234 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



United States fishermen, this study was largely 

 limited to an investigation of that stock and fol- 

 lowing comments apply to it. 



1. Landings from the southern New England 

 stock declined from 63 million pounds in 1942 to 

 10 million pounds in 1949. During this same 

 period, landings from Georges Bank stock in- 

 creased from 2 million pounds to 16 million. 



2. Between 1943 and 1947 a total of 37,075 fish 

 were selected randomly from the landings and 

 measured and their sex recorded. Females were 

 twice as numerous in the catch as males. The 

 mean length of both sexes was 35.69 cm., with 

 males averaging 33.34 cm. and females 37.21 cm. 

 There was no trend toward smaller fish in the 

 landings between 1942 and 1947; however, later 

 reports show that such a trend developed after 

 1951. 



3. The length-weight relation, by sex and quar- 

 ter, was determined for 1,113 yellowtail taken 

 from the landings during 1943. Regression 

 formulas were used to estimate the weight of each 

 sex at the mean length of 35.869 cm., and the fe- 

 males were consistently the heavier — this differ- 

 ence between the sexes probably being even 

 greater at onset of spawning in early April. Dif- 

 ferences in the length-weight relation among the 

 quarters also Avere considerable, and yellowtail of 

 average length of both sexes were heaviest in the 

 first quarter of 1943 and lightest in the third. 



4. Data collected by quarters on the catch by 

 area and time fished from about 30 percent of the 

 landings revealed that the catch per day was 

 greatest during the third quarter of the year. De- 

 spite this seasonal fluctuation, the change in ap- 

 parent relative abundance as reflected in the catch 

 per unit of effort approximately paralleled the 

 downward trend in the catch during the years 

 1942 through 1949. 



5. Growth data were developed from the at- 

 tained length at time of capture of 9,204 yellow- 

 tail for which the ages were determined from 

 scales. The females attained a greater length 

 than the males of the same age, being 4.5 percent 

 longer than the males at age 2 and up to 9.1 per- 

 cent longer at age 5. The mean lengths of both 

 sexes for comparable quarters revealed no upward 

 or downward trend in length and only a slight 

 change in growth rate from 1942 to 1947. Scale 

 readings indicated an unusual rate of growth in 



the young yellowtail. The first year's growth ap- 

 pears to be only from 3 to 5 cm., whereas during 

 the second year the juvenile attains a length of 

 nearly 30 cm. 



6. There was no trend toward a greater propor- 

 tion of young fish in the catch between 1942 and 

 1947. The average age composition of yellowtail 

 in the landings, in numbers of fish, was 1.3 per- 

 cent 1-year-olds, 28.1 percent 2-year-olds, 35.5 

 percent 3-year-olds, 19.3 percent 4-year-olds, 9.6 

 percent 5-year-olds, 5.1 percent 6-year-olds, and 

 1.0 percent 7-year-olds and older. 



7. The estimated total mortality rate among 

 yellowtail completely available to the fishery was 

 86 percent a year. 



8. Study of the age and length at maturity of 

 288 fish taken at random from the landings at the 

 peak of the spawning season in May 1943 revealed 

 that most yellowtail of both sexes mature during 

 their second or third year of life. Of the females 

 aged, 52 percent were mature at 2 years and 100 

 percent at 4 years or more; of the males, 84 per- 

 cent were mature at 2 years and 100 percent at 4 

 years or older. Most males mature before enter- 

 ing the fishery and mostly before they attain 26 

 cm., while 50 percent of the females in the land- 

 ings were mature at 31.98 cm. and 90 percent at 

 40.17 cm. The catch during the spawning season 

 in 1943 included only 6 percent immature males 

 and 16 percent immature females. 



9. Examination of the ovaries of 1,157 females 

 sampled periodically from the landings in the 

 spring of 1943 revealed that 90 percent of the fish 

 spawned between April 12 and June 26, and that 

 the peak of spawning was May 20. The period 

 of heaviest spawning was from May 4 to June 4 

 during which 50 percent of the females became 

 spent. 



10. We were unable to collect either eggs or 

 larvae of the yellowtail during our investigations, 

 but Sette (1943) recorded considerable data rela- 

 tive to these stages during his mackerel investiga- 

 tions in 1929 and 1932. During those earlier 

 surveys, eggs and larvae of the southern New 

 England yellowtail were found to be abundant 

 over most of the Continental Shelf off New York, 

 New Jersey, and Delaware — much farther south- 

 west than the center of the fishery during the 

 spawning seasons from 1942 to 1949. 



