[quote=Boondoggle]Boondoggle, it is certain that we over-emphasize gape when talking about optimum lengths. The part we miss is the difficulty of capture and time between successful captures during which LMB are expending energy which are thus part of the energy cost of consumption. If we assume that realized capture reflects optimum energetics, then the prey with the highest frequency of consumption is the most energetically optimum. It is not prey between 30% and 50% the length of the LMB. For fusiform prey, it is between 25 and 30% of the LMB and for BG it is between 16 and 20% the length of the LMB. Why is this important? Let say you want to supplement forage. Let's say you have 20" LMB and use 30% the length BG to feed them. You will be stocking 6" BG and I can assure you that very few of them will be eaten beyond the first day or two. This stocking will make matters worse actually because the will survive and compete with other adult BG for limited resources reducing the production of BG fry. Furthermore, they will compete with LMB for BG by eating BG < 25mm in length. Sounds good under the premise of gape to define "energetically optimum" but it will never work because LMB do not in reality consume > 30% length BG as a high proportion of their diet. Not enough of them will be consumed.
Hmmm. I'm not sure where exactly I came across the 30-50% on optimal forage size and will do some work to try to track it down. I remember some discussions on the topic relating to supplemental forage and rainbow trout use in the fall but that was more for mature fish and trying to push some bigger/trophy type monsters. Perhaps my memory was a little faulty and inflated the numbers on accident. I'll keep digging to see if I can get a link to add in.
I did come across this info though by the American Fisheries Society as it relates to Juvenile LMB and forage (what I'm trying to track down).
AFS - Predator and Prey SizeIt appears as though in the article they mention Juvenile LMB taking on GS from 33-65% and BG/FHM from 25-48% of the LMB length with a preference toward larger GS in comparison to BG/FHM.
