Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Culling HSB ???

I think I know what to do, but it's painful :

I stocked 100 HSB April 2005, they seem to be doing well...for the most part. The problem I have is that it appears that 15-20% are severely undersized. My largest HSB are fat and plump, they weigh more than double the smaller ones. Should I simply cut my losses and remove the smaller ones ? Or should I let them go waiting to see if they get a growth spurt ? I would hate to cull a 12" HSB, but do these fish have an upside or will they always remain runts ? I have carrying capacity and ample forage...these small fish are almost always caught in somewhat shallow water, while the big boys remain in open water. Any input would be appreciated.

Eastland,
I'll be watching to see what replies you might get. I have the same situation here and wondered if it was worthwile to cull the smaller fish.You observation on catching the smaller ones in the shallows is the same as here.
Are you feeding your fish?
Chip

Wow that is a hard one to answer without a full assessment of the pond. I assume they are not skinny but just small. With plenty of forage and no capacity constraints and plenty of good quality water I would wait until next summer to decide. At 2 years you could still have some good growth and it appears like there is no down side to waiting. They should be a good cool water predator and should help with forage control while getting some growth this winter when the other predators slow down. I will check a couple things and report back.

If I was considering the HSB as put-and-take, fun fishing plus food production, I'd harvest the bigger HSB as they were caught, leaving the smaller HSB to grow some more.

If I was after the biggest HSB I could grow, I think I'd try to remove the smaller ones to leave a little more forage for the fast growers.

Obviously, there aren't any genetic angles to figure in this case.

Interesting, it sounds as though the two different groups are occupying different enviromental niches in your pond, possibly utilizing different prey or prey sizes than the other group. That might not be a bad thing depending on your goals.

Thanks guys. Chip, I am running a feeder...There's more than enough to eat, it's purely the fish's fault he's not growing They have tilapia, golden shiners, and threadfins too.

I like Ewests advice, I'll give them a little while longer. I'll never get the survival rate of the initial 100, replacements will have a slim chance of surviving my advancing predator population.

All good points, I was leaning towards waiting until they'd been in for 2 years (next May) before doing much. We'll harvest some for a fish fry in a few weeks and those will be the first we've taken out.
Chip

OK, while pondering my "runts", I have a few general HSB questions.

1) Do HSB spawn and lay infertile eggs, or are the re-absorbed ? Is it possible my smaller HSB are spawned out females ?

2) Do the females generally weigh more than the males, like the ratios we see with LMB ?

As I'm for diversity in my pond regarding species, I'm also for having various sizes of the same species.

I think this provides for more enjoyment regarding the anticipation of what is on the end of your line.

I would leave them in.

Eastland, I believe that we have the same 2005 class of HSB from the same supplier.
They are running between 12 to 14 inches with occasional 15 inchers.

I love the 12 inch HSB as well as the 15’s from this class – they put up a longer, harder fight than a LMB twice it’s size – a blast on a 5wt fly rod…

Same experience with the smaller fish in shallower water around feeders, whereas larger HSB in open deeper water, most likely chasing bait.

I would definitely leave them be…

1. I believe that I recall Bruce commenting on HSB spawning rituals. Perhaps he will comment.

2. Based on extensive striped bass experience, females defintely become much larger than the males. I would expect their progeny to follow the same characteristics.

Eastland here is some info but you should read the SARC fact sheets on HSB.

http://srac.tamu.edu/index.cfm?catid=12

SRAC 300 Hybrid Striped Bass: Biology and Life History

Hybrids grow rapidly during their first two years of life. Growth to 275 to 375 mm in length and 225 to 350 grams in the first year and 450 to 550 mm in length and 1 to 1.5 kg in the second year is common. Growth rate declines rapidly with increasing age and is similar in males and females. Maximum reported weight for a hybrid striped bass is approximately 10 kg. The typical size of hybrids caught by fishermen generally ranges from 2 to 5 pounds, but fish in the 10 to 15 pound range are not uncommon. The usual life span of hybrid striped bass is 5 to 6 years-- more similar to white bass than to striped bass (30 to 40 years).


Spawning

Hybrid striped bass, unlike some
other hybrids, is fertile. It is
oviparous (egg-laying) like the
parental species and produces eggs
and sperm in the spring when
temperatures are 15 to 20° C. Some
males mature at the age of 1 year
(approximately 250 mm long and 500
grams), and all are mature at 2 years
of age. A few females are mature at
2 years of age, but all are mature at 3
years. Females produce an average
of 160,000 eggs per pound of body
weight and spawn once a year.
Males may spawn many times over
the spawning season.
Natural spawning of hybrids has
been verified in a few instances.
They may participate in spawning
runs with striped bass or possibly
white bass. There are also confirmed
cases of reproduction in reservoirs
that contain only hybrid striped bass.
Hybrid striped bass produce sperm
and eggs during the spring when
water temperature is between 55 to
70° F. Temperatures of 65° to 68° F
are ideal for spawning hybrids and
the parental species. Spawning occurs
from mid-March through May
depending on location. Spawning
season in any one location usually
lasts 4 to 5 weeks. Hybrids have been
observed participating in spawning
acts in areas that contain clear shallow
rocky shoals that are 1 to 3 feet
deep. Females come to the surface
during the spawning act and several
males accompany her. The males appear
to bump and butt the female
which may stimulate egg release.
Released eggs are immediately fertilized
by the males.
The eggs of striped bass x white bass
hybrids are intermediate in size to
those of the parental species. They
are semi-buoyant like striped bass
eggs, although they seem to be
heavier than striped bass eggs. Eggs
of this cross are generally not adhesive
like white bass eggs and must
be buoyed up by the turbulent water
flow till they hatch. Other hybrid
crosses such as striped bass x white
perch have adhesive eggs.
Eggs hatch in approximately 2 days
at water temperatures of 65 to
68° F. At colder temperatures eggs
may take over 72 hours to hatch.
Newly hatched fry do not have fully
developed mouth parts and do not
feed until they are approximately 5
days old. During this swim-up stage
the relatively large oil droplet is used
as a food source.

If I recall Dave Wills in another post explained that HSB unlike some other hybrids, is fertile but that hatching conditions wrt the eggs greatly decrease hatching success.

Great stuff, this is now peaking my curiousity ! I sure would like to know if they have anything in common.

Linkmaster (a.k.a. Ewest) Can you put me on a link that shows how identify the sex of HSB ?

I have a decent digital camera, I'm going to snap a few shots next weekend if I get another small one interferring with my tilapia harvest !

George, We did both get them from Todd...but I purchased 3-6" 4/16/05, and may have had some holdovers. I seem to recall you got yours a month later and possibly had YOY. Let me know when you bought yours...I'll e-mail Todd to see if he can assist with info here. A guy like Todd who's from A&M, and runs one of the finest hatcheries, will surely give us his 2 cents worth.

Ewest, I don't see anything there that would classify them as a hybrid.

Dave you lost me. Many species crosses (hybrids) in fish are not sterile. HSB and HBG and a bunch more lepomis crosses are all capable of reproduction. In the Centrachid Time Clock study almost all had some degree of cross viability except the Crappie with LMB IIRC.

"In biology, hybrid has two meanings.

The first meaning is the result of interbreeding between two animals or plants of different taxa. Hybrids between different species within the same genus are sometimes known as interspecific hybrids or crosses. Hybrids between different sub-species within a species are known as intra-specific hybrids. Hybrids between different genera are sometimes known as intergeneric hybrids. Extremely rare interfamilial hybrids have been known to occur (such as the guineafowl hybrids).

Interspecific hybrids are bred by mating two species, normally from within the same genus. The offspring display traits and characteristics of both parents. The offspring of an interspecific cross may be sterile. Sterility is often attributed to the different number of chromosomes the two species have, for example donkeys have 62 chromosomes, while horses have 64 chromosomes, and mules and hinnies have 63 chromosomes. Mules, hinnies, and other normally sterile interspecific hybrids normally cannot produce viable gametes because the extra chromosome cannot make a homologous pair at meiosis, meiosis is disrupted, and viable sperm and eggs are not formed. However, fertility in both female mules and hinnies has been reported with a donkey as the father.[2]

While it is possible to predict the genetic composition of a backcross on average, it is not possible to accurately predict the composition of a particular backcrossed individual, due to random segregation of chromosomes. In a species with two pairs of chromosomes, a twice backcrossed individual would be predicted to contain 12.5% of one species' genome (say, species A). However, it may, in fact, still be a 50% hybrid if the chromosomes from species A were lucky in two successive segregations, and meiotic crossovers happened near the telomeres. The chance of this is fairly high, 1/2^(2×2)=1/16 (where the "two times two" comes about from two rounds of meiosis with two chromosomes); however, this probability declines markedly with chromosome number and so the actual composition of a hybrid will be increasingly closer to the predicted composition."