FISHERY BULLETIN: VOL. 80, NO. 4 



Proportions of male, female, and nonspawning 

 sandworms of various lengths are shown in Fig- 

 ure 3. There is an increase in numbers of mature 

 males and females with increasing size. Worms 

 >30 cm show a preponderance of mature females 

 over mature males. More than 30% of the largest 

 worms showed no sign of sexual development. 



Oocyte Development 



The results of oocyte growth studies are pre- 

 sented in Figure 4A, and water temperatures 

 associated with these data are shown in Figure 

 4B. Eggs of about 50 ^ were first observed in 

 the coelom in October-November. Diameter in- 

 creased from 80 to 160 m during the rapid-growth 

 phase which occurred between August and De- 

 cember. Prior to spawning, the rate of egg 

 growth decreased. Maximum mean egg diame- 

 ters obtained were 183 /x (1967) and 194 M (1968). 

 A Student's t-test revealed a significant differ- 

 ence between these mean diameters (t = 4.65910; 

 P<0.05; 14 df). Spawning occurred in April and 

 May during a 4-5 wk period, and few egg-bearing 

 worms were found after the beginning of June. 

 The maturation of gametes required 18-20 mo, or 

 as little as 12 mo, depending upon when the eggs 

 were ovulated into the coelom. Annual spawning, 

 together with a maximum development period of 

 18-20 mo, accounted for the presence of two gen- 

 eral egg sizes in sandworms inspected between 

 October-November and April-May. Eggs ap- 



proaching spawning size varied the least in di- 

 ameter (the smallest standard deviation) (see 

 Figure 4A). During the period of rapid egg 

 growth, both mud and bottom river tempera- 

 tures were decreasing (see Figure 4B). 



Numbers of Eggs Laid 



The numbers of eggs laid by sandworms of 

 various lengths are recorded in Figure 5. The 

 range varies between about 0.05 and 1.3 million 

 eggs for worm lengths of 16 and 54 cm, respec- 

 tively. 



Environmental Conditions During 

 Spawning 



Spawning first occurred in the Wiscasset re- 

 gion on 28 April 1967 and 17 April 1968. A sum- 

 mary of hydrographic conditions associated with 

 spawning on 2 May 1967 and 19 April 1968 is 

 presented in Table 1. Table 1 shows that mean 

 surface-water temperatures of 7.0°C (1968) and 

 8.1°C (1967) and bottom water temperatures of 

 6.7°C (1968) and 7.6°C (1967) were associated 

 with the onset of spawning. During both years, 

 initial activity in the Wiscasset area occurred 

 4 d after full moon during the period of spring 

 tides. The stage of the tide during which spawn- 

 ing activity occurs was investigated on 23 April 

 1968, using scuba techniques. During a series of 

 six dives beginning just after high water (08:28 



LENGTH ,CM 



Figure 3.— Proportions of male, female, and nonspawning sandworms of various lengths col- 

 lected prior to spawning during February 1967. 



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