Originally Posted by ray2828
Captive breeding of P. Motoro – A personal experience
The purpose of this article is to narrate my personal experience in the captive breeding of P. Motoro. I hope that my experience would be useful in helping fellow hobbyist who may be keen in breeding motoro.
For the ease of reading and perhaps to make this article more structured, I will cover the following topics:
(1) Water in breeding tank
(2) Selection of brood stock
(3) Conditioning of brood stock
(4) Mating and pregnancy
(5) Care for the pups
(1) Water in breeding tank
It’s no secret that water conditions play an important consideration in breeding all tropical fish. While the conventional wisdom is to perform partial water changes weekly, when it comes to breeding even weekly water changes could cause too much disturbance and stress to the motoro.
I achieve good water quality by putting in place a good filtration system. For example, my breeding tank, a FGT, of 10X6X3 is filtered using a 5 chamber 16 ft long and 4 ft high filter. Water is crystal clear even though the tank is placed outdoor in direct sunlight. No water changes are made, although every week I will top up the water in the tank loss due to evaporation. When in rains, I don’t bother. Filter chambers are washed every 2 months.
Updates:
i) Changing water regularly is still important to get rid of a build up of nitrates. Having an efficient bio-filiter means that its a nitrate producing machine. Mature rays can tolerate higher levels of nitrate well. However, excessive nitrates eg >50ppm tend to reduce the appetite of pups. This might be detrimental to their growth and in some cases lead to pups not feeding and slowly dying off.
ii) There must be a good balance between water changes and maintain stable water parameters. This is best achieved using the drip system.
iii) Raining is a big problem as experience in March 2008 is an indication. Caused havoc in water para and some rays stop feeding. Still seeking a solution even thought parameters have stablised for now. Keep your rays indoors if you have a choice.
I believe that maintaining a stable environment is more important than striving to achieve a particular PH or KH when it comes to breeding motoros. Coral chips are also used in the filter chambers with the intention of stabilizing PH and KH. I do know the exact water parameters as I do not monitor them.
Update:
i) Monitoring water chemistry is important when dealing with more sensitive rays esp young sp. Key items to monitor include ph, ammonia, nitrites and nitrates.
It’s also important to install a skimmer. The skimmer will remove the layer of liquid waste (ammonia) that floats on top. Motoro are heavy feeders and this layer of waste can build up very fast.
(2) Selection of brood stock
The one of the important factor in breeding motoro is selection of mature specimens for breeding.
Typically, sexing male motoros are easy. Once the claspers are developed and open, the ray is ready. Males are typically developed their claspers at around 10 inch disk size. The development of claspers is stimulated by the presence of mature females. An immature male can developed full and open claspers within 2-3 months of exposure to mature females. This usually means that within 2-3 months, males with 3 cm claspers can develop 3 inch open claspers.
The selection of females is usually trickier. Females mature at a larger disk size. Typically females are ready at 12 to 13 inch disk size. Most hobbyists over estimate the size of their rays. Strictly speaking, ray with a 12 inch disk (actual measurement) will usually be classified as a 15 inch specimen. When selecting breeders, use healthy specimens that are at least 3 inch thick at the belly area.
(3) Conditioning of brood stock
Once your brood stock have been selected, its time to condition them for breeding. This is when heavy feeding should start. It is usually not sufficient to feed them just market prawns to bring them into breeding condition.
A variety of foods should be fed to ensure they have sufficient nutrition. The below are foods that I found to be useful to condition the breeders:
Oyster/clams
Humans consider the consumption of oysters as an aphrodisiac. The use of oysters can bring out the desire to mate among the rays. Do not feed raw oysters. They contain too many bacteria and foul the water easily. Boil the oysters in hot water before you feed the oysters to your rays. However, do not overcook your oysters as this would destroy the nutrients within.
Snails
Rays love snails. The freshwater apple snails are most ideal. Simply crush the snails and feed them to the rays. They will know how to split out the crushed bits. These snails can be bought from LFS or you can take a walk along many of Singapore’s reservoirs and simply pick them out of the water.
Earth worms
Red earth worms (not tubifex worms) are another of the ray’s favorite food. They grow very fat on this diet and go into breeding condition very fast. The problem with feeding earthworms is that the worms are hard to come by in Singapore as LFS or bait shops seldom carry them.
Update:
i) Can also feed small fish like kunning, tampan and squids. Remember its always better to feed a variety of foods. Balance diet.
(4) Mating and pregnancy
After (1) to (3), mating usually occurs without much need for intervention by the hobbyist. Motoro mating usually occurs at night. I noticed that my rays are especially active after mid-night. Courtship usually begins with the male approaching the female and lingering around the tail area. The male seems to “sniff” around to determine whether the female is ready. At this stage the female usually rejects the male by pushing him away with her tail.
Upon rejection, the biting starts. The male will place himself over the female’s disk and bite her. The pair will then swim in cycles. That is why a wide tank is necessary for breeding. Actual copulation occurs very quickly, the female flips over and the male will insert his one of his claspers into her virgina. Thrusting actions are made and sometimes thick semen can be seen ousting out from the female’s virgina. The whole process takes 30 seconds to a minute. Then mating is over. Motoros are polygamous. The females will mate with several males when she ovulates.
The female can sustain serious injuries when mating. Its quite common for females to end up with torn disks (one of my females lost 1 inch of her lower disks on each side), punctured disks (especially if she was being rammed against water inlet pipes) and scratches. There is nothing to worry about unless she gets so stress that she stops feeding. Should that happen, you should remove her from the tank into a quarantine tank until she begins normal feeding. It is important to remove a badly damaged female that stop feeding from the breeding tank lest she starves and fade away.
Some females are not ready when the male is introduced. The male will literally rape her. That is when she will be so stressed by the male’s presence that she stops feeding. Removing her from the tank usually solves the problem.
Usually a female’s appetite will double after mating. So the first sign of pregnancy is torn disks (indicates copulation) and increase in appetite. A typical 15 inch female consumes about 15 pieces of big market prawns per feeding, three times a day. That is easily 1.5 kg of MP per day (before shelling). As her pregnancy starts to develop, the hump on the back becomes more noticeable.
The gestation period for motoros under heavy feeding conditions is approximately 3 months. I split them into three trimesters as follows:
(a) First trimester
This is the period immediately after copulation. Her appetite increased tremendously. A usually shy female will start to rush for food during feeding time. In addition, she seems to be ignored by the males. It is important that pregnant females get enough food. Insufficient food will lead to an overly long gestation period and result in stunted or still-born pups. The growth rates of such pups will also be affected.
(b) 2nd trimester
The hump on her back becomes more noticeable. This hump is unlike the hump when rays are full. Its will began developing as 2 separate humps on both sides of the tail where the ovaries are. I am not sure but I suspect that a female motoro can ovulate when she is in the second trimester as males will start to take interest in her again and mate with her again. I have also notice my females getting pregnant almost immediately after the birth of her first litter. I usually quarantine my females after birth and her ability to get pregnant again without any further copulation seems to support my above observation.
(c) 3rd trimester
The humps on both sides of the tail will merged into one big hump. Movements can also be seen inside the hump. The hump can be a big as 7 inches thick immediately before delivery. When your ray is about to deliver, you will notice that the hump will developed into a kind of box, with right angles near the tail. Immediately preceding birth, feeding stops. She appears restless and starts climbing the walls of the tank like a young ray. Delivery is usually at night as well although I also have come across births in the afternoon.
Remember to do a 50% water change after delivery as a lot of biological waste and fluids are produced. Failure to change water may lead to a rapid deterioration of water parameters which may be fatal.
(4) Care of pups
Unlike cichlids, rays do not exhibit parental care behaviors for the pups. Most of the time they will ignore the pups. It is advisable to remove the pups from the breeding tank as they are very fragile and cannot withstand too many knocks from adult rays swimming around. In addition, feeding the pups together with the parents may pose some difficulties.
For higher survival rates, I house each batch of pups in a different tank. Older pups have been observed to bite the younger ones. This can result in a broken tail or even death if the injuries are too severe. Young pups are fragile, it is best to keep them indoors with constant temperature and water parameters.
Feeding of pups
The pups usually have not fully absorbed their egg sacs during the first 2 days after birth. Feeding is not necessary at this stage. The first food for pups is usually live tubifex worms. The pups will pounce upon it instinctively. Within the week, they can be graduated to frozen blood worms. The reserves in the pups are low and they cannot go without food for more than 6 hours. I usually feed my pups 4 times a day in the first 2 weeks after birth. Each pup will consume approximately 1 cube of blood worm per feeding. Due to the heavy feeding partial water changes, 10 per cent every day is necessary. Insufficient feeding is usually the cause of most pup fatalities.
After the first month, the pups can be taught to eat MP bits. In addition, torsats and ghost shrimps can also be feed to supplement their diet. To boast immunity of the pups, I also gut load the feeders with vitamin B complex and vitamin C.
The water soluble forms of these vitamins can be easily bought from pharmacies and feed to greedy feeders like torsats.
Never purchase a motoro before they reach a month old as they are usually too fragile to withstand shipping and a change in environment.
Conclusion
Breeding P Motoros take a lot of time and effort. It’s usually not commercially viable given that a typical 15 inch ray will produce only about 6 to 10 pups each litter twice a year. It is however, my hope that fellow hobbyist will be willing to devote the time and resources to breed motoros and other freshwater sting rays so that the pressure on the wild population will be reduced. What is not commercially viable for farms and commercial organizations can be made viable if we, the hobbyist can remove the profit element and put in the passion that is required. After all, this is what a hobby is about.
For buyers, please support captive breed rays. They may be slightly more expensive but well worth the price as you can a healthy ray without side effects.
Happy breeding.
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31-03-2008, 06:38 PM
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