The Ecological and Evolutionary Consequences of Marine Reserves

Here we review the population, community, and evolutionary consequences of marine reserves. Responses at each level depend on the tendency of fisheries to target larger body sizes and the tendency for greater reserve protection with less movement within and across populations. The primary population response to reserves is survival to greater ages and sizes plus increases in the population size for harvested species, with greater response to reserves that are large relative to species' movement rates. The primary community response to reserves is an increase in total biomass and diversity, with the potential for trophic cascades and altered spatial patterning of metacommunities. The primary evolutionary response to reserves is increased genetic diversity, with the theoretical potential for protection against fisheries-induced evolution and selection for reduced movement. The potential for the combined outcome of these responses to buffer marine populations and communities against temporal environmental heterogeneity has preliminary theoretical and empirical support

Quantifying the potential for marine reserves or harvest reductions to buffer temporal mismatches caused by climate change

Climate change has caused shifts in seasonal timing of climatic events such as the onset of spring upwelling, which can lead to temporal mismatches between fish spawning and production of zoopklankton prey. Fishing may exacerbate mismatches through age truncation, particularly when offspring survival is dependent on maternal age, but no-take reserves or harvest reductions might buffer this effect. To quantify the potential for management to buffer synergistic interactions between fishing and climate, we developed a dynamic population model of a harvested species where larval survival depended on spring transition timing and maternal age. We applied this model to rockfishes (Sebastes spp.) after verifying empirically that spring transition timing affects their recruitment success. We found that yield and persistence changed more with maternal-agedependent larval provisioning than maternal-age-dependent spawning timing across a range of spring transition timings, especially with environmental stochasticity. Either implementing reserves or reducing fishing can mitigate impacts on larval survival, but reserves convey the added benefit of decreased sensitivity of yield and persistence to fishing. However, reserve buffering effects decreased with the inclusion of environmental stochasticity

Quantifying the potential for marine reserves or harvest reductions to buffer temporal mismatches caused by climate change

Climate change has caused shifts in seasonal timing of climatic events such as the onset of spring upwelling, which can lead to temporal mismatches between fish spawning and production of zoopklankton prey. Fishing may exacerbate mismatches through age truncation, particularly when offspring survival is dependent on maternal age, but no-take reserves or harvest reductions might buffer this effect. To quantify the potential for management to buffer synergistic interactions between fishing and climate, we developed a dynamic population model of a harvested species where larval survival depended on spring transition timing and maternal age. We applied this model to rockfishes (Sebastes spp.) after verifying empirically that spring transition timing affects their recruitment success. We found that yield and persistence changed more with maternal-agedependent larval provisioning than maternal-age-dependent spawning timing across a range of spring transition timings, especially with environmental stochasticity. Either implementing reserves or reducing fishing can mitigate impacts on larval survival, but reserves convey the added benefit of decreased sensitivity of yield and persistence to fishing. However, reserve buffering effects decreased with the inclusion of environmental stochasticity

Transient responses of fished populations to marine reserve establishment

Implementation of no-take marine reserves is typically followed by monitoring to ensure that a reserve meets its intended goal, such as increasing the abundance of fished species. The factors affecting whether abundance will increase within a reserve are well characterized; however, those results are based on long-term equilibria of population models. Here we use age-structured models of a generic fish population to analyze the short-term transient response. We show that it may take decades for a fished population to reach postreserve equilibrium. In the meantime, short-term transient dynamics dominate. During the transient phase, population abundance could either remain unchanged, decrease, or exhibit single-generation oscillations, regardless of the eventual long-term result. Such transient dynamics are longer and more oscillatory for populations with heavier fishing, older ages at maturity, lower natural mortality rates, and lower larval connectivity. We provide metrics based on demographic data to describe the important characteristics of these postreserve transient dynamics. ©2012 Wiley Periodicals, Inc.

Transient responses of fished populations to marine reserve establishment

Implementation of no-take marine reserves is typically followed by monitoring to ensure that a reserve meets its intended goal, such as increasing the abundance of fished species. The factors affecting whether abundance will increase within a reserve are well characterized; however, those results are based on long-term equilibria of population models. Here we use age-structured models of a generic fish population to analyze the short-term transient response. We show that it may take decades for a fished population to reach postreserve equilibrium. In the meantime, short-term transient dynamics dominate. During the transient phase, population abundance could either remain unchanged, decrease, or exhibit single-generation oscillations, regardless of the eventual long-term result. Such transient dynamics are longer and more oscillatory for populations with heavier fishing, older ages at maturity, lower natural mortality rates, and lower larval connectivity. We provide metrics based on demographic data to describe the important characteristics of these postreserve transient dynamics. ©2012 Wiley Periodicals, Inc.

Critical assessment and ramifications of a purported marine trophic cascade

When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions