Freshwater Fragmentation Effects on Brown Trout

By Rowena Humphrey

October 19, 2006

Life History

Two life-history tactics: • Stay in “home” freshwater stream

• Migrate downstream to the sea

Distribution

Salmo trutta L.

Habitat

Dams

Consequences of Fragmentation

• Water Characteristics

• Mobility

• Vegetation

• Genetic Diversity

• Habitat Components

Water Characteristics

• Water level

• Depth

• Temperature

• Velocity

• Discharge

• Turbidity

• Substrate

Mobility

Obstructions effect:• Isolation of the watershed • Accessibility of tributaries• Migration

• Difficulty depending on water level, location, and structure.

Fish Ladders

Vegetation

• Dramatically shifting vegetation

• Fluctuation between high production and mortality for terrestrial and aquatic plants

Genetic Diversity

Reproductive Isolation Within Watersheds Irregular Gene Flow

Genetic Diversity

Reproductive Isolation Within Watersheds Irregular Gene Flow

Decreased Diversity

Ineffective• Single species • Localized • Individual obstructions

Effective• Multi-species • Encompass all

life-stages • Movement • Reconstruct the

sequence and structure

Conservation and Restoration

Ineffective• Single species • localized • individual obstructions

Effective• Multi-species • encompass all

life-stages • Movement • reconstruct the sequence

and structure

Conservation and Restoration

Temporary solutions

Long-term solutions

Sustainability

• Initial design

• Materials of construction

• Physical characteristics of the water systems

• Appropriate monitoring and maintenance programs

Global effects on biodiversity

Questions?