BRINTON: POPULATION BIOLOGY OF EUPHAUSIA PACIFIC A 



1 1 r 



10 METER TEMPERATURE 



CONTOUR INTERVAL I.O°C 



J I I L 



120° 115° 



Euphausia pacifica 



AVERAGE FOR ALL STATIONS 

 LINES 60-123. CRUISE 5510 



Cc 1000 



UJ 



CD 



500- 



E AVERAGE FOR SOUTHERN AREA ONLY. 

 LINES 80-93. CRUISE 5510 



October 1955 ( Cruise 5510) 



2 4 6 8 10 12 14 16 18 20 22 

 BODY LENGTH (mm) 



Figure l.-October 1955 data (cruise 5510). a, Surface streamlines showing areas of current reversals off California and b, 10-m 

 temperatures indicating upwelling centers along Baja California, both associated with c, aggregations of Euphausia pacifica larvae. 

 Length-frequency distributions of E. pacifix:a are averages for d, all nighttime stations and e, stations within southern California area. 



The length-frequency (L-F) diagram for E. 

 pacifica in the California Current as a whole 

 (cruise 5510) shows four modes present in the 

 overall population: 3-4 mm (larvae), 7-8 mm, 10-12 

 mm, and 15-16 mm (Figure Id). Time progressions 

 in such modes are used below to estimate popula- 



tion development, including growth and mortality. 

 The southern California part of the population is 

 characterized by small (10-12 mm) and large adults 

 (15-16 mm). It will be shown below that each of 

 these two October 1955 modes is distinguishable 

 within a month-to-month L-F sequence of cohort 



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