ABUNDANCE AND DISTRIBUTION OF EGGS AND LARVAE AND SURVIVAL 

 OF LARVAE OF JACK MACKEREL (TRACHURUS SYMMETRICUS) 



By David A. Farris, Fishery Research Biologist 

 Bureau of Commercial Fisheries 



The purposes of this study are to delimit both 

 spatially and temporally the spawning of the 

 jack mackerel, Trachurus symmelricus (Ayxes) 

 1885, and to estimate the abundance of the 

 eggs and the survival rate of the larvae. Quan- 

 titative data collected on monthly cruises of the 

 California Cooperative Oceanic Fisheries Investi- 

 gations, 1951 through 1954, are utilized in the 

 study. 



Data derived from the stud}^ of eggs and larvae 

 may give insight into the present abundance and 

 future fluctuations of the adult population, and 

 estimates of larval mortalitv' may aid in predict- 

 ing future recruitment to the fishery. With 

 knowledge of the fecundity, estimates of egg 

 abundance may be used to ascertain the present 

 size of the adult population. These data may 

 also be compared vni\\ phj'sical, chemical, and 

 other biological data gathered by the California 

 Cooperative Oceanic Fisheries Investigations. 



To accomplish the stated purposes of this study, 

 the following information was needed: 



1. Boundaries of the area occupied by devel- 

 oping eggs and larvae. 



2. Seasonal distribution of the eggs and larvae 

 within those boundaries. 



3. Quantitative depth distribution of the eggs 

 and larvae. 



4. Relation between temperature and rate of 

 development of eggs and larvae. 



The author appreciates the help and encourage- 

 ment given him by E. H. Ahlstrom, D. E. 

 Wohlschlag, and John C. Marr during the course 

 of this study; the assistdnc* of O. E. Sette in the 

 preparation of the manuscript; and the valuable 

 advice of Bruce Taft in the preparation of the 

 statistical portion of this paper. George Mattson 

 prepared most of the figures. Also, without the 



help of members of the Cahfornia Marine Re- 

 search Committee and its cooperating agencies 

 and the staff of the South Pacific Fishery In- 

 vestigations ' this study could not have been 

 undertaken. The laborious proofreading was 

 done by Mrs. Paula K. Farris. 



REVIEW OF THE FISHERY 



The carangids most commonly found in the area 

 surveyed by the California Cooperative Oceanic 

 Fisheries Investigations are listed by Barnhart 

 (1936) and Fowler (1944). The family is largely 

 tropical or subtropical in its distribution, Tra- 

 churus symmetricus being a notable exception. 

 Only three members of the family are taken in any 

 numbers by the California Cooperative Oceanic 

 Fisheries Investigations: yellowtail, Seriola dor- 

 mlis Gill; Mexican scad, Decapferu.<t hypodufs Gill; 

 and jack mackerel, TrachuruN syinmetncus (Ayres). 

 The larvae of all tliree species are known, so that 

 identification is possible. The yellowtail and jack 

 mackerel are the only carangids of any economic 

 importance in the area (Clothier and Greenhood, 

 1956). 



Well over 80 percent of the jack mackerel fishery 

 is located in waters off southern California (i.e., 

 from Point Conception to the Mexican border). 

 In some j-ears 99 percent of the catcli is made in 

 this region. Less than 1 percent of tlie total catch 

 is taken in waters as far north as Eureka, Cali- 

 fornia (i.e.. Point Conception to Evu-eka). 



Before 1947 the jack mackerel catch never ex- 

 ceeded 7,550 tons (Rocdol, 1949: p. 31-32), and 

 since then it has not fallen below that figure. Dur- 

 ing 3 years, 1947, 1950, and 1952, the catch ex- 

 ceeded 62,500 tons. The fluctuations of the jack 

 mackerel catch more or less complement fluctua- 

 tions in the sardine catch (Clothier and Greenhood, 



-Note— The author's official address is San Diego State College, San Diego, 

 Cali/omia. 

 Approved for publication. May 25, 1959. Fishery Bulletin 187. 



' Presently the Bureau of Commercial Fishoriis Biological Laboratory. 

 La Jolla, Calif. 



247 



