Not published, but will put it out there. I maintained a group of 800 yoy LMB that were trained to eat pellet. Grading employed later to ensure uniformity of size and stocking density. After feed training, they were split into three groups. Fish were given pelvic fin clips to ID later. Then fish were then treated with one of three feeding regimens while maintained at 25 C for 28 days. Control group was not fed and lost a good amount of weight. Fish lipid group was fed a basal diet with supplemental menhaden fish oil for a total lipid content of approximately 12%. A tallow lipid group has same basal diet except beef tallow was used as the lipid source so diet again had same total lipid level. Fish in second two groups doubled in weight during that interval. Then groups were combined in replicated units where each had 30 fish from each group in 200-gallon tanks for a simulated fall-winter-spring cycle. There were four such tanks each with a biofilter and chiller and a light on a timer. Tanks were then chilled at 5 degree Celsius increments with chilling events occurring within a day on 28-intervals. After months temperature was down in the 4 - 5 Celsius range which was maintained for 2 months. Then temperature was brought up in the reverse of the temperature reduction. Mortalities of significance did not occur until the temperate started coming back up and it was restricted to the control group. Mortalities appeared to be more closely tied to energy reserve quantity rather than fatty acid profile.
I did this in same lab as Kelly and Kohler looking to see if I could replicate and expand upon there findings. My emphasis was on large mouth bass which were a hot topic at the time.
Working with sunfishes still, often in production ponds over winter, there have been times where monitoring fish under ice was important. Temperature, dissolved oxygen, total ammonia, nitrite, nitrate, pH, harness and alkalinity were all followed. Temp and DO daily while others weekly. When high death rates occurred, is was seldom related to water quality.
I have also seen where Bluegill grown on a natural forage did better under ice than pellet fed. Other things varied with dietary treatment so real cause not known.
Two lines of evidence indicate something else is at play. As a result, some assumptions whether published or not, are in the realm of dogma that are preventing a better understanding of the problem. Nutrition and temperature interactions very likely involved, as is something else that I think involves a pathogen(s).
Winter mortality is of concern to me even now. Harsh winters can cause unsustainable losses for producers.
