However, what we forget is that there are two types of rainbows:
One with chaniging conditions during the year and one with
rather permanently the same ones throughout the year (as far
as we know, see above). To my personal opinion the rainbows
with changing conditions can't be really changing their sex with
the temp while this might cause problems throughout certain
times of the year. Some people breeding herbertaxelrodi found
that this fish would bring nearly only males bred at higher
temps. Their natural habitat has 22°C with only minor changes
as it's nearly at the equator. But that's just a hypothesis.
Harro
was:-----------------------------------------------------------------------------------
I guess where I'm trying to go with this is, nature rarely develops a
trait that isn't somehow directed towards survival. It could be both
pH and temp effected fry ratios are in effect for similar reasons and
mark the same change in seasons. I've really never seen any info on
the seasonal changes in fish populations and water chemistry. It seems
most specie are often collected either very rarely and always in the
same season when its easiest to get to them. If the water conditions
were tested on the collection date, do we really know what variations
are going on through the whole season? If there is some data on this,
it could help to explain why nature may have developed a temperature
or pH advantage to the sexes.
Cary Hostrawser
Minnesota Aquarium Society
http://www.mn-aquarium.org/
Rainbowfish Study Group of North America
http://home.earthlink.net/~sbuckel/index.html