ASPECTS OF REPRODUCTION OF THE BLUE MUSSEL, 



MYTILUS EDUUS (PELECYPODA: MYTILIDAE) 



IN LONG ISLAND SOUND 



Diane J. Brousseau 1 



ABSTRACT 



A population of Mytilus edulis in Long Island Sound, Fairfield, Conn., was studied for 2 years to determine the 

 sequence of gametogenic development of gonadal tissue and the frequency and duration of spawning under 

 natural conditions. This population spawned annually in May- June. "Dribble spawning" occurred during the 

 winter months of 1982. Sexes were distinguishable in all size classes studied, except those individuals in an 

 "inactive" condition (stage 0). A low incidence of simultaneous hermaphroditism suggests thatM edulis is a 

 stable gonochoric species. There was no evidence of protandry. Sex ratios ofM. edulis 26.0-72.1 mm shell 

 length did not differ significantly from 1:1. Photomicrographs of the gametogenic cycles of both male and 

 female mussels are included. 



The edible blue mussel, Mytilus edulis, is a widely dis- 

 tributed species, common to littoral and shallow sub- 

 littoral habitats in boreal and temperate waters of 

 both Northern and Southern Hemispheres. The 

 literature on the reproduction of M. edulis is exten- 

 sive, probably because of the species' ubiquity in 

 nature, as well as its commercial value (see Bayne 

 1976). Most of the studies have been done on Euro- 

 pean populations of M. edulis, which, in general, are 

 characterized by extended spawning seasons with 

 gamete release possible throughout the year (Lebour 

 1938; Lubet 1957; Havinga 1964; Andreu 1968; Jen- 

 sen and Sakshaug 1970). 



Limited information on North American pop- 

 ulations suggests that although spawning can occur 

 throughout the year (Moore and Reish 1969), the 

 majority of the populations have a well-defined 

 breeding season. On the basis of a 6-mo study (April- 

 September) of the larval settlement period of M. 

 edulis, Loosanoff and Engle (1944) concluded that 

 the spawning period for blue mussels in Long Island 

 Sound is May- August. Similarly, Hrs-Brenko (1971), 

 after a 5-mo study (March-July) involving the 

 examination of gonadal tissue, concluded that the 

 spawning season of blue mussel in the southwestern 

 part of Long Island Sound occurred with a single 

 release of gametes during May and June. Since 

 neither study followed the reproductive cycle for an 

 entire year, however, it is difficult to draw con- 

 clusions about the annual spawing cycle of blue 

 mussels in this locale. 



'Department of Biology, Fairfield Universitv, Fairfield, CT 

 06430. 



In the most complete study to date in the Long 

 Island Sound region, Newell et al. (1982) concluded 

 that M. edulis from Stony Brook, Long Island, 

 (southeastern shore of Long Island Sound) spawn in 

 the spring, while they noted that a population at the 

 same latitude on the southern shore of Long Island 

 spawns 3 mo later. Clearly, it is difficult to make 

 generalizations about the spawning behavior of 

 this species. 



In an attempt to more clearly define the breeding 

 habits of M. edulis in Long Island Sound, the results 

 of a 2-yr study to determine 1) the age of maturation 

 and annual gametogenic development in a natural 

 population and 2) the frequency of spawning of blue 

 mussels along the southwestern shore of Long Island 

 Sound are presented in this paper. 



MATERIAL AND METHODS 



Monthly collections of M. edulis were made from the 

 mouth of Southport Harbor in Fairfield, Conn., (lat. 

 41°08'N, long. 73°17'W) from September 1980 to 

 January 1982 and March 1982 to August 1982 (Fig. 

 1). In February 1982, two sampling collections were 

 made, one in the beginning of the month and the 

 other at the end. Sample sizes varied from 18 to 25 

 mussels, 26.0-72.1 mm shell length. A total of 534 

 mussels were examined and used in the analysis of 

 the reproductive cycle. 



In the laboratory, M. edulis samples were num- 

 bered, their maximum length (±0.1 mm) measured, 

 and their gonad color noted. A section of the mantle 

 with gonad was removed and fixed in 10% buffered 



Manuscript accepted May 1983. 



FISHERY BULLETIN: VOL. 81, NO. 4. 1983. 



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