Research Paper to Read: (2011) Masculinization of the ornamental Siamese fighting fish with oral hormonal administration

Source: ResearchGate.

(1) Oral administration of 17a-methyltestosterone (MT) hormone of 3 and 4 mg/kg doses resulted in 100% masculinization or all males within a spawn.

Why this paper?
Discussion with different breeders shared their experiences buying Betta sp. broodstock from neighbouring country (hint: north) that cannot or won't breed. They have long suspected that the broodstock was somehow treated with certain chemicals that make it harder for the pair to mate and spawn. We've read some papers that probably can explain the root cause of the broodstock that can't breed, masculinization. From early stage of larvae, Through exposure to MT hormone that reverse sex in Betta sp. from early stage of larvae, a breeder can control the sex of the fry by turning the spawn into almost all males Betta sp. This allows the breeder to gain more profits as the male Betta sp. fetches way higher prices compare to female Betta sp. in the ornamental fish market.

Material and methods
The research starts with fry production using 4 pairs of Betta sp. of crowntails, veiltails, and spaidtails strain in four separate 15 litres plastic tank. Once eggs have been fertilized it's extracted and removed to a separate bowls. The spawning was done into two sessions, once in January and another one in May where each experiment group produced around 400 fries. For each experiment group, equal number of 80 fries were placed into 5 separate 2 litres cages within a large 160 litres aquarium tank. The experiment designs in shown in the table below.

Feeding were done 6 times per day (assuming it's 4 hours interval) with different feeding post hatching schedule and diet. DPH is referring to days after post hatching.

(1) Experiment A
- 4 DPH till 7 DPH with artemia nauplii.
- Feeds with MT (Classic AAF-F) until 30 DPH
- Feeds with MY (Lucky Star 2) until 56 DPH.

(2) Experiment B
- 4 DPH till 11 DPH with artemia nauplii enriched with red pepper.
- Feeds with MT (Classic AAF-F) until 30 DPH
- Feeds with MY (Lucky Star 2) until 56 DPH.

The experimental group of A0 and B0 is the control group where no treatment was added. Experiment groups of A2, A3, A4, B3, and B4 shows 100% sex reversal. Mortality rates does not have significant statistical difference.

There are quite a number of confusion in this paper that raise many unanswered questions. Bar chart is not a suitable presentation to summarize the result of the experiment compare to a table with figure. It's very hard to visually identify which experimental group have yield 100% sex change to monosex population.

These treatment were used on ornamental fishes instead of farm fish for food consumption. Hence, it is recommended to use cheaper MT hormones to reduce cost and increase profit.

Further Questions
(1) Why the needs of two separate experiment groups done in two separate period (6 months interval)?
(2) Why both experiment groups have different diet and schedule feeding DPH?
(3) Is MT hormone really have 100% sex reversal impacts on Betta sp.? Can we consider that these fishes is 100% male or in between?
(4) What are the ecological side effects if these fishes were released in the wild?
(5) What are the possible legislative issues on using MT hormone?
(6) Does long exposure to MT hormone affects the mortality rates?

UMT MOOC: Ornamental Fish Culture - Topic 7: Seed Production - Factors to be Considered for Feeding - Species & Water Medium

Continue from previous post.

Besides the consideration of tank or pool size when rearing larvae, fry, or hatchling, the next item we should look into is feeding in the grow-up tank or pool. We will go through all these factors that will influence the feeding as listed below:

(1) Species
Before a fish egg becomes a fry, it have to go through different development stages of the body parts which consists of: (1) incubation period, (2) eye pigment, (3) mouth formation, (4) fins development, (5) digestion system. Different species have different body and egg sizes. Hence, feeding volume should take this into the consideration. For example, feeding an Arowana fry is totally different from Betta sp. fry as both species have different rate of growth development. An Arowana fry have bigger yolk-sac volume than a Betta sp. fry. Furthermore, ornamental fish values is based on its colours and patterns. Hence, diet that promotes good pigmentation in term of certain colours and patterns should be factored in as well.

(2) Water medium
This is something that we never thought off. Using "Green water" when feeding the fry after the yolk-sac have been used up. Basically "Green water" is just plain fresh with Chlorella sp. (micro-algae which have green pigment due to Chlorophyll) which can serve as initial and additional live food for fry and juvenile fish. This means Chlorella sp. cannot be used as the only feed and must combined with other live food sources like Rotifier sp., Artemia (Miona nauplii) for optimal growth (one of the research paper I've reviewed indicates this as well).  For normal rate of larval rearing, the density level should be 10×3-5 cells with water changes every 7 till 10 days (it was in the slides, not sure why so).

There are two ways to produce Chlorella sp., either naturally or in the lab. For the former method, just take and a bucket of water and put it under the natural sunlight or artificial fluorescent light (similar to green algae found in your aquarium tank). The aged water will slowly turn greenish and you will have your Chlorella sp. If you need pure Chlorella sp. without any contamination, you can culture it within a lab or facility as shown in the video below.