Table 18. — The upper and lower confidence limits about the slope (b) of bloodworm and sandworm length-weight regressions. 





Slope 



1 SEoffc 



1.96 SE of 6 



95% 



confidence limits 



95% 



confidence limits 





(b) 



(68% confidence limits) 



(95% confidence limits) 



about 6-upper range 



about b-lower range 









Bloodworms 











Males (all areas) 



2.20052 



+ 0.09987 



±0.19974 





2.40314 





1.99789 



Females (all areas) 



2.34133 



±0.07225 



±0.14450 





2.53256 





2.15010 



All areas all sexes 



2.32236 



±0.01573 



±0.03146 





2.35319 





2.29153 



combined 

















Eastern Maine 



2.42910 



+ 0.03297 



+ 0.06594 





2.49373 





2.36447 



Sheepscot River 



2.28381 



±0.02636 



±0.05272 

 Sandworms 





2.33549 





2.23214 



Males (all areas) 



2.24379 



+ 0.04789 



+ 0.09578 





2.33766 





2.14993 



Females (all areas) 



2.21353 



+ 0.04627 



+ 0.09254 





2.30422 





2.12283 



All areas all sexes 



2.23996 



±0.02022 



±0.04044 





2.27960 





2.20033 



combined 

















Eastern Maine 



2.40194 



+ 0.02786 



+ 0.05572 





2.45656 





2.34733 



Sheepscot River 



2.18866 



±0.03385 



±0.06770 





2.25500 





2.12231 



Table 19.— The numbers of bloodworms and sandworms per pound. 









Bloodworms 





Sandworm 



s 





Length 



Weight' 





Length 



Weight' 









(cm) 



(g)~ 



Worms/lb 



(cm) 



(g) 



Worms/ lb 



1973 

















6-moX 





18.72 



2.07 



219 



26.11 



5.49 



83 



X+1.96SE 





19.90 



2.40 



189 



28.03 



6.42 



71 



X-1.96SE 





17.54 



1.78 



255 



24.19 



4.63 



98 



Max. month 



X 



20.81 



2.66 



171 



31.36 



8.30 



55 



Min. month. 



X 



16.99 



1.66 



273 



21.00 



3.37 



135 



1974 

















6-mo X 





19.84 



2.37 



191 



26.22 



5.53 



82 



X+1.96SE 





20.58 



2.60 



174 



27.55 



6.22 



73 



X-1.96SE 





19.10 



2.18 



208 



24.89 



4.94 



92 



Max. month 



X 



21.68 



2.93 



155 



28.16 



6.52 



70 



Min. month. 



X 



17.82 



1.85 



245 



24.25 



4.67 



97 



1975 

















6-moX 





20.74 



2.63 



172 



26.77 



5.82 



78 



X+1.96SE 





21.90 



2.99 



152 



27.81 



6.32 



72 



X-1.96SE 





19.58 



2.31 



196 



25.73 



5.30 



86 



Max. month 



X 



23.10 



3.39 



134 



32.32 



8.84 



51 



Min. month. 



X 



19.15 



2.20 



206 



24.31 



4.67 



97 



1976 

















6-moX 





20.83 



2.66 



171 



25.69 



5.30 



86 



X+1.96SE 





21.89 



2.99 



152 



26.51 



5.68 



80 



X-1.96SE 





19.77 



2.37 



191 



24.87 



4.94 



92 



Max. month 



X 



22.98 



3.35 



135 



27.45 



6.17 



74 



Min. month. 



X 



18.57 



2.05 



221 



23.74 



4.42 



103 



'Weight values derived from length-weight conversions (all areas, all sexes 

 combined). 



Approximate values for a restriction on limited entry can be 

 obtained from yield-effort curves (Pinhorn and Halliday 1975). 

 Yield-effort relationships for bloodworms and sandworms are pre- 

 sented in Figure 16 (A and B). These results suggest that the maxi- 

 mum sustainable yield (MSY) in numbers of bloodworms and 

 sandworms harvested was obtained with an effort of approximately 

 1 ,300 licensed marine worm diggers. 



Prior to 1973, no attempt was made to record whether diggers to 

 whom marine worm digging licenses were issued were engaged 

 mainly in bloodworm or sandworm digging, or digging for both 

 species. This information was extracted from licenses issued dur- 

 ing the period 1973-78 and the results are presented in Table 21. 

 The assumption has been made in Table 21 that the proportions cal- 

 culated from completed application forms also apply to that 

 10.9-20.0% of the applicants who did not file completed applica- 

 tions. On the basis of the information presented in Table 21 and 

 assuming that the percentage of licensed diggers who dug only 

 bloodworms or sandworms prior to 1973 was the same as it was 

 between 1973 and 1978, the MSY was obtained with approxi- 

 mately 815 bloodworm diggers (62.66% of 1,300), 386 sandworm 

 diggers (29.72% of 1,300), and 99 diggers (7.62% of 1,300) who 

 dug both species. A yield-effort relationship consisting of com- 

 bined bloodworm and sandworm landings plotted against the total 

 number of licensed marine worm diggers is presented in Figure 

 16C. These results suggest that the MSY for both species combined 

 could be obtained at a limited entry figure of approximately 1 .300 

 licensed marine worm diggers. 



Where sufficient data exist on the total cost of digging, and the 

 value of the catch over a period of time, a limited entry figure for 



Table 20. — The numbers of bloodworms and sandworms per 

 pound reported prior to 1970. 





Bloodworms 



Sandworms 





Date 



(no. /lb) 



(no. /lb) 



Source 



1950-52 



44 



40 



Cates and McKown 

 (text footnote 36) 



1964 



100 



50 



Dow (1964) 



1964 



115 



57 



Cates and McKown 

 (text footnote 36) 



1966 



106 



63 



Walton (text footnote 

 35) 



1968 



142 



— 



Walton (text footnote 

 35) 



1969 



150 



80 



Dow (1969) 



Table 21.— The percentage of licensed marine worm 

 diggers digging bloodworms, sandworms, and both 

 species (1973-78). 





Percent 



of licensed diggers 



digging 



Year 



Bloodworms 



Sandworms 



Both species 



1973 



64.77 



28.42 



6.81 



1974 



61.39 



29.45 



9.16 



1975 



61.36 



30.23 



S.41 



1976 



64.80 



28.08 



7.12 



1977 



63.88 



29.99 



6.13 



1978 



59.78 

 '62.65 + 0.86 



32.16 



S.06 





'29.72+0.60 



'7.62 + 0.46 



'Mean 



+ 1 SE. 







49 



