Mussels and Oysters at the Marine Station

Two Days at Pelican Point

1Every fall, Farida Nasser's sixth-grade class spends two days at the Pelican Point Marine Station. The station's educator, Dr. Keoni Akana, showed the class two long-term growth studies: one on the rocky shore below the station and one in the oyster nursery out in the bay. On the first morning, the class walked the shore at low tide with field guides, keeping to bare rock and well away from the waves.

2Mussels attach to rocks with strong threads. They feed by pumping seawater through their shells and filtering out tiny drifting living things called plankton, which they can do only while they are underwater. Twice a day the tide rises and falls. Rocks low on the shore stay covered for most of the day, while rocks near the top are covered for only a few hours.

3Station scientists marked mussels of one species that were all about 30 mm long. They left groups at four heights on the shore and measured them again one year later. They also moved 20 marked mussels from the highest rocks down to mesh cages bolted to the lowest rocks, where they could still feed.

4In the nursery, the station raises young oysters of one species from two parent groups. The fast line comes from parents that were chosen over many generations because their young grew quickly. The wild line comes from oysters collected along the coast. Young oysters from both lines, all the same age and about 5 mm long, were placed in mesh bags at two sites. Each bag hung from a floating line, so the oysters stayed underwater all day and night. The inner estuary, where a river meets the bay, has water rich in plankton. The outer bay has clearer water with less plankton. After 12 months the class helped measure the shells.