MORSE: SPAWNING AND FECUNDITY OF ATLANTIC MACKEREL 



1.90 



log F 5 264+0 840llogAI 



N 197 



r 76 



Sy X 084 



FIGURE 6. — Relationship of fecundity and age and the predic- 

 tive logarithmic (base 10) regression for Atiantic mackerel 

 in 1977. 



Observations of spawning times of various 

 temperate-water fish have indicated peak spawn- 

 ing dates may be relatively fixed. Gushing (1969) 

 postulated an indirect link between the fixity of 

 spawning season and the primary production cy- 

 cle. Ware (1977) investigated the relationship of 

 spawning time of Atlantic mackerel at St. Georges 

 Bay, Nova Scotia, to the size and abundance of 80 

 /xm plankton. He found the mean peak egg produc- 

 tion date was 1 July ± 1 wk and coincided with the 

 maximum abundance of summer plankton. It 

 would appear, at least for the southern contingent, 

 that the time of peak spawning is more variable 

 than that indicated for St. Georges Bay. Sette 

 (1943) determined maximum spawning occurred 

 during mid-May (1928-32) off Middle Atlantic and 

 southern New England States. Ichthyoplankton 

 surveys during the mackerel spawning season in 

 1966 and 1975-77 (Berrien 1978; Berrien et al. see 

 footnote 6; Berrien and Anderson') within the 

 Middle Atlantic Bight indicated spawning peaked 

 during May in 1966 and 1975 and during April in 

 1976 and 1977. In fact, eggs were collected as early 

 as 13 April in 1977. Berrien and Anderson (see 

 footnote 7) attribute the April 1976 spawning 



Bemen, p. L., and E. D. Anderson. 1976. Scomber scom- 

 brus spawning stock estimates in ICNAF Subarea 5 and Statisti- 

 1Q7C T ^' ^sed on egg catches during 1966, 1975, and 

 ly/b. Int. Comm. Northwest Ati. Fish., Res. Doc. 76/XII/140 

 i-U p. 



peak to increased water temperatures within the 

 study area. 



The factors controlling the spawning time of 

 Atlantic mackerel are unclear. The regularity 

 shown by Ware (1977) would indicate internal 

 control or a constant external stimulus such as 

 photoperiod. Sette (1943) presented evidence indi- 

 cating water temperature is a limiting factor con- 

 trolling migration and in turn the timing of 

 spawning in a fixed location. Gushing ( 1967, 1969) 

 suggested that some fish spawn at a relatively 

 fixed date that is linked to planktonic productivity 

 and that changes in plankton production would 

 cause dramatic changes in year-class success. It 

 appears that a variable spawning date, as shown 

 by the southern contingent— linked to the factors 

 affecting plankton productivity, e.g., tempera- 

 ture, photoperiod, nutrient content— would in- 

 crease the chances for larval survival. 



The fecundity estimates presented here must be 

 considered as maximum potential egg production 

 because, as reported by Macer (see footnote 3), 

 resorption may significantly reduce the number of 

 eggs spawned. Preliminary observations by Macer 

 indicated an average of 11.4% ofyolked eggs were 

 being resorbed. Bara (1960) observed degc lera- 

 tion in a "few" mature eggs though no quantita- 

 tive data were presented. Studies are needed to 

 define the extent and possible annual changes of 

 resorption rates and their relationship to fecun- 

 dity. 



ACKNOWLEDGMENTS 



I wish to thank Darryl Ghristensen and others 

 who provided samples from the recreational 

 catches throughout the course of this study. I ap- 

 preciate the critical reviews and comments by E. 

 Anderson and S. J. Wilk. Special thanks to M. 

 Montone for typing this manuscript and M. Gox for 

 preparation of the figures. 



LITERATURE CITED 



Bara, G. 



I960. Histological and cytological changes in the ovaries 

 of the mackerel, Scomber scombrus L., during the annual 

 cycle. Rev. Fac. Sci. Univ. Istanbul, Ser. B, 25:49-86. 

 BERRIEN, P. L. 



1975. A description of Atiantic mackerel. Scomber scom- 

 brus, eggs and early larvae. Fish. Bull., U.S. 73:186-192. 

 1978. Eggs and larvae of Scomber scombrus and Scomber 

 japonicus in continental shelf waters between Mas- 

 sachusetts and Florida. Fish. Bull., U.S. 76:95-115. 



107 



