FISHERY BULLETIN: VOL. 76, NO. 2 



season advances, so that by the end of the season 

 the catch is composed almost entirely of this age- 

 group. The considerable variation in the relative 

 numbers of the two major age-groups from year to 

 year is probably a reflection of the differences in 

 the relative abundance of each year class. Small 

 numbers of a third age-group of still younger fish 

 may enter the fishery in some years in August or 

 September. 



Juvenile Tagging 



An advantage of tagging juveniles is that the 

 age of each fish is known when it is recaptured. 

 Unfortunately, recovery of some tags a year or 

 more after they had entered a plant caused some 

 fish to appear older at the time of recapture than 

 they actually were. Although the number was rel- 

 atively small, it had an important bearing on in- 

 ferences pertaining to longevity and the propor- 

 tion of older fish in the catch. 



By the end of the 1974 fishing season 1,137 field 

 tags had been recovered (Table 2). Of these 1,069 

 (94.0%) were recovered in the 2 yr following tag- 

 ging, 62 (5.5%) in the third year, and 6 (0.5%) in 

 the fourth year. Only tags applied in 1970 had an 

 opportunity to be recovered in the fourth year, and 

 only tags applied in 1970 and 1971 had an oppor- 

 tunity to be recovered in the third year. 



The tendency for test tags to remain in plants for 

 one or more years leads us to believe that all field 

 tags recovered in the fourth year and most of those 

 recovered in the third year were holdovers from 

 previous years. All of these tags were recovered at 

 plants that had the highest percentage of test tag 

 holdovers. 



We conclude, therefore, that at least 97% of Gulf 

 menhaden caught in the purse seine fishery are 

 age 1 or age 2, and that very few, probably less 

 than 1% — live to age 3. If ring marks are valid 

 annuli, they also should indicate that the catch is 

 composed primarily of age-1 and age-2 fish. 



Incidence and Spacing of Scale Rings 



The scale length-fish length relation for Gulf 

 menhaden was linear. Correlation coefficients for 

 1971, 1972, and 1973, based on fish ranging from 

 95 to 225 mm FL, was 0.790, 0.765, and 0.768, 

 respectively; for log transformed data the coef- 

 ficients decreased to 0.729, 0.695, and 0.681. Sam- 

 ple sizes were 4,674, 4,457, and 4,902, respec- 

 tively. The regression equation for the 3 yr 



Table 2. — Numbers of field tags of juvenile Gulf menhaden 

 recovered from 10,458 fish tagged in 1970, 15,511 in 1971, 15,262 

 in 1972, by plant. 



combined was: Scale length = 5.392 + 0.865 Fish 

 length. 



Not all fish had scales with clearly discernable 

 rings. The percentage with no rings varied from 

 45.0 to 55.8. Of the fish considered as age 2, <2% 

 had a ring in the number one position only and 

 25.1% in 1971, 39.1% in 1972, and 30.6% in 1973 

 had a ring in the second position only. A relatively 

 small number offish had scales with three clearly 

 discernable rings. 



The length frequencies from May to September 

 of fish with one or two rings clearly indicated two 

 distinct ages. In Tables 3-5 length groups below 

 the first containing fish with both one and two 

 rings have been lumped into one group. For one- 

 ring fish the mode is the group, other than the 

 lumped one, containing the most fish. The only 

 exception is for May 1971 when the mode for fish 

 with one ring was 155 mm. It is clear that the 

 modes and means of one- and two-ring fish in- 

 creased and that the distributions shifted toward 

 larger sizes as the season progressed. 



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