Altering Aquatic Connectivity: Ecological Considerations

Humans have a long history of altering the connectivity of aquatic systems. Changes in connectivity were typically a by-product of activities related to human sustenance or commerce and there was little understanding of the ecological consequences of enhancing or reducing connectivity. Today, the ecological consequences of altered connectivity play a prominent role in fish management and conservation. Maintaining or restoring connectivity can enhance migratory populations, help maintain genetic diversity, allow organisms to access complementary habitats to meet life history needs, and facilitate recolonization after extirpations. On the other hand, reducing or eliminating connectivity can prevent the spread of nonnative species or exotic diseases, eliminate hybridization between hatchery and wild stocks, or prevent individuals from becoming entrapped in sink environments. Strategies for fragmenting aquatic systems include maintaining existing natural barriers, taking advantage of existing anthropogenic features that impede movement, severing artificial connectivity created by human actions, and intentionally creating new barriers. Future challenges for managing fragmentation include maintaining hydrologic connectivity while blocking biological connectivity in water development projects; identifying approaches for maintaining incompatible taxa such as sport fishes and small nongame species; and developing selective barriers that prevent passage of unwanted species while allowing normal life history movements of other species.