FISHERY HULl.KTIN: VOL. 86, NO 1 



ture = 12.0°C). Where no significant differences 

 in growth were found, i.e., between LA and TX 

 February 1982 samples, the respective mean 

 water temperatures were 14.7° and 14.4°C. Nei- 

 ther of those growth curves were significantly dif- 

 ferent from the curve for larvae from the FL 

 February 1982 sample where the mean water 

 temperature was 16.4°C. However, the paucity of 

 larvae >23 days old caught off Florida in Febru- 

 ary 1982 (Fig. 7d) suggests that comparisons of 

 that data set with the data sets for larvae caught 

 off Louisiana and Texas in February 1982 would 

 be of little value. 



The estimated spawning period for gulf men- 

 haden extended from mid-October to mid- 

 February (Fig. 8). These results agree with Fore 

 (1970) and Christmas and Waller (1975) who, 

 using the occurrence of eggs and larvae, esti- 

 mated that gulf menhaden spawned from mid- 

 October through March. Gonad weight-body 

 weight ratios of adults (Lewis and Roithmayr 

 1981) and morphological and physiological fea- 

 tures of ovarian tissue (Combs 1969) also indicate 

 that spawning extends from October to early 

 March. Based on the movement of late larvae into 

 Lake Pontchartrain, Suttkus (1956) presumed 

 that gulf menhaden spawning began in October 

 and ceased in February. He suggested that the 

 beginning and end of the spawning period fluctu- 

 ates from year to year, and that there is no spawn- 

 ing activity during the spring and summer 

 months as Higham and Nicholson (1964) have 

 reported for the closely related Atlantic men- 

 haden. 



Most larvae caught in December were spawned 

 in November (Fig. 8) regardless of the year. Lar- 

 vae caught in February were spawned mostly in 

 January but estimated spawning dates extended 

 from mid-December to mid-February. For any 

 given cruise, larvae from off Texas and Louisiana 

 were spawned at about the same time. There was 

 also considerable overlap in the spawning dates 

 in any cruise off Florida and the other areas. The 

 distribution of the central 507^ of spawning dates 

 from the Louisiana sample in February 1980 ex- 

 tended over a 29-d period and was wider than for 

 any other data set. This unusually wide distribu- 

 tion may have been due to the presence of two 

 distinct cohorts, one spawned in late December 

 and one in late January, collected on the Febru- 

 ary 1980 cruise. Combs (1969) found that this 

 species had intermittent total spawning. Lewis 

 and Roithmayr (1981) inferred that gulf men- 

 haden were intermittent, or fractional spawners. 



Christmas and Waller (1975) noted a modal tem- 

 poral distribution of eggs in the region from the 

 Mississippi delta to east of Cape San Bias. Bal- 

 dauf sampled young menhaden in the lower 

 Neches River, TX, from November through April 

 and found two incoming populations from which 

 he suggested that there may have been two 

 spawning peaks. Only in the larval collections of 

 December 1981 did spawning date distribution 

 appear to be bimodal; 7 and 20 November for Lou- 

 isiana and 8 and 19 November for Texas. Future 

 sampling throughout the spawning season will be 

 necessary to determine the seasonal periodicity 

 and peaks of gulf menhaden spawning. Relative 

 numbers of larvae in cohorts within the spawning 

 season could then be compared with measure- 

 ments of environmental conditions as a test of the 

 match-mismatch hypothesis (Cushing 1975) and 

 to further test, as Methot (1983) has done, 

 whether larvae spawned during favorable envi- 

 ronmental periods constitute the greatest per- 

 centage of the year class. 



ACKNOWLEDGMENTS 



I thank the following persons of the Beaufort 

 Laboratory: M. Boyd who extracted, mounted, 

 and aged otoliths, W. Hettler who spawned gulf 

 menhaden and furnished eggs for the laboratory 

 experiments, A. Chester who advised on statisti- 

 cal procedures and problems, D. Ahrenholz and 

 A. Powell who reviewed early drafts of the 

 manuscript, and the crew and scientists on the 

 RV Oregon II cruises. P. Ortner of the Atlantic 

 Oceanographic and Meteorological Laboratories, 

 NOAA, Miami, FL, provided raw data from which 

 zooplankton counts were summarized. This re- 

 search was supported by a contract from the 

 Ocean Assessments Division, National Ocean 

 Service, NOAA. 



LITERATURE CITED 



Bernard. D R 



1981. Multivariate analysis as a means of comparing 

 growth in fish. Can. J. Fish. Aquat. Sci. 38:233-236. 

 Campana, S. E., and J D. Neilson, 



1985. Microstructure of fish otoliths. Can. J. Fish. 

 Aquat. Sci. 42:1014-1032. 

 Christmas. J Y , and R S Waller. 



1975. Location and time of menhaden spawning in the 



4Baldauf R. J. 1954. Survey and study of surface and sub- 

 surface conditions in and around Beaumont, Texas. Biological 

 survey of the Neches River in the region of Beaumont, 

 Texas. Texas A&M Res. Found., Mimeo. Rep., 184 p. 



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