FISHERY BULLETIN: VOL. 80. NO. 4 



first. These free-swimming spawners displayed 

 two characteristic types of swimming behavior: 

 1) Swimming more or less in a straight path (with 

 occasional tumbling and back swimming) with 

 typical lateral undulations of the body, and 2) 

 swimming in circles typically 10-15 cm in diame- 

 ter. Spawning worms appeared to be distributed 

 randomly over the flats. During peak spawning, 

 the density of worms observed swimming near 

 the surface of the mud was about 1 worm/m 2 . All 

 male spawners collected in the Wiscasset area 

 were definitely epitokous individuals, having 

 undergone morphological changes. Mature fe- 

 male sandworms dug from the flats were typi- 

 cally dark green, males that had just emerged to 

 spawn were lighter green, and males that were 

 "spawned out" but still swimming were a dark, 

 bluish green. Some male sandworms may spawn 

 during more than one tide. Numerous male sand- 

 worms were observed burrowing back into the 

 flats during scuba dives. None, however, bur- 

 rowed deeply into the mud. The reproductive 

 strategy of the sandworm qualifies it as a "mono- 

 telic" species, i.e., it breeds once in its lifetime, all 

 gametes are released in one or two large batches, 

 and the spent animals die immediately or shortly 

 afterwards without developing more gametes 

 (Clark cited in Stancyk 1979). Some nearly 

 "spent" individuals were observed to contain 

 large numbers of a parameciumlike ciliate. 



Predation 



During receding tides in the Wiscasset vicinity 

 during April, an increasing number of herring 

 gulls, Larus argentatus Pontoppidan, circling 

 the flats, anticipated the ensuing spawning activ- 

 ity of Nereis virens. At the height of spawning, 

 thousands of gulls could be observed feeding on 

 male spawners. 



DISCUSSION AND CONCLUSIONS 



Salinity and Temperature of 

 the Sandworm Habitat 



The salinity and temperature regime encoun- 

 tered by Nereis virens in other geographical 

 areas is incomplete. Brafield (1968) 7 indicated 

 that water and interstitial salinity encountered 



7 A. E. Brafield, Department of Biology, Queen Elizabeth 

 College (University of London), Campden Hill Road, London, 

 England, pers. commun. 1968. 



by the Southend, England, sandworm popula- 

 tion varied between 28-32%o and 27.5-31.5% . and 

 water temperature varied between 3.2°C (Janu- 

 ary) and 22.5°C (August). The Wiscasset popula- 

 tion is subjected to more estuarine salinity condi- 

 tions and cooler water temperatures than in 

 England. The temperatures recorded for Brandy 

 Cove, New Brunswick, by Snow (1972) are very 

 similar to the temperatures recorded in Figures 

 1 and 4B. 



Length-Related Observations 



The concave nature of the length-frequency 

 data presented in Figure 2 is consistent with a 

 highly variable recruitment pattern resulting 

 from larval mortality and intense predation soon 

 after settlement (Warwick cited in Coull 1979). 



The absence of sexual products in the coelom of 

 a proportion of the largest sandworms (see Fig. 

 3) appears to be characteristic of the species. 

 Both Snow and Marsden (1974) and Brafield and 

 Chapman (1967) have made similar observa- 

 tions. The fate of these large nonspawners is not 

 known. They possibly emigrate to subtidal or 

 downriver habitats or succumb to natural or dig- 

 ging mortality without spawning. 



Considerable variation exists in the maximum 

 size of Nereis virens reported from different geo- 

 graphical locations. The largest individual re- 

 ported in Figure 2 was 31 cm. Sandworms of 70- 

 75 cm (anesthetized length) have been dug from 

 the Back River in Boothbay, Maine (lat.43°54' 15" 

 N, long. 69°40' W). Sveshnikov (1965) reported 

 catching epitokous individuals 45 cm in length 

 and also reported that the heteronereid form of 

 N. virens reached a length of 90 cm along the 

 coast of England and 1 m in Japan. Khlebovich 

 (1963) reported mature individuals reaching 

 38.5 cm in the White Sea. 



The sex ratio of Nereis virens collected prior to 

 spawning varies with geographical location. In 

 our studies, the sex ratio of small potential spawn- 

 ers was approximately 1 female: 1 male, whereas 

 the sex ratio of individuals >30 cm was approxi- 

 mately 2 females: 1 male. There is no reason to 

 believe that these changes in sex ratios with size 

 result from nonspawners (in February) becom- 

 ing sexually mature by spawning onset in April. 

 Our observations reveal that the maturation rate 

 of both eggs (see Figure 4A) and sperm requires 

 considerably more than 2 mo. The change in sex 

 ratio may indicate that larger potential males 

 are more disposed to either free-swimming in the 



740 



