On March 14th, Dr. Mallory Sea (Project Coordinator at Kelly Tarltons Marine Wildlife Trust) flew down to the South Island to meet with mussel experts at the SpatNZ hatchery in Nelson. This facility selectively breeds green-lipped mussels to produce a consistent and reliable supply of spat (baby mussels) for the aquaculture industry—but while the typical destination for these baby mussels is local mussel farms, the mussels collected on March 14th embarked on a very different journey.
Green-lipped mussel restoration projects were first initiated in the Hauraki Gulf nearly a decade ago. While we’ve learned a lot, there are still questions that need answering. One of those questions involves primary settlement (the movement of mussel larvae from the water column to fine, filamentous materials—like seaweeds—on the seafloor before finally settling back onto adult mussel beds or rocky reefs). We know that seaweeds are important for the primary settlement of mussels; on the west coast, mussel spat entangled in seaweeds are gathered and transported to mussel farms across the country for out-planting, a process that supplies up to 80% of mussels grown by the industry. On the east coast (Hauraki Gulf), we know that mussel larvae exist in the water column, but they aren’t forming adult beds as they once did. This means there is a ‘bottleneck’ in the lifecycle of green-lipped mussels, and it’s possible that a lack of primary settlement structure (like seaweeds!) could be a limiting factor in mussel recruitment. We hope to better understand this relationship between baby mussels and seaweeds to make restoration efforts even more successful in the Hauraki Gulf.
After touring the incredible mussel-growing facilities at SpatNZ, Mallory boarded her afternoon flight back to Auckland with a chilly bin containing a small glass container. Incredibly, this sandwich-sized container from SpatNZ held roughly 40,000 mussel larvae that were barely visible to the naked eye!
These tiny mussels were swiftly transferred to a research tank at Sealife Kelly Tarlton’s Aquarium. In this tank, the mussels were greeted by a variety of red, green, and brown seaweed species collected by Mallory and her team from around the Hauraki Gulf.
Mallory hopes to observe and document successful mussel settlement onto these local seaweed species and identify if certain seaweeds lead to higher settlement rates than others. Identifying important seaweed species for mussel settlement could have a wide range of implications for future mussel restoration efforts, but will hopefully result in restoration practitioners seeing more baby mussels survive and thrive on the seafloor someday soon.