TABLE 19. Coefficients of variation (CV) for abundance indices of various life stages of Niantic 

 River winter flounder. 



Life stage 



Abundance index used 



CV 



Eggs 



Stage 1 larvae 

 Stage 2 larvae 

 Stage 3 larvae 

 Stage 4 larvae 

 Early juvenile 

 l^te juvenile 

 Age 3 recruits 

 Adults 



Relative index of egg production 



a parameter of Gompertz function 



a parameter of Gompertz function 



a parameter of Gompertz function 



a parameter of Gompertz function 



Mean CPUE at station LR (mid-June-early July) 



Mean CPUE at station LR (late August-September) 



Age 3 recruitment index (R) 



Parental stock index (P) 



Number of observations. 



Summary 



Indices of abundance estimates (Jolly com- 

 posite abundance index and trawl CPUE) of 

 the Niantic River spawning population of 

 adult winter flounder have been made since 

 1976. The 1987 abundance survey had the 

 latest start since 1980 because of ice cover in 

 the river. The 1987 Jolly index showed a 

 slight increase over the 12-year low abun- 

 dance index of 1986, but remained below the 

 levels of abundance from previous years. The 

 1987 median trawl CPUE also increased over 

 1986. This median was similar in magnitude 

 to those for 1984 and 1985, but was only 

 30-60% of CPUE values for 1976-83. 



Median CPUE values of juvenile ( < 1 5 cm) 

 winter flounder taken during the adult surveys 

 were very low in 1986 and 1987. The small 

 values implied poor reproductive success in 

 recent years. However, factors such as dif- 

 ferential distribution among the Niantic River 

 sampling stations probably affected tliis index 

 of abundance. 



Annual 5-mean CPUE values were computed 

 for the first time for aU winter flounder taken 

 by the trawl monitoring program (TMP) 



from 1976 through 1986. The 5-mean abun- 

 dances did not perfectly track the Niantic 

 River median CPUE values. The peak in 

 5-means persisted from 1977 through 1983 

 and was not as pronounced as it was in the 

 Niantic River. The 1985 and 1986 5-means 

 were greater than those in 1977 and 1978, 

 whereas for the Niantic River medians the 

 opposite was true. 



The TMP catches were mostly made up by 

 fish larger than 15 cm (55-75%). However, 

 smaller fish predominated from January 

 through April. Catch of the latter fluctuated 

 less outside of the Niantic River during the 

 spawning season than inside and 5-means for 

 1986 and 1987 suggested that juvenile abun- 

 dance was not as low as the Niantic River 

 median CPUE for these fish would have in- 

 dicated. 



Annual Niantic River median CPUE values 

 and TMP 5-means were compared to other 

 regional indices of abundance. With few ex- 

 ceptions, most indices were significantly cor- 

 related and thus described real trends in abun- 

 dance that occurred throughout Southern 

 New England. 



216 



