Fish Habitat Alteration

• Root cause of habitat alteration is world population growth, development, and urbanization.
• Habitat alteration is a major factor contributing to the decline of native fish species in North America and plays a role in fish biodiversity crises.

How Fish Habitat Can Be Lost

• Drying up or flooding can inappropriately affect habitat.
• Sedimentation can fill the habitat with dirt and debris.
• Vegetation or debris can block access and reduce habitat quality.
• Toxicants can contaminate and make the habitat unsafe for fish.
• Eutrophication or deoxygenation can lead to oxygen depletion and poor water quality.
• Structural damage or removal can cause destruction or homogenization of natural habitat features.

Major Causes of Decline in Native Fish Species

• Physical habitat alteration results in destruction or modification of habitats.
• Introduced/invasive species compete on native fish.
• Chemical alteration, contamination, or pollution results from chemicals, including nutrient loading.
• Overharvesting involves unsustainable exploitation of fish populations
• Chemical alteration can be grouped into physical.

Habitat Issues: Lakes

• Deforestation raises temp turbidity and organic input.
• Draining and filling of marshes and isolation of wetlands harm lakes.
• Lakes are often found in close proximity to filter water and maintain the water.
• Blockage of tributary streams is an issue.
• Dredging of harbors and channels is an issue.

Rivers and Streams

• Deforestation of river basin leads to habitat loss.
• Heavy logging near streams increases stream temps, stressing ecosystems.
• Insufficient riparian buffers will affect water quality, habitat, and stream ecosystems.

Additional Problems

• Livestock grazing increases turbidity and sedimentation, affecting water quality.
• Sediment destroys spawning areas for species relying on clean, gravelly streambeds.
• Channelization removes natural bends in streams to create uniform, straight channels and loss of deep pools where fish find refuge and natural habitats where fish hide or wait for food.
• Channelization is typically done for navigation or flood reduction.
• Roads built over streams can lead to habitat degradation.