Research Technical Report

Mapping Benthic Habitats And Ocean Currents In The Vicinty Of Central California's Big Creek Ecological Reserve

Yoklavich, M., R. Starr, J. Steger, H.G. Greene, F. Schwing, and C. Malzone (1997)

NOAA Technical Memorandum: NOAA-TM-NMFS-SWFSC-245.

ASTRACT

Characterizations of benthic fish habitat and coastal ocean circulation patterns are critical steps in evaluating the effectiveness of the Big Creek Ecological Reserve at protecting and enhancing coastal fishery resources. With the coordinated efforts of geologists, biologists, and physical oceanographers, geophysical and oceanographic data were collected during a 4-day (3-6 June 1996) research cruise onboard the NOAA ship McArthur. We used side scan sonar to survey 24.6 km² of the continental shelf along the Big Sur coast in water depths from 30 to 200 m, and created maps of bottom types. We identified and quantified eight types of potential benthic habitats, ranging from sediment ripple fields with low relief to extensive rock outcrops and isolated pinnacles. About eight percent of the survey area, both inside and outside the reserve, was made up of complex rock bottom types with relatively high relief; these likely are suitable habitats for many benthic species of rockfishes. Our habitats characterizations will help direct future efforts to assess the fishes and their habitat associations within the reserve.

We also characterized patterns of ocean circulation over the continental shelf and upper slope to a distance of 40 km offshore. Upwelling and substantial offshore transport off Point Sur and Lopez Point were evident in temperature, salinity, and current data collected at sea and in satellite sea surface temperature (SST) imagery. Counter to the traditional view of a southward flowing current over the shelf, we found a coherent 10-20 km-wide coastal current flowing northward at a rate of 8-15 cm/sec through the Big Creek Ecological Reserve and extending from the surface to 200 m in depth. This northward flow contributes to convergence and offshore transport of water at Point Sur. This information will help define the physical processes that affect the distribution, transport, and survival of young fishes, and clarify our expectations for recruitment from the reserve to nearby unprotected areas.