Interactive Effects of Climate Change and Marine Reserve Management on Rockfish (Sebastes melanops)

No-take reserves have emerged as the primary tool for marine ecosystem management, with the idea that reserves will serve to sustain fisheries, protect biodiversity, and in more recent thinking, mitigate detrimental effects of climate change.  Unfortunately, the latter assertion remains quantitatively untested.  One shortfall in the progression toward a quantitative understanding of how climate change may affect the potential benefits of reserves as a management tool is the absence of temporal environmental variation in marine reserve models.  This represents a critical knowledge gap, because temporal environmental variation is a greatly influential force regulating temperate marine ecosystem dynamics.  In particular, recruitment dynamics have major implications for the efficacy of marine reserves; therefore, knowledge of climate-change impacts on recruitment dynamics is essential to facilitate the development of marine reserve designs that can meet their conservation targets.  Here we address how climate-change-dependent variability in recruitment affects population persistence and fishery yield, thereby providing insight into whether reserves can mitigate climate-change threats.  To accomplish these objectives, we developed dynamic, spatial, age- and size- structured models with density dependence, incorporating environmental and maternal effects on larval survival.  We present analytical results applicable to a wide variety of taxa, in addition to simulations addressing how black rockfish (Sebastes melanops) persistence and yield can be affected by phenological mismatches between S. melanops larvae and their prey, caused by temporal variability in the timing of spring transition date and negative correlations between maternal age and parturition date.  Preliminary results from the simulations indicated that probability of S. melanops persistence was actually lesser in current climate conditions (base case with greater larval survival likelihood for individuals birthed by older mothers than younger mothers) than in climate-change scenarios with delayed spring transition (in which maternal-age-specific larval survival likelihoods were inverted).  This result was counter-intuitive, as we expected that the majority of total egg production would be from older age classes because older female rockfish produce at least an order of magnitude more offspring than younger females.  Perhaps this occurred because fishing mortality reduced the number of older individuals to the extent that increased reproduction in these age classes was not enough to compensate for losses of reproductive success in the younger age classes.  If this is the case, fished stocks with this type of maternal effect may actually experience short-term benefits from delays in spring transition date, whereas unfished stocks (or populations within reserves) may not be appreciably affected.