Pauly, D.

English

Research Papers in Economics

...
A Simple Index of Metabolic
Level in Fishesa
DANIEL PAULY
ICLARM
TO.61 x AO.52
Model for estimating the annual food consumption
(Q) per unit biomass (B) of a population of car-
nivorous fishes:
attribute with regard to these two questions. This
aspect ratio (A) is defined, for any fish species with a
caudal fin, as:
...1) A =h2/s
where h2 is the height of the caudal fin, and s its
surface area (Lindsay 1978, and see Fig. 1).
[Obviously, this index will work only in fishes in
which the caudal fin is the only, or at least the main,
organ ofpropulsion, see Lindsay1978.]
A preliminary study was recently concluded at
ICLARM in which the usefulness of the aspect ratio
of fishes' caudal fin as an index of metabolic level
was tested. The results exceeded expectations: the
variable A explained over50% of the variance in a set
of 33 population-weighted food consumption esti-
mates! (See Box.)
Follow-up studies show that A, besides correlating
withfood consumption, also has close relationships -
other things being equal - with (i) natural mortality,
(ii) longevity, (iii) red muscle content, (iv) gill area,
(v) growth performance, etc. I.E. Gray would have
been happy about that.
t
h
+
Epinephelus fauvina
Aspect ratio: 1.4
."-,'-/'VV''''
Gray(1954) noted that "it is desirable, but difficult,
to obta;in comparative metabolism data on marine
fishes. From necessity;most data are obtained from
sluggish and moderately active species. Active
speciesare hard to keep in captivity,or even to get to
the laboratories, without becoming partially
asphyxiated."This problemhas notchanged in the 35
years since Gray'scomplaint, and I have noted in the
literature, besides Gray's, several comparative
studies on physiological process in fishes which
would have benefited from the availability of an
easy-to-estimate index ofmefabolic level in fishes.
Two questions can be asked with regard to such
index: (i) whichexternal attributescommon to a large
number of fishes is most different between species
with different habits? (ii) can the attribute identified
in (i) be easily turned into a number, such that
different species can be compared in quantitative
terms?
Several years ago, I figured that the aspect ratio of
the caudal fin of fishes might well be a promising
Q/B""
1.2 x WO.2
i
h
!
where T is the meanwater temperature (0C), W is the
asymptotic (or maximum) live weight of the fish (g)
in the populationin question and A is the aspect ratio
of their caudal fin (Palomares and Pauly in press).
The log linear version of this model has a value of R
= 0.865 and residuals (mean= 0.22 loglO units) evenly
distributed about the predicted values.
Fig. 1. Definition of the aspect ratio of the caudal fin of fishes.
Note large differences between pelagic and demersal species.
aExcerpts from the text of a lecture entitled "Population
physiology of fishes: a new look at old data," given on the 21st
March 1989 at the Alfred-Wegener Institute for Polar and Marine
Research, Bremerhaven, Fed. Republic of Germany at a seminar
to celebrate the 60th Anniversary of its Director, Prof. Dr. Gotthilf
Hempel, to whom this note is dedicated.
References
Gray, I.E. 1954. Comparative study of the gill area ofmarine fishes.
BioI. Bull. Mar. BioI. Lab. Woods Hole 107: 219-22,5.
lindsay, c.c. 1978. Form, function and locomotory habits in fish,
p. 1-100. In W.5. Hoar and D.J. Randall (eds.) Fish
Physiology Vol. VII Locomotion. Academic Press, New
York.
Palomares,.M.L. and D. Pauly. A multiple regression model for
predicting the food consumption of marine fish
populations. Auslr. J. Mar. Freshwat. Res. 40 (in press).
22 FISHBYTE
7(1) :22

Comparative study of the gill area ofmarine fishes.

Form, function and locomotory habits in fish,

A simple index of metabolic level in fishes

http://www.worldfishcenter.org/Naga/na_2901.pdf

A simple index of metabolic level in fishes

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