Moreno Amich, Ramon

Revistes Catalanes amb Accés Obert

SClENTlA gcrundensrs, 11 61-64, (1985) 
A COMPUTER PROGRAM FOR GUT-CONTENTS 
ANALYSES 
Dept. of Animal and Vegetal Biology and Ecology and Institute of Aquatic Ecology. Col.legi 
Universitari de Girona. 17071 Girona. Spain. 
RESUM 
Es presenta un programa d'ordinador per I'analisi de dades provinents d'analisis de 
continguts estomacals en estudis de r2gims alimentaris de peixos. El sistema organitza 
les dades segons classes definides per I'usuari, i calcula els índexs i coeficients 
alimentaris modernament utilitzats en aquests tipus d'estudis. 
Se presenta un programa de ordenador para el análisis de datos provenientes de 
análisis de contenidos estomacales en estudios de regimenes alimentarios de peces. El 
sistema organiza 10s datos según clases definidas por el usuario, y calcula 10s indices y 
coeficientes alimentarios moderzmente utilizados en este tip0 de estudios. 
ABSTRACT 
A computer program for analysis of feeding data of gut-content analyses of fishes is 
described. The system organizes data into functional classes with ranges defined by the 
user, and calculates a recently used series of indices and feeding coefficients in those 
kinds of studies. 
Key words: computer program, gut-contents analysis, feeding ecology. 
INTRODUCTION 
A computer program, REGIM, has been developed to interpret large data 
sets of guts analyses. REGIM organizes data with measures of central 
tendency and calculates simultaneously a series of indices for feeding 
studies. 
Study of diet based upon analysis of estomach contents is now standard 
practice in fish ecology but exists diferents methods which may be 
.employed. There are severa1 review papers by Hynes (1950), Pillay (1952), 
62 R. MORENO-AMICH 
and Langler (1956) which discribe the methods of analysis in use at those 
times. More recently Hyslop (1980) reviews the methods of dietary analysis 
in use at present and examine each of them, illustrating its advantages and 
disadvantages. 
Hynes (1950) have stated that important items in the diet will be 
obvious irrespective of the method of stomach analysis employed. This 
statement hinges on the definition of <<important items in the diet>> and each 
method will show items important in the diet according to the attribute it 
was designed to measure (ocurrence, number, weight, volume, points, 
etc.). 
It seems realistic to base assessment of dietary importance upon these 
unrelated methods (Hyslop, 1980), and Windell (1971) has stated that 
indices combining values from different sources are more representative. 
The indices calculated by REGIM have been selected from occurrence, 
numerical and gravimetric (or volumetric) methods, as well as indices 
combining these values. Also includes global descriptors of diet as feeding 
intensity, feeding diversity, index of emptyness, etc. and a descriptor of 
diet overlap between groups. All of these indices are listed in table 1. 
Table 1. Measures of feeding ecology calculated by REGIM. 
GLOBAL DESCRIPTORS 
Mean number of specimens per gut. 
Biomass ingered pergut 
Mean weight of preys. 
Index of emptyness: rate of empty guts. 
Index of mean feeding intensity, K (Aoyama, in YASUDA, 1960). 
Index of feeding diversity: Shannon's index (SHANNON & WEAVER, 1963). 
IMPORTANCE OF PREY 
Percentage by number. 
Percentage by weiglit. 
Percentage of occurrence. 
Mean number of specimem pergut. 
Mean weight of prey. 
Main food, Q (HUREAU, 1969). 
Index of relative importance, IRI, PINKAS et al. (1971). 
DIET OVERLAP 
Schoener's index (SCHOENER, 1970). 
DATA INPUT 
REGIM accepts only gut-contents data for -one species of predator. The 
data set is a list of the quantities of prey types found in each gut. Each prey 
type is identified by a number code and measured as count and weight. 
GUT-CONTENTS ANALYSES 63 
Individual prey types may be combined into broad groups representing 
a multi-leveled hierarchy e.g. plankton, benthos or crustacean, isopod, 
amphipod, etc. 
To aid data manipulation further, each gut can be coded with values 
designating specimen, sample, date (month), size (total length), body 
weight (total weight) and total gut-contents weight. These values allow 
grouping of samples into functional classes with ranges defined by the user. 
To help the user to enter correctly the data in a computer sequential 
file, a program is also available to write the data in the format needed by 
REGIM. This litle program, ENTRY, request the data set in logical order, 
although it is not necessary to repeat every time the common information 
of each sample group (e.g. sample code, date). ENTRY permits also to 
correct entered data. 
OUTPUT 
The output summarizes in two sections the contents of those guts analized. 
The first displays the total number of guts analized. Also the number of 
specimens of prey found in these guts and the total weight of these 
specimens are given in absolute number and as mean number per gut; and 
the number of empty stomachs, in absolute number and as rate of 
occurrence of empty stomach (Index of Emptyness). Besides the Shannon's 
index (Shannon & Weaver, 1963), as index of feeding diversity, and the 
average of Index of Feeding Intensity, K, are given. This last index was 
proposed by Aoyama (Yasuda, 1960) and represents the amount of food 
eaten: the weight of the gut-contents as percentage of the total weight of 
predator. 
Section two is a summary table arranged by prey type. The summary 
table displays the mean weight, and frequency of ocurrence, total counf 
and weight as percentages of the total. Also calculated for each prey type 
are the Index of Relative Importance, IRI, (Pinkas et al., 1971) and Main 
Food, Q, (Hureau, 1969). 
All percentages are calculated in relation to the total number of guts 
which were not empty. 
The prey type is displayed by its specific name which will be entered in 
a direct access file through the litle program ENCODE. 
There is an output for each group defined by size and date of sampling. 
Normally, the size is a size class with ranges defined by the user, and the 
date is the month or a superior period of time (season, year). 
Finally, two output matrices show the acrors values of Schoener's index 
(Schoener, 1970). In the first matrix this index is a measure of diet overlap 
between rize classes and in the second it represents a measure of affinity 
between periods of time. 
64 R. MORENO-AMICH 
COMMENT 
REGIM, ENTRY and ENCODE are written in FORTRAN 77. These 
programs are now running on VAXIVMS environment and they were used 
successfully by the author in the analysis of diet of Lepidotrigla cavillone 
(Moreno and Matallanas, 1983). The program package is available from the 
author as a print-off copy or on magnetic tape at cost. 
References 
HUREAU, J.C. 1969. Biologie comparée de quelques poissons antarctiques (nothot- 
henidae). Bull. Inst. Oceanogr. Monaco 68: 1-44. 
HYNES, H.B.N. 1950. The food of freshwater sticlebacks (Gasterosteus aculeatus and 
Pygosteus pungitius) with a review of methods used in studies of the food of 
fishes. J. Anim. Ecol. 19: 36-58. 
HYSLOP, E.J. 1980. Stomach contents analysis-a review of methods and their 
application. J. Fish. Biol. (1980) 17: 411-429. 
LANGLER, K.F. 1956. Freshwater Fishery Biology. Dubuque. Iowa: Wm. C. Brown. 
421 pp. 
MORENO, R. and J. MATALLANAS. 1983. fitude du regime alimentaire de Lepidotrigla 
cavillone (Lacépede, 1802) (Pisces: Scorpaeniformes) dans la mer catalane. 
Cybium, 1983 7(3): 93-103. 
PILLAY, T.V.R. 1952. A critique of methods of study of food of fishes. J. 2001. Soc. 
India 4: 185-200. 
PINKAS, L., M.S. OLIPHANT, and I.L.K. IVERSON, 1971. Foods habits of albacore, 
blue fin tuna, and bonito in California waters. Fish. Bull. Cal. 152: 1-105. 
SCHOENER, T.W. 1970. Non-synchronom spatial overlap of lizards in patchy habitats. 
Ecology 51: 408-418. 
SHANNON, C.E. and W. WEAVER, 1963. The mathematical theory of communication. 
Univ. Illinois Press, Urbana. 
WINDELL, J.T. 1971. Food analysis and rate of digestion. In Methods for assessrnent 
of Fish Production in Fresh Waters (W.E. RICKER, ed.) pp. 215-226. Oxford: 
Blackwell Scientific Publications. 
YASUDA, F. 1960. The types of food habits of fishes assured by stomach contents 
examination. Bull. Jap. Soc. Scient. Fish. 26: 653-662. 


A computer program for gut-contents analyses

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