Table 3. — Condition factors of ocean and laboratory-reared specimens of Pacific mackerel 



^From Fitch (l95l). 



^Reared at BCF Fishery-Oceanographj- Center, La Jolla, Calif. 

 December 28, 1966. 



Hatched June 20, 1966, died 



3.53 Response to stimuli 



Pacific mackerel are attracted to nightlights, 

 either as a response to the lights or to the food 

 attracted by the lights. 



4 POPULATION 



4.1 Structure 



4, 1 1 Sex ratio 



Unpublished data from the California De- 

 partment of Fish and Game assumes a 50-50 

 ratio of male to female (see footnote 4). 



4.12 Age composition 



See 3.31. 



One-year-old fish do not spawn, but most 

 2-year-olds and all older fish do (see 3.12). 



4.13 Size composition 



The length composition of the catch for each 

 age group for the seasons 1939-40 through 

 1963-64 was as follows: 



Range of length (mm.) by age group 



I n III IV 



168-332 218-385 235-392 278-405 282-400 



V VI VII VIII IX 



315-410 332-422 330-430 362-425 385-415 



Fish at 7 years (6-f) were collected in the 

 1964-65 to 1966-67 seasons. 



4.2 Abundance and density (of population ) 



No data available. 



4.3 Natality and recruitment 

 No data available. 



4.4 Mortality and morbidity 



From analysis of tagging results, Fitch 

 (1952) calculated that the mortality rate for 

 the Pacific mackerel was between 74 and 78 

 percent per year for the seasons 1940-41 

 through 1942-43 (Fitch, 1952). He stated fur- 

 ther that in age studies mortality rates for 

 fish 2 years of age and older were calculated 

 for two 5-year periods, 1938-42 and 1943-47. 

 For the first, the rate was calculated at 48 

 percent between ages 2 and 3, 62 percent 

 between 3 and 4, and 70 percent between 4 and 

 5. For the second period the rate increased to 

 55, 77, and 80 percent per year for 2-, 3-, 

 and 4-year-old fish. 



4.5 Dynamiics of population (as a whole ) 

 No data available. 



4.6 The population in the community and 

 the ecosystem 



No data available. 



II 



