shape caused by selection practices (Corti
et al. 1988; Eknath et al. 19911, or provide
information on the origin of populations
present in mixed stock fisheries: as for
Atlantic salmon off the Greenland coast,
where different stocks have been deline-
ated according to scale morphology and
growth patterns (Thorpe, in press).
Morphometry has been recently de-
fined as "traditional (multivariate)
morphometrics" or "geometrical
morphometrics" (Reyment 1991). The
former is the formal codification of
morphometrics as we generally know it,
an extension of the univariate and
multivariate statistics applied to biologi-
cal characters that are generally repre-
sented by meristic characters (in fish, for
instance, number of vertebrae, fin rays,
gill rakers, etc.) or by distance characters
(total length, maximum height, fin length,
etc.). Numerical techniques (principal
components and derivates, canonical
analysis, etc.) have been developed and
are widely used to study morphological
variation in fish.
Geometrical morphometrics
(Bookstein 1991) represents a completely
new approach that analyzes the form
described in space by a set of landmarks
through superimposition methods, an
extension of D'Arcy Thomson's (1917)
intuition: differences in the form are
geometrically described by the deforma-
tion of the plane given by the superimpo-
sition of one form over the other. Given
a formal description of the algebra
(Bookstein 1991), it is evident that this
approach is particularly suited also to study
how an individual changes in shape dur-
ing growth, relative to differences in the
environment. This has particular interest
in aquatic animals.
Starch-gel Electrophoresis
of Enzymes
Among biochemical techniques,
starch-gel electrophoresis of proteins isthe predominant tool for population ge-
netics, and databases of proteins are con-
stantly expanding. Its success is based on
being a quick and simple technique that
provides high resolution. Indeed, the
combination of gel electrophoresis and
histochemical staining is the fastest and
most economical method for surveys of
variation at a large number of loci. Since
their introduction in the early 1960s'
electrophoretic techniques have been
widely used by population geneticists to
clarify the status of various taxa, and to
document the status of wild and cultured
stocks.
Many questions in fisheries and
aquaculture, like stock assessment, analy-
sis of mixed stock fisheries or recognition
of hybrid populations, can be addressed
readily through the study of genetic vari-
ability within and among populations (e.g.,
Ryman and Utter 1987; Ferguson and
Thorpe 1991; Gauldie 1991; Whitmore
1991). Althoughmostinformationis avail-
able on temperate species, studies are
spreading to tropical species as well, es-
pecially those with economic interest.
Indeed, stock identification is essential to
both fish conservation and fisheries and
aquaculture management.
Correlation between the level of indi-
vidual multiple locus heterozygosity and
performance traits (such as growth rate
or growth-related traits, etc.) has been
suggested for different cultured organ-
isms (Leary et al. 1984; Macaranas and
Fujio 1986; Sbordoni et al. 1987; Kohen
1991).Mitochondria1 DNA
Restriction enzyme analyses of
mitochondria1 DNA(mtDNA) have greater
resolving power and require fewer Sam-
ples than allozyme studies. The relative
ease of applying this method to fish and
the rapid rate of mtDNA nucleotide diver-
gence have made mtDNA analysis a very
powerful method, now more and more