3.44 Metabolism 

 No data. 

 3.5 Behavior 



3.51 Migrations and local movements 



Practically nothing is known about the nni- 

 grations and movements of the population. Very 

 large specimens, to over 76 cm. and 2 l/4 kg. 

 are taken in the inshore waters of, southern 

 California a month or two each summer by 

 sport fishermen. These fish rennain in the 

 area a relatively short time and numbers 

 caught fluctuate greatly from season to season 

 as is shown in the following table (Fitch, 1956), 



Sports catch of jack nnackerel 



3.52 Schooling 



The jack mackerel is a schooling fish, and 

 tends to school by size. It is taken in com- 

 pany with Pacific mackerel and sardines as 

 well as in pure schools. 



3.53 Responses to stimuli 



The jack mackerel is attracted to lights at 

 night, or at least by the food attracted to the 

 lights. 



4 POPULATION 



4.1 Structure 



4.1 1 Sex ratio 



The sex ratio of the catch appears to be 

 about 1:1. 



4.12 Age composition 



Most of the jack mackerel in the comnner- 

 cial catch have been less than 6 years old and 

 the majority either 2, 3, or 4 years. 



Sexual maturity is attained by 50 percent of 

 the female mackerel at age 2 and 100 percent 

 at age 3, 



Very large mackerel, nnore generally taken 

 by the sport fishery, are as old as 30 years or 

 more. 



4.13 Size composition 



Most of the connmercial catch consists of 

 fish 20 to 38 cm. total length. 



Sexual maturity is attained by 50 percent of 

 the female nnackerel at 25 cm. fork length 

 (2 years old) and 100 percent at 35 cm. fork 

 length (3 years old). 



Jack mackerel taken erratically in the salt- 

 water sport fishery range from 45 to over 75 

 cm. total length and to 2.3 kg. These large jack 

 mackerel appear in inshore waters only a 

 month or two during the summer (Fitch, 1956). 



From preserved material fork length was 

 found to equal 1.08 times standard length, and 

 total length was 1.19 times standard length. 



4.2 Abundance and density (of population) 

 No data available. 



4.3 Natality and recruitment 

 No data available. 



4.4 Mortality and morbidity 

 No data available. 



4.5 Dynamics of population (as a whole) 

 No data available. 



4.6 The population in the connnnunity and 

 the ecosystem 



No data available. 



12 



