The microsporidian parasite, Glugea slephani, was observed in some individuals collected. Mortality 

 caused by this parasite can be relatively high in winter flounder (Takvorian and Cali 1984; Cali et al. 

 1986). Incidences of the pathenogenic bacterium Vibrio anguillarum, which also can result in fatal infections 

 in winter flounder characterized by fm erosion, dermjd ulceration, and hemorrhaging (Levin et al. 1972; 

 Watkins et £il. 1981; Sindermann 1985), were not noted. 



Abundance (age 1) 



An attempt was made in 1981 and 1982 to estimate with the Jolly model the abundance of 6- to 

 1 5-cm juvenile winter flounder present in the Niantic River during the spawning season. Fish were marked 

 with freeze-brands during the adult surveys in late winter and released. However, apparent high rates of 

 marking mortality made the Jolly estimates biased and unreliable (NUSCo 1983a) and no further attempts 

 were made to mark small fish. 



The median CPUE of juvenile winter flounder smaller than 15 cm in length was calculated for fish 

 taken during the adult winter flounder surveys in the Niantic River from 1976 through 1986 (Table 28, 

 Fig. 28). Nearly all of the fish in this size grouping were age 1 yearlings and represented the year-class 

 spawned during the previous abundance survey. Data were restricted to the mid-March to mid-April 

 period for comparability among years and to stations 1 and 2 because small winter flounder appeared to 

 have been less abundant in the upper river than adults. Inclusion of data from upper river stations could 

 have biased inter- year comparisons because few or no tows were made there prior to 1981. 



Juvenile catches were more variable than those of adults and had larger coefficients of variation and 

 skewness. Less uniformity was seen between the median and mean, even after tows were standardized in 

 1983. Peak abundance was observed in 1981 (1980 year-class), with a median of 87.2. Second and third 

 highest medians were found in following years (61 in 1982, 50.1 in 1983). Abundance declined greatly in 

 1984 to a median of 16, increased to 27.7 in 1985, and fell to an ll-yr low of 3.6 in 1986. Juvenile 

 abundance, which began to increase in 1979 and peaked in 1981, was generally followed by increasing 

 adult abundance, which peaked in 1982. Abundance of both groups declined through 1984. Juvenile 

 catches were recently reported to have been correlated with adult abundance a year later (NUSCo 1986a), 

 but the addition of 1986 data made this relationship non-significant. Although juvenile CPUE in 1985 

 was 73% larger than that in 1984, adult abundance did not increase in 1986. 



99 



