RE: NANFA-- I. captive fish and breeding cycles II. migrations

Hoover, Jan J WES (
Fri, 17 Dec 1999 10:34:44 -0600

>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.

Shireen -

Check this out:

Taylor, M.H. 1990. Estuarine and intertidal teleosts. pp. 109-143 in
Reproductive seasonality in teleosts: environmental influences. A.D. Munro,
et al., (eds), CRC Press, Boca Raton.

Lots of info on mummichogs. Gonadal maturation was stimulated when fish
were exposed to long days (> 13 h) AND warm temperatures but not so on short
days (< 12 h) regardless of temperature. Author also talks about "skeleton
photoperiods" (light cycles interrupted by a dark period, effectively adding
hours to the following light period and acting like a long day). Sorry if
that doesn't make sense. Its easier to understand in the chapter. Anyway -
depending on your water temperature, and the timing of your aquarium lights
relative to ambient daylight, you may be fooling your Fundulus into thinking
that spring is on its way.

- Jan

P.S. In the spirit of the season: I had a botany professor in Florida that
said poinsettias were very sensitive to such skeleton photoperiods. He
maintained that even low levels of light that interrupted long dark periods,
if positioned correctly, would prevent poinsettias from blooming fully and
timely. He pointed out that bushes growing near streetlights typically had
fewer or smaller blooms, or bloomed at odd times of the year.

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