In my experience and those opinions of some fishery pros with yellow perch and with a few other fish species such as LMB, I am not sure that the feeding consumption for all ages of fish keeps increasing when temperatures are close to the reported lethal temperatures. Lusk contends that big LMB slow feeding levels when in water that is near the reported lethal range. LMB do grow fast and big in waters with high summer temperatures. However a lot of these warm waters develop thermal stratification during summer. This temperature layering of the water column does allow fish to seek a lower temperature area or depth zone where a temperature comfort level is "better" and less stressful than the warmest water layer at the surfce. IMO when when hunger occurs the big fish makes feeding forays into the warmer water that is less comfortable to satisfy the hunger urge. t has been proposed that strong or complete continual mixing of the water column of smaller water bodies during the hottest part of the summer can be temperature stressful in ponds with the biggest LMB.
When reading the published articles on this feeding temperature topic most all of the research I have found was done using small or young individuals due to convenience for laboratory testing. When using the published literature to formulate universal guidelines, I think one has to pay close attention to the methods used in that specific research work so as to not to conclude all the results presented to be universal gospel for all ages or sizes of that specie or all fish species. Variations of species sizes and ages I think are natural features of all species.
My experiences are younger fish are able to feed and grow very well in warmer temperatures compared to the older or oldest individuals. Those younger fish are more temperature tolerant and remain more active during the high ends of temperature tolerance. This physiological feature allows optimum grow of young fish. This is probably why the term "dog days of summer" and lower catch rates were coined by anglers due to a slow down of catch results by anglers during the hottest part of summer. As many species age toward end of life span, I think these big old individuals do not feed, consume and behave as they once did as younger fish. This could be mainly due to reduced metabolism and or different hormone levels. The food and growth needs of the individual fish can I think change when big old fish are near the end of its life span.
When from long time dealing with all sizes of yellow perch (YP), the younger ones will from visual observation aggressively consume food at most all higher water temperatures compared to the large and largest individuals. YP up to a size or maybe age will actively feed and grow when in water temps are near their reported upper tolerance iimits. Whereas the large and largest individuals cease or significantly slow their active feeding rate when in water near the upper end of the reported active optimum temperatures. I think this feature could also apply to individuals of bass and other freshwater fish species.
Let's consider fish feeding activity at the other end of the temerature spectrum - cold or colder water. It is commonly known that fish (as cold blooded, warm and cool water species) significantly slow down their feeding activity during winter conditions as water temperature drops below 50F, then 40F or 39F. Optimum Metabolism is less thus feeding is less. My premise is why would this similar colder water feeding activity slow down or gradually decrease when big or old fish especially older larger fish with higher biomass are in water temperatures that are increasing toward or approaching above their optimum preferred upper warm water temperatures toward the lethal limits?. I contend too warmth can be uncomfortable or a stressor for that aged near end of life individual. One does not eat normally or the best when it is under some form of stress. When you are feeding pellets to fish and they quit eating there is almost always a stressor that is causing the lack of eating.
Last edited by Bill Cody; 09/24/25 01:41 PM.
