Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Fourth Gen Hybrid Bluegill

This should be our 4th Generation of HBG out of a small grow out pond. How are the genetics looking? Are the GSF traits starting to show? Water temp was 52

This fish still looks close to a regular F1. Decent size any idea how old it is?

Bill it will be 9 months in just over a week. Semi-fed every other day.

How are you determining that fish is an F4?

The pond is a grow out bait pond for catfishing, we've drawn it down twice a year and seine it out for 3+" GSH and any GSF 3+".

So you're not systematically producing your own HBG, but letting things run their own course?

If so, I'm not sure how it's possible to know with any certainty what generation or age that fish is?

100% correct sprkplug, once we run the nets if they aren't keepers they go back in the pot. Normally 3 size classes non keepers, 3-5" and 7-10".

It is possible that is a F4 HBG or maybe a F3. Meadowlark also saw good growth for HBG in later generations. More work and practical research needs to be done on this topic.

Any fish (lepimos/sunfish)other than HBG in there ?

While possible the odds of F-4s from one stocking are small.

Ewest the pond use to be a cattle watering hole 1/16th acre max 5ft depth the pond at that time was full of odd ball fish BH,BG,GSF,GSH. The pond was cut off from the cows and was pumped dry during a summer. My uncle sealed the bottom and refilled during winter. Stock first spring with GSH, and stocked with HBG in the same fall. The stocking of HBG was not checked for other sunfish or other trash fish, but being our 6th draw down to seine we should have capture a lone BG or RESF surely?

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.

It seems one benefit of such a study, if it is found the later F generations are not a problem, mixing BG and HBG during initial stocking might not be such a bad management option.

From what I have read on this forum, for the most part mixing BG and HBG during initial stocking is generally frowned on. But it might actually be a management option if a person was more certain of the outcome of any crosses.

I agree. Even after all this time and all of the studies, there are still unanswered questions regarding these fish.

If I understand Brunson's study conclusion correctly "Attempts to backcross male bluegill x green sunfish hybrids with females of each parental species were unsuccessful both in ponds and in the laboratory", the male 'standard' HBG will not cross with female BG nor GSF. However we do know that the male & female HBG will successfully produce offspring, thus the need for predator control in a HBG pond. Brunson's conclusion of "The reduced population fecundity resulting from the low percentage of females results in low recruitment of F2 hybrids and consequent avoidance of overcrowded conditions." is not absolutely correct. I think the use of "consequent avoidance of overcrowded conditions" was a biased statement and somewhat exaggerated by the author; reduced chances of overcrowded yes, avoidance no.

So with the HBG being able to reproduce among themselves it is very possible to have a year class of mongrel HBG (F generation) each year, thus production of a F4, F5, F6, etc individuals. I am not aware of any detailed genetic studies of the offspring FX generations from HBG. FX meaning subsequent backcrossing of the hybrids.

To read about Meadowlark's experiences with FX generation HBG see information in this link:
http://www.meadowlarkponds.com/TGG.htm

The study posted by ewest is confusing. One moment it claims no successful backcrossing in either ponds or laboratory settings, then it cautions pond managers to be aware of the potential for backcrossing.

This apparent discrepancy is explained by the author/s as being due to genetic history of the broodstock used, as well as their geographic origins....I would welcome a little clarification and further detail regarding this statement.

Has there been further study in this area?

It might just be a CYA statement? It's really hard to say something can "never" happen.

Edit Bill D.

With statistical analysis of any data set, a probability curve can be created. You will never end up with 100%. There is always that outside chance.....

See the link as well for another study by Brunson et al about HBG offspring in LMB ponds in a 4 way study. That should help.

Cody note: I think this is the link that ewest refers to: see ewest's post on 23/07/08 at 9:49pm.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=126303&page=1

IMO what now needs to be studied is the long term effects of backcrossing and interbreeding of the hybrids.

For the next draw down period late spring, if I was to take photos of the harvested fish would we be able to tell visually what mixes of sunfish are present in my HBG population?