Hi Gianluca,
Maybe this can help: M. J. Lechowicz. 1982. The sampling characteristics of electivity indices. Oecologia: 52 (1), 22-30, DOI: 10.1007/BF00349007 That it is a revision of different electivity index; also my recommendation it is to compute electivity values only for countable preys (as was appointed by David, uncountable items are so difficult to equate abundance). For those uncountable prey items probably is better to use other methodology, e.g. Costello’s graphical method: Costello, M.J., J. Edwards & G.W. Potts. 1990. The diet of the two-spot goby, Gobiusculus flavescens (Pisces). J. Mar. Biol. Assoc. UK 70: 329–342. Best wishes, Carles 2011/8/2 Chandrima Home <[email protected]> > Hi Gianluca > > You could also use IRI index (Index of Relative Importance) where you can > you use your bulk (volume) data along with frequency. But this would not > exactly be selectivity...it would be saying which is more important amongst > the different prey. Infact this was first used for fishes. Refer to : > Pinkas, > L., Oliphant, M.S., Iverson, I.L.K., 1971. Food habits of Albacore, Bluefin > Tuna and Bonito in California waters. California Department of Fish and > Game, Fish Bulletin 152, 1-83. > > Hope this helps to some extent > > Regards > > Chandrima Home > > On Tue, Aug 2, 2011 at 11:10 AM, Gianluca Polgar > <[email protected]>wrote: > > > Dear all, > > > > I'm going to estimate the food selectivity of some fishes and I'd like to > > adopt the food selectivity index of Berg (1979). > > > > This index utilises the numerical abundance of food items, measured both > in > > the gut and in the habitat. > > Nonetheless, a considerable percentage of food items is NOT countable > (e.g. > > detritus, plant material)... > > > > My question is: would it be a feasible option to utilise a measure of > bulk > > of food items (e.g. volume) instead of amounts? > > Is anyone aware of any other indexes of food selectivity that could be > > adopted with non-countable items? > > > > Any suggestion will be more than welcome! > > > > All the best, > > > > > > Gianluca > > > > -- > > Gianluca Polgar Ph.D. > > Senior lecturer > > Institute of Biological Sciences > > Institute of Ocean and Earth Sciences > > Faculty of Science, University of Malaya > > 50603 Kuala Lumpur, Malaysia > > Tel.: 017-6223549 > > Fax (ISB): 03-79674178 > > e-mail: [email protected] > > www.themudskipper.org > > > > O___!||||__/////__ > > {__)_\ > > > > > > -- > Chandrima Home > PhD Student (Conservation Science & Sustainability Studies) > Ashoka Trust for Research in Ecology and the Environment (ATREE) > Royal Enclave, Srirampura, Jakkur P.O. > Bangalore 560 064 Karnataka, India. >
