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Subject:

Reef fish

From:

Daniel Bebber

Date:

Wed, 18 Aug 1999 13:34:28 +0100

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 ```I think you need to consider the biological reality of the community of interest. You need a model of the species-abundance curve for this particular community, where the relative abundance of each species on the reef is known. So, instead of writing "Sample 1, 6 Fish, 3 Species" you need to determine how many of each species there are. Simply noting how many species in a catch doesn't help. You can then use the resulting species-abundance curve to determine the probability of getting one fish of each of the seven species in any one sample. Dan ____________________________ Mr. Daniel P. Bebber Department of Plant Sciences University of Oxford South Parks Road Oxford OX1 3RB Tel. 01865 275000 Fax. 01865 275074 > -----Original Message----- > From: [log in to unmask] > [mailto:[log in to unmask]]On Behalf Of Coomaren Pillay > Vencatasawmy > Sent: 18 August 1999 13:21 > To: [log in to unmask] > Subject: Help with a probability question > > > Dear all > > I got this request from a friend: > > In theory, the more fish there is on a reef, the more species are > expected > to exist by chance (if fish of different species have a random chance of > joining the community). My own hypothesis is different so I am trying to > disprove the hypothesis that different fish species appear at random in > a > fish community. > > So he took 150 samples, each containing up to 12 fishes. > > For example he has (out of a maximum of 7 species) > > sample 1 6 fish 2 species > sample 2 4 fish 1 species > sample 3 8 fish 5 species > > He needs to determine the expected number of species in each sample or > the probability of observing sample 1. > > According to me (and him) he is testing the hypothesis prob(getting > species i)=1/7. So in principle in a sample of 6, he should get 6 > species. > > This seems intuitively wrong. > > Can anyone help please? > > Coomaren > > > ........................................................................ > ........................................................ > Dr Coomaren P Vencatasawmy > Senior Research Fellow > Spatial Modelling Centre (SMC) > P.O. Box 839 > S-981 28 > Kiruna > Sweden > [log in to unmask] > Telephone: 46 980 67013 > Fax : 46 980 67190 > "Perfection is achieved, not when there is nothing more to add, but when > there is nothing left to take away." - Antoine de Saint Exupery > ........................................................................ > ........................................................ > > %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ```