mous or potamsdromous). If only one species is Gerbilskiy 1957, Kazansky 1962, Artyukhin 1988).
present, it is usually anadromous. The Northeast Some of the terms and discussions are contradicto-
Atlantic region (Figure 4) has a high frequency of ry and difficult to follow, particularly because it is
rivers, particularly in western France and the Iber- not always possible to link migration times, spawn-
ian Peninsula, that have only one anadromous spe- ing sites and specific migrants. Also, the terminol-
cies, A.sturioThe absence of a second species in ogy does not easily translate to conditions in North
these rivers is not due to anthropogenic effects, but American rivers, many ofwhich are shorter, smaller
instead reflects the historical situation Holcík∨ coastal streams than are the major rivers of the
1989). It is unclear why the pattern that is so com- Black and Caspian Sea basins for which the termi-
mon elsewhere is not followed in the northeast At- nology was originally developed. The simplified
lantic region. scheme summarized in the box in Figure 5 draws
In Figure 1, most taxa are scored with eitheran ‘A’ primarily from Kynard (1997) and Gerbilskiy
for anadromy or ‘P’ for potamodromy; only one (1957). It classifies spawning migrations as having
species (A. brevirostrum) is marked ‘FWA to indi- one or two steps, with a variable length of time be-
cate freshwater amphidromy because without bet- tween the actual migration and the time of spawn
ter telemetric and tagging studies, we cannot know ing. This scheme can be readily used to describe
how inany seemingly freshwater species actually either anadromous, amphidromous or potamodro-
use patterns of freshwater amphidromy. Future nious acipenseriforms and individual variation
work will almost certainly change some of our ‘P’ within populations.
scores to ‘FWA’ scores. In some cases, a species may One step spawning migrationsare those in which
be potamodromous in one river basin and anadro- fish move directly upstream to the spawning site,
mous in another; in such cases, we scored the spe- spawn, and return downstream. Depending on the
cies‘A’. bioenergetic reserves of the fish, the migration may
be short or long, and occur in winter or spring. This
is usually thought to be the most common pattern
for living acipenseriforms, although the few data
available (mostly catch records) are conflicting. It
corresponds to Gerbilskiy’s (1957) migrant type I,
in which the oocytes have reached their final size
and spermatogensis is finished by the time migra-
tion starts. Fat deposits in connective tissue and
muscles arc depleted, and the stomach and diges-
tive tract are empty and inactive indicating that
feeding stopped some time before migration. Such
migrants typically use spawning sites in the lower or
middle reaches of rivers.
Short two step spawning migrationsinvolve up-
stream migration, usually in the fall, followed by
overwintering near the spawning site, followed by a
very short migration to spawn the following spring.
This pattern enables fish to use bioenergetic re-
serves gained during summer foraging for their ini-
tial long upstream migration. This corresponds
roughly to Gerbilskiy’s (1957) migrant type II, in
which late stages of oogenesis are in progress, and
the oocytes are still embeddedinfatty tissue. Sper-
matogenesis is in the ‘first wave’ of divisions. There
Patterns of spawning migrationsWithin acipenseriforms, variations in the pattern of
spawning migration are found at the species, pop-
dation, and individual levels. The genetic basis of
spawning migration characteristics is well establish-
ed for salmoniforms, for which extensive selection
experiments have been done (also see papers in
Groot & Margolis 1991). Virtually nothing is known
about the heritability of spawning migration char-
acteristics of acipenseriforms, but we expect a simi-
lar genetic basis to that known for salmonids. The
existence of different spawning migration patterns
in sturgeons has been discussed by many authors,
including Berg (1934, 1959), Artyukhin (1988) and
Kynard (1997 this volume). Berg (1934) introduced
the termsvernalandwinterraces to describe groups
of anadromous fishes migrating into rivers for
spawning in the same year (vernal races) or next
year (winter races). These terms stimulated a long
discussion in the Russian literature concerning Eur-
asian sturgeons (reviewed by Barannikova 1957,