>I. Captive fish and breeding cycles
>
>In the wild, fish typically breed in the spring and
>summer when food is plentiful. This is when males
>usually take on their splendid colorations.
>
>What triggers it? Is it something as simple as
>daylight duration? Is it temperature induced?
>Or are there other more complicating factors at
>work? Has this ever been studied in a lab?
>
>I'm asking because one of my mummichogs is starting
>to get colorful. I've had him for almost 2 years.
>My tank, heavily planted, gets 14 hours of light
>and is kept at a constant 76F. It's fairly close to
>a window so some indirect sunlight also filters
>through. OK, so i've totally messed up his internal
>clock with my artificial lighting and constant
>temperature. But it's got me thinking about why
>he's starting to color up in December.
>
>II. Migrations
>
>My second question is about basic fish migration.
>Can anyone direct me to some references on how they
>do it?
>
>Speaking of migration... bird use many cues in
>following their migratory routes. Before they start,
>they display a behavior called migratory restlessness,
>or "zugenruhe." In some species, this is manifested
>as the bird facing a particular direction and flapping
>its wings.
>
>There are many factors that direct birds on their
>journeys, such as the Earth's magnetic field, land
>formations, daylight duration, the polarization of
>sunlight, and even navigating by the stars!
>
>As someone trained in astronomy, I find that last
>factor especially appealing. In the 1960s, a student
>at Cornell raised Indigo Buntings in a planetarium.
>Instead of having the dome of stars rotate around
>Polaris, the north star, he had them rotate around
>Betelgeuse, a star in the constellation Orion. And
>guess what... when the buntings matured and started
>displaying migratory restlessness, their "north" was
>in the direction of Betelgeuse!
>
>This, of course, makes me wonder about the migratory
>behavior of fish, and the factors that influence
>their navigation. Comments and references would be
>greatly appreciated.
>
>thanks,
> shireen
>
>
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Bonnie
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