The median CPUE also increased relative to 1986 and was similar in magnitude to those for 1984 and 

 1985. However, this abundance index was only 30 to 60% of the estimates for 1976 through 1983. 



Annual median CPUE was also determined for juveniles ( < 1 5 cm) taken in the Niantic River during the 

 adult population abundance surveys. Juvenile catches were more variable than those of adults. Compar- 

 atively low medians were found in 1986 and 1987, which suggested poor reproductive success in recent 

 years. However, factors such as differential distribution within the river among the years most likely 

 affected the reliability of this index of abundance. 



The winter flounder was the most common fish taken in the trawl monitoring program (TMP). Annual 

 TMP 5-mean CPUE values were computed for the first time for all winter flounder taken each year from 

 1976 through 1986. The pattern of annual 5-mean abundances differed from that for the Niantic River 

 median CPUE values. The peak in S-means persisted from 1977 through 1983, but was not as pronounced 

 as it was for the Niantic River medians, which were highest in 1981 and 1982. The §-means for 1985 and 

 1986 were greater than those in 1977 and 1978, while the Niantic River median CPUE in recent years 

 indicated lower abundance than during the 1970s. 



About one-half to three-quarters of the fish taken by the TMP were larger than 15 cm. However, small 

 ( < 15 cm) fish made up about two-thirds of the total from .January through April as larger fish congregated 

 on the spawning grounds. Catch of smaller fish outside of the Niantic River as measured by the 8-mean 

 fluctuated less than the corresponding median CPUE. This suggested that juvenile abundance may not 

 have been as low as recent catches in the Niantic River surveys indicated. 



Both the armual Niantic River median CPUE and the TMP 5-means were compared to other regional 

 indices of abundance, including two commercial fishing CPUE for Rhode Island and one for Connecticut 

 and a University of Rhode Island research trawl time-series. With a few exceptions, most indices were 

 significantly correlated and thus described real trends in abundance that occurred throughout Southern 

 New England. Examination of the Rhode Island historical time-series showed that winter flounder 

 abundances have typically fluctuated over time. Sharp increases in catches were most likely related to 

 occurrences of particularly large year-classes. Recent declines in winter flounder populations have reduced 

 abundance to levels at or below those found in the early 1950s and early 1970s. 



The sex ratio of winter flounder spawning in the Niantic River over the past 11 years was 1.33 females 

 for every male. However, during the past 2 years more males than females were tsiken. The length of 

 females at 50% sexual maturation was 26.8 cm, which corresponded to a fish 3 or 4 years old. Spawning 

 in the Niantic River was usually completed by late March or eariy April and appeared to have been related 

 to water temperature, with proportionately fewer females spawning earlier during colder years. Based on 

 the abundance indices of females and their size distribution, annual indices of egg production were deter- 

 mined. This index peaked in 1982 and has declined about 80% since then. However, as shown below, 

 adult abundance and absolute egg production alone were not the only factors in determining reproductive 

 success. 



A stock and recruitment relationship for Niantic River winter flounder was determined using the 1 2 years 

 of abundance and life history data with the Ricker model. For each year, parental stock was defmed as 

 all winter flounder age 3 and older and recruits were those fish turning 3 years old each spawning season. 

 The two-parameter Ricker model only explained 44% of the variability seen in annual recruitment, with 

 large differences in year-class strength seen for similar-sized parental stocks. Annual February water 

 temperature deviations from a long-term mean were found to have been significantly and inversely correlated 



Executive Summary 



