Hormone injected offspring

[emartin]

A lot of companies hormone inject their Synodontis catfish to make offspring from wild parents.

Out of curiosity, what exactly are they injecting and does it affect the health of the offspring? Is it just a hormone that gets the males and females laying eggs and breeding, or is it artificial fertilization or what?

For example an importer near me has a Synodontis petricola wild colony but they said they hormone inject them to make the 1-2" petricolas they currently sell on their website.

~Ed

[Mike_Noren]

They presumably buy breeding kits; such are available from a couple of Czech firms, and come with hormone and a protocol.

To the best of my knowledge they use carp or salmon gonadotropin hormone. The procedure is to inject the fish with the hormone, thereby triggering maturation of sexual products without having to supply any environmental trigger (e.g. drops in conductivity and temperature, signalling the start of the rainy season, are common environmental triggers for catfish). When the sexual products have matured, the fish are stripped of their milt and eggs, the eggs fertilized in vitro, and artificially incubated until hatching.

The fact that one do not have to reproduce the natural environmental triggers makes artificial breeding comparatively easy and efficient, but there are are downsides to artificial breeding.

Firstly it is common for parent fish to die from the injection trauma or secondary infections, and the habit of re-using injection needles without sterilizing them spread a range of fish pathogens. I personally suspect, but can not prove, the reason so many czech-bred fish have fish tuberculosis is due to this.

Secondly many, perhaps most, of the captive-bred Synodontis sold in the hobby are hybrids. The in vitro fertilization of the eggs means that all behavioral barriers to interbreeding are gone, making it as easy to produce hybrids as to produce pure species, but no-one seems to know exactly why the breeders seem to prefer to produce hybrids. Some think it's due to parent fishes being in short supply, some believe it's due to the desire to created new breeds, and some, like me, suspect it's because hybrids usually are healthier, faster growing, and less likely to reproduce, than the pure species.

Thirdly, and this is a bit speculative, it is my personal impression that species which for many generations have been maintained through artificial breeding lose their natural breeding behavior. This is especially unfortunate for species which are rare or extinct in the wild, e.g. Bicolor Shark.

[MatsP]

Secondly many, perhaps most, of the captive-bred Synodontis sold in the hobby are hybrids. The in vitro fertilization of the eggs means that all behavioral barriers to interbreeding are gone, making it as easy to produce hybrids as to produce pure species, but no-one seems to know exactly why the breeders seem to prefer to produce hybrids. Some think it's due to parent fishes being in short supply, some believe it's due to the desire to created new breeds, and some, like me, suspect it's because hybrids usually are healthier, faster growing, and less likely to reproduce, than the pure species.

Another factor may be that some species are more prolific (mainly that the female produces bigger number of eggs), which makes it easy to produce a large number of pretty looking fish that sell for high amounts, using a male that is "pretty".

Since no synos are particularly easy to breed in captivity, I don't think they really care about the likelihood of reproduction. The number of offspring from a female would be much more important in the profit margin calculation.

--
Mats

[Richard B]

but no-one seems to know exactly why the breeders seem to prefer to produce hybrids. Some think it's due to parent fishes being in short supply, some believe it's due to the desire to created new breeds, .

I know the second reason to be true, albeit a particular breeder has tried to cross (for example decorus x multipunctatus) to see what the offspring look like (his quote was something like "imagine a foot long multi with the dorsal extension of a decorus!") by completely natural methods (no injection) in artificial environments.

The first point is certainly a contributory factor in some cases - look at granulosus - few genuine available & (historically) then loads of young appear which we've never seen before, which we all buy & they turn out to be petricola x nigrita hybrids! Now Granny's HAVE been bred we know that the young actually do look like minature adults, with white fin edges. This is all driven by MONEY!!!

Mats point is well made as, using granulosus as an example, they produce very few eggs at each spawn but if crossed with nigrita can produce hundreds of eggs. I am not sure on liklihood of reproduction as if you go on youtube you can find videos of genuine species spawning & hybrids spawning

Mike - you make some interesting & intuitive other points which deserve wider consideration.

[Chrysichthys]

suspect it's because hybrids usually are healthier, faster growing

This of course is known as 'hybrid vigour.' One more reason breeders might prefer hybrids is if they have trouble producing good quality purebred stock due to deformities, etc., caused by inbreeding.

[Haavard Stoere]

I think today's breeders would benefit from producing non hybrids. May bee even alongside hybrids labelled as what they really are.They could sell them for a much higher price if they could convince buyers that the fish are genuine. It may not have been like this in the past when all we had for comparison were a few books on fish in general. I would not have been aware of the hybrids before I got internet. The old literature I inherited from my father mentions very little on synodontis in general, and certainly nothing about hybrids.

[aquaholic]

I have used hormone induced spawning for several years since I think this is just another aspect of fish keeping and breeding. It is quite a challenging and difficult science/art just like other facets of fish keeping. Photo-period lengths, water temperatures, environmental conditions, different individuals of the same species etc will all affect results. In most cases you will still need to observe the more traditional aspects of fish breeding to get results.

There have been many different types of hormone trialled. The most common commercial product is a Gonadotrophin Releasing Hormone (GnRH) which may also be called Luteinising Hormone Releasing Hormone (LHRH). The more successful formulations will also include a dopamine inhibitor with a method to keep hormones inert for longer storage. Simply put, the GnRH encourages the release of natural gonadotrophins from the fish's own pituitary while the dopamine inhibitor reduces inhibition of the fishes own GnRH release. (The fishes own stored hormones are stimulated/released and used in breeding process). This does not affect natural viability or fecundity but makes possible the synchronised maturation and release of gametes which can drastically improve fertilisation rates and improve predictability and preparation. Fish can either be allowed to spawn naturally on their own or by hand stripping both gametes and artificially mixing and incubating.

Hormone induced breeding invariably leads to the topic of hybridization which is interesting. While it has definitely made hybridizing easier, I am confident intentional hybridizing would still occur by other means if hormone induced breeding was not available. The assumption that hormone induced breeding simply means creating hybrids is quite ludicrous. (As an aside, there ARE many reasons and situations when hybrids are desireable).

To address some of the issues already raised:

• Simple common sense and good husbandry practices will result in correct injection sizes and hygiene. Secondary trauma, death or infection is directly related to the amount of care a fish keeper uses just like all other fish keeping practices.
• Importantly, it has been my experience that hormone induced fish actually learn to spawn in artificial environments. Successive induced spawns are usually easier and in several of my own cases , hormones were not necessary eventually.
• Probably the most significant is that captive breed generations are DEFINITELY easier to spawn in captivity too. Some of fish species which aquarists are finally starting to spawn "naturally" in tanks (previously thought to be unbreedable) have probably (almost certainly) come from parents which have been induced on fish farms IMO.