In relation to the recent news item on the Hidden side effects of MPAs? based on the paper Effects of population density and body size on disease ecology of the European lobster in a temperate marine conservation zone.
Density dependence is a well recognised central tenet of population ecology, i.e. as the density of a population is restored back to unexploited levels, a number of 'natural' trends will increase, such as increased prevalence of disease amongst more crowded populations and older 'senile' individuals (as natural age structure is restored), along with increased competition for space, sexual partners, food, etc., leading to increased fighting related injuries. Per capita production will also decrease due to competition for food, cannibalism, etc. This is naturally what happens when you stop thinning a population through harvesting. It certainly is not hidden or unexpected, nor is it a threat to a successful marine conservation story. It is simply what should be expected to happen when a population is restored back to natural levels.