Armstrong: Distribution and abundance of Pleuronectes putnami and Pleuronectes americanus 
415 
tributions (Terborgh, 1971) and can lead to the gen- 
eration of testable hypotheses. 
Methods 
Study area 
Great Bay Estuary (Fig. 1) is a complex embayment 
comprising the Piscataqua River, Little Bay, and 
Great Bay. It is a tidally dominated system and is at 
the confluence of seven major rivers and several small 
creeks, as well as the water from the Gulf of Maine 
(Short, 1992). Great Bay Estuary is a drowned river 
valley, with high tidal energy and deep channels with 
fringing mud flats. The main habitat types within 
the estuary are mudflat, eelgrass, salt marsh, chan- 
nel bottom, and rocky intertidal. This study was con- 
ducted in the upper estuary, referred to as Great Bay, 
although preliminary sampling took place in the 
lower estuary also. Great Bay is a large, shallow 
embayment having an average depth of 2.7 m, with 
deeper channels extending to 17.7 m (Short, 1992) 
and a tidal range of about 2 m. The water surface of 
Great Bay covers 23 km 2 at mean high water and 11 
km 2 at mean low water (Turgeon, 1976). Greater than 
50% of the sediment surface of Great Bay is exposed 
mud or eelgrass flat at low tide. The Squamscott and 
Lamprey Rivers are major sources of freshwater to 
Great Bay. River flow varies considerably on a sea- 
sonal basis but is generally highest during spring 
runoff. Vertical stratification of Great Bay is rare 
because of strong tide- and wind-induced currents, 
although partial stratification may occur during pe- 
riods of high freshwater runoff, particularly at the 
upper tidal reaches of rivers (Short, 1992). 
Smooth and winter flounder were sampled monthly, 
May 1989 through September 1991, at five sites in 
upper Great Bay Estuary (Fig. 1). Ice cover prevented 
sampling from December through March in all study 
years. A 4.8-m otter trawl of 38-mm stretch mesh, 
with a 25-mm stretch mesh codend and a 6-mm 
codend liner, was used for sampling. Preliminary 
studies indicated that the net retained flounder as 
small as 25-mm total length (TL). A sample consisted 
of all flounder collected in one 10-minute tow at 
approximately 2.5 knots. Four samples were taken 
at each site from April to November. Two samples 
were taken within two hours (±) of low slack tide, 
one tow with the tidal current and one tow against, 
and two samples were taken similarly around high 
slack tide. All flounder collected were measured to 
the nearest mm TL. Bottom temperature and salin- 
ity were measured after each tow with a Beckman 
Model 510 temperature, conductivity, and salinity 
meter. 
70 ° 50 ‘ 70 ° 40 ' 
Figure 1 
Study area. Survey sites were all located in Great Bay Estuary, New Hampshire, as indicated. 
