Sunday, March 31, 2013
I spent most of the last week enjoying warm sun and red sandstone in beautiful southeastern Utah. I didn't think about fish much at all. Therefore, I don't have a post prepared for this week. I'll be back next week. In the meantime, give me some ideas - what do you want to see me write about?
Sunday, March 24, 2013
The third and final installment of our discussion of the Fraser will highlight Kaibab Park, in the town of Granby. This is the public reach of river adjacent to the baseball fields. I've been surveying a 650-foot reach of river there since 2009. The upstream terminus of the station is the town's big rock diversion structure immediately downstream of the Highway 40 bridge.
The adult trout habitat on this reach is not great, and this portion of the river definitely experiences low flow/high temperature issues in late summer some years. There is not much of a rainbow component here, so the whole story of this reach is what's going on with the browns. Below are the population estimates for the four years I've electrofished it.
Things were pretty consistent here until 2012, when a couple population parameters went somewhat haywire. First of all, the density of quality dish plummeted. I think that this has to be a response to drought conditions in 2012. During the periods of time last summer when there was as little as 17 CFS of water being recorded at the Northern gauge, it didn't take an expert to look at the stream and quickly determine that there was very little adult trout habitat available. There are some private reaches downstream that are a little better off physically, with undercut banks, etc. I suspect that the larger browns moved down into that area to weather the drought conditions.
The next big difference in 2012 was the 243% increase in number of fish per mile greater than 6". To see what happened there, look at the length-frequency histograms below:
At the same time that the adult brown trout population was declining drastically, we had a huge year class show up in 2011. Normally we don't associate giant water years with strong year classes of browns, but things behaved differently in this location. Due to the fact that this reach is toward the downstream end of the river, I think what happened in 2011 is that this part of the river received fry that were displaced by the high flows from several miles of river upstream, including probably all of the canyon. That 2011 year class stuck around and we saw them again in 2012 as a big age-1 year class. The abundance of this group of fish is what caused the fish-per-mile estimate to increase so much.
The third big difference in the 2012 sample is the huge number of sculpin we picked up. This is the most dense sculpin population I've seen to date. I think the reason for this increase is the same reason that I just described above, with the small brown trout. Also, the 2012 low water in this reach probably benefitted the sculpin to the extent that there were not as many predators (in the form of adult brown trout) around.
A lot of people spend years fishing these waters and never see firsthand the species that is the most numerically common fish here. They're surprisingly elusive critters, especially when you realize how many there are in certain areas. So I'll finish up this week's post with a couple shots of sculpin - definitely one of my favorite fish.
Sunday, March 17, 2013
Continuing with our discussion of the Fraser River, this week I'll share some information about what I call the Safeway station. I call it that because it's a 600-foot reach of river directly behind Safeway, in the town of Fraser.
This is on the downstream end of what was called FREP, the Fraser River Enhancement Project. The town of Fraser partnered with us, TU, and other entities to construct a stream habitat improvement project. Work on this reach was finished in 2005. This is one of my favorite stream habitat projects I've seen. The main reason is that to the untrained eye, or if you're not looking for it, it's not obvious that the stream was worked on. That's the best way for habitat projects to turn out, in my opinion.
We've got a good survey history at this site; I've electrofished it every year that I've been here, and my predecessor Bill Atkinson established the station in 2003. This has always been a fascinating reach. It represents the transitional zone where the river is changing from a (historically) brook trout-dominated montane stream above (see last week's post), to a classic brown trout stream below in the Fraser Flats. Since the completion of the habitat project, this section has held a nice mix of browns, rainbows, and brook trout. The graph below displays the biomass estimates over the years for all three species:
You can see that in 2003, prior to the habitat project, things were in really bad shape. The total trout biomass estimate, for all species combined, was 12 pounds per acre. In 2012, that estimate was 163.
The big spike in rainbow trout densities seen in 2008 is the result of me stocking Colorado River rainbow brood culls in the river. We did that for a few years right after the habitat project was done. The idea behind that was to get some rainbows in as "place holders" in the river in order to create a rainbow fishery and compete with the browns as they recolonized the reach. It wasn't intended to be a long-term thing. 2008 was the last time I stocked any of those. I had originally hoped that we might possibly see some reproduction out of those fish, but it didn't happen.
I've been stocking HXC fry in this reach since 2010, at the same time as I've stocked Confluence Park. That is the cause of the rebound in rainbow trout biomass that has occurred in 2011 and 2012. These plants have performed nicely here as well, but we haven't seen the complete takeover here that we have seen at Confluence Park.
Below are the rainbow trout size distributions for the past three years:
In 2010, we were pretty much starting out from scratch with the rainbows. The brood culls hadn't stuck around, and that year's HXC plant actually went in at 3.5", on September 13 (after this survey), so they don't show up here. In 2011, the 2010 plant was present in good numbers and appeared to have formed a nice little year class, and doubled their average length at 7". The 2011 fry plant shows up at 2", and that bar is somewhat higher than the graph. In 2012, we can see that the 2010 fish have put on another four inches and are now hitting 11" (2" larger than the same year class up at Confluence Park), and the 2011 plant grew nicely, to 8". It was a little bit disappointing that there weren't more fish in that 8" size group in 2012, suggesting that the 2011 plant had possibly experienced relatively high mortality. That's probably to be expected here, because we do see browns up to 18" or better at this site, so there is certainly more predation going on here than at Confluence Park.
Now, here are the brown trout size distributions over the same time period:
The graphs going all the way back to 2003 look very similar to the 2010 and 2011 graphs. In fact, the one concern that I have had about the habitat project is that prior to 2012, it appeared that there was very little or no successful brown trout spawning taking place - as suggested by the absence of age-0 or age-1 year classes. I thought that this was possibly a result of the habitat project representing a trade-off which sacrificed spawning and fry-rearing habitat in favor of maximizing adult holding water. However, the reach had maintained a decent adult brown trout fishery, and the theory I had to explain this was that adult brown trout migrated into this reach at a steady rate -- probably from Fraser Flats -- and stayed, because the habitat quality is high. 2012 threw me for a loop. As you might have guessed, many of those bars are cut off in order to maintain consistent axes on the three graphs. But the 3" bar actually extends up to 107, and the 7" bar extends up to 33. In other words, in 2012 this reach was just loaded with age-0 and age-1 browns, which we had never seen here before, and which seemingly appeared out of nowhere. The reason I say that is because the group at 7", which would have been born in 2011, should have showed up in large numbers in the 2011 sample at 3" or so, but they weren't there at all in 2011.
The big age-0 year class, at 3", is easy enough to explain. Low water years result in very high survival in baby brown trout. They don't have to fight a big runoff, and warm water results in higher growth rates and a longer growing season for them. But I haven't thought of any good reason for the appearance of the big age-1 group. That will probably remain a mystery.
Anyway, that's the Safeway station in a nutshell. It's a fascinating place to observe the ever-shifting dynamics of these three species and their interactions.
Sunday, March 10, 2013
I get asked a lot about the Fraser River and the status of its fish populations. That's always a difficult question to answer, because the Fraser is an extremely dynamic stream, in which there are hardly two miles of river that resemble each other. This is a stream that undergoes many transitions in its relatively short run from its Berthoud Pass headwaters to its confluence with the Colorado at Windy Gap. To call it a river (at least in its modern state) is a little bit of a misnomer, as it's really more of a large creek. There are certainly more extreme examples in this state though -- the Swan River near Breckenridge is the one that always comes to mind.
So, I thought maybe I'd do a series of posts based around each of the electrofishing stations that I survey regularly on the Fraser. I've got two locations that I've been hitting anually, one that I get to less often than that but still regularly, and a number of places I've surveyed one time. The single-visit sites are mostly on private land and have served to fill in information gaps and give us a better big-picture overview of the Fraser. However, because those sites are on private land I won't comment on them here.
The farthest upstream station that I survey regularly is called Confluence Park, and is located in the town of Winter Park. The station is 570 feet long and the upstream end is the pool where Vasquez Creek joins the Fraser. I have electrofished that reach in 2007, 2009, and 2012. We were astounded at the changes we found on this reach in 2012.
This reach of river is still a pretty cold, montane type of a stream with a bit more gradient than what is found below. It's heavily shaded with spruce-fir and willow stands along the banks. Brown trout are rare on this reach. It's always been more of a brook trout stream, producing some fish beyond the 13" mark in recent years.
I have been telling you about the successes we have seen planting small (1.5-2") Hofer x Colorado River Rainbows (HXC) down in the mainstem Colorado. We have also been planting them in this reach of the Fraser since 2008. Obviously, we don't float a raft down in July on the Fraser to stock, like we do on the Colorado. We have been stocking them by hand in a handful of locations.
Here is the length-frequency histogram for brook trout and rainbows when we surveyed the reach in 2009:
As you can see, brook trout were the dominant trout species. Both of the size-groups of rainbows can be traced to two different plants we made in 2008, one of CRR brood culls (the larger fish) and the first batch of HXC fingerlings (the 4" fish) to be stocked. I was surprised that those HXC's were still sitting at only 4"; that is the size they had gone in 11 months before this survey, and didn't appear to have grown at all. Beginning in 2010, we shifted to the smaller HXC's, stocked earlier in the summer. I didn't have a lot of high hopes to make this reach of the Fraser into a wild rainbow fishery, but it was a unique location as far as where we had been trying the HXC's, and I just wanted to see what they would do.
I finally managed to get back to survey Confluence park this past year. Here is what we found in 2012:
There were two very strong year-classes of HXC's (at 6" and at 9"), and adult brook trout were almost nonexistent. The HXC's at 2" were just stocked 2 months prior to this survey. The bar at 2" for those fish actually extends up to about 600 but it's cut off here.
Here is a picture of the three size groups of rainbows present:
Here's what a typical dipnet full looked like:
It appears that what we have seen at Confluence Park is a conversion of the trout population from being brook-trout dominated to being overwhelmingly dominated by these HXC's. We know that this strain is an aggressively-feeding, fast-growing strain, but as far as I know, this is the only example to date where we have converted a brook trout stream to a rainbow trout stream with them.
I'm not making any value judgements here that it's better to have this reach of stream be rainbow-dominated rather than brook trout-dominated; in fact, those 13" brookies were definitely special fish. I'm just saying that I was caught completely by surprise at the success of these plants at this location. These HXC's have picked up the ball and run quite a bit further with it than I expected them to in this situation.
Just to elaborate on the point, here is the table of population estimates from the two surveys:
|Total trout lbs/acre||65||127|
|# Sculpin captured||38||211|
|Date of survey||3-Sep||7-Sep|
Forgive the shoddiness here; I haven't figured out how to make tables look nice in this blogger format. But the point is to look at what the biomass estimates did: the RBT biomass exploded by approximately 10X, while the BRK biomass has reduced to approximately 1/10th.
I want to go back again in 2013 to verify that the 2012 survey wasn't some weird fluke. I would also like to do some prospecting for wild rainbow fry before we stock the HXC's. After another year or so I'll probably back off a bit on the HXC stocking and see if we can arrive at some kind of a nice balance, where we have the twin luxuries of a wild rainbow fishery as well as the occasional brook trout larger than 12 inches.
On another note, don't forget about our State of the Fish meetings coming up: this Wednesday, the 13th, at the Granby library at 6:30 PM, and next Monday, the 18th, at the Silverthorne library at 6:30 PM. Hope to see you there!
Sunday, March 3, 2013
Hi all, just wanted to let you know that we are going to host a couple meetings that I'm calling "State of the Fish" meetings. One in Granby at the public library on Wednesday, March 13, at 6:30 PM. We'll do another one in Silverthorne on Monday, March 18, at the public library also at 6:30 PM.
I'd like to run these meetings with a "data workshop" format. That is, I won't necessarily have a canned power point presentation to show people. Rather, I'd like to start the meeting by asking folks in attendance to call out the name of a water body. Then, I'll walk everyone through data, stocking records, future plans, etc. regarding that body of water. It will be important for this to be a collaborative meeting, with a lot of give and take. Hopefully the flow of information will be in both directions, as the purpose of these meetings is just as much for me to gather the anglers' perspectives on these waters, as for me to give folks information. So, I hope folks can make it out for that.
Meanwhile, I've got four new reports up on the web page, check these out and chime in with any comments or questions:
Now, From Bennett -
Hi John thanks for the reply on the Tiger Muskie. I am really hoping that you plan comes to fruition. As far as the lake trout are concerned in Grandby is what your seeing a cyclic problem? Every few/many years we can expect an imbalance? Or is there a greater concern such as what you are seeing at Blue Mesa and a serious management approach needs to be taken. Also, in Colorado do we have any good self sustaining lake trout lakes or do all of them need to be fed with kokanee or rainbows?
Bennett, the biggest difference between Blue and Granby is the presence of mysis in Granby. When conditions are unfavorable for kokanee in Granby, it's not just due to a simple overabundance of predators - it's also due to an overabundance of COMPETITORS (in the form of mysis, preying on the same zooplankton that kokanee prefer) who happen to do well in the same conditions that favor lake trout reproduction. Once all three species (mysis, lake trout, kokanee) were present at Granby, it's always been on a cycle where conditions swing wildly back and forth. When the kokanee can't maintain themselves, a big predator such as lake trout is basically a luxury that the lake can't afford - that is, they have no forage base. We're going into a period now, though, that is going to be unfavorable to both lake trout reproduction and mysis densities. With the way that Granby has been dropping through the winter, there will be very few or no lake trout born in the lake in 2013, because the eggs are getting dried out or frozen as we speak. So, it's like a pendulum that swings back and forth in response to drought/wet weather cycles. One big drawback is that we really can't depend on Granby for eggs to stock other waters any more - if we get them, that's great, but we can't count on them.
When you ask about "self sustaining" lake trout lakes, I think you're using a little bit different definition than normal. We usually use that term when we mean that a species of fish maintains itself with no stocking to maintain its numbers over time. In that sense, pretty much all our lake trout lakes are self-sustaining -- that is, we don't stock them. They do a good job of reproducing on their own. But what I think you're asking is, are there any lakes that produce their own forage for lake trout, without any stocking to augment their prey base. I'm not aware of any. Granby may be the closest, if you just consider the life stage of lake trout up to 21-24 inches. Prior to reaching that size, they do really well feeding on mysis. But there is always some predation of fingerling rainbows, age-1 kokanee, etc. So that's close to a self-sustaining system in the sense that you're talking about. Then they make the prey switch and start eating stocked fish. That is one reason why kokanee are such an important link in the chain - they are far cheaper to maintain as a forage base for lake trout than stocked rainbows are.
Again, I hope to see folks come out to the State of the Fish meetings. See you there.