[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Incubation Times Please
Dear Brian
Please if you have a list made of incubation times and temperatures be
kind enough to post it to me or the killie list. I would like to hang it
next to my storage area in the fish room. I find times listed for the old
types of fish but the new ones I cannot find listed.
Thanks.
BREED YOUR FISH
TODAY MAN'S OVER
POPULATION IS KILLING
THE WILD SUPPLY
1819967 ICQ NUMBER
-----Original Message-----
From: Brian R. Watters <bwatters at sk_sympatico.ca>
To: killietalk at aka_org <killietalk at aka_org>
Date: Tuesday, July 14, 1998 6:27 PM
Subject: Sex ratios
>"Sam" (yungfamily at sympatico_ca) wrote....
>
>>
>> Subject: Re: KillieTalk Digest V2 #269 (N. foerschi)
>>
>> At the beginning of the year, I did my grade 8 science project on the
>> affect of pH on the sex of N. foerschi. I hatched a batch of about 40
>> fry in normal tap water (approx. pH: 7.2, total hardness: 90 ppm).
>> After a week, I separated half the fishes into water w/ a pH of 6.4 nd
>> the other half into water w/ a pH of 8.4. (used sodium phosphate to
>> lower pH and baking soda to raise it). The water in the lower pH tank
>> had pH: 6.4, total hardness: 90 ppm. The water in the higher pH tank
>> had pH: 8.4, total hardness: 90 ppm. I tested the water in the tanks
>> every 4 days, and tried to keep the chemistry in the tanks from changing
>> throughout the experiment. I "controlled" as many variables as I could
>> think of, and everything I did to one tank of fishes was done to the
>> other. After about 8 weeks, I counted 1 male : 19 females in the tank
>> w/ the 8.4 pH. In the 6.4 pH tank, I counted 5 males : 14 females. If
>> you take the results at face value, it means that the 8.4 pH produced a
>> sex ratio of 1 male to 19 females, and the 6.4 pH produced a sex ratio
>> of 1 male to about 3 females. Incidently, the males raised in the 6.4
>> pH showed better colouring and more vigour. Just wanted to tell my
>> experiences w/ the whole sex ratio thing.
>
>
>An interesting experiment. An interesting follow-up would be to see what
the
>results would be if, for example, every specimen in both batches was raised
>in its own separate container (see my comments below).
>
>The water in my tanks is invariably alkaline - it comes out of the tap at
>about pH 8.1 and may drop to about 7.5 depending on how much peat I have in
>the tank, how many fish are in the tank, etc. Except for the first few days
>after hatching, I always raise my fry in bare tanks (little or no peat) so
>the water remains alkaline. I also invariably get more males than females
>(see further comments below).
>
>Lilia Stepanova wrote.....
>
>> Subject: Re: Sex ratios and water
>>
>> Hi,
>> Here is some info from book published in Russian (A.S.Polonskii
>> "Soderjanie i razvedenie aquariumnih rib", 1991).
>>
>> "Temperature and chemical composition of the water can affect sex ratio
>> in the fry of Cyprinodontidae. For example, at t=22-25 C most of the fry
>> will be females, if the temperature is not constant, most of the fry will
>> be males. At the same pH=6.0, E.dageti will have more female offspring
>> (>90%) in the soft water (dH about 5 degrees), in the hard water (dH 24)
>> about 90% of fry will be males. A.gabunense in the acidic water (pH 5.0)
>> will give more females, at higher pH=6.5 - more males."
>>
>
>I would also be interested to know about other factors involved in these
>experiments (e.g. population density, were the experiments repeated, etc.)
>and what the controls were. However, this information appears not to be
>available.
>
>I am sure it has not escaped the attention of many of you that the results
>of Polonskii's experiments, at least so far as pH are concerned, are
>opposite to those reported by "Sam", which underlines the point that this
>whole question of sex ratio in killies is far from that simple. There are a
>large number of factors that should be taken into account.
>
>I find some aspects of Polonskii's statement rather ambiguous in that he
>claims that "at t=22-25 C most fry will be females". Does he mean any
>constant temperature within that range or temperatures fluctuating within
>that range ? And, if he means the latter then that would appear to
>contradict the statement that temperatures that are not constant will favor
>the production of males. I would be interested to know what sort of a
>temperature range he regards as "not constant" - greater than a 22 to 25 C
>variation ? He also suggests that soft water will result in "more female
>offspring". More than what ?
>
>Assuming that the sex of the fry is determined at or shortly after hatching
>(which may not be the case), then this latter observation about soft water
>is contrary to what I have experienced in my fish-room. While I keep my
>adult Nothos in hard alkaline water, my fry are hatched and raised in
>moderately soft water (about 80-100 ppm TDS) until about the time they
start
>to color up. They certainly don't change sex after I switch them over to
>harder water and yet I still get a dominance of males in most cases (see
>below for exceptions).
>
>As I have said before, I don't think that the answer to skewed sex ratios
>lies in a single simple factor such as pH (or temperature). While I have
>certainly not conducted controlled experiments in this respect, one
>observation that I have been able to make consistently over the years is
>that if I raise a large batch of Nothos (or South American annuals for that
>matter) under fairly crowded conditions, I invariably get a large dominance
>of males. I also don't believe that in my situation this is a matter of the
>faster growing males killing off the slower growing, and therefore smaller,
>females. In contrast, smaller batches raised under less cramped conditions
>usually (but not always) produce more even sex ratios.
>
>As an extreme example of the latter situation, I always raise my N.
>ocellatus fry individually, each specimen to its own tank, from within a
few
>hours of hatching. I do this because of the extreme aggressiveness of this
>species (the fry are also ultra-cannibalistic). I always get fairly even
sex
>ratios with this species; it may vary to a small extent from batch to batch
>but overall the sex ratio is essentially 50:50 males to females.
>
>As I mentioned in an earlier communication, I am of the opinion, therefore,
>that environmental conditions in relation to population density may be a
>primary factor in determining sex ratio. Of course, one critical question,
>as George Slusarczuk has already pointed out, is at what point in the
>reproductive process is the sex of the embryo or the fish determined ? I
>have discussed this matter with biologists and it seems that, in fish at
any
>rate, this is simply not known. Apparently, it seems likely that it can
>happen at various times in the process, depending on environmental
>conditions. This unknown factor alone introduces a variable that makes it
>very difficult to conduct controlled experiments. Certainly, controlled
>experiments are possible but to be meaningful in any way they would have to
>be extremely comprehensive and as a consequence, quite complex.
>---------------------------------------------------------------------------
-
>-
>Brian R. Watters
>University of Regina
>Regina, Saskatchewan S4S 0A2, Canada
>Ph: (306) 584-9161 (home); (306) 585-4663 (work)
>Fax: (306) 585-5433
>E-mail: bwatters at sk_sympatico.ca
>