The question becomes are they all HBG X HBG crosses or are there BG X HBG or RES X HBG crosses also.
See this thread. The study below is only one and not beyond error.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=126303&page=1 Reproductive Isolation between a Hybrid Sunfish and
Its Parental Species
MARTIN W. BRUNSON
Rice Research Station
Louisiana Agricultural Experiment Station
Louisiana State University Agricultural Center
Post OJfice Box 1429
Crowley, Louisiana 70527, USA
H. RANDALL ROBINETTE
Department of Wildlife and Fisheries
Mississippi Agricultural and
Forestry Experiment Station
Mississippi State University
Mississippi State, Mississippi 39762, USA
Abstract-.- Attemptst o backcrosFst male bluegill( Lepomis
macrochirus) x green sunfish (Lepomis cyanellus)
hybrids with females of each parental species were unsuccessfubl
oth in ponds and in the laboratory. In laboratory
experiments, fertilization was accomplished but
embryos failed to survive longer than 36 h. In ponds,
nesting and courting activity were observed but successful
reproduction did not occur. Additionally, 1,874
of 1,983 Ft hybrids examined (94.5%) were males.
TABLE 1.--Fertilization success and survival of eggs
in artificial fertilization studies involving female bluegills
(BG) and green sunfish (GS) crossed with male F 1 bluegill
x green sunfish hybrids.
Number----------------- eggs ---------- ---eggs------% fertil----% sur-
Female-----Male-------stripped-------- fertilized----ization----vival
BG-------- BGxGS ---- 1,293--------------- 991--------- 77----------0
GS---------BGxGS ---- 1487--------------- 1103---------74----------0
Of 200 BG x GS hybrid sunfish examined in
the laboratory, 191 (95.5%) were males and 9
(4.5%) weref emalesD. uring the courseo f another
study involving 12 farm ponds stocked with these
hybrids, 1,783 hybrids were collected, measured,
and sexed over 24 months (Brunson and Robinette
1986); of these 1,683 (94.4%) were males.
These results are similar to results reported from
Illinois by Childers (1967) for the same hybrid.
Laarman (1973), however, reported 87% hybrid
males in Michigan, and Crandall and Durocher
(1980) reported 66-68% hybrid males in Texas.
These variable sex ratios indicate geographical differences
in genetic makeup within the respective
species, and point to the importance of genetic
backgroundo f brood fish in successfupl roduction
of desirable hybrids.
The preponderance of males in the F• generation
results in a favorable influence upon fish
growth and average size. The reduced population
fecundity resulting from the low percentage of females
results in low recruitment of F2 hybrids and
consequent avoidance of overcrowded conditions.
Reduced population fecundity combined with
predation by largemouth bass results in essentially
no recruitment of F2 fish. Brunson and Robinette
(1986) found that largemouth bass can effectively
control F• production in ponds, limiting F• densities
to 35 fish/hectare. In ponds without largemouth
bass, the average F2 density after 2 years
was 2,142 fish/hectare.
Producers of BG x GS hybrid sunfish should
be aware of potentially variable sex ratios and must
be careful to use brood stocks with the genetic
capacityt o yield high percentageso f males in the
F• generation. Highly skewed sex ratios are perhaps
the greatest contributing factor to the desirable
characteristics of this hybrid. Pond managers
should also be aware of the potential for backcrossingo
f hybrid fish with parent speciesin their
production ponds. This potential, as well as sex
ratios,w ill likely be a function of geographico rigin
and genetic history of the brood stock.