The eight tidal cycles sampled since 1983 clearly indicated a net loss of smaller larvae that lacked fin 

 rays and had little or no locomotion. However, larger larvae with developed fin rays apparently utilized 

 vertical migration in relation to tidal currents for passive movement back into the Nicintic River. This 

 vertical migration of larvae after fm ray development was also apparent in the 24-h studies conducted at 

 station C in the river (Fig. 12). Other researchers also reported vertical migration in early life history 

 stages of fish. Diel movements of larval yellowtail flounder {Limanda femiginea) were found to increase 

 with larval size (Smith et al. 1978). Atlantic herring larvae synchronized vertical migration with flood tides 

 to minimize seaward transport (Fortier and Leggett 1983). Post-larval spot {Leiostomus xanthurus), Atlantic 

 croaker {Micropogonias undulalm), and Paralichthys spp. flounders used vertical migration in response to 

 tides as a retention mechanism (Weinstein et al. 1980). Larval North Sea plaice {Pleuronectes platessa) 

 demonstrated selective horizontal transport by swimming up from the bottom during flood tides and 

 remaining near the bottom during ebb tides (Rijnsdorp et al. 1985). Most winter flounder larvae found 

 in Niantic Bay probably were tidally flushed from the Niantic River during early developmental stages. 

 After fin ray development, at least some of the older larvae in the bay utilized vertical migration in relation 

 to tidal flow to reenter the river and those within the river demonstrated a similar behavior to remain there. 



Table 27. Estimated percent return of larval winter flounder on a flood tide 



that were Rushed from the river on an ebb tide presented by size- 

 class with R^ values of the harmonic regression models. 



Size Percent R of 



class return model 



3 23.4 0.80 



4 60.0 0.66 



5 131.8 0.90 



6 114.2 0.89 



7 140.9 0.88 



90 



