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TOM WHEELER:

Welcome to Econews Report. I'm your host this week, Tom Wheeler, Executive Director of EPIC. And joining me is my friend and colleague, Jen Kalt, Executive Director of Humboldt Waterkeeper. All right, Jen, you are going to be the emcee of today's show. What are we talking about?

JEN KALT:

We are talking about coho salmon in urban streams, specifically in Arcata.

WHEELER:

Hey, that's really exciting. Well, so we have two great guests with us, Colton Dixon, who is a master's student in fisheries at Cal Poly Humboldt. Hey, Colton. Hey, there. And Darren Ward, professor at Cal Poly Humboldt in the fisheries department, and he is a fisheries biologist and a freshwater ecologist. All right, Jen, take it away.

KALT:

Thanks so much for being on the show today. So you studied coho salmon in two creeks in Arcata, Janes Creek and Jolly Giant Creek. And so before we get into everything about coho, talk a little bit about these two creeks and why you wanted to study coho in them.

DARREN WARD:

I can talk a little bit about that. So, Janes and Jolly Giant Creeks are two of the smaller tributaries to Humboldt Bay, draining into North Bay through the city of Arcata. And they're much smaller than Freshwater Creek, Jacoby Creek, Elk River, the larger tributaries that sort of come in from the east. And we got interested in sampling the fish in Janes and Jolly Giant Creek for a couple of reasons. The sort of direct impetus was the city of Arcata Department of Environmental Services got in touch with me and asked if I would be interested in establishing a sampling program there. They had been doing some sampling in the past and hadn't had personnel and folks to continue that effort. And they approached me to see if I'd be interested in ramping it up again. And Colton is a grad student in my lab. As a grad student, I get stuck with doing all sorts of interesting side projects in addition to their thesis. So, I hired Colton to run the sampling program on the creeks.

KALT:

Oh, very cool. So Colton, what is your thesis on then, if it's not this?

COLTON DIXON:

So my thesis is looking at the impacts of seabird predation on coho salmon in Humboldt Bay. So there is a man-made island out in the bay called Sand Island. I know it's a really creative name, but a lot of local seabirds like Caspian terns and double-crested cormorants nest on this island. And back in 2017, Rebecca Garwood from CDFW started doing some scans on the island using an antenna and found that there was lots of pit tags on the island. And so then those pit tags are coming from salmon and mostly from salmon in or from Freshwater Creek here that flows into Humboldt Bay. So then multiple years of scanning has been done on this island and we are just trying to understand like how much of an impact or like how many fish are getting eaten. Now we're not gonna be able to have like an exact number like the whole population, but we know how many tags are ending up on that island and we're just trying to understand what sort of an impact seabirds could be having on local salmon populations.

KALT:

Wow, very interesting. So Sand Island, presumably, was created by dredge spoils being dumped there when you say man-made island. Describe for our listeners where Sand Island is.

DIXON:

So if you're walking over by Cloth Lake in the Arcata Marsh and you look to kind of like the southwest, you might see just barely above the water level, a little mound of sand, basically. But that's from kind of like that area in the marsh. It's like a mile and a half away from there. And so just this small little lump of land that a lot of birds like to hang out on.

KALT:

Oh, very interesting, we'll have to have you back when you have some findings to report. So I just want to chime in for our listeners that a lot of people know Butcher Slough and McDaniel Slough. And so it's kind of curious that a lot of streams around Humboldt Bay have these different names where the waters are brackish, meaning the tides coming in and out and mixing with the freshwater. So Butcher Slough is the lower reach of Jolly Giant Creek, and you can see that by the Arcata Marsh Interpretive Center, that's Butcher Slough. And then McDaniel Slough is the lower reach of Janes Creek. So if we use those terms, we mean the same water body, basically. Okay, so the headwaters of both of these creeks originate in the Arcata Community Forest, and then they go underground when they come into Arcata. So can you talk just briefly about the creeks and what sort of land uses they're traversing as they're going through your sample sites?

DIXON:

Colton. Yeah, I'll take that one. So like you said, these creeks are starting up in the community forest, which we know is mostly like second generation growth redwoods, kind of the aftermath of logging. And so even up in those reaches, or that that part of the creek, you can see kind of some of the historical effects from logging, usually lots of lots of sedimentation, or just like silts and sands and loose gravel washing down into the creek. And so in that section, we might consider that we might call that like, oh, like, that's like, the wild quote, unquote, wild section of these creeks, but quickly leaving the community forest and then enters into urban arcada. And it's interesting to compare the two creeks because I feel like they once they get into town, they are dramatically different. So Jolly Giant, I mean, pretty much right, as it leaves the community forest, it just goes into a very long culvert that goes under Highway 101, spans all the lanes, and then it comes out into Shea Park. And then that's a nice park. And but then Jolly Giant then continues to go through a series of just like culverts and channels under the city, a few little sections that are daylighted or meaning that like, oh, look, there's like a random creek in someone's yard, and then it goes back underground. But Jane's mostly is, well, exposed, right? Everyone can see it, but going through behind housing development through agricultural fields, and eventually leading out there into to Humboldt Bay.

KALT:

So, you know, Shea Park, that whole section of the creek used to be underground as well. And a friend of mine who is in her 40s now, when she was in high school, she was part of the Arcata High School class that started hauling old couches and stuff out of there and digging out and daylighting that creek. So it's pretty wild to think about that now. It also goes past some contaminated lumber mills, Janes Creek and Jolly Giant Creek, both of them. So that's kind of where where I study these creeks and also bacteria pollution and so on. But they both end up at the Arcata Marsh Wildlife Sanctuary. And then there are some restoration sites along the creek. And that's where we can get into why you chose your sample sites where you did. And what is it you're trying to actually look at? What questions are you trying to answer with this study? So, Darren, why did you want to study these creeks? What did the city want to address and what kind of questions are you trying to answer with this study?

WARD:

That's a good question. So like you mentioned, Jim, both of these creeks have a history of some restoration work that had been done in the past. And there has been some fish monitoring that's been done, but not a lot. And so mostly what we're interested in is really just documentation. We want to know what fish are there, whether they're occurring within the areas where people have already conducted some habitat restoration, or maybe they're occurring in areas where there hasn't been any restoration yet. We might suggest that that could be a target for some future efforts. And then one of the big problems that often occurs on these urban streams is passage barriers, a culvert that's hanging that the fish can't jump through, or a long culvert that the fish might be reluctant to swim through. So that's really one of the really basic things that we wanted to know is where there's those kind of potential barriers. Are there fish that are getting above them? Like, are there fish upstream of those where it sort of demonstrates that at some point in their life cycle, they've been able to pass through that barrier? Because these are salmon, they have to go to the ocean at some point. So if we find them above those barriers, that's a good indication that there's fish passage. So, I mean, these are really, really basic sort of questions. We want to know where the fish are occurring. It's really as simple as that.

KALT:

So did you choose your sample sites then based on what you thought were fish passage barriers and what sites you thought might be good for restoration or was it mostly chosen by where the current restoration projects have been done?

WARD:

of those. So the city had some places they wanted us to sample because, for example, on Janes there had been a barrier removal in the past few years, so they wanted to sample on either side of that. And then some past, some restoration efforts, and also just to follow up on the little, on the sampling that had been done in the past. We picked some of the same locations so that we could sort of follow on, continue the record of data that we have coming from the same site. So it was a combination of all those. And what we ended up with is kind of a nice design, because for both of the creeks we have sample sites all the way from the marsh up into the forest, sort of evenly distributed as good as we could through town. It's a little bit challenging on Jolly Giant Creek because you can't, you don't have that much choice on Jolly Giant Creek. You've got to sample where the water is. We sample inside the culverts a little bit, but we're not going to bring all our sampling gear deep into the bowels of the city and try to drag seeds around inside the pipes.

KALT:

Crawling through tunnels.

WARD:

Jolly Giant Creek, we really are through town pretty much sampling every place where the creek appears, you know, where you can get to.

KALT:

Rhea Olson just did a great tour through Jolly Giant Creek, the section that you're talking about right now. So we'll link that in the show notes. It's really cool to see all those different sites and there's one right behind the co-op. Maybe people have seen it and thought, what is that water? It's actually a creek. So I read a little bit about your study and I know that you had 10 sample sites on each stream and you sampled them eight times. So why don't you tell us a little bit about what you found and what surprised you the most and that sort of thing.

DIXON:

So we are just, I guess, for the clarification part, we sampled in Janes Creek eight times and then Jolly Giant three times for our first sampling season. But in Janes Creek, I mean really just, it was the very first time Darren and I, we went in November last year, well I guess two years ago now, November 2022, to do our first sampling and one of our sites just were behind some apartments and we pulled out a coho salmon. And it was just like, it was just really surprising just because you look at that creek and you're just like, it's not what you really imagine as coho habitat. But then as we continued, we ended up getting 31 coho salmon in Janes Creek in our first round of sampling. But not only did we find coho salmon, but we also found endangered tidewater gobies and that were living in, they were behind into someone's backyard over kind of right, right as it was starting to enter into the marshy area. And so finding endangered species as well, but then also just the diversity. We, in Janes Creek, we found, there's like 13 different species of just fish living in Janes Creek alone. But then just going into Jolly Giant Creek when we were doing that, like I think that was the even more shocking for finding fish. So we had sampled there for the first time in, it was April 2023, and in Shea Park. And we had minnow traps, which are like a small mesh cage with like a little opening on either side that fish can swim in, but they're not as good at swimming out. And we pulled it up at the kind of right as the creek was leaving the culvert and entering into this little pond right behind the baseball fields in Shea Park, and there were coho salmon in that. Like, and then in that, also just in that pond, like just a lot of this like still low oxygen water, like they're just big fat coho salmon juveniles hanging out in there. And so that was just very like, this is amazing. Like, and it's really cool to learn that.

WARD:

If you're not familiar with the area, that's upstream in Jolly Giant Creek. So those fish, I mean, something went all the way through, all the culverts, all the way through downtown and up into Shea Park to get fish up there at the outflow of the culvert under 101.

KALT:

That's amazing. And so when you say juvenile coho, what, how big are these fish? What are we talking about?

DIXON:

kind of the the size range that we were catching. I'm just going to scan over to what our sizes were. I think kind of our smallest fish were in the 70 millimeter range and then so that's you know maybe just barely the size of like your finger, right? And then and then the biggest one we got was I think this was in Janes Creek and it was 169 millimeters long so that's like it's like six inches longer than 169. So I mean fish that were I mean we we assume that are between like one to like one and a half years old potentially could be older.

KALT:

Wow.

KALT:

So, okay, so these are not spawning coho. What are these coho doing in these creeks?

WARD:

You've been on one of our real uncertainty. So we find juvenile coho salmon in both of these creeks, but we don't know where those fish are born. So there's three possibilities. It's possible that adult coho salmon got up there in the previous winter and spawned, and that those fish that we captured grew up in Janes and Jolly Giant Creek. Or it's possible that those fish were born in one of the larger tributaries to Humboldt Bay, like Freshwater Creek or Jacoby Creek. And then at some point in their life cycle, they left that creek and moved through the bay. And then they're not ready for saltwater yet, really, at that life stage.

So they were looking for Freshwater, and they may have just moved up into Janes or Jolly Giant Creek. And now I'm realizing, like I said, they said there's three possibilities. Those are really the two possibilities. They were either born there, and they moved in there from one of the other tributaries. And my hypothesis at this point is that they moved through the bay as juveniles. We know that that happens. Colton mentions that there's lots of fish that are pit-tagged in some of the other Humboldt Bay tributaries. That's monitoring programs for salmon, often tag the fish so that we can keep track of them. And we have had it happen before, where one of those fish that's pit-tagged in one tributary shows up again later in another tributary. We know from its tag number that it moved through the bay, and we recaptured it somewhere else.

So we know that those juvenile fish can move through the bay, so that's a possibility. So we know it's possible. And then we haven't seen any evidence that adult coho are spawning in the tributaries. We never saw any adults up there. We never saw any of their nests. There is a little bit of potential spawning habitat. It's certainly possible that coho could get up there and spawn in either of these tributaries. But to me, the most conclusive piece of evidence we have so far that the fish didn't spawn up there is that when we sampled in the springtime, when the next generation of coho would be born and coming up out of the gravel, we didn't see those little tiny, tiny baby coho, the brand new ones, in either Janes or Jolly Giant Creek. Usually, if you're sampling in a place where coho are spawning, when you go out in the springtime, you'll find some of those brand new baby fish there. We're talking half the size of the ones Colton mentioned, or even less, like little, little tiny ones. And we didn't see any of those little tiny fish in either Janes or Jolly Giant Creek.

So my hypothesis right now is that those fish that we're seeing there were born in one of the other Humboldt Bay tributaries. At some point, probably when it rained in the fall or something, they either got washed out or decided to leave, and then they moved through the bay into one of these sites. So that means that those juvenile fish that we found way up in Jolly Giant, through all the culverts, at some point in their life, probably swam through Humboldt Bay, swam through the city of Arcata, and passed through all those culverts, and then took up residence in the upper part of Jolly Giant Creek, and that's where it was deciding.

KALT:

Yeah, so Colton you found you found coho in the upper parts of both creeks. Is that right? How far up?

DIXON:

So, like I was mentioning, Shea Park was the farthest up that we found them in Jolly Giant, but then in, in Janes Creek, there is a site right, kind of right where the South Fork, I guess, meets with North Fork, the confluence of those two.

WARD:

We wouldn't want to.

DIXON:

It's like the trailhead site for the South Janes Creek trail into the community forest. We didn't see any go above that because we had sampled up into the community forest and we just never found any coho up there. So we assume that kind of around that point of, or by 101 like Darren said, we think that's about as high up as they went there.

KALT:

Wow, so they're not making it up into the forest.

DIXON:

It doesn't appear to be that, at least not from our sampling.

WARD:

There is a pretty dramatic change in the stream at that point. It goes from low gradient and slow water to steeper and faster water. And coho salmon like the slow water. So you wouldn't necessarily expect them to see them up in the faster flowing water in the forest. That's a cutthroat trout up there, but not, we haven't seen.

DIXON:

I just wanted to mention something, too, when Darren was talking about how we didn't find any coho, like the very young coho salmon, but we did find cutthroat trout juveniles that are like really young, probably born that year. So that was just further evidence to be like, well, we see that the cutthroat trout in these streams are spawning, but we didn't have any reason to believe that the coho were spawning, too.

KALT:

So Darren, you mentioned something that I wanted to follow up on, which is the juvenile coho aren't ready for saltwater yet. And this is something that I'm totally fascinated by and don't really know much about how they get ready. How do they go from being born in freshwater to becoming ocean going fish, which is the definition of a salmonid, right? Basically, they're born in creeks, and then they go out and they come back and spawn in freshwater. Is that right?

WARD:

That's the definition of an anadromous fish. Oh yeah, right. Salmonid is the family of salmon and trout, and some of them are anadromous. They go to the ocean and some of them don't. But yeah, there's a lot of the salmon do that, and it is an incredible process. It requires that these fish that are all of the different species of salmon spawn in freshwater. So their juveniles are born in freshwater, but as those juveniles are growing in freshwater, they start to undergo a physiological transformation that happens well in advance, really, of when they actually are going to swim downstream and take up their long-term residence in the ocean. And there's lots of different challenges that fish face when they make that transition from freshwater to the ocean, but the big one is actually, it's just the salt. When they're living in freshwater, their internal concentrations of salt are much higher than the concentrations of salt in the water around them. And if you remember from basic chemistry, if you have a semi-permeable little bag of salt in freshwater, all that salt's going to try to diffuse out of the fish. And so the fish is constantly fighting a battle when it's in freshwater to hold on to its salts and prevent them from diffusing out. And it's fighting the opposite battle to keep all that water in the surrounding environment from diffusing into its body and blowing it up like a water balloon because the osmotic pressure from the freshwater surrounding it is so high.

So that fish in freshwater is fighting to hang on to its salts and fighting to keep water out of its body. And a fish in the ocean has the exact opposite problem. A fish living in the ocean, the ocean concentration of salt is much higher than the concentration of salt inside its body. And the fish need some salt inside their body, but they don't need a lot of salt. And so if they get too much salt, it kills them. And so they have to fight to keep the salts from infiltrating their body when they're in the ocean. And then for water, they have the opposite problem that they do in freshwater. The osmotic pressure gradient is opposite. And so they have to fight to hold on to their water in the ocean instead of fighting to keep the water from invading their body. So it's a big part of a fish's energy budget just to regulate the concentration of salt inside its body. That's what they use a lot of their calories for. And salmon and other anadromous fish has to be able to do it both ways. They have to be able to hold on to their salts in freshwater and then change gears and all of a sudden start getting rid of their salts when they go out to the ocean. And that's probably more boring details than people are interested in knowing, but it all happens in the gills. And so there's these special cells in the gills that can act as pumps and they basically have to reverse them. So when they undergo this physiological transformation, those cells in their gills go from salt retaining cells to salt exporting cells. Allow them to be able to live in both environments.

KALT:

Amazing.

WHEELER:

Pretty cool. So we've, we've talked a little bit about how these creeks are seemingly inhospitable. You know, there's culverts, there's agricultural lands, there's roads, there's housing, and yet the fish are here. Are, are there, are they there because it's, it, Fisher are small brained and they are swimming up and they, they've found themselves there. Are the conditions in these creeks actually good for juvenile salmon?

WARD:

So this is another question that what we know at this point is that there were fish there, right, that they're occupying those habitats. The fish that we catch, they seem to be in good condition. You can get some information about how a fish is faring by looking at the shape of its body, if it's relatively rotund, that suggests that it's eating well. And then we know that when we catch these fish, we tag them, just like we do in a lot of the other monitoring programs. And we know that the fish that we tag and then recapture again later are putting on a decent amount of mass, like they're growing pretty well.

So those things suggest that the fish are doing okay in these places. But we don't really know anything at this point about the long-term fate of these fish. We don't know if they're surviving and potentially, the fish that we tagged last year, that we encountered last year, if they survived their trip out to the ocean and are out there waiting to come back as adults. It's possible that there are things in these streams that could impair their health over the long term in a way that we wouldn't have seen when we were sampling. Like they could have been exposed to industrial chemicals or something like that that would affect their ability to survive once they got out to the ocean. But the indications we've seen so far suggest that they are actually doing okay. Whether it's a net benefit for the individuals or for the populations that these fish belong to, them using these habitats, that's totally an open question. I suspect, like I said, I suspect that these are fish from other tributaries that ended up out in the bay and they weren't ready for saltwater. They hadn't changed their gears yet on their salt pumps. And so they went up into the first freshwater that they could find. And for these individuals that happened to be those streams, that's my hypothesis about what is happening. And we know that they got in there and were surviving up to that point.

So I suspect that the fact that those little streams are there provided a place for those fish to rear through the winter that maybe they wouldn't have otherwise had if there weren't access to these tributaries. And that maybe there could be room for more fish in these streams if the habitat was improved further. But we still have a lot to learn about the role of habitats like this in supporting the sort of larger coho salmon populations in Melville Bay.

KALT:

So I was going to ask Colton, did you recapture any fish that were tagged in your surveys?

DIXON:

Yeah so in Jolly Giant we didn't catch any and I think that was mostly just due to the fact that we only had three sampling opportunities there but in our eight sampling opportunities in Janes Creek we had two recaptured fish and we had one fish that we had first captured on April, it was April 11th and it was 130 millimeters long so this is kind of going off of what Darren was saying about the growth rate so from April 11th 2023 to May 6th 2023 it grew or it grew to 142 millimeters long so it was growing at 0.48 millimeters a day which for for coho like that's that's good that's a pretty good growth rate that suggests that like and also like Darren was saying a lot of these fish when we catch them like they're they're just a big round bellies suggesting that they were eating a lot of vertebrates that were living there in the creek so it seemed like they were doing really well then there's another one that we caught on January 16th last year and it was at 79 millimeters long and then we caught it again April 11th and it was 120 so it almost doubled in size in that time so we had a few recaptures but like what like what we said the ones that we did recapture they seemed to do be doing really well

KALT:

So that suggests it's good habitat for the babies, and it's really important for them to get big before they go out into the ocean, right? That's that's an indicator of survival. Very cool.

WHEELER:

Well, I'm sure that we'll have a future show because there are a ton of management implications of this, right? If, if these aren't kind of barren streams, but if they are, are important juvenile rearing habitat, that, that makes a difference in that, that has management implications for the city of Arcata for Humboldt Bay. So this is really exciting stuff. And it's fantastic that y'all went out and did the work and thank you listeners for joining. Join us again next week on this time and channel for more environmental news from the North Coast of California.