--Bruce Stallsmith
along the Tennessee
Huntsville, AL, US of A
>From: "Todd D. Crail" <tcrail at UTNet.UToledo.Edu>
>Reply-To: nanfa-l at nanfa.org
>To: <nanfa-l at nanfa.org>
>Subject: Re: NANFA-L-- Diversity Indicies
>Date: Thu, 29 Sep 2005 12:44:56 -0400
>
>Yeah IBI isn't going to work. I didn't describe my situation very well,
>sorry about the argument there.
>
>So if I'm understanding what I'm reading about Hill's, it will account for
>the discrepantcy in the biomass? I'm just looking for a simple way to
>compare multiple yet similar sites within a watershed, using the fish
>community sampled as the response variable.
>
>The problem I'm running into is something like this:
>
>One of my sites consisted of:
>bluntnose(13)
>fathead(15)
>green sunfish(1)
>least darter(95)
>johnny(4)
>orangethroat(24)
>
>If I caluculate Simpsons on that site alone, I get 1.15, in part, because
>least darter are so proportionately more represented than other species
>when
>you compare it to another replicate site:
>
>bluntnose(4)
>fathead (1)
>johnny(3)
>least(2)
>
>...which comes out 1.28.
>
>The second site is more "diverse"? It's definately more even, but c'mmon!
>And we also loose the fact the least darter is a large proportion of the
>individuals found at the first site, and more aggrivatingly, is a SSC fish.
>The whole diversity issue irons out when all the replicates are taken in
>consideration, but I'd rather drive my point home with a hammer, rather
>than
>some feather-like p value that doesn't make any sense to anyone besides the
>0.05% I work with lol.
>
>What I'd really like to do is find a way to compare each site against the
>whole of the sample, where each replicate receives a score against the
>whole. I would think there'd be some way to compare stream segments along
>a
>gradient (perhaps by stream order?) but I guess everyone has been too busy
>counting mayflies and snails they can't speciate to look at something
>easier
>to identify, like fish.
>
>I dunno. I dunno if this works for on-list traffic either. I guess I
>rationalize it that if there isn't an easy way to compare parts of streams
>by a response variable such as fish community, then the NANFA list is
>making
>something useful and doesn't require understanding how greek symbols relate
>to each other to figure out if part of a stream fares better than another
>part of the same system. It sure seems can't voice my opinion here at
>school... Apparently masters students are to only be seen and not heard.
>Oh
>bondage... {obscure x-ray specs reference}
>
>Thanks for your help and continued tolerance :)
>Todd
>Madness!
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