The sub-lethal effects of marine heat waves and of gradual changes in productivity through time were simulated for an abalone fishery using the ‘aMSE’ R-package, with all such impacts being imposed by changing recruitment or settlement success. In all cases, throughout the simulated years, the current Tasmanian harvest strategy was used to generate management advice on each year’s total allowable catch and its spatial distribution through the fishery. Simulations were conducted of the outcomes expected from imposing one to three marine heat waves, at defined intervals across 30 projected years, with each event reducing recruitment success in the following year by between 60 – 90 % (a sub-lethal impact). Similarly, the effects of gradually reducing settlement success across a 30-year period was simulated for reductions between 10 – 40%. A single marine heat wave event either led to reductions in stock size or slowed stock recovery. Multiple heat waves between three and five years apart led to serious reductions or a reversal of stock recovery. Relatively small mean decreases in productivity (10 – 20%) can be difficult to distinguish from expected noise in stock recruitment over 30 years. Larger decreases in settlement success led to more serious declines in biomass and CPUE and lead to more serious catch declines. In all cases, the empirical harvest strategy, which is dependent only upon fishery dependent information, was slow to respond to an actual decline in productivity. Marine heat waves can be identified independently of the fishery, and precautionary harvest strategy meta-rules have been proposed that can make some allowance for their effects; these have yet to be implemented. Longer term, slow declines in productivity are more difficult to demonstrate and solutions are still being sought.