Here is a little more. Like I stated early on I think it depends on several factors.
The Effects of Growth, Predation, and First-Winter Mortality on Recruitment of Bluegill Cohorts
Victor J. Santucci Jr and David H. Wahl
Transactions of the American Fisheries Society 2003; 132: 346-360
All sizes of age-0 bluegills grew during winter in our study, suggesting that starvation was not a factor influencing winter survival. In contrast, predation was a likely factor reducing bluegill survival overwinter.
* this was in Ill.
SEASONAL GROWTH RATES OF FISHES IN RELATION
TO CONDITIONS OF LAKE STRATIFICATION
Glen E. Gebhart and Robert C. Summerfelt
Oklahoma Cooperative Fishery Research Unit†,
Seasonal periodicity of growth has been reported which shows a reduced rate in
midsummer. This coincides with the onset of summer stratification and severe hypolimnetic oxygen depletion.
Beckman (5) found that 85% of the expected growth of bluegills in a Michigan lake was completed between the
end of April and mid-July. Sprugel (6) found bluegill growth in Iowa was most rapid in June and little growth
evident after July. Anderson (7) also found bluegill growth to be most rapid in June with most growth occuring
in May, June and July and the total growing season extending from 1 May to 31 October. Winter temperatures
are generally too low for optimum growth of most warm-water fishes, but even normal summer surface
temperatures can exceed the optimum range for warm-water fishes as ascertained from laboratory and field
studies of the preferred temperatures of fish (8).
The generally held view on seasonal variation in fish growth in North America is that growth is fastest in
the spring and early summer, slows in the late summer and fall, and virtually stops in the winter (7).
More later.