Biology Reference
In-Depth Information
ifornia, and Florida. Several tilapia forms, which may be in part the result
of hybridization, make up most of the commercial stock. These hybrids
are believed to have originated mostly from crosses of blue tilapia with
Nile, Mozambique, and Zanzibar tilapia. Some genes from other species
also seem to be present.Two of the most popular hybrids are the Florida
red, a cross between blue and Mozambique tilapias, and a hybrid between
blue and Nile tilapias.The blue tilapia is favored as one parent because of
its tolerance to cold water.Active breeding programs for tilapias are being
conducted at several locations.
Several tilapia, including some that are likely to be hybrids, occur in
the wild in the southwestern United States (Courtenay et al. 1984; Costa-
Pierce and Doyle 1997). Nile tilapia, possibly including fish with hybrid
contributions from blue tilapia, are established in the lower Colorado and
Gila Rivers and irrigation canals in southeastern California and south-
western Arizona (Courtenay et al. 1984). Fish similar to Mozambique
tilapia, but possibly with hybrid contributions from Warm River tilapia,
occur in Los Angeles County, the Salton Sea, and some irrigation ditches
in southern California (Courtenay et al. 1984). Other hybrids have been
reported from central Arizona and southeastern California, but their sta-
tus is uncertain (Courtenay et al. 1984). Redbelly tilapia also occur in the
Salton Sea (Costa-Pierce and Doyle 1997).
Hybrid sport fish of several types have been produced and stocked in
fresh waters. For instance, several hybrids between species in the salmonid
genera
Salmo
and
Salvelinus
have been produced in captivity and the fish
stocked in Canadian lakes (Crossman 1984). In the family Centrarchidae,
hybrids have occurred naturally and been produced in captivity with sev-
eral sets of close relatives (see, e.g., Epifanio et al. 1999). Hybrid sunfish,
for example, are usually a cross between the bluegill (
Lepomis macrochirus
)
and the green sunfish (
L. cyanellus
). These and other centrarchid hybrids
are commonly stocked in ponds used for sportfishing. Another sport fish,
tiger muskellunge, is a sterile hybrid between northern pike (
Esox lucius
)
and muskellunge (
E. masquinogy
). Although these hybrids occasionally
occur naturally, most tiger muskellunge are artificially propagated and
stocked.This hardy hybrid has been stocked in numerous lakes and rivers
in eastern North America.
Hybridization Between Alien Microbial Species
The potential for origin of new invasive forms by hybridization extends
to fungi and other microbial forms. Molecular genetic techniques have
