Juvenile mussels (spat) attached to filamentous
algae from the surf zone (free floating), and from
algae attached to the bottom at 15 m water depth
(subtidal site) were collected at Ninety Mile Beach,
northern New Zealand. Individual mussels (0.5–3.0
mm in length) were carefully removed from their
original algal substratum, and placed in a water tank
with seawater on the same day. A mixture of mussels
of different size classes from 0.5 to 3.0 mm in length
was prepared. From this mixture, subsamples of 179–
268 surf zone and 149–265 subtidal mussels were
separated using a standard plankton splitter. The
mussel subsamples from the surf zone were then
placed in each of the 27 tanks used in the previous