Bhattacharya method in Fisat software

[Alastair Grant]

I don't have experience of that particular program.  But what I do know is 
that one needs to exercise extreme caution when trying to separate age 
classes on the basis of population size fequencies.  See:  

Grant, A., P.J. Morgan and P.J.W. Olive, 1987. On the use made in marine
ecology of methods of separating age-groups from size-frequency data. Marine
Biology 95, 201-208

and

Grant, A., 1989. The use of graphical methods to estimate demographic
parameters. J. mar. Biol. Ass. U.K. 69, 367-371

for details

Alastair
_______________________________________________
Alastair Grant
School of Environmental Sciences, University of East Anglia, Norwich, NR4
7TJ, UK
Web page http://www.uea.ac.uk/~e130
Phone 01603 592 537  Fax 01603 507 719 Mobile/Voicemail 07941579036


-----Original Message-----
From: owner-annelida at net.bio.net [mailto:owner-annelida at net.bio.net]On
Behalf Of Roman
Sent: 14 February 2001 19:09
To: annelida at net.bio.net
Subject: Bhattacharya method in Fisat software


Using the Bhattacharya's method routine, included in the FISAT software
(DOS version), to estimate cohort parameters in a polychaete population,
I have observed that chi square test may show different values for the
same cohort distribution each time the sample is reanalyzed. The
problem may consist in the estimation of the number of freedom degrees,
so it may vary in successive analysis even for the same value of X2.

Since Bhattacharya method and FISAT software are usually utilized in
polychaete population dynamics studies, it is possible that somebody has
observed a similar problem and knows an alternative.

Sincerely, Roman rporras at mail.ono.es


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