Stella Posted October 25, 2009 Report Share Posted October 25, 2009 Over the past 36 hours my giant kokopu has been laying eggs in my aquarium! She had been off her food for a few weeks and I was getting a bit worried. Strangely she still looked rather full (though kokopu are big, fat fish anyway) and I was worried maybe the mealworms I had been feeding her were not agreeing with her. Then yesterday morning I noticed she was sitting on the ground outside her usual daytime hiding hole, making me more worried something was really wrong. Then in the evening I realised there were eggs in the tank where she had been sitting! I had absolutely no idea she was female (they are sexually monomorphic) and equally no idea she was gravid (I thought the egg mass would be lower down their body). So she has slowly been laying for 36 hours. Just sitting on the substrate, very slowly releasing eggs. They are slightly demersal and sticky, so they form small masses stuck to the stones. I assume things would happen a bit faster if there was a male with her. note white mass below her vent Normally kokopu breed in autumn during floods. They wriggle into the vegetated stream edges newly inundated with water and spawn there. As the floodwaters retreat the eggs are stranded. They rely on the flood returning in a few weeks and submerging the eggs which stimulates them to hatch. The fry are then (usually) washed downstream to the sea where they grow and return a few months as whitebait in spring. Note: spawning happens in autumn....! I have done a bit in my uni papers this semester on seasonality and how day length regulates fertility and reproductive cycles. As the days lengthen or shorten (according to species etc) the reproductive system switches on and starts doing its thing. This fish is in fairly constant day-length because of the aquarium lights. However a good few weeks ago the timer died, so the 'days' have been shortening (ie I forget to turn it on until much later if at all). Not sure how long it takes for a fish to become ripe, and not sure how long ago the timer died, so this may or may not have had an effect. So I figure either: She is 'free running' due to artificial lighting and her reproductive system switched on naturally, without being tied to seasonal changes. OR The death of the electric timer and shortening 'days' switched on her reproductive system, as would happen naturally with the shortening days in autumn. Either way I am most intrigued as I always assumed seasonal spawning in fish was a temperature thing. If it is indeed regulated by day length, it is an interesting to note that this fish is mostly nocturnal and spends its days lurking under logs or rocks in dark swampy streams. There must be enough light reaching the fish to be able to be used for cycle regulation. (here endeth the thinking-out-loud biology lesson!) Quote Link to comment Share on other sites More sharing options...
SamH Posted October 25, 2009 Report Share Posted October 25, 2009 Congratulations Stella! If anyone could do it, it'd be you! Quote Link to comment Share on other sites More sharing options...
smidey Posted October 25, 2009 Report Share Posted October 25, 2009 that is very interesting regarding the seasonal senses & breeding. i have had a lean winter when it comes to fry but as of the last 3 weeks i have females of every species i own holding. Quote Link to comment Share on other sites More sharing options...
phoenix44 Posted October 25, 2009 Report Share Posted October 25, 2009 I support the circadian rhythm theory. Those have got to be the neatest, weirdest looking eggs ever! Quote Link to comment Share on other sites More sharing options...
Nymox Posted October 25, 2009 Report Share Posted October 25, 2009 I think so too, Seems everything I have is spawning at the moment! Well done Stella! Must means shes a happy fishy! Quote Link to comment Share on other sites More sharing options...
Stella Posted October 25, 2009 Author Report Share Posted October 25, 2009 actually, everyone else's fish breeding at the moment does not necessarily support the idea that light is the fertility 'switch'. Your fish are presumably also under constant day length (especially if you have an electric timer on your lights) AND constant temperature (if you heater is decent). So why aquarium fish should have a spring spawning season is a little weird. What cues *are* they using? My kokopu had shorter days because of the broken timer, but she was also feeling increasing temperature with spring (bearing in mind that my fish are coldwater fish so there is no constant temp from artificial heating). If temperature was the cue, it would certainly not be now that she should be reproductively active, rather it would be timed with the decreasing temperature of autumn. Quote Link to comment Share on other sites More sharing options...
smidey Posted October 25, 2009 Report Share Posted October 25, 2009 i tend to think its more gravity or something that sets them off, my friends are always sucessful at fishing in the harbour when my fish are more active in my tank. Quote Link to comment Share on other sites More sharing options...
Stella Posted November 1, 2009 Author Report Share Posted November 1, 2009 ok, she is STILL laying eggs.... that is over a week! She is a lot more svelte, looking like she hasn't eaten in a few days (when in reality she hasn't eaten in a few weeks!) She had bit of an infection around head,looked like columnaris but was very small and slow growing. She was breathing faster and generally lying around doing nothing. I was worried that she might have an infection in her gills. I salted the hell out of the tank and tonight she is showing signs of behaving like a normal fish again. HUGE RELIEF! It does seem excessive, spawning for eight days... Quote Link to comment Share on other sites More sharing options...
preacher Posted November 1, 2009 Report Share Posted November 1, 2009 Oh boy, that must be a huge relief. I remember seeing her when I came up your way last year, what a beautiful fish. Pity you don't have a boy too Do you know of any aquariums that have a male? Is artificial fertilisation a possibility? What an awesome opportunity that would be to see a hatching in the tank. I guess I will have to be patient with my little bullies and hope Peter Quote Link to comment Share on other sites More sharing options...
Caryl Posted November 1, 2009 Report Share Posted November 1, 2009 A week! She has my sympathies :-? Quote Link to comment Share on other sites More sharing options...
Stella Posted November 1, 2009 Author Report Share Posted November 1, 2009 Even if I did have a boy, I have no idea what would happen, as they are supposed to spawn at the water's edge during floods. Maybe the eggs need to be out of the water to develop higher oxygen? And any fry would most likely die as they couldn't go to sea... NOT THAT THAT WOULD STOP ME TRYING! Sadly I really don't have the room for another giant. And not going to borrow one due to disease fears (I am so attached o this fish). Now I know about this daylength cue, I am tempted to try it on my mudfish. I only have three and they are also sexually monomorphic, so who knows what I have, but it would be great if they did breed. Will also try it on my shortjaw kokopu next autumn when they should be reproductively mature. Peter, looking at the awesome condition and growth of your bullies, I would be astonished if you DIDN'T have babies! Quote Link to comment Share on other sites More sharing options...
preacher Posted November 2, 2009 Report Share Posted November 2, 2009 I hope they do Stella, that would really make my day. Have you made any plans to get a black flounder yet? P. Quote Link to comment Share on other sites More sharing options...
Stella Posted November 2, 2009 Author Report Share Posted November 2, 2009 Still want a flounder, not sure where I would put one though. I could cope with a tiny one... For the Turangi aquarium I will be needing some, so at least I will get to find and enjoy them even if they are not in my own living room! (why do you ask? have you seen some?) Quote Link to comment Share on other sites More sharing options...
djsurfs Posted November 2, 2009 Report Share Posted November 2, 2009 :bounce: Wow! neat... thanks for sharing the news & pics Quote Link to comment Share on other sites More sharing options...
Guest Posted November 2, 2009 Report Share Posted November 2, 2009 Wow, thats awesome. So theres no male in the tank? Quote Link to comment Share on other sites More sharing options...
Stella Posted November 2, 2009 Author Report Share Posted November 2, 2009 hi Cam, Nope, no male. I think he would have had a thing or to to say about her spawning without him if there was one! Tis good that they can release eggs like this. One of the other galaxiids, the inanga, can't and usually dies (before or after they pop!). Quote Link to comment Share on other sites More sharing options...
preacher Posted November 2, 2009 Report Share Posted November 2, 2009 Lol Stella, no I haven't seen one (I wonder if they are in the Hutt River...?). Bullies, Shrimp and Eels galore but that's about it usually. Mind you it's just too wet and rough to see much at the moment. How big do black flounder get? I suspect my wee ponds are a touch small... P. Quote Link to comment Share on other sites More sharing options...
Cricketman Posted November 2, 2009 Report Share Posted November 2, 2009 My fish have also started laying eggsand breeding. they are under constant light/dark cycles and constant temperature. My theory is that the cycle of barometric pressure changes with the seasons, and being the only thing that is not a constant in the tank, it must be air pressure that causes them to recognise a season and spawn. Could do an interesting experiment in a barometric chamber. Quote Link to comment Share on other sites More sharing options...
alanmin4304 Posted November 3, 2009 Report Share Posted November 3, 2009 I have noticed that submersed aquatic plants that fold their leaves at night do so regardless of the cycle the lights are on and wether the blinds are open or not so you would have to assume that fish have even more savvy than them. Quote Link to comment Share on other sites More sharing options...
turtlemantaken Posted November 13, 2009 Report Share Posted November 13, 2009 From my observations, particularly with reptiles,I agree with cricketman, I think its barometric influence. Stella, how long and how old is your giant? I spent many hours saving whitebait this season from people who were just going to eat them! so I could get some giants, have 300 or so ex-whitebait living in a soup of Daphnia in hopes I have some kokopu but all look pretty much the same to me, there are a few that are smaller and darker in colour than rest of shoal but of course those are the ones I released to main pond so retrieval is a big ask. Quote Link to comment Share on other sites More sharing options...
repto Posted November 13, 2009 Report Share Posted November 13, 2009 have heard that the giants run towards the end of the season?Stella may be more in the know?there are still reasonable numbers in the wellington region if you know where to look. Quote Link to comment Share on other sites More sharing options...
turtlemantaken Posted November 13, 2009 Report Share Posted November 13, 2009 Case of right place, right time.......tried for last time this season 2 weeks ago.........................did actually see ONE !!! whitebait but other than that just read a book Quote Link to comment Share on other sites More sharing options...
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