Triploids And Alberta

[DonAndersen]

Guys/Gals,

 

Here is some educational materials for your reading enjoyment.

 

A couple of things that are interesting:

 

1] The male trips used in Alberta may "jack" and exhibit spawning chatacteristics. Jim Wagner says that Alberta fish don't Jack.

2[ Brian Chan, venerable Fish Bio. previously from Kamloop area, suggests that "jacking" is most apparent in very productive waters.

3] About 1/2 of all males that "jack" die @ age 2

 

Copied below are some educational materials:

 

From the site below is copied:

http://www.gofishbc.com/specstrains.htm

Non-reproductive treatments

In addition to the development of different strains, the FFSBC has gone one step further

and developed special treatments for some of the strains to further enhance the angling

experience while protecting wild populations through preventing potential genetic

interactions. These treatments are triploidization and the creation of all-female stock.

Such treatments increase the cost on a per-fish basis but the benefits can be substantial.

Currently, the majority of lakes in BC are stocked with diploid (2N) rainbow trout.

However, some treatment has been applied for releases into almost 40% of lakes to

improve the fishery and minimize interactions with wild populations of fish (Table 1).

Triploidization (3N) – Currently, the FFSBC induces triploidy through the

application of hydrostatic pressure shocking or heated water to the eggs shortly after

fertilization. This technique results in the retention of the second polar body normally

extruded shortly after fertilization creating three sets of chromosomes instead of the usual

two sets. The result is sterility in both males and females. This triploidization method

can achieve 100% triploidy if the technique has been optimized for the species.

The benefits of sterility include increased size due to the fact that energy usually diverted

into reproductive development can go to somatic (body) growth, and the inability to

reproduce or mate with other hatchery or wild individuals. Sterility is different

depending on the sex of the fish. Female triploids are hormonally and functionally sterile

6

(i.e. no ovary development or behaviour changes). Male triploids are infertile but still

produce hormones that cause changes associated with maturation including deterioration

of flesh quality, early mortality and the development of testes and other secondary sex

characteristics. In addition, they demonstrate “false” spawning behaviour, including

migration and interactions with other fish on the spawning beds but an inability to

reproduce.

All-female (AF) – The creation of an all-female population of fish is labour-intensive.

The FFSBC produces all-female populations of fish by crossing sex-reversed females

with normal females. To create sex reversed females, normal fry are exposed to

testosterone derivatives to halt ovary development and produce normal testes. These

“masculinized” females remain genetically female (XX) but functionally male although

the sperm must be expressed by hand as these fish do not develop a sperm duct. Once

mature they are crossed with normal XX females to create all-female progeny for release.

The benefits of all-female stock include slower maturation in females compared to males,

and therefore more time available to the fishery, larger fish, and no male drop-out from

the fishery associated with precocious maturation (or “jacking”) and high post-maturation

mortality. In addition, the stocking of all-female progeny in the absence of males

effectively creates a functionally non-reproductive population.

All-female triploids (AF3N) – The production of AF3N fish for stocking derives the

benefits of both processes. In addition, the double treatment ensures that the small

percent of individuals that may be missed during the triploidization process are still

unable to reproduce because all progeny are all females.

 

In an email from Jim Wagner we get:

 

Don:

 

Currently Alberta is only using the Triploidization (3N) process. The

fish culture program has examined the All-Female process and the

managers are concerned about the amount of labour and space that this

program would require. We intend to review it further once we have

perfected the 3N process for all of Alberta's trout species and strains.

 

Please contact me if you would like to discuss this further.

 

 

Jim Wagner

Provincial Fish Hatchery Specialist

Edmonton, Alberta

(780) 427-7959

 

Don:

 

There is nothing in the information I have given you that is proprietary

so you can use it.

 

One point of clarification is that we are working on perfecting the 3N

process for all of Alberta's DOMESTIC trout species and strains. We are

not currently trying to triploid any native species (i.e. CTTR, BLTR or

Athabasca RNTR).

 

I would also caution you on referring to "jacking" rates in 3N males. BC

uses natural trout populations and we do not know if the 3N process is

increasing the rate of "jacking" over what occurs naturally. Alberta

observes a very low incidence of "jacking" in its domestic brood stocks.

 

Jim Wagner

 

 

 

For further discussion on the why and wherefor's of trips on the site below we find:

http://www.flybc.ca/forum/index.php?showtopic=8443

 

Hi Don,

 

The issue of precocious male drop-out has been well studied. So to set the stage, precocious males are defined as males who sexually mature as they approach 2 years of age. In any population of salmonids there will be a percentage of males that are precocious, it is natures way of ensuring there will be some males to spawn with the females if the older, bigger males do not make it to the spawning grounds.

 

What we have found in BC is that the rate of precociousness has a strong correlation with the productivity of the lake. In nutrient rich lakes such as Roche, Jacko, Tunkwa, Leighton, Dragon the incidence of precociousness can be as high as 75% or more. For example, if 10,000 yearling Pennask rainbows were stocked into a high TDS lake in the southern interior of BC, theoretically there would be 5,000 males and 5,000 females. Of the 5,000 males, 70% could become precocious, that means 3,500 of the 5,000 males could sexually mature at 2 and a very high percentage of those mature males will die from the maturation process. So, the number of fish making it past age 2 and entering the fishery as 2+, 3, 4 and 5 years is reduced. The elimination of precocious males or males in general does make it easier to control the overall population of trout in the lake. Remember we are talking about lakes where natural reproduction is not available because of being landlocked or having only seasonally flowing inlets or outlets.

 

the research on precocious males led to the development of all females and then triploiding and triploid all females.

 

Hope this helps you out,

 

cheers,

 

Brian

 

 

^{And so ends your education. All trips are not equal.}

 

 

regards,

 

 

Don