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Spawn And The "magic Number" For Water Temps

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So here in Colorado we've been getting the weirdest weather, which for Boulder/Denver is the norm.  For March April, and now May we've had days up into the 80's, and two days later, it's snowing and 29 degrees outside.  Water temps during most of march and April when I was actually on the water were up and down all over the place ranging from 49-60.  


Questions - Does this confuse the bass?  In other words, will bass move in to spawn or build nests when water temps hit 60 for a day or two, then get "tricked" and move back again to deeper water without laying their eggs when the water temp drops drastically?  Or do they just wait and wait and wait for sustained water temps of about the magic number of 60 to move in to spawn?  


Question -  Is that sustained water temp "magic number" the same in all cold weather states?  Are bass in Illinios triggered to spawn at the same sustained water temps as bass in Colorado, Iowa, and NYC?


Question - How long does that "trigger temperature" have to be happening before the bass will feel comfortable spawning?  A week?  3 days?  Two weeks?


Question - Lastly, how long do/can bass hold onto their eggs before they have to get them into the nest?  I caught a few egg filled bass in the beginning of March but water temps haven't been out of the 50's yet since then.  Are those females I caught i early March STILL holding on to their eggs until water temps get into or around 60 degrees sustained?







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Hey Todd. Good to hear you are getting out some.


LM spawn when water temps stabilize around 60F. My present understanding is that this is the case throughout the country (including Florida strain). Whether this is due to the widespread stocking of bass narrowing genetic diversity or an older deeper seated requirement I dunno. (That floridanus is similar makes me think this is deep seated.) The critical factor seems to be that egg mortality goes through the roof around 55F.


The problem in small waters is that water temps can fluctuate more drastically than bigger waters do. In smaller shallower waters the bass generally spawn earlier than those in bigger deeper (more voluminous) waters do.


On some years, some really shallow ponds can warm to spawning temps well prior to the normal spawn window, but the bass do not spawn. Egg maturation is still required and I don’t think it’s entirely temperature dependent. Endogenous (internal) rhythm, entrained and likely mediated by photoperiod, plays a big role.


So there is a spawn window, heavily influenced by temperature at the final stage, with the actual timing varying a bit –a week or two dependent on temperature. What happens during “unseasonable” weather on our little shallow ponds is those eggs already laid, die. The result is part of the “boom-n-bust” cycles common in small waters. Larger waters can usually absorb such turns in the weather. Most of our ponds, with any depth, absorb it pretty well too. First, water holds heat well. Second, the sun is high enough at this time of year that its ability to warm, esp dark colored areas -like ponds- is powerful. Just bc there’s snow on the bank doesn’t mean the water is as cold. Realize that cold water sinks too, so it ends up at the bottom of the pond, and the sun heats the shallows pretty quickly. Water temperature drops do affect bass though, but this late in the year things rebound very quickly. One things for sure –it is NOT winter.


If bass are held at bay from spawning due to ill-timed weather (and it usually has to be pretty extreme –like we’ve been having!) the females can wait for a period as their ovaries are active and producing for a period of time. In some waters, esp in the south, with plenty of food and warm temperatures, individual females can participate in more than one egg-laying wave. Up here I believe our fish lay once, but I am not certain of this. If they are indeed dashed, they can resorb some or all (pretty rare) of their eggs.


Here's some more on the subject of spawn timing:


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