Through regional scuba surveys, the researchers found that in 2003 the population of juvenile bocaccio using natural reefs as near-shore nursery grounds was small by comparison to the populations at the platforms.
According to the researchers, juvenile rockfish need something hard, like a rock overhang or a man-made structure, to "settle out" and develop a home base. Then they join a school and swim around their structure. The school helps to protect them from predators. Staying in one place allows them to eat the plankton that drift by in the ocean currents. If the juveniles were to drift out to sea with the currents, they would likely be eaten by predators, or starve to death once they ate all the nearby plankton floating with them. The platforms provide structures that the rockfishes need to thrive.
"Natural reefs are small," said Love, "and before the time the fish finds one it often gets eaten." By contrast, platforms cover the entire water column.
Brian M. Emery, a physical oceanographer with MSI, is the lead author of a second paper which reports on ocean currents in the region of Point Conception to Point Arguello, north of the Santa Barbara Channel and near Platform Irene. The results of a study of ocean currents, using high frequency radar, show that Platform Irene almost certainly increases the survival of young bocaccio in this region. The study was conducted twice, in 1999 and 2002, from May through August, the season when young bocaccio settle out.
Emery explained that the research team used radar equipment housed at three locations along the coast and provided by the National Oceanic and Atmospheric Administration and the W.M. Keck fou
Contact: Milton Love
University of California - Santa Barbara