Figure 2.Map of the distribution ofcaptures ofA. sturioin the easternAtlantic andNorth Sea.emission from males. In the other cases, we checked
the gonads by making asmallabdominal cut. We
determined thereproductivepotential offemales
by examiningthreecharacteristics of theeggs:their
meanlargestsize (n =15);theirpolarization index
(PI),defined as theratio of thedistanceseparating
the germinalvesiclefrom theanimalpole to the
largest dimension of the egg (Kazanskii et al.1978);
and the in vitromaturation competence ofeggs (ob-
servation of germinalvesicle break down: GVBD; n
= 30), according to the method described for A. bae-
rii(Williot et al.1991) andalsoused on white stur-
geonA. transmontanus(Lutes et al.1987). We char-
acterized males asimmature (do not yield any
sperm, even bystripping), running (sperm is run-
ningnaturally), and non-motile sperm(running but
spermatozoa do notmove inwater).
To induce spawning, we injectedfishwithcarp
hypophysispowder at arate of 5 mg kg–1and 2 mg
kg–1of bodyweight for thefemales and males, re-
spectively.Sperm was removed from themales by
massage and ovawere collected bylaparotomy (ap-
proximately 5 cm long)near and above thegenital
opening. Theabdominal cut wassewn up withfour
crossstitches. Processes used for insemination, neu-
tralization of thesticky eggenvelope, andincuba-
tionmethods,were thesame asthose used forA.
baerii(Williot etal. 1991).During all of the above