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zoogeography, dispersal, and bioassessment

Started by Guest_darter1_* , Feb 03 2010 10:51 PM

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8 replies to this topic

#1 Guest_darter1_*

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Posted 03 February 2010 - 10:51 PM

Bioassessments provide scientists with a means to monitor environmental degradation within a watershed. I have read some literature on assessment tools for fish (Karr and Angermeier), and after some conversation with local biologists, I have come up with a few questions. How is zoogeography applied to the creation of bioassessments? It would seem that relict populations and hot spots for biodiversity have the potential to overload the "species list" used to create bioassessment metrics. What about chemical and physical barriers that may not provide equal dispersal rates throughout a watershed (subbasins)?
Am I overlooking something... any ideas are welcome.

Thanks,
Tim

#2 Guest_fundulus_*

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Posted 03 February 2010 - 11:19 PM

Many bioassessments are simplifications of nature and natural processes that would hopefully communicate information to uninformed people like politicians. So my gut reaction is that they inherently neglect complications like relict populations and hot spots, although "hot spot" in recent usage can be a fairly large area like the Cape Floristic Province in South Africa. So all of this is an approximate measure.

#3 Guest_Newt_*

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Posted 04 February 2010 - 11:36 AM

Diversity indices can be adjusted to the watershed in question, and the bioassessment typically compares the study stream to a reference stream in the same drainage, rather than just looking at the raw index score.

#4 Guest_fundulus_*

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Posted 04 February 2010 - 12:48 PM

Diversity indices can be adjusted to the watershed in question, and the bioassessment typically compares the study stream to a reference stream in the same drainage, rather than just looking at the raw index score.

If done correctly, probably so. No diversity indices or bioassessments are exactly the revealed Truth, although for sheer simplicity people tend to accept them as such.\

#5 Guest_ashtonmj_*

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Posted 04 February 2010 - 02:49 PM

If done correctly, probably so. No diversity indices or bioassessments are exactly the revealed Truth, although for sheer simplicity people tend to accept them as such.\

Are they supposed to be (Truth) though? Rareness, unique fauna, hot spots, are a whole thing all to themselves for a reason. I think there is plenty of literature that points out the pitfalls of traditional multimetric indicies when predicting, protecting, or in general having any influence upon it by the presence or absence of a rare species. At face value one may think they should overlap each other, but there is a reason something has a relict population, and expecting it to be explained by % lithophilic spawners, # of intolerants, etc. is almost unreasonable. Blackwater streams with an improperly calibrated, out of context IBI would have "poor" conditions, but it does not mean they are poor or the unique fauna that inhabits the ecosystem are indicators of poor water quality. It's the myth of an A+ stream, I'd even argue A- maybe down to B+ streams if you want to go down the Biological Condition Gradient way of thinking.

#6 Guest_fundulus_*

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Posted 04 February 2010 - 04:18 PM

Matt, you're right. You assume rational planning and interpretation of such studies; I'm being skeptical of the necessary connection between intent and interpretation. Something like an IBI is purely to put a simple-to-say numerical value on something that most of here would quickly understand in more nuanced ways. But none of us are bureaucrats or politicians.

#7 Guest_farmertodd_*

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Posted 04 February 2010 - 05:23 PM

You were onto it in the first couple posts Bruce. People who paid for development of these things want to know "Is it good? Is it bad? Is it okay?" and not a whole lot more than that.

Nor does the answer to any of those qualitative responses usually solicit any kind of action after the answer, like "Should we protect it? Should we fix it? Should we leave it alone?"

Todd

#8 Guest_gerald_*

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Posted 04 February 2010 - 05:37 PM

North Carolina's version of the IBI has different scoring criteria for certain "metrics" in different river basins, physiographic areas, and drainage basin sizes. See pages 13 to 15 in the NC-DWQ Fish IBI Operating Procedures:

http://www.esb.enr.s....2006.Final.pdf

Like others have said, it's more for water quality policy use than for fishery management or scientific use. Its one of several tools used for assigning stream "use support ratings" and identifying impaired streams than need remedial action. Note that IBI is part of our state Water Quality agency, NOT our Fish & Wildlife agency. SO it doesnt need to be terribly accurate in ecological terms. Either a high IBI score OR presence of rare species can be used to assign "high quality waters" or "outstanding resource waters" that get special protection rules.

#9 Guest_darter1_*

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Posted 04 February 2010 - 06:09 PM

Thanks for all the post!! I hate to see the loss of natives to introduced generalist fish. But it seems like the balance between ubiquitous natives and ubiquitous introduced species may be the most important metric within any bioassessment. Noticing these trends may be more important to protection then comparing a stream to a reference that is unattainable. We have to help out those politicians if we are ever going to get anywhere in conservation.