Recruitment, abundance, and predation on the blue mussel (Mytilus edulis) on northeastern estuarine rocky shores

Abstract

We report on patterns of abundance, recruitment, and predation on the blue mussel (Mytilus edulis) in three human‐dominated estuaries in the northeastern United States. Through replicate field experiments and observational studies at multiple sites nested within each of the three estuaries, we investigated the relative influences of local and regional scale variation in select bottom‐up and top‐down factors on blue mussel populations on wave‐protected rocky shores. The most striking result was the decoupling between adult abundance and recruitment: mussel recruitment rates were highest in the most northern estuary, Casco Bay, while adult abundances were highest in the most southern estuary, Long Island Sound. We detected evidence of top‐down forcing on adult abundance by consumers in the two more southern estuaries, Narragansett Bay and Long Island Sound, but not in Casco Bay. Finally, we observed some indications of bottom‐up forcing on mussel abundance and recruitment at the within‐estuary scale, but these signals were not consistent among estuaries or across the responses measured (e.g., adult abundances and recruitment rates). Our results support previous work demonstrating the importance of both top‐down and bottom‐up influences on rocky shore populations, and also highlight how future research—particularly integrating studies of the different ontogenetic stages of mussels—could further advance understanding of biological population dynamics in this and other systems.

Keywords

• abundance
• estuary
• marine
• mussel
• Mytilus edulis
• northeastern United States