Troutnut Forum > Fly Fishing Discussion > Mayfly Hatch Decline?
| Taxon | February 18th, 2007, 5:11 pm | |
| Mercer Island, WA Posts: 506 | The following question was posed to me by brntrout on another forum:I'm not sure if you have the answer for this question. However, I'll ask anyway, maybe you have some idea of what's happenning! And, I answered it thusly: Let me preface this response by saying I have no specific information about the trend of mayfly hatch density in SE Minnesota which would confirm your observations, nor for that matter, any information which would rebut your observations. However, the question has really sensitized me to the issue, and I’m wondering whether (or not) others may have noticed a significant decline in mayfly hatches (similar in circumstance to the SE Minnesota observation) in their own home waters. | |
| Roger Rohrbeck www.FlyfishingEntomology.com | ||
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| CaseyP | February 18th, 2007, 11:25 pm | |
| Arlington, VA/ Mercersburg, PA Posts: 267 | another bit of anecdotal evidence: on Dickey's Run in south central PA, the sulphur hatches used to "boil the water", according to our elderly informant. in the three years we've fished there, we've seen obvious hatches, but nothing that would begin to suggest that vivid image, and E. I. has expressed his regret at the passing of something else in the natural world. | |
| "You can observe a lot by watching." Yogi Berra | ||
| GONZO | February 19th, 2007, 12:13 am | |
| "Bear Swamp," PA Posts: 951 | This is always a troubling and puzzling question, Roger. As a fervent follower of the hatches in the rather broad range of streams that I'm proud to consider my homewaters, I've noted over about forty years both decreases and increases in mayfly populations that seemed to be cyclic, some that were probably attributable to catastrophic events like sustained severe flooding and subsequent slow recovery, and others that were more insidious and disturbing. Here in the Cumberland Valley, for example, we have a number of small limestone spring creeks that once held outstanding populations of "sulphurs" (especially E. invaria, but also others). I mention this example because invaria seems to be a particularly resilient and adaptable member of the Ephemerella genus and because these spring creeks are generally quite stable and fertile environs. While the wild trout populations in these creeks are still pretty good in many cases, they are sustained now primarily by scuds, sowbugs, and midges. The land surrounding these streams has long been prime agricultural real estate, but land use trends are rapidly changing, and suburban sprawl and its associated baggage are consuming more and more of this fertile ground. The pressure for farmers to produce more on less land along with the pressure to develop the land makes me worry about the future of many of these streams. In a few, I seem to see an increasing ratio of sowbugs to scuds, which is usually not a good sign. In contrast, I can point to a few waters where improvements have occurred and mayflies are on the increase. The invaria populations are often the first mayflies to respond to these positive changes. There are also baffling incidents that I cannot explain. Last season on the Yellow Breeches (one of the two main streams that cut across the valley) we saw the first good hatch of Hendricksons (E. subvaria) that most of us can remember seeing in many, many years. (They used to be quite strong and a reliable harbinger of the renewal of the fly-fishing season.) Of course, we all took this as a happy and encouraging event. Different mayfly species have different sensitivities and face different challenges. In my other home region, the Poconos, multiple years of severe flooding have altered stream courses, overwhelmed sewage treatment plants, and flushed trout and insects from any stream section where the flood waters were unable to spread out. I expect that the streams can recover from this over time, but the resulting "cleanup" that follows in the wake of such events is often done in thoughtless and damaging ways, and further exacerbates the problems for trout and mayflies. (Most of the Easterners here know that the Catskill streams and upper Delaware Basin were also hit hard by these events.) Only time will tell what the result will be for trout, mayflies, and fly fishing there. Before the devastating floods of Hurricane Diane hit the Northeast in the '50s, the Brodheads (and a number of other Pocono streams) had nice hatches of green drakes (Ephemera guttulata). Some attribute their loss directly to the floods, while others blame the widespread spraying of DDT that followed for their demise. Whichever is the case, except for a very small relict population in a short section of the Lehigh, they seem to be gone forever. This is certainly one of the sadder sides of fly-fishing today, and I also wonder about the larger compounding effects of climate change and global warming. The future of fly fishing may seem like a petty concern in the light of issues as large as these, but it is certainly precious to me, and without a hatch to match it loses much even now. | |
| Troutnut | February 19th, 2007, 1:03 pm | |
| Fairbanks, AK Posts: 1122 | I haven't been fly fishing long enough to observe the long-term trends myself, but I've heard about the same trends Taxon and Gonzo describe many times, and in many places. The major directly human-caused factors seem to be
None of these things bode well for trout or cold-water insects. Luckily many streams are protected by park services from the worst impacts of watershed development, but global climate factors are cause for concern over almost any river. I wouldn't anticipate a large net loss in insect biomass from these changes (although I'm not really qualified to speculate on that). I would guess that the result, instead, will be a shift in the dominant species. Gonzo described some cases of that above. So the problem isn't really that the invertebrates are disappearing, but that the ones we like are going to disappear first. Many of the most treasured mayfly hatches (like the Hendricksons) are canary-in-the-coal-mine species. | |
| Jason Neuswanger The Troutnut | ||
| GONZO | February 19th, 2007, 1:40 pm | |
| "Bear Swamp," PA Posts: 951 | Many of the most treasured mayfly hatches (like the Hendricksons) are canary-in-the-coal-mine species That is my impression as well, though I have also seen the Hendrickson described as "hardy." I suppose that begs the "compared to what?" question. The habitat requirements of subvaria and its sensitivity to changes seem pretty acute, even when compared to the closely related invaria species. The invaria seem to occupy a wider range of habitats (even within a stream section) and seem able to hold on after subvaria has dwindled or disappeared in a stream. Epeorus pleuralis also seems to be a particularly sensitive Eastern species (perhaps even more so than the Hendricksons), and is noticeably on the wane in many streams of my experience. Jason, I know that when benthic invertebrates are surveyed as a tool to assess the overall health of a stream or section, they are given a rating based on their relative sensitivity. Do you know if these ratings are sufficiently species-specific to provide a point of comparison with my (admittedly anecdotal) observations? | |
| Troutnut | February 19th, 2007, 2:46 pm | |
| Fairbanks, AK Posts: 1122 | Jason, I know that when benthic invertebrates are surveyed as a tool to assess the overall health of a stream or section, they are given a rating based on their relative sensitivity. Do you know if these ratings are sufficiently species-specific to provide a point of comparison with my (admittedly anecdotal) observations? Most invertebrate biomonitoring is done at the order or family level, I think. I'm sure some experts use genus as well, but comparison of individual species for that purpose is probably rare if it's used at all. I don't know all that much about it. | |
| Jason Neuswanger The Troutnut | ||
| GONZO | February 19th, 2007, 3:16 pm | |
| "Bear Swamp," PA Posts: 951 | Thanks, Jason. As just another point of interest, does anyone know anything about the effects of large-scale spraying against black flies or mosquitoes upon other aquatic insect populations? | |
| Jlh42581 | February 19th, 2007, 4:29 pm | |
| Milesburg, Pa Posts: 24 | Spring Creek here in Central Pa used to have Green Drakes, they're gone now due to a Chemical spill from PSU. We also have experienced major floods in the past ten years, I can tell you, the sulphurs(dorthea?) are slim to none now. But to me, that seems a little weird seing that we have an over abundance of Tricos(naming?). The baetis hatchs last year seemed to suck, but then again, we had a flood two years ago, at beatis time. | |
| Jeremy | ||
| DMM | February 19th, 2007, 6:04 pm | |
| Posts: 141 |
Every study I've been involved in has gone to genus level. It really depends on the purpose of the study. It is also dependent on taxa used. Often, Diptera are only identified to family, mites are all called Hydracarina/Acarina, but Plecoptera, Ephemeroptera, and Trichoptera are often taken down to genus level. For purposes of sensitivities, inverts are often identified to species level. I don't know anything about eastern indicator species, but I know the literature talks about them. As just another point of interest, does anyone know anything about the effects of large-scale spraying against black flies or mosquitoes upon other aquatic insect populations? It depends on the spraying method. Often, a taxon specific pathogen is used as control. For instance, there is a bacterium that is sprayed on Simuliidae, and no harm to other taxa has been observed when it is used. | |
| David | ||
| Martinlf | February 19th, 2007, 6:42 pm | |
| Palmyra PA Posts: 932 | My experiences with the little olives on Spring Creek in State College PA match Jeremy's. In 2004 there were heavy hatches. In 2005 and 2006 I found some fish rising to olives in March, but not nearly as many as in '04 when there were bugs everywhere each grey, drizzly day I was able to get on the water. Folks I have talked to suggest that these differences may be due to natural cycles. In 1996, 1997 and 2001 I fished great Hendrickson hatches on a small tailwater that is not so well known, and will remain nameless. Local Trout Unlimited members I talked with told me that it is believed a spill in 2002 virtually wiped the Hendricksons out. I came looking after that but the bugs were gone. Last year one angler told me they were making a comeback in the upstream waters, and all the local flyfishers I've talked to are hopeful that the hatch will reestablish itself. In the past this had been a magnificent hatch, bringing up lots of big fish that now are rarely, if ever, seen feeding on top. I'd second Gonzo's observation that it appears that some variations are cyclic, that some are caused by human intervention, and that it's difficult without hard evidence to know which at times, or if some combination of natural factors and the absence or presence of pollution best accounts for immediate changes. I also believe that climate change may have some long term effects on reducing habitat for both mayflies and trout. | |
| Louis Is it not an art to deceive a trout with an artificial fly? A trout! that is more sharp-sighted than any hawk . . . and more watchful and timorous than your high-mettled merlin is bold! --Izaak Walton The Compleat Angler | ||
| GONZO | February 19th, 2007, 10:16 pm | |
| "Bear Swamp," PA Posts: 951 | Thanks, David, for clarification on both points. Can you point me in the direction of the literature you mention? And Louis, I'll pry the name of that little tailwater out of you one way or the other! :) | |
| DMM | February 22nd, 2007, 2:24 am | |
| Posts: 141 | GONZO, I will try to help you out, but it is not an easy task. Biomonitoring protocols are varied and meant to address different concerns. In terms of macroinvertebrates, different species are indicators for different conditions. In other words, some species are more sensitive to heavy metals (you know, like Winger...ooohh, sorry about that, bad joke), some are more sensitive to pH, some are better at maintaining position in a stream during high flows, etc. Species assemblages are therefore often used to evaluate the health of a system. I would start my search, if I were you, with one of three options. First, contact your state fish and wildlife agency, and ask about biomonitoring protocols they use for assessing watershed health. State agencies often publish "gray literature," or simply print bulletins with protocols. These are not widely available to the public, but are usually available upon request for free (sometimes a small printing cost is involved--a dollar or two). Sometimes universities have collections of these bulletins too. Alternatively, some of the papers are available online--they can supply a link. Another option is to try the EPA. If you have a local office, it may make things easier, but it may be worth some effort even if you don't. They often have more general information, but it covers a larger geographical area. They may even have protocols online--they have protocols for everything. Finally, you can try a local university if they have a water pollution/entomology/aquatic ecology program. You can always search through the literature on your own, too. This can be painful, though. I will supply a few good biomonitoring citations for you at the end of this post. They can describe the principles behind the process, if you want background. If you want an explanation about specifics (like stepwise regression models) just ask. I hope this helps. It's kind of hard to give you specific answers without specific questions, and without knowledge about your local waters. Klemm, Donald J. et al. Methods Development and use of Macroinvertebrates as Indicators of Ecological Conditions for Streams in the Mid-Atlantic Highlands Region. Environmental Monitoring and Assessment, Volume 78, Number 2 / September, 2002, pp. 169-212. The preceding is written by EPA people. My citations are not to any standard because I'm lazy, but I think you'll be able to track them down. Kimmel, William G. et al. Macroinvertebrate community structure and detritus processing rates in two southwestern Pennsylvania streams acidified by atmospheric deposition. Hydrobiologia, Volume 124, Number 2 / May, 1985, pp. 97-102. These people are from U Penn and Penn State. K. W. SIMPSON, R. W. BODE, J. R. COLQUHOUN (1985) The macroinvertebrate fauna of an acid-stressed headwater stream system in the Adirondack Mountains, New York Freshwater Biology 15 (6), 671–681. I cut and pasted the last one. They are from NY state agencies. Weigel, Brian M. Development of stream macroinvertebrate models that predict watershed and local stressors in Wisconsin. Journal of the North American Benthological Society: Vol. 22, No. 1, pp. 123–142. The author works for a state agency. This is a very good journal to check out. Environmental Biomonitoring and Assessment Program--Surface Waters: Field Operations and Methods for Measuring the Ecological Condition of Non-Wadeable Rivers and Streams. Edited by Lazorchak, James M. et al. This is an EPA publication. A few more thoughts... Some people are using Chironomidae as indicator species. A stream typically has a "ton" of species. They are tricky to identify, especially without a really good scope. Don't be surprised if you find articles about them, though. Amphibians are widely used as indicator species due to their generally sensitive nature. Finally, sometimes EPT is written in these papers. It's an acronym for Ephemerotpera, Plecoptera, Trichoptera. I hope this helps. Happy hunting. | |
| David | ||
| GONZO | February 22nd, 2007, 10:32 am | |
| "Bear Swamp," PA Posts: 951 | Thank you very much, David. I can see that I've got my work cut out for me, but I greatly appreciate your thorough response. | |
| Brntrout | February 25th, 2007, 4:29 pm | |
| S.E. MN Posts: 5 | Thanks TAXON, for posting my question on this forum. From reading the replies to this question it appears that what is happening in S.E. Minnesota is also taking place in other locations of the country. I wonder if the loss, or severe reduction in the numbers of certain invertebrate species will cause any long term health issues(poorer body condition/survival) for trout? The reason I ask this question is the loss of some of the major invert. species has to have reduced the overall abundance of forage availablity for trout at DIFFERENT times of the year. Since most mayflies can be readily captured by trout, their availbility as food source has to be superior to other forage species that aren't as readily available or as easilly captured. Will the loss of many differennt invertebrate species effect the health/survival/size of trout in many of our stream? What to you guys think? | |
| brntrout | ||
| Konchu | February 25th, 2007, 5:01 pm | |
| Indiana Posts: 211 | WL Hilsenhoff (Univ. Wisconsin) put out several papers with aquatic insect species used to come up with a Biotic Index of water quality. Each has been assigned a tolerance value. I didn't notice his work mentioned in the discussion up to this point. Example: Hilsenhoff, WL. 1987. An improved biotic index of organic stream pollution. The Great Lakes Entomologist 20: 31-39. | |
| Littlejunia | March 7th, 2007, 11:28 am | |
| Posts: 1 | I know the diversity and numbers of macros on Spruce Creek in Pa have been on the decline, the stream flows almost entirely through farmland. There is a COA, 2000 cow dairy operation on the stream which produces an ungodly amount of "stuff" plus uses 50 to 100 gallons of water PER DAY per animal (I would think the higher amount in this operation?) At 100 gallons per animal that would be 73 million gallons per year. Check the flow of the Little Juniata River and note the decrease in flow. (USGS site) | |
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