DeCelles and Cadrin: Movement patterns of Pseudopleuronectes americanus in the southern Gulf of Maine 
409 
70“42'W 70°40'W 70‘38'W 70‘36'W 70'341/V 
Map of the study site showing the locations of Plymouth Bay and 
Plymouth Estuary in the Gulf of Maine where the movements of winter 
flounder (Pseudopleuronectes americanus) were tracked with passive 
acoustic telemetry. Locations of tag releases and acoustic receivers 
are shown. Receivers used to track winter flounder movements from 
November 2007 to November 2008 are shown as solid black circles 
and receivers added to the array in December 2008 are shown as 
open circles. Circles are not drawn to scale and do not represent the 
detection radii of acoustic receivers. 
dividuals spawn in coastal, rather than 
estuarine habitats, these fish would 
represent contingents within the larger 
population. Contingents may provide 
populations with enhanced stability 
and resilience because of the variable 
survival rates of early life history stag- 
es in different habitats (Secor, 2007; 
Kerr et al., 2010). Divergent spawning 
migrations increase the distribution 
of eggs and larvae, which may reduce 
the probability of a failed recruitment 
event (Lambert, 1990). For winter 
flounder that spawn demersal eggs, the 
conditions encountered by the early life 
history stages are largely determined 
by the locations where the adults 
spawn. Therefore, divergent spawning 
migrations may have a large effect 
on the recruitment success of local 
populations. 
We chose to monitor adult winter 
flounder in Plymouth Bay and the ad- 
jacent Plymouth Harbor, Kingston Bay, 
and Duxbury Bay estuary. Plymouth 
Harbor, Kingston Bay, and Duxbury 
Bay estuary are commonly referred 
to as the Plymouth Estuary, and that 
name will be used throughout this ar- 
ticle. Winter flounder is a dominant 
member of the groundfish community in 
the Plymouth Estuary, and the estuary 
serves as an important nursery area 
for this species (Lawton et ah, 1984). 
Winter flounder are known to spawn 
in the Plymouth Estuary, where peak 
spawning occurs in March and April 
(Entergy 1 ). In addition, Plymouth Bay 
has been identified as an area where 
coastal spawning likely occurs (NMFS, 
1999). 
The goal of this study was to obtain 
high-resolution data on the seasonal 
distribution, migrations, and spawning 
behavior of winter flounder in the southern Gulf of 
Maine. In particular, three primary objectives were 
addressed during this study: 1) to determine if adults 
in this region exhibit divergent spawning migrations; 
2) to investigate the seasonal distribution of winter 
flounder in the region, in association with water tem- 
perature; and 3) to compare the seasonal distribution 
observed in this study to that observed in past research 
in the Gulf of Maine where static sampling methods 
were used. 
1 Entergy. 2001. Ichthyoplankton entrainment monitoring 
at Pilgrim Nuclear Station, January-December, 2000. In 
Marine ecology studies related to operation of Pilgrim Station. 
Report no. 57, 65 p. Entergy Nuclear Generation Company. 
Plymouth, MA. 
Materials and methods 
Study site 
The Plymouth Estuary and Plymouth Bay are located in 
the southern portion of the Gulf of Maine (Fig. 1). The 
Plymouth Estuary is bordered on its seaward side by two 
barrier beaches. Tidal exchange between the Plymouth 
Estuary and Plymouth Bay occurs through a 2020-m 
opening between Saquish Head and the northern extrem- 
ity of Plymouth Beach. The estuary is well mixed and 
approximately 66% of the water is replaced during each 
tidal cycle, creating strong tidal currents (Davis, 1984). 
Plymouth Bay is bordered by Cape Cod Bay to the east. 
The average depth within Plymouth Estuary is 3.3 m 
at mean high water and 2.1 m at mean low water, and 
