It is likely that this assumption has also been violated during the 

 Niantic River surveys. Since a highly mobile population seems to be 

 present during the spawning season, differential movement of ripe and 

 spent fish may occur to some extent. In addition, the movements of 

 sexually immature fish probably differ as they have no inherent reason 

 to enter the River spawning grounds from offshore wintering areas unless 

 they move in response to preferential water temperature or food availability. 

 The proportion of females, males, and those of unknown sex at time of 

 branding and at time of recapture (Table 11) was examined by the G-test 

 of independence (Sokal and Rohlf 1969) . In all cases (year and segment 

 within a year) , a significant difference was indicated between the 

 proportion of each sex category branded and recaptured. The relative 

 proportion of unknown fish always increased in recaptures and that of 

 males and females decreased from time of tagging. This change in 

 proportions indicated a probable violation of the assumption and a 

 source of error in population estimation. Several possible hypotheses 

 exist to explain this finding. One is that differential movement occurred 

 among the mostly sexually mature males and females and the sexually 

 immature fish not sexed, as was suspected by Worobec (1981) . Secondly, 

 the susceptibility of capture may differ for the larger, sexed fish and 

 the smaller, unsexed fish. Unfortunately, since relatively few fish 

 recaptured were measured this could not be ascertained. Thirdly, the 

 differences in proportions may have resulted from the method in which 

 the winter flounder were sexed. Males have ctenii on the scales of the 

 ventral caudal peduncle whereas the scales of females are smooth (Smigielski 

 1975). A much easier way of sexing, of course, is if the individual is 

 ripe and extrudes readily identifiable eggs or sperm. A relatively 



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