Overfishing, Shifting Baselines, and Marine Protected Areas

Historical overfishing is the predecessor and the cause of pollution, eutrophication, hypoxia, physical destruction, climate changes, and the collapse of entire oceanic ecosystems. Along with the dramatic increase in human populations, the perpetual migration toward coastlines, and the advancement of technology, the rate at which fish are caught has exceeded that in which they are produced, resulting in the depletion or collapse of many fisheries.

Retrospectively analyzing paleoecological, archaeological, and historical data, Professor Jeremy Jackson, et. al, provides evidence of the changes caused by overfishing worldwide. Where there was once 40 million giant turtles in the Caribbean and an abundance of whales and sharks in Chesapeake Bay, drastic overfishing has driven species toward extinction as their numbers become inadequate at interacting with other species, disturbing the diversity of an entire ecosystem and prefiguring its collapse. The reduction in shellfish and the proliferation of kelp forests, suggests that many fished species serve as predators, integral to the regulation of ecosystems. The characteristics sought by fisherman, such as large size, are ecologically adaptations from natural selection that ensures the survival of the species. The theory of natural selection suggests that individuals which possess the most beneficial phenotypic attributes to a specific environment tend to have a greater survival rate, allowing for greater reproductive success and thus the proliferation of the species and those attributes. The high mortality of these phenotypes results in the selection of individuals that possess less than optimal traits leading to the overall degradation of the species, as evidenced by records of average Cod size and its drastic decline over a century.

Many lack awareness to the situation’s severity as shifting baselines have left the public with a skewed outlook on overall marine health. Shifting baselines are reference points that absorb small, gradual changes, that go unnoticed in comparison to large-scale events, leading to the acceptance of a present, deteriorated state as the norm, or baseline. Studies have shown periods of decades or centuries may elapse before the consequences of overfishing occur as the effects are synergistic, contributing to the difficulty of detecting the deteriorating state of the ocean.

Remediation may only occur if previously overfished species are given the opportunity to proliferate.