Walleye. In the Deschutes River?

The fish have spoken. And those fish are walleye. Remarkably, there are now walleye in the lower Deschutes River. As far as anyone is aware, this has never happened before. We wish this was good news. But it’s not.

We’ve been getting reports of walleye being hooked and landed as far upriver as Kloan, at River Mile 7. We’d not mentioned it yet as we were waiting for documentation of a landed walleye. Now we have it–the walleye in the photo below was landed at River Mile 4.5.

Photo provided by Deschutes River guide Brad Staples, pictured on the right.

In addition to walleye, smallmouth bass continue to be been taken in good numbers in the lower river this summer, for the second straight year. Trout and steelhead, not so much.

What does this mean for the lower river? As the lower river ecology and habitat changes due to Selective Water Withdrawal operations, so do the species that thrive in the new conditions. Warmer water attracts warm water fish. As insect populations decrease, piscivorous fish (fish that feed on other fish) increase.

Further, this is not good news for salmon and steelhead juvenile migration. Juvenile steelhead and salmon are preferred food items for walleye and often for bass, much as they are for northern pikeminnow. Bass and walleye are also capable of feeding on crawdads, worms and insects, and generally are known for being highly predatory feeding machines.

Looking into the mouth of the walleye. Photo from American Expedition.

We are repeatedly told by the agencies responsible for Deschutes River management that nothing has changed in the lower Deschutes River since the implementation of surface water withdrawal at Round Butte Dam. But lets consider the list of easily observable changes:

  • Bass and walleye incursion
  • Increased water temperatures throughout the lower river’s 100 miles, from mid-winter through spring and summer
  • Black Spot Disease widely spread in trout, steelhead, and bull trout
  • Invasive nuisance algae
  • Significant change in insect community structure, and decline in adult insect abundance
  • Observations of declining bird populations

Clearly, this is no longer the river we knew prior to 2010. But fortunately, we know these problems are not inevitable. A return to cooler, cleaner water discharged from the Pelton Round Butte Project can begin alleviating these discouraging ecological changes in the lower river. It’s time for the responsible agencies, dam operators, and other parties to admit that the Selective Water Withdrawal tower is responsible for some serious unintended consequences, and begin charting a new path forward for lower river management.

The Deschutes River Alliance will remain on the front lines of the battle to restore this treasured river. Please join us in our efforts.


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2016 Stonefly Hatch: A Recap

Photo by Rick Hafele.

Photo by Rick Hafele.

It’s come and gone. No one is even talking about it any longer. Why? Well, it wasn’t exactly epic. Or was it?

Here’s the lowdown on the 2016 stonefly hatch based on personal observation; reports from friends, guides and outfitters; emails; and reports to our hatch observer database. This collectively represents hundreds of fishing days, if not over a thousand. None of this will be a surprise to those who were there for it. And many were there! The annual stonefly hatch remains the single largest trout fishing frenzy on the lower Deschutes River.

The first salmonflies were seen mid-April once again this year. Golden stones were seen not long after. Both were first spotted down below Sherars Falls. The big bugs appeared very sporadically until early May. Then numbers began to pick up and the hatch spread further upstream to well above the locked gate at the upper end of the access road above Maupin.   There were a few scattered reports of good numbers of stoneflies during that time. If you were fortunate enough to be on the river those days, the fishing was off the hook.

Then harsh weather set in. It got colder and there were heavy rains and the hatch all but disappeared but for a few hardy bugs clinging to grass and alder leaves.

Days later, the bad weather turned back to good weather and the hatch started back up, progressing up to the Kaskela area. Once more, if you were on top of the hatch in the right location, fishing was excellent. Then once again the weather turned wet and cold for days on end. The bugs again became hard to find. The quality of the fishing suffered. The last guide report of large numbers of salmonflies or golden stones seen on the river was May 17th. Only low to moderate numbers were seen after that until the final observed golden stones were reported on June 5th.

Photo by Brian O'Keefe

Photo by Brian O’Keefe

When weather conditions in the canyon were wet and cold, it was hard to find a stonefly anywhere. The trees and grass were bare. The big bugs were hiding from the conditions. If they aren’t out crawling all over the place, they aren’t finding mates. If they aren’t finding mates, no mating takes place.

This pattern repeated itself three times. Finally a meager representation of the hatches of earlier years hung on for about a week and half, reaching all the way up to Dizney Riffle. Then it fizzled out all together.

Mixed in with the stoneflies in mid-May was about a week and half period where everything was hatching. Green drakes, pale morning duns, pale evening duns, Beatis, caddis, it was all happening at once. There were even a few Antocha crane flies seen! But all of that ended as quickly as it began. And the total numbers weren’t all that exciting. It was perplexing to see June and July hatches in mid-May.

We are still getting some reports of good numbers of caddis in the tops of alders at last light on calm evenings. But the mayfly hatches of early to mid-summer are now totally missing in action.

What meaning does all of this have for the lower Deschutes River and the future of aquatic insect species? If this year had been a one time, one-off affair, it would probably mean little, being what biologists call annual variability. But it’s become a common way for spring to unfold on the lower river.

Most disconcerting is the role this might be playing in stonefly reproduction. Salmonflies emerge after three to four years as nymphs, golden stones after two to three years as nymphs.   Any impact of this year’s weather on mating won’t be seen until 2018 to 2020. The problem is this: with warmer winter and early spring river temperatures as a consequence of surface water withdrawal at Round Butte Dam, stoneflies emerge sooner and into the often harsh conditions of early spring, not late spring/early summer as they used to. The consequence is that reliably they are now challenged to find mates and get their reproduction needs accomplished.

Anyone who has spent years on the lower Deschutes River knows that stonefly numbers are down. Way down. According to Portland General Electric’s Lower Deschutes River Macroinvertebrate and Periphyton Study (page 97), “Stoneflies were not numerically abundant, but were widely distributed and contributed substantially to the invertebrate biomass by virtue of the often large size.”  That was some nice positive spin in the end of that quote, but the reality is that stoneflies are no longer “numerically abundant.” Unlike with many of the mayfly species and Antocha crane flies, this is probably not linked to the nuisance algae growth in the lower river.

Salmonflies as nymphs are detritivores, meaning they scavenge broadly across a river bottom eating dead material, mostly from plants. Golden stoneflies are roving predators and tend to feed on slow moving macroinvertebrates like midge larvae and worms. So the documented increase in worm populations in the lower river should be benefiting them. Nuisance algae are less likely to affect stoneflies as they spend time crawling between or under rocks, avoiding the algae covered top and side surfaces.

That means the declining numbers are most likely due to something else. Most likely that “something else” is hatching early into weather conditions not conducive to mating activity for much of the short adult phase of their relatively long lives. If reproductive success declines, the population declines.

June was a much warmer, drier month than May this year (like most years) on the lower Deschutes River. We’re guessing the stoneflies would have preferred those conditions.

Photo by Brian O'Keefe.

Photo by Brian O’Keefe.

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The Problem With the Water Quality Data in the PGE Lower Deschutes River Report by R2 Consultants

Pic 1 R2 Report

The above report (published in March of this year), as noted in prior DRA blog posts, was of a two-year study of the lower Deschutes River. The purpose of the report was to determine the magnitude of biological changes in the river due to the implementation of surface water withdrawal at Round Butte Dam. A baseline study was conducted in 1999-2001, which Portland General Electric (PGE) summarized in a report published in 2002.

Both studies were contracted and paid for by PGE and were a requirement of the Federal Energy Regulatory Commission license to operate the Pelton-Round Butte dams.

The water quality data from the most recent study can be found on pages 47 and 48 of the 2014-2015 report. The results document violations of the basin and statewide water quality standards in both years of the study. The most egregious violations were of the pH standard as established in Oregon Administrative Rules (OARs) 340-041-0021 and 340-041-0135. The Deschutes Basin Standard for pH is a maximum pH of 8.5. A pH of 7.0 is neutral (neither acid nor alkaline, greater than 7 is alkaline).

The authors attempt to diminish these violations by noting on page 46 of the report that, “Regarding the unusually high pH measurements taken in Spring 2015, since these are uniformly high, even in the reference sites, it is highly likely that the meter we used was off in its calibration. Therefore, any in situ measurements taken should be considered preliminary at best, and compared to official measurements taken by PGE or agencies.”

There are many problems with this statement.

R2 Resource Consultants are self-proclaimed experts in water quality monitoring and modeling, so one has to wonder how and why they would be unable to produce accurate water quality data? Why would they have calibration problems? If their equipment wasn’t functioning properly, why wouldn’t they use backup pH measuring equipment? If they didn’t have backup equipment, why couldn’t they borrow equipment or have it shipped in via overnight express? The pH measurement problems they most specifically refer to occurred over several days in April of 2015. That should have been enough time to correct any equipment problems.

There were also very high pH measurements in the three days of sampling in April/May of 2014 (10 out of 12 lower Deschutes River sites were above the 8.5 pH water quality standard). Were their instruments faulty then too?

Or is this an attempt to discard and disregard data that are indicative of water quality problems?

There is another potential reason that the high pH values were recorded during spring sampling in both years. When algae bloom, it increases pH. It does this by absorbing CO2 from water to conduct photosynthesis. The by-products of photosynthesis are sugar and oxygen. Notably, the dissolved oxygen levels on the dates of the high pH levels were also high, with dissolved oxygen saturation levels reaching up to 138%. This occurs when there is excessive algal growth.

We have noted extensive algae growth in the lower river this year, starting in February. We have also recorded pH levels of greater than 9 in April and May 2016.

Algae, early March 2016. One mile below Pelton-Round Butte Reregulating Dam.

Algae, early March 2016. One mile below Pelton-Round Butte Reregulating Dam.

Algae, late March 2016. One mile below Pelton-Round Butte Reregulating Dam.

Algae, late March 2016. One mile below Pelton-Round Butte Reregulating Dam.

We are troubled by the lack of explanation for R2’s “calibration problem(s).” It is standard procedure to have a quality control plan that includes details for meter calibration and procedures if they fail calibration. At the DRA, we maintain a log for each instrument we own. Recorded in each of these logs are the calibration dates, times and results. All instruments are calibrated before each day of water quality sampling. We carry backup equipment.

In the case of our in-river dwelling data instrument, once a month we perform “field audits” where we cross check the data it produces with independent meters and manual techniques. We cross check the performance of our meters.

We have such a stringent quality control program because two of our field staff worked for the Oregon Department of Environmental Quality (ODEQ) for decades, doing water quality work. We exercise the same quality control methodology that ODEQ uses. We would suggest that PGE require the same of contractors doing water quality work.

DRA water quality staff at work:

Larry Marxer measuring dissolved oxygen in river water, using the Winkler method.

Larry Marxer measuring dissolved oxygen in river water, using the Winkler method.

Rick Hafele doing water quality measurements on Lake Billy Chinook.

Rick Hafele doing water quality measurements on Lake Billy Chinook.

Greg McMillan going old school on water quality measurements in 1979 (when old school was just school, or maybe pre-school).

Greg McMillan going old school on water quality measurements in 1979 (when old school was just school, or maybe pre-school).

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The Troubling Loss of Antocha Crane Flies

By Greg McMillan and Rick Hafele

Antocha Crane Fly. Photo by Rick Hafele.

Antocha crane fly. Photo by Rick Hafele.

Antocha is just one genus of the family Tipulidae, a group well known as crane flies. As crane flies go Antocha is rather small, and while most crane fly larvae live in slow moving or stagnant water with silty or muddy substrate (some are also terrestrial), Antocha larvae prefer riffle areas of streams with clean cobble substrate. This little crane fly is found throughout North America, including most if not all of the streams in the Deschutes watershed. Until recently it was one of the insects of the lower Deschutes River that appeared every summer in moderate to large numbers. Whether trout found it of interest could be debated, but its presence was one of those reminders that summer had arrived on the lower Deschutes – but no longer.

Rick Hafele and Greg McMillan first noted the absence of Antocha crane flies in the lower Deschutes River in July of 2013. Until that time these dipterids had been abundant in the lower Deschutes River. By the summer of 2013 other species of aquatic insects had also been observed to be in decline, but Antocha just seemed to have disappeared.

We waited until 2014 to confirm our 2013 observations regarding the missing Antocha before saying anything publicly. We reported our observations here in our blog, and then through the observations of others in our 2014 Lower Deschutes River Macroinvertebrate Hatch Activity Survey Results. Our reports regarding the missing crane flies were initially met with little interest, if not skepticism, by resource management agencies and the Pelton-Round Butte Dam operators, but then confirmed by the R2 Resources Interim Report in the Portland General Electric Aquatic Macroinvertebrate and Periphyton Study. The final report from that study also notes that the disappearance of the crane flies in the lower Deschutes River occurred after the inception of selective water withdrawal at Round Butte Dam.

Antocha crane flies mating and laying eggs in the lower Deschutes River before surface water withdrawal began at Round Butte Dam. Photo by John Hazel.

Antocha crane flies mating and laying eggs in the lower Deschutes River before surface water withdrawal began at Round Butte Dam. Photo by John Hazel.

The final report from the PGE Lower Deschutes Aquatic Macroinvertebrate and Periphyton Study also mentions studies done on the Crooked River and Middle Deschutes (Vinson, 2005; and Vinson and Dinger, 2007; Reports prepared for U.S. Department of the Interior, Bureau of Land Management, National Aquatic Monitoring Center) that showed declines in Antocha populations in those rivers. It is worth noting that those studies were done in the years prior to implementation of surface water withdrawal from Lake Billy Chinook at Round Butte Dam in late 2009.

The PGE study concludes that:

“… Antocha crane flies were widely distributed in pre-SWW samples above and below the project but nearly absent post-SWW from nearly all sites including the Deschutes and Crooked Rivers upstream from the project. Significant numbers were observed post-SWW only in the Metolius River, a unique spring-dominated system with minimal development compared to the Crooked and Deschutes systems. Most likely, this change is a result of a broader environmental pattern as opposed to project-related effect. It is unknown whether this pattern represents normal annual variability or a longer term (sic) trend. However, this observation highlights the value of the upstream study sites in distinguishing project from non-project changes.” (Final Report, Lower Deschutes River Macroinvertebrate and Periphyton Study, R2 Resource Consultants, 2016, page 100.)

That conclusion seems to be hastily arrived at, and appears to us to be biased towards exonerating dam operations as a contributor to the disappearance of Antocha in the lower river. Yes, studies show that Antocha crane flies have nearly disappeared from the Crooked and Deschutes rivers above the project, and that decline happened prior to surface water withdrawal from Round Butte Dam. Even though the loss of Antocha is still evident a decade after it was first reported, the PGE report suggests that this could be due to “annual variability.”

The study’s authors go on to suggest that the only other alternative is that this is due to a “broader environmental pattern.” Yet they state that the Antocha population is intact in the Metolius River.

In another aquatic invertebrate study of Whychus Creek, Antocha was found to be present from 2005-2014 (Mazzacano, Effectiveness Monitoring in Whychus Creek; Benthic Macroinvertebrate Communities in 2005, 2009, and 2011-2014, The Xerces Society for Invertebrate Conservation, page 58).

Whychus Creek is a tributary to the Middle Deschutes River. The confluence of Whychus Creek and the Middle Deschutes River is about three miles above Lake Billy Chinook. A great deal of habitat restoration work has taken place in Whychus Creek in recent years thanks to the work of groups like the Deschutes Land Trust, the Upper Deschutes Watershed Council, Trout Unlimited, and others. The Portland General Electric Pelton Fund, along with other sources, has provided funding for this work.

So in at least two other streams the Antocha populations are intact. It would be interesting to look at other streams in the basin to see what the status of Antocha is. We believe it was very hasty and preemptive to draw the conclusion that this is due to a “broader environmental pattern” when only limited data is available from other streams.

Basin studies show that the Middle Deschutes and Crooked rivers have large anthropogenic influences due to population centers and agricultural runoff. That in turn results in higher levels of nutrients that lead to algae growth. As noted in our 2015 Lower Deschutes River Macroinvertebrate Hatch Activity Survey Results, Antocha crane flies lay eggs in the splash zone of river rocks. Stalked diatom algae, which have become common in the lower Deschutes River since implementation of surface water withdrawal from Lake Billy Chinook, form a barrier to the bare rock Antocha seem to favor for reproduction in the lower Deschutes River. This probably makes egg laying impossible.

Stalked diatom algae covering splash zone of rocks in lower Deschutes River. Photo by Greg McMillan.

Stalked diatom algae covering splash zone of rocks in lower Deschutes River. Photo by Greg McMillan.

From mid-November until late May the water discharged from the Pelton-Round Butte Hydroelectric Project consists of 100% surface water draw from Lake Billy Chinook. Even during summer and fall months, there is a minimum of 35% surface water draw (Pelton Round Butte Project, FERC No. 2030, Water Quality Report, 2015). We know that for much of the year, surface water in the forebay of Round Butte Dam consists primarily of water from the Crooked and Middle Deschutes rivers (Deschutes River Alliance 2015 Water Quality Report and unpublished data from 2016, pending publication in 2017).

Given that Antocha crane flies disappeared from the Crooked and Middle Deschutes rivers prior to the institution of surface water withdrawal, and surface water withdrawal is heavily influenced by the water quality of these rivers, we believe that there is another hypothesis for the massive decline of Antocha in the lower Deschutes River. We propose that the causative agent of Antocha decline in those rivers is now being passed down into the lower Deschutes River as a consequence of surface water withdrawal at Round Butte Dam.

That cause could be any, or a combination, of several possible agents.

The first is the nutrients in surface water withdrawal at Round Butte Dam fueling the stalked diatom proliferation in the lower river, which is denying access to clean rock surfaces necessary for Antocha mating and egg-laying.

The second possible cause is that a pesticide or other agent entering the Crooked and Middle Deschutes Rivers is being transferred downstream in surface water from Lake Billy Chinook.

Antocha crane flies have also been found to be susceptible to parasitic infestations (International Review of Hydrobiology, Vol. 92. Issue 4-5, pg. 545-553, August 2007). This raises a host of issues that could possibly be related to the ecological changes brought by surface water withdrawal from Lake Billy Chinook. A parasite could have been transported to the lower river via surface water withdrawal at Round Butte Dam, or water conditions changed by surface water withdrawal, could now be favoring a parasite that has possibly infected Antocha.

How important is the disappearance of Antocha crane flies? That is hard to tell. However their disappearance from the lower Deschutes River, and the Crooked and Middle Deschutes rivers, should be taken as an indication of an ecological change. Their disappearance warrants deeper investigation and not just casual dismissal of a phenomenon that could be indicative of a larger ecological problem.

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More On Portland General Electric’s Report on Periphyton (algae) and Aquatic Macroinvertebrates (The R2 Report)

Since the release of PGE’s report on their two-year study of algae and aquatic insects, we’ve received a lot of inquiries from our supporters.  So let us update everyone on where things are at related to our response to the report.

We’ve been able to get four Ph.D. experts in fields related to the ecology of rivers to agree to review the R2 report.   It will take us until early June to get the evaluations back from these individuals.  We think it will be worth the wait.  Please stay tuned.

We’ll also be writing up some of our own assessments of the study.  We have some resident experts of our own on the DRA’s Board of Directors.  You’ll be seeing some of their thoughts within the next couple of weeks.

Photo by Rick Hafele.

Photo by Rick Hafele.

Stonefly Hatch!

In the meantime, we’re headed into late April.  That means the stonefly hatch should be starting anytime.  Please send us your reports on the stonefly hatch to info@deschutesriveralliance.org.   Although our trained hatch observers will be on the river sending in reports, we’d like to hear from all of you.

Several times during recent presentations, PGE’s contractor from R2 Resource Consultants described the wealth of stoneflies he’d seen while doing kick-screening on the lower Deschutes River.  However, the actual R2 report says something else.  “Stoneflies were not numerically abundant, but were widely distributed and contributed substantially to the invertebrate biomass by virtue of the often large size.” (R2 Resource Consultants, Final Report, Lower Deschutes River Macroinvertebrate and Water Quality Study, Prepared for Portland General Electric, 2016, page 97.)

“Not numerically abundant” is more consistent with our observations based on kick-screening and observational adult insect hatch data over the past few years.

So help us out.  Given recent temperatures, the stonefly hatch should begin in a few days to a few weeks.  As Hafele and Hughes said in The Complete Book of Western Hatches, “It is a show that should not be missed.”  Although it seems to be a less dramatic show in the past few years.  We would like to hear about your experiences during the hatch.   Tell us when and where you see the big bugs, what sorts of numbers you see, and how the fish are responding.  Let us know by writing to us at info@deschutesriveralliance.org.  We’ll not disclose any secret fishing locations, nor divulge any other information until after the hatch is over.

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Portland General Electric Releases Report and Results Of Two Year Study of Lower Deschutes Macroinvertebrates and Periphyton

Study described as finding “post-Selective Water Withdrawal conditions similar to pre-Selective Water Withdrawal, or improved.”

The final report for the Portland General Electric Company’s Lower Deschutes River Macroinvertebrate and Periphyton Study was presented on April 6th and 8th, at meetings hosted by PGE.  R2 Resource Consultants of Redmond, Washington conducted the study, which was completed under contract to, and funded by, PGE.  It was a two-year study conducted over two months (April and October) each year starting in October 2013.  The study was a required condition of the Federal Energy Regulatory Commission licensing of the Pelton-Round Butte Hydroelectric Complex.

Yes, you read the stated conclusion of the study correctly.  Conditions in the lower Deschutes River are “not significantly different, post implementation of surface water withdrawal at Round Butte Dam in 2009, than conditions prior to surface water withdrawal.” In fact, according Tim Nightengale of R2 Resource Consultants, the “health of the river is probably better(!) now.”   (We have been unable to find this actual statement in the published version of the study.)  So why the serious disconnect between the described study results and what we are seeing on the lower Deschutes River?

As one property owner said at the Portland presentation of the study results, “I’ve been on the river for over fifty years and the river has never looked like it has in the last few years.”  His disappointment was that none of the negative changes are reflected in the report.  We had the same disappointment.

Again, why the disconnect?

Over the next few months we’ll be answering that question.  The full published version of the study is a 283-page pdf file.  It will take us some time to fully analyze the study and its purported results.   There appear to be a large number of issues that require full examination.

We will also be sending the study out for review and analysis to independent experts.  Following those reviews, we will be publishing an analysis and critique of the study.  We expect this process to take two to three months.

For now, we do want to be clear that we already see some troubling statements and findings in the report.  We will be following up on some of those statements via this blog, prior to publication of the comprehensive review.

Copies of the full report are available here (pdf):

https://www.portlandgeneral.com/-/media/public/corporate-responsibility/environmental-stewardship/water-quality-habitat-protection/deschutes/documents/deschutes-bmi-final-report.pdf?la=en

 

Unusual bloom of algae in March of 2016, approximately one mile below Pelton Reregulation Dam. Photo by Rick Hafele.

Unusual bloom of algae in March of 2016, approximately one mile below Pelton Reregulation Dam. Photo by Rick Hafele.

Greg McMillan and Larry Marxer taking water quality measurements in February, 2016. Photo by Andrew Dutterer.

Greg McMillan and Larry Marxer taking water quality measurements in February, 2016. Photo by Andrew Dutterer.

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Black Spot Disease Seen in Lower Deschutes River Fish

By Greg McMillan

We started receiving reports of “black spot” disease in lower Deschutes River bull trout a few weeks ago.  The first report was from Andrew Perrault from the Gorge Fly Shop in Hood River.  He sent along these photos and it is pretty easy to tell these black spots are not normal on bull trout.  Many of us know that bull trout are species Salvelinus and thus members of the char group.  These fish don’t have black spots as normal coloration.

Photo by Andrew Perrault.

Photo by Andrew Perrault.

Photo by Andrew Perrault.

Photo by Andrew Perrault.

Close up of lesions assumed to be due to black spot disease. Photo by Andrew Perrault.

Close up of lesions assumed to be due to black spot disease. Photo by Andrew Perrault.

Black spot disease on lower Deschutes River bull trout. Photo by Ryland Moore.

Black spot disease on lower Deschutes River bull trout. Photo by Ryland Moore.

Since that first report we’ve heard of other observations of black spot disease on both bull trout and red band trout.  The presence of black spot disease has been confirmed by sources at Oregon Department of Fish and Wildlife.

Black spot disease is caused by a flatworm (trematode) parasite known in the scientific community as Uvulifer ambloplitis, and also known as “neascus”.  This parasite has a complicated life cycle that starts with eggs in water, which hatch and become juveniles known as miracidia, which in turn infect aquatic snails.  In snails this form of the parasite matures into the next life form, known as cercariae.  Cercariae are shed by the snails and become free swimmers, which attach to fish.  Once the cercariae have attached to the flesh of fish, the fish develops an immune response that causes the dark spot.

Kingfishers are the next host, which become infected when they ingest infected fish.  The cercariae develop into adult flatworms.  The parasite then produces eggs, which are shed in feces by kingfishers, and deposited in water where the life cycle is reinitiated.

Black spot flatworm. Illustration by Bruce Worden.

Black spot flatworm. Illustration by Bruce Worden.

These flatworms do not appear to be fatal to fish, or other hosts.  There are scattered reports of fish stressed from other sources dying while infected.  No human infections have been reported, but there is no real surveillance mechanism to detect human infections.  Although probably safe for human consumption after thorough cooking, there are no study data to confirm that.

None of us who have fished the lower Deschutes River for decades can say that we’ve seen many, if any, fish with this condition.  There are reports indicating there have been infected fish in the lower Deschutes River and tributaries in the past, but they aren’t common.  So what has changed?  Is this random?  Or linked to the ongoing ecological changes we are all seeing in the lower river?

This might be related to an increase in the snail population in the lower Deschutes River.  Portland General Electric’s Year 1 Data Summary Report from their Lower Deschutes River Macroinvertebrate and Periphyton Report Study published in 2014, indicates that there has been a significant increase in snail populations in the lower Deschutes River.  This increase in population in the intermediate host (snails) might be related to the increase in black spot disease noted in fish.  The snail population increase is likely linked to the increase in algae in the lower river.

Is this a catastrophic occurrence?  Probably not.  But it could be another indication of ecological change in the lower Deschutes River.

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