Locations of green-lipped mussel attachment within macroalgal substrates on a mussel reef in New Zealand

The six possible locations of mussel attachment on different macroalgae species were; the holdfast, stipe, lower branches, lower branch nodes, upper branches, and upper branch nodes. The presence of juvenile mussels in each size class attached to each location within each macroalga species is reported binomially (i.e., present: 1, absent: 0) in the "Juvenile Mussel Presence" column. For smaller juvenile mussels <10 mm, attachments to the branches and branch nodes of macroalgae were far more common than for juveniles ≥10 mm, suggesting that juvenile mussel attachment is more likely to be influenced by the branching morphology of macroalgae earlier in juvenile development.

For juveniles <10 mm SL, attachments to the upper branches and nodes of macroalgae were more common at Waipū Cove than at Pākiri Beach, where smaller juveniles were more often attached to the lower portion of macroalgae. Lastly, macroalgal holdfasts were the most common location of attachment in this study for juvenile mussels ≥10 mm, and for juveniles smaller than 10 mm, it was as common of an attachment location as the branch nodes of macroalgae.

These results suggest that juvenile mussels attached to macroalgae are likely to be influenced by a macroalga’s holdfast morphology throughout all stages of development but especially in later development.