FISHERY BULLETIN: VOL. 74, NO. 2 



Table 7. — An analysis of covariance between the 20- and 

 50-day survival poljmomials of Cancer magister larvae. Null 

 hypothesis: no significant difference between 20- and 50-day 

 survival polynomials. 



'Not significant, F 95,5 25, =2.44. 



be minimal. Forty-five percent survival would 

 still occur, even after an unrealistic period of 50 

 days at nonconservative temperatures and 

 salinities. 



Gut-Fullness Analysis of 

 Planktonic Larvae 



The physical appearance of C. magister larvae 

 was examined for clues to the difference in the 

 larval populations between the two seasons, 1970 

 and 1971. Whatever happened to the larvae oc- 

 curred early in their development during the 

 months of February and March 1971, as a marked 

 decrease in the total larval population was ob- 

 served by the second zoeal stage. Those larvae 

 examined from the 1971 season appeared more 

 flaccid wdth a soft exoskeleton, had less eye pig- 

 mentation, and were more transparent compared 

 to the larvae caught during the 1970 season. 

 However, these features of appearance could not 

 be readily quantified. Further examination indi- 

 cated a possible difference on a population basis 

 in the amount of food in their guts among stages, 

 stations, and years. Differences in larval gut- 

 fullness may indicate good versus poor food 

 availability, or possibly a dying larval population 



weakened by some factor in their environment 

 other than food. 



Food and/or feces in the guts could readily be 

 seen through the body wall up to the fourth or 

 fifth zoeal stage and a close estimation of the per- 

 centage fullness could be made by noting the 

 proportion of gut segments filled with food. The 

 larval body can be divided into eight equal seg- 

 ments; the thorax constituting twice the length of 

 an abdominal segment. The food or feces was con- 

 sidered to be of the same approximate diameter 

 and could be estimated to within 3% of the total 

 gut length. A sample size of 30 larvae was neces- 

 sary before any significant difference could be 

 considered. 



The 0.2-m bongo net samples were used to com- 

 pare the 1970 and 1971 larval seasons at stations 

 NHOl, NH03, NH05, and NHIO. Samples were 

 combined with both meshes of the 0.2-m bongo 

 nets. Only whole larvae were used and usually 

 the entire sample was analyzed. Specimens from 

 the 0.7-m bongo net samples were used to com- 

 pare inshore-offshore larval gut-fullness between 

 the 12 stations, NHOl through NH60, for the 

 1971 season. 



Zoea 1 larvae from the 1970 season showed 

 maximum mean percentage gut-fullness at sta- 

 tions NH03 and NHIO compared to those from 

 NHOl and NH05 (Table 8). A general decrease in 

 gut-fullness was observed with increasing stage 

 of development. Surprisingly, all zoeal stages of 

 larvae caught during the 1971 season showed an 

 increase in gut-fullness over those of the 1970 

 season. The notable exception occurred for zoea 1 

 larvae at station NH03, where the 1971 gut- 

 fullness is significantly lower than that for the 

 1970 season. 



The onshore-offshore comparison showed that 

 the greatest gut-fullness for any larval stage oc- 



TABLE 8. — A eomparison of Cancer magister larval gut-fullness' between 1970 and 1971 at four New- 

 port Hydrographic line (NH) stations.^ 



Stage 



Year 



NHOl 



NH03 



NH05 



NHIO 



'Gut-fullness is expressed as a reconverted arcsinVpercentage transformed mean followed by its standard error and the number 

 of observations in parentfieses. 



^Tfie station samples in tfiis table represent tfie combined specimens from bothi mesh sizes of the 0.2-m bongo net sampler. 

 "1% level significant difference bietween yearly means based on a two-sample (-test. 



364 



