Spawning Red fin bully's

[Mcculloch]

Any one had these guys spawn for them?

From my rudimentary understanding they spawn in fresh water then the fry get washed out to sea for a time then return upriver ??

[blueether]

That is how I understand it as well.

[Mcculloch]

So has anyone had them spawn for them in their tank and if so what happened?

[Stella]

Nope, I haven't had them spawn, though I had two pairs for several years.

I don't recall hearing of them spawning in aquaria, though I don't see why they wouldn't. I have had common bullies spawn repeatedly in aquaria, and they are also diadromous.

[Mcculloch]

Thanks Stella do you have any ideas why the red fins don't seem to spawn ?

Do you think it could be something to do with seasonal temperature fluctuations or lack there of in home aquaria?

Oh and isn't there some common bullie populations that stay land locked?

thanks 8)

[blueether]

There a lots of landlocked common bullies around. Some of mine have come from a landlocked population, and one fry might have survived as I have a small common that I can't remember capturing and placing in the tank.

Both the common and Cran's bullies are always spawning in my large aquarium. I don't have a redfin male for my (small) females although they have never looked gravid.

[Stella]

I had some bullies turn up once that must have come in as fry when I dumped some aquatic insects in a tank. I was astonished to find them later - there had NEVER been fish of any sort in that tank!

[F15hguy]

ok has anyone done any research on WHY the bullies need to go to sea?, it seems to me that id a diadromous species such as the common could become landlocked then the effect of the ocean trip must be minor enough for a landlocked population to have a sufficient survival rate to evolve.

which also brings me to the point, if someone was to get redfins to breed in an aquarium, what would stop them from creating an artificially landlocked population.

I currently have a nice male /female pair, and am planning on setting up a dedicated tank to test this theory in the near future. any links to research on redffin spawning would be handy

[M@.]

Im not sure about redfins specificaly, but was reading a study about this the other day.

Couldnt find it in my quick google re-searching, but think the jist of it was: zooplankton is a lot smaller in the sea than in fresh water. Therefore, diadromous species can lay more, smaller eggs. I think it said that landlocked poputlations of common bullies had larger eggs than their counterparts, and tent to only exitst in lakes where the conditions are right for lots of zooplankton.

so potentialy if you could provide a small enough food source they might survive? although it wouldnt suprise me if there was some physiological factors that would affect the fry aswell (osmosis might be an issue without the salt?)

My redfins spawned on tuesday, so I will let you know how that goes! :happy2:

[F15hguy]

cool, any special tips for spawning them or just extra love?

according to the data I have seen the fry are approximately 3mm long so easily able to handle infusoria, good luck.

btw if you are sucessful I may be interested in a captive bred specimen.

[M@.]

didnt do anything out of the ordinary to get them to spawn, just had a nice cave for the male.

If i had to guess, i would say it could be because I caught them a couple of months ago, then change to slightly warmer tank water might have tricked them into thinking it was spring

I hadnt actually considered trying to raise the fry... thought at best they would provide a little snack for the other fish

hmm, might have to have a think about that one and give it a try at least

edit- photo of the eggs here: http://www.fnzas.org.nz/fishroom/viewtopic.php?f=41&t=62955&p=694454#p694454

[Stella]

M@t. is onto it. The likely reasons for diadromy include a combination of:

Food size and density at sea

Lack of adult parasites and diseases at sea

The trade off of being able to have smaller and therefore more eggs

The ability for the species to disperse farther and not have such a precarious existence in such a volatile country with glaciers, volcanos and tectonic action.

Generalist species can cope better with habitat differences and change

Conversely the reasons in favourite of losing diadromy include:

Lower risk to larvae by staying put (including not getting lost, or the physiological strain of biome change)

The trade off of being able to have larger eggs and therefore more developed and faster growing larvae.

The ability for a species to specialise and become finely evolved for a specific habitat type

Being able to utilise habitats that migratory species can't access (eg further inland, beyond barriers)

It is looking like, for most amphidromous species, there will be a tiny proportion of individuals that do not go to sea, despite having access to it. In some instances this may just be luck of geography or where the larva wound up, but others may not have such an 'urge' to go. If a landslide happens which then isolates some fish from the sea, it is the offspring of these few individuals that are more likely to start a new landlocked population.

HOWEVER conditions must be right for the larvae to be able to survive, and this is probably the main limiting factor.

Looking at the diadromous galaxiids, there are many populations of landlocked koaro and banded kokopu, a good number of landlocked giants, about five known of inanga and one known of shortjaws. So this indicates that the rearing requirement for the larva of each species are quite different, and occur more frequently for some species and not others.

Looking closer at each species there are geographic differences as well. Landlocked banded kokopu populations are far more common in the North Island than the South. Koaro are the opposite (landlocked koaro in the central North Island lakes were mostly translocated by early Maori). Landlocked Giant kokopu are mostly in the lower South Island, and landlocked inanga (including the dwarf inanga and dune lakes galaxias, which were originally landlocked inanga) are only found in Northland. This all indicates differences in larval rearing requirements, which may relate directly to temperature, productivity of the waters, zooplankton community and who knows what else.

Back to your redfins. They will spawn in captivity. The eggs will hatch. Without a labourious artificial transition to sea water and back, they will all die. The is a very very small chance that a few might survive. The offspring of those fish might have a slightly elevated chance of rearing in fresh water, they might not. There are no known landlocked populations of redfins, although a tiny proportion of fish in certain sampled populations have been shown to never enter sea water, thus the rearing conditions are very picky.

Sounds likely that the warmer water may have tricked their biological clocks. Probably also the day/night period changed, this is also a huge factor in seasonal fertility in animals (inc farm animals).