Boondoggle,
12-14" LMB could take 4-6" RBT. Even so, we need to take into account other factors in order to understand the impact of predation on the forage stocking. Per realized consumption data, the optimum weight (energetically ... time and effort expended for energy gained) of laterally compressed prey is ~0.86% of the body weight of the LMB. So for a 12" LMB this equates to 2.2" BG. Applying a similar weight proportion to RBT prey we get the ideal length of 2.64". Larger or smaller prey have economy ... that is to say ... they will yield more energy than expended but will not be as favorable for the LMB. A 4" RBT is most favorable for the economy of 18" LMB.
Statistically we find that 68% of the consumption by number of laterally compressed prey lies between 16.7% and 20% of the the length of the LMB. For fusiform prey, the range of the first standard deviation lies between 19.5% and 25% the length of the LMB. So from a probability standpoint we can eliminate 84% of the probability that an RBT will be consumed by 12" LMB by stocking at a minimum length of 3". To be sure, 12" LMB will consume >3" RBT but the frequency will be in line with energetics where the frequency will decline as the proportion of the RBT body length increases. By the time the RBT reaches 6" it is, in a very practical sense, off the menu of 12" LMB unless it is sick, dying, or dead.
If I calculate the consumption of RBT for the season for a 15" LMB consuming 2.2 times its maintenance ration, the gain from this consumption will be 52% of the LMB body weight. Smaller LMB consume at higher rates and grow faster as a % gain. From Dec 1 to May 7 the estimate of individual RBT consumed is 36. Now I will mention that this is probably WAY too rosy for a stocking of 4" RBT. At 4" the initial proportion already exceeds 25% of the LMB length (26.7%) and so we have eliminated 84% of the probability that 4" trout will be consumed by 15" LMB. Applying probability we can then calculate that consumption is probably limited to 6 RBT for the 15" LMB. Furthermore, most of these will occur very close to the stocking date. At the time of stocking the 1.83 lb 15" LMB will consume 4 RBT every 6 days to consume 2.2 times maintenance. By the end, the consumption is estimated at 1 every 5 days. So somewhere in the middle the RBT have grown too much to be food for that LMB.
IMHO. The most optimum forage size to stock is forage that is of the length of the bottom of the first standard deviation. This provides a window through the most energetically favorable lengths of the prey and provides the longest span of time across these most favorable lengths. The consumption will be maximized with such a strategy and so consequently growth will also be maximized. For RBT, this is 19.5% of the length of the minimum target length to feed. Stocking at 4", one will be focusing on growing >20" LMB most optimally.
Last edited by jpsdad; 12/16/23 12:32 PM.
