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Growth of Nothos

Tyrone Genade wrote:

> 
> On 30 Aug 2001, at 11:27, Paul Jablinski wrote:
> Hi Paul
> 
> As well as testing my current mailing issue I thought I 
> would address this question:
> 
> >    Would anybody out there know how long Nothos should grow 
> > after one month of life after hatching?  I heard that they breed after
> > 5 weeks after hatching - is this true???
> >    Bro. Paul
> 
> N. foerchi can be ready for action in 6 weeks.
> N. orthonotus takes about 8 as does rachovii.
> Kafuensis can take 12 weeks before all the fish have 
> matured and sexed out.
> 
> A lot of the time depends on tanks size and feeding. 
> Feed well, grow them out in a big tank with frequent 
> water changes and they will rocket into growth.
> 
> Most can be ready for action in 8 weeks. A large 
> proportion can be ready at 6.  4/5 weeks is pushing it 
> but not impossible.
> 

I agree with what Tyrone has written about the growth rate of Nothos 
and would emphasize that growth rate in captivity will vary enormously 
depending on the conditions under which the fish are being raised. If 
the fish are fed heavily with a good varied diet, and given 
plenty of space and clean water, they will grow at a 
tremendous rate. Higher temperatures (within reason) will also promote 
more rapid growth.

To give some specific examples:

About 3 weeks ago I hatched out various batches of Nothos, including a 
small batch of about half a dozen N. flammicomantis Kisaki TAN 95-5. 
I gave them plenty of space and in just 3 weeks they have reached a 
size of just over an inch in length, are fully sexed out and the males 
are starting to drive the females. In contrast, I have a few other 
batches of various Nothos hatched out at the same time but comprising 
an estimated 200-300 fry each and these, in spite of being 
subject to the same feeding regimen, are quite a bit smaller with only
the largest (males) starting to sex out. Even though I have them in 
larger tanks, they are still vastly more crowded than the N. 
flammicomantis and their slower growth rate is the result.

A few years ago, I raised a very small batch of N. furzeri, the males 
of which were sexable within 12 days after hatching and were driving 
the females at 21 days.

N. ocellatus, which reaches a length of 7-8 inches when adult, will 
initially grow at the rate of about one inch per week if fed well and 
given adequate space.

There is very little documented information about the growth rate of 
Nothos in the wild but I do know for a fact that N. orthonotus can 
achieve a size in excess of 2 inches within 5 weeks from 
hatching so one can assume that they would have started to spawn 
when about 3 weeks old. I have also, on numerous occasions found 
juvenile Nothos at certain locations and then gone back to the same 
locations 2 weeks later and found near adult sized fish.

However, don't be too concerned if your Nothos in captivity do not grow
at the same rate as those in the wild. Nothos tend to keep growing 
until they die, albeit increasingly more slowly as they mature. So,
given that your aquarium specimens will generally live for much longer 
than those in the wild, they can still reach pretty impressive sizes in
captivity.
______________________________________________
Brian R. Watters
Professor and Head
Department of Geology
University of Regina
Regina, Sask. S4S 0A2, Canada
Tel: (306) 585-4663
Fax: (306) 585-5433
E-mail: Brian.Watters at uregina_ca

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