Sea star census
Pisaster ochraceus, generally known as the purple sea star, is a common seastar found among the waters of the Pacific Ocean. Pisaster ochraceus is a predator of the California mussel, Mytilus californianus and reduces its abundance. This allows for other macroinvertebrates to persist. In an experimental removal of Pisaster ochraceus, it was shown that Mytilus californianus becomes almost completely dominant of the intertidal community. When Pisaster ochraceus is present there is a diverse intertidal community.
Fanny Bay on Vancouver Island hosts extensive oyster farming operations. In the early 1990.s the companie used rocky reefes to grow oysters but these were heavily predated on by seastars. The companies were constantly involved in physicall removing seastars from the reef but in the mid 1990, they turned to using "floaties" that suspends juvenile oysters in floating trays suspended in open water channels. These trays prevent seastars from reaching the oysters.
On three occasions between 1997 and 1998 and as part of the open water certification, we ask students to count different species of seastars along rocky bottoms along a 10 meter transect. We placed a 10 meter line along the rocky bottom and students were asked to swim along this transect counting all seastars a meter either side of the line. We conducted this survey on Saltspring Island, at Whitecliffs Park and at Porteau Cove at depths of 5 to 8 meters.
Pisaster ochraceus, generally known as the purple sea star, is a common seastar found among the waters of the Pacific Ocean. Pisaster ochraceus is a predator of the California mussel, Mytilus californianus and reduces its abundance. This allows for other macroinvertebrates to persist. In an experimental removal of Pisaster ochraceus, it was shown that Mytilus californianus becomes almost completely dominant of the intertidal community. When Pisaster ochraceus is present there is a diverse intertidal community.
Fanny Bay on Vancouver Island hosts extensive oyster farming operations. In the early 1990.s the companie used rocky reefes to grow oysters but these were heavily predated on by seastars. The companies were constantly involved in physicall removing seastars from the reef but in the mid 1990, they turned to using "floaties" that suspends juvenile oysters in floating trays suspended in open water channels. These trays prevent seastars from reaching the oysters.
On three occasions between 1997 and 1998 and as part of the open water certification, we ask students to count different species of seastars along rocky bottoms along a 10 meter transect. We placed a 10 meter line along the rocky bottom and students were asked to swim along this transect counting all seastars a meter either side of the line. We conducted this survey on Saltspring Island, at Whitecliffs Park and at Porteau Cove at depths of 5 to 8 meters.