collections were found for Stage 1 and 2. For Stages 3 and 4, percentages were noticeably higher during 

 the night at stations B, NB, and EN, but not at C. These diel differences have been attributed to vertical 

 movement of larvae from on or near bottom into the water column at night (NUSCo 1984). This behavior 

 pattern appears during Stage 3 following development of fm rays. The predominant length range of Stage 

 3 larvae is 5.0 to 7.5 mm (NUSCo 1984, 1985, 1986a) and the behavior pattern found for Stage 3 and 4 

 larvae agreed with the results based on size-classes. The lack of diel vertical movement of Stage 3 and 4 

 larvae at station C suggested that other factors in the lower river, such as tidal currents must have affected 

 their behavior. 



Comparison of day and night collections showed that abundance estimates based on daylight collections 

 could underestimate the abundance of 5 mm and larger larvae. This was the reason for reducing sampling 

 in the Niantic River to only night during May and June starting in 1984. Entrainment sampling remained 

 balanced between day and night for the estimation of entrainment. Sampling at station NB remained 

 balanced because this station was also used to monitor other species. The daylight sampling bias severely 

 limited the usefulness of earlier data in examining the abundance and distribution of larval winter flounder. 

 In 1974 and 1975, collections were only made at night once a month andlTrom 1976-78 and none were 

 made during the larval winter flounder season. In addition, the special- larval winter flounder sampling in 

 the Niantic River during 1979 consisted of only daylight collections. 



24-h studies 



Sampling was conducted over 24-h periods at station C to examine the effect of tidal stage on the 

 sample density of larval winter flounder (Fig. 11). Two studies in 1983 occurred when the predominant 

 developmental stages were 3 (62%) and 4 (30%). During 1984, when two additional studies were 

 conducted. Stage 1 (48%) and 2 (51%) dominated. There was an apparent tidal effect on sample densities 

 in both studies in 1983 and the March 19 study in 1984. Harmonic regression was used with log-transformed 

 data to relate changes in density to tidal stage for these three studies (NUSCo 1984, 1985). A 12-h tidal 

 period was used with slack low at hours 0, 12, and 24 and slack high at hours 6 and 18. Satisfactory 

 fits were achieved for Stage 1 larvae (/?^ = 0.58) in the March 19, 1984 study and the combination of Stage 

 3 and 4 larvae on both sampling dates (R^ = 0.45) in 1983. Analysis of covariance of the 1983 studies 

 (NUSCo 1984), with tidal effect as described by the harmonic regression as the covariate, showed 



64 



