Aggregation
Blue mussels occasionally form clumps, or aggregates, of individuals when population density is low.The mussels attach to one another via collagenous protein strands called byssal threads. The aggregates are observed mostly in Mussel fields, which are short-lived populations of Mussels, usually exhibiting a clumped distribution pattern. It is hypothesized that the mussels form these aggregates to increase reproductive success in low density populations. This hypothesis, however, has yet to be conclusively proven. Alternative possible reasons for the behavior include resisting wave action and increasing water flow through the siphons of the mussel. The significance of the behavior is its relation to the formation of mussel beds from mussel fields. Mussel beds are persistent, dense mussel populations. Beds generally form from fields that persist long enough to establish a dense population. Thus in areas where blue mussels are threatened, such as the Wadden Sea, it is of great importance to enhance the survival of mussel fields, of which mussel aggregates are the primary component.
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