HUNTER and KIMBRELL: EARLY LIFE HISTORY OF PACIFIC MACKEREL 



2000 - 



1000 r 



500 



100 



50 



^ 10 



£ 



X 



C2 



UJ 



>- 

 cr 



Q 



05 



01 



0.05 



001 



Ln W= -4.660 + (-672l + 6.333 Ln l)°-S'° 



I I h 



I I I 



2 4 6 8 10 20 40 6080100 



STANDARD LENGTH (mm) 



Figure 4. — Relation between dry weight (W) of larval and 

 juvenile Pacific mackerel in milligrams and standard length (L) 

 in millimeters. Points are observed values for individuals >18 

 mm and for larvae <18 mm; points are means for groups of 15 

 larvae. 



stopped, drew back the tail, and held it in a 

 slightly recurved, high amplitude position while 

 the rest of the body remained relatively straight. 



Table 2. — Tail beat frequency and amplitude and speed of 3-5 

 mm larval Pacific mackerel ix = 4.23 ±0.09 mm SL) expressed as 

 a function of standard length. 



Tail beat 



Swimming speed (SUs) 

 Class interval 



18 

 30 

 9 

 3 

 3 

 1 



0.01- 

 1.01- 

 2.01- 

 3.1  

 10.1 



1.0 

 2.0 

 3.0 

 5.0 

 15.0 



E 

 o 



Q 



UJ 

 UJ 

 Q. 

 Ul 



CO 



.3 .4 .5.6.7.8 1.0 2.0 3.0 

 STANDARD LENGTH (cm) 



Figure 5. — Relation between swimming speed and standard 

 length of Pacific mackerel larvae (log^g scales) at 19° C. Each 

 point <2.0 cm is the mean of 15-25 observations. For ^2.0 cm, 

 individual fish were measured. 



Feeding involved driving the tail posteriorly and 

 opening the mouth. Larvae often attacked the 

 same prey two or more times if the previous strike 

 was unsuccessful, and repositioned for subsequent 

 strikes by moving backward. Handling times were 

 negligible because the prey was engulfed instan- 

 taneously. Older Pacific mackerel larvae de- 

 veloped a set of motor patterns for feeding on fish 

 larvae; larvae were seized from the side and car- 

 ried crosswise in the mouth. Larger prey were 

 repeatedly released and grasped until they ceased 



95 



