The Conservation of Aquatic Systems

Aquatic environments are among Earth’s most species-diverse ecosystems, yet remain under-protected. Rivers face multiple threats, the most systemic being alteration of streamflow through human withdrawals or impediments by dams. Dam removal, once rare, is an increasingly used technique to restore stream flows. Marine populations are most threatened by overharvest, with more than 60% of commercial stocks classified as overfished or collapsed. Bycatch, the inadvertent capture of animals when fishing for something else, threatens non-target species, with losses to marine mammals alone between 300,000 and 600,000 individuals annually. Time and area closures, fishing effort reduction and gear modification can reduce bycatch mortality. Marine reserves produce increasing fish populations under “no-take” management as well as in commercial catches if harvest areas within the reserve are limited.