Fisheries, the latter by the Scripps Institution 

 of Oceanography. 



The methods and equipment for taking plank- 

 ton hauls have been standard since 1951. The 

 nets, constructed of No. 30 xxx grit gauze (an 

 extra heavy silk bolting cloth) are 1 meter in 

 diameter at the mouth and about 5 meters in 

 length. The hauls are oblique from approxi- 

 mately 140 meters deep to the surface (depth 

 of water permitting). This has been our 

 standard method of taking plankton tows since 

 1951, so volumes are compared only with those 

 taken from 1951 through 1958. During 1949 and 

 1950 the tows were taken from depths of about 

 70 meters to the surface (depth of water per- 

 mitting). 



The method used for determining the wet 

 plankton volume of a sample by displacement 

 is as follows: The plankton is separated from 

 its preserving liquid (3-percent formalin) by 

 filtering, allowed to drain, then placed into a 

 graduated cylinder to which is added a known 

 volume of 3-percent formalin. Two volumes 

 are obtained for each sample: (1) the total 

 volume of all plankton material and (2) the 

 volume of smaller organisms after removal 

 of larger organisms, such as jellies, fish, 

 squid, salps, pyrosomes, larger mollusks, 

 and larger crustaceans. "Larger" organisms 

 are those with individual volumes greater than 

 5 cubic centimeters (except juvenile or adult 

 fish). 



The portion of the CalCOFI survey area 

 most consistently occupied during the years of 

 the surveys lies between Point Conception, 

 California and Point San Juanico, Baja Cali- 

 fornia, station lines 80-137 (fig. 1). This area 

 has been divided into two approximately equal 

 parts (80-107 and 110-137) for convenience 

 in comparing 1959 plankton volumes with those 

 of earlier years. 



Coverage in these areas was usually made 

 at monthly intervals, during the period of 

 heavy sardine spawning, in the first 7 months 

 of the year, and less frequently during the 

 remaining 5 months of each year. 



northern Baja California (lines 80-107) for the 

 years 1951 through 1959 are given in table 3. 

 The months of August and September were not 

 included for comparison in the northern area 

 because of inadequate coverage during recent 

 years. Except for June, July, and October, the 

 monthly averages during 1959 were smaller 

 than during any of the preceding years. Similar 

 information for the southern area (lines 110- 

 137) is given in table 4. The last 2 months of 

 the year are omitted because of lack of con- 

 sistent coverage. 



The 1959 plankton volumes are compared 

 graphically with the average plankton volumes 

 taken between 1951 and 1956, and with those 

 taken during 1958. The year 1957, not included 

 in figure 2, appears to be a transition year 

 between the years of high and low plankton 

 volumes. 



In the northern area (lines 80-107) average 

 plankton volumes during the 6-year period 

 (1951-56) were greatest during the summer 

 months. The 1958 and 1959 plankton volumes 

 followed the same trend (on a reduced scale), 

 averaging only one-third the average plankton 

 volumes taken during 1951-56. The compara- 

 tively high plankton volumes taken in this area 

 during October 1959 were due to an influx of 

 tunicates (primarily small salps) in the south- 

 ern California region. Tunicates declined again 

 during November and December, and the 

 average plankton volumes were the smallest 

 on record. 



In the southern area (lines 110-137) the 

 plankton volumes were the smallest on record. 

 In only 4 of the 10 months were smaller 

 volumes recorded previously, these in 1958. 



The principal table in this report (table 5) 

 serves a twofold purpose. It is (1) a record of 

 basic information for all plankton hauls made 

 during 1959, and (2) a record of the volume of 

 plankton obtained in each haul. The information 

 given for each plankton haul includes station 

 number, position, date and time of collection, 

 volume of water strained, depth of haul, and 

 plankton volume. 



Average monthly plankton volumes in the 

 area off southern California and adjacent 



The distribution charts in this report are 

 based on the volume of smaller organisms. 



