Originally Posted by milt spawn
Interesting topic. What happens to these seasonal spawning patterns when these species are introduced in the southern hemisphere? Are there any trout or salmon native below the equator? milt. (DR- There are "Bull Trout", a char species, and bull trout, males of a species. BPS probably doesn't have char in their store.)
Yes, I'm not sure how many countries but trout and salmon are a naturally reproducing introduced species in Chilean & Argentinian Rivers. Most noteably in the Tierra del Feugo reigon. Then there are the trout and salmons over in New Zeland also.
I was starting into a dissertation about the affect of light & darkness on the whole reproductive process but held up short. It is those 2 things that influence the timing for the spawning. The debate is ongoing as to whether it is the hours of light or the hours of darkness that has the primary factor but saying daylight sounds better so I'll go with that. When you consider the relative hours of day light before and after the December equinox there are days & weeks that are identical in length. Take the thought process further and you begin to see the marvle of the natural order. Spring and fall spawners, the timing of salmon, steelhead, and sea run trout & char runs. All of these fish share in many cases the same watersheds and spawning grounds. All are finely tunned so that the breeding periods interlock like the teeth of a zipper as it closes. Quite amazing but still a simple marvel at its base, sunlight.
Of course there is much more to be said and people who are better schooled than I to say it but that synopsis will do for a layman eh.