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on communications with M. Ulibarri, Dexter NFH&TC, on grow out of bony tail chub). The model also assumes that wild mortality rates remain in place once the fish are stocked (i.e., there is no additional post release mortality). The model is useful in that it provides a magnitude for the number of stocked fish that might be needed to arrest a continued expected decline or to achieve a positive population response. We have used the model to predict the number of fish that may need to be stocked to 1) arrest decline and maintain the abundance of age-4+ fish at levels estimated in 2000, and 2) achieve a positive population response and return to the abundance of age-4+ fish estimated in 1990. As stated above, since the model can be set up using varying assumptions about wild survivorship rates, we present a range of numbers (Table 2) that include a best and worst case scenario. With no additional stocking, the three variations of the ASMR model (i.e., using three different assumptions about wild survivorship rates inclusive of a best and worst case scenario) predict that if wild annual recruitment continues to be stable, the spawning population will soon stop declining, and will stabilize at an average spawning abundance -1,900 to 2,300 fish. This is in agreement with the initial predictive assessment made by Coggins et al. (2003). Table 2. Predicted numbers of humpback chub using Age Structured Mark-Recapture modeling that would need to be removed at age-O, grown in captivity to 171 mm and released into the wild in order to stabilize the abundance of age-4+ fish at the level estimated in 2000 (arrest further decline) and to increase the abundance of age-4+ fish back to levels estimated in 1990 (effect a positive population response). ASMR base model ASMR+ high mortality ASMR+low mortality Stabilize at 2000 level Remove age-O Stock age-3 1,350 1,080 960 768 1,414 1,131 Recover to 1990 level Remove age-O Stock age-3 4,294 3,435 6,358 5,086 5,963 4,770 The model suggests that if -960 to 1,400 age-O humpback chub were captured per year from the LCR, and grown out to -170 mm before release, this should arrest a decline and maintain the abundance of age-4+ humpback chub at levels estimated in 2000 (Figure 3). Alternatively, the model predicts that if -4,300 to 6,350 age-O fish were captured per year from the LCR, and grown out to -170 mm before release, this should effect a positive increase in the abundance of age-4+ fish estimated in 1990. It should be kept in mind that these numbers may need to be inflated somewhat if the fish are only grown to 150 mm, or deflated somewhat in fish are grown to 200 mm. It should also be recognized that the terminal abundance estimates that the model is predicting apply to the year 2020 with stocking beginning in the year 2005, suggesting these effects will take over a decade to fully achieve. Prior to any final decisions being made, the designer of the model should be further consulted. This is in part because one of the key assumptions in using the model for these predictive purposes is that future 29