RECORD OF THE LARVAE OF THE JACK MACKEREL 

 ( TRACHURUS SYMMETRIES ). 1955 



The distribution and relative abundance of jack mackerel larvae are 

 shown in figure 5. The categories of abundance are identical to those al- 

 ready described for sardine larvae; individual station values represent the 

 cumulative standard haul total for the year. 



The larvae are recorded by size classes in table V. They have the 

 following midpoints and ranges: 



The data are summarized in text table 6 by month and area. There 

 were no occurrences of jack mackerel larvae off southern Baja California, 

 and only 1.7% of the larvae was taken off lower central Baja California. 

 The greatest abundance occurred off southern California (43.2% of total), 

 and the next highest abundance was in the adjoining area to the south. 



Latitudinal changes in distribution month by month were more marked 

 than in previous years (cf. Ahlstrom and Ball 1954, tables 7 and 8). No 

 larvae were obtained during January. In February, most larvae were taken 

 in the area off Cedros Island (lines 110-120). Larvae were moderately 

 abundant during a five-month period in this area, with the peak occurring 

 in April. The peak also occurred in April off northern Baja California. 

 Larvae were uncommon off southern California until May, and a marked peak 

 occurred in June. No larvae were obtained off central California in May, 

 but fair numbers were taken in June and July. There was only one occurrence 

 after July on the regular survey cruises. 



The interesting distribution found on "Norpac" (cruise 5508) has been 

 commented upon by Ahlstrom (1956: 39, fig. 19): jack nackerel eggs and 

 larvae were taken as far north as Washington, and as far offshore as 150° 

 W. longitude (over 1000 miles offshore). The egg and larval collections 

 taken by Pacific Oceanic Fishery Investigations (POFI) on "Norpac" have been 

 examined subsequently to determine if jack mackerel eggs and larvae occurred 

 in the area between 155°-180° W. longitude, and 40°-50° N. latitude. None 

 were found. 



55 



