In 1949, the cruise transects were determined by lines drawn on nautical charts perpendicular (true bearing 330 degrees) to the California coastline 40 nautical miles apart. Stations in the coastal regime were spaced every 20nm or closer, around features such as basin or islands. Offshore stations were spaced 40nm apart to create a 40x40nm grid. The main goal was the measurement of onshore-offshore gradients strongly influenced by the California Current & bathymetry. Most oceanographic features off the California coast are influenced by the southward flow of the California Current and a seasonal, northward, near-shore counter current. Having transects oriented at right angles to the coastline allows better resolution of transition zones than if they were along the lines of latitude and longitude. In referring to a station number under the present plan, the line number is given, then a decimal point, then the station number. This scheme facilitates quick identification of the station location within the pattern: station 90.60 is station 60.0 on line 90.0, for example.
A Sea-Bird Electronic carousel water sampler (SBE 32) utilizes a magnetically-activated pylon lanyard release latch system to close 24 ten-liter plastic (PVC) bottles equipped with epoxy-coated springs and Viton O-rings. Each cast usually samples ~20 depths to a maximum sampling depth of 525 meters, bottom depth permitting. Occasionally, stations have multiple bottles tripped at the same depth to provide more water for ancillary programs. The sample spacing is designed to sample depth intervals as close as 10 meters around the sharp upper thermocline features such as the chlorophyll, oxygen, nitrite maxima and the shallow salinity minimum. Salinity, oxygen and nutrients were determined at sea for all depths sampled. Chlorophyll-a and phaeopigments were determined at sea on samples from the top 200 meters, bottom depth permitting.
Ichthyoplankton sampling is done on all survey cruises and processing of these samples is done at the Southwest Fisheries Science Center (SWFSC) laboratory in La Jolla, California. There, plankton displacement volumes are obtained for each sample and the fish eggs, larvae, and juveniles are separated from the invertebrate zooplankton, and subsequently identified, staged, measured. The resulting data form the CalCOFI Ichthyoplankton Data Base. The fish eggs, larvae, and juveniles are archived in the SWFSC Ichthyplankton Collection and the invertebrate plankton is transferred to the Scripps Institution of Oceanography Invertebrate Collection. CalCOFI surveys are the basis for NMFS research on the population biology of the major coastal pelagic fishes (Pacific sardine, northern anchovy, hake, Pacific mackerel, and jack mackerel) of the California Current System.