Differential migration in Chesapeake Bay striped bass

Area of Science:

• Ecology
• Fisheries Science
• Animal Behavior

Background:

• Differential migration, where larger individuals migrate more, is common in species and offers spatial buffering.
• Striped bass (Morone saxatilis) exhibit plasticity in migration behaviors, making them a key species for study.
• Understanding these behaviors is crucial for effective fisheries management and conservation.

Purpose of the Study:

• To investigate differential migration patterns in striped bass from the Potomac River.
• To determine the consequences of differential migration on survival and reproductive patterns.
• To inform stock assessment and management strategies for striped bass populations.

Main Methods:

• Acoustic transmitters were used to track the coastal migrations of size-stratified striped bass over four years.
• Telemetry receivers were deployed along the Mid-Atlantic Bight and Southern New England shelves.
• Generalized linear mixed models were employed to analyze migration predictions and survival rates.

Main Results:

• Over 50% of large male and female striped bass (>80 cm) migrate out of the Chesapeake Bay, primarily through its mouth.
• Migrating fish reached Massachusetts shelf waters and repeatedly returned in subsequent years.
• Small resident striped bass had significantly higher annual loss rates (70%) compared to migratory coastal emigrants (37%).

Conclusions:

• The study confirms a size threshold for emigration and different mortality rates between resident Chesapeake Bay and migratory ocean contingents.
• Findings support a two-contingent population model for striped bass: smaller residents and larger ocean migrants.
• Understanding differential migration allows for refined stock assessments and tailored management strategies for different population sub-components and stakeholders.