of the more northern ⁓ rainbow trout populations, say in Alaska, where I gave the example earlier of if you don't get big enough, it's not beneficial to go to the ocean because survival is still low. But there's this opposite end of the spectrum where

Tom Rosenbauer (33:39): Mm-hmm. Okay. Yeah, yeah.

Katie Kobayashi (34:05): If the growth opportunities in the stream are so good that the benefit of going to the ocean and risking that marine survival ⁓ experience is, you know, not worth it. ⁓ That, you know, they may still have that migratory gene, but the trigger to migrate has... ⁓

Tom Rosenbauer (34:19): Mm-hmm.

Katie Kobayashi (34:36): you know, moved so far to one end of the meter that they never actually hit that threshold and migrate. So one possibility is in some of these systems where there are big growth opportunities and food subsidies, you know, there's tons of big meaty terrestrial insects for fish to get fat on in the stream in Chile, in some of these systems. The... ⁓

Tom Rosenbauer (34:57): Yeah, yeah, yeah, yeah.

Katie Kobayashi (35:03): benefit of migrating just isn't there the same way.

Tom Rosenbauer (35:06): Mm-hmm.

Katie Kobayashi (35:08): So that could be one part of it. Part of it could be where fish are introduced from. So a lot of these ⁓ introduced populations internationally are from, you know, originally hatchery strains that probably had a pretty high ⁓ frequency of the rainbow trout gene versus the steelhead gene to begin with. So the variation might just not be there in the first place. So these are kind of the things we're trying to tease apart and understand.

Tom Rosenbauer (35:09): Mm-hmm. Yeah. Okay. Yeah. Mm-hmm. Mm-hmm. Mm-hmm.

Katie Kobayashi (35:38): Yeah.

Tom Rosenbauer (35:38): Cool stuff. Cool stuff. Yeah, it's interesting because southern Alaska has steelhead, right? And as you go north, you lose the steelhead populations, but there's still plenty of resident rainbows that have access to the sea.

Katie Kobayashi (35:44): Great. Yep. Yeah, yeah, it's interesting. There's definitely, we've found there's a pretty ⁓ predictable latitudinal gradient where at the far north and the far south ends of the native range of steelhead and rainbow trout, those high north and far south extremes are. ⁓ there are lower rates of that anadromy steelhead gene, sorry, not the gene, but the life history type itself compared to that kind of intermediate range. So it seems like there's kind of a, there's a Goldilocks, right? There's a too small, just big enough, too big kind of curve. ⁓

Tom Rosenbauer (36:25): Yeah. Mm-hmm. Yep. Yep. So it's nature and nurture. OK.

Katie Kobayashi (36:42): nature and nurture and yeah where on that scale the trigger occurs is probably has is where that gene comes into play so yeah yeah

Tom Rosenbauer (36:53): Okay. Fascinating stuff. I love it. I love I love hearing about it. I love hearing about it. Well, thank you, Katie. I really appreciate you taking the time from your busy schedule as a biologist to come on the podcast and educate us on it was really, I think it's more fun fishing at Patagonia Baker Lodge.

Katie Kobayashi (37:13): my gosh, this was so much fun. ⁓ Sure sure, but you know, I have a whole year before I get to think about that again. So in the meantime, nerding out about fish is the next best way to spend my time.

Tom Rosenbauer (37:25): Yeah. Yeah, nobody's feeling sorry for either you and me and our jobs, are they? All right, Katie, it was great to see you and thanks again.

Katie Kobayashi (37:33): No, sure aren't. Thank you, this was great.