Able et al.: Larval abundance of Paralichthys dentatus as a measure of recruitment and stock status 
69 
size and larval and juvenile abundance. Brodziak and 
O’Brien (2005) found that summer flounder recruitment 
lagged after the North Atlantic Oscillation (NAO) index 
by two years (i.e., recruitment in 1990 was related to 
the NAO in 1988). Analyses conducted during a recent 
stock assessment confirmed this relationship (NEFSC 1 ), 
but a mechanistic recruitment hypothesis has yet to be 
developed. Recruitment is the result of the integration 
of survival from spawning through the juvenile stage, 
whereas the stage at which recruitment is determined 
can be inferred by examining the abundance indices at 
successive life stages (Nash and Dickey-Collas, 2005). 
In an attempt to resolve these issues, we examined 
the relationship between two long-term time series of 
summer flounder larval abundance at ingress, recruit- 
ment, and spawning stock biomass over the period of 
presumed stock recovery. We evaluated whether these 
data sets 1) contribute to an improved understanding 
of stock identification; and 2) result in indices that cor- 
relate with patterns of abundance relative to spawning- 
stock biomass and recruitment. In prior studies of the 
abundance of larval summer flounder at ingress, the 
timing, size, and developmental stage of inlet samples 
at the New Jersey (Able et ah, 1990; Szedlmayer et ah, 
1992; Keefe and Able, 1993, 1994) and North Carolina 
(Williams and Deubler, 1968; Burke et ah, 2000; Taylor 
et al., 2009) sites were determined from a shorter time 
series. A combined analysis has not been attempted 
until now. 
Materials and methods 
General life history of summer flounder and study sites 
Summer flounder spawn during an offshore migration 
from estuaries and bays to the outer continental shelf. 
This spawning event occurs during fall and early winter 
and the larvae are transported inshore from where they 
enter estuaries, settle to the bottom, and grow quickly. 
Most fish are sexually mature by age 2 and it is about 
this time that they begin to be caught in the commercial 
fishery. 
The locations of data collections were Little Egg Inlet 
(New Jersey) and Beaufort Inlet (North Carolina) from 
the northeast and southeast United States continental 
shelf ecosystems, respectively (Fig. 1). Little Egg Inlet 
is the primary source of Atlantic Ocean water that en- 
ters the Great Bay-Little Egg Harbor estuarine system, 
which is polyhaline and shallow (average water depth 
1.7 m). The system is composed of a drowned river val- 
ley (Mullica River), an embayment (Great Bay), and 
an adjacent barrier beach estuary (Little Egg Harbor). 
This estuary has a broad, seasonal temperature range 
(-2° to 28° C) and a moderate tidal range (-1 m; Ken- 
nish, 2004). Sampling was conducted from a bridge over 
Little Sheepshead Creek (water depth ~3 m), a thor- 
oughfare connecting Great Bay and Little Egg Harbor, 
located 3 rkm from the creek mouth and 2.5 km from 
Little Egg Inlet. Atlantic Ocean water flows into the 
estuary through Little Egg Inlet during flood tides, and 
portions are diverted into the mouth of Little Sheeps- 
head Creek (Charlesworth, 1968; Chant et al., 2000). 
Recent work has shown that ichthyoplankton samples 
collected from this location are representative of dynam- 
ics occurring in the estuary proper (e.g.. Witting et al., 
1999; Chant et al., 2000; Neuman et al., 2002; Able 
and Fahay, 2010). 
Beaufort Inlet connects several estuarine systems 
and two sounds, Back Sound and Bogue Sound, to the 
Atlantic Ocean (Churchill et al., 1999). The area around 
the inlet shares many characteristics with other estua- 
rine systems in the southeast United States. Seasonal 
temperature variation (8° to 30°C) is more moderate 
than that at Little Egg Inlet, whereas tidal range is 
similar (~1 m). Sampling is performed from a bridge 
(~1.5 km inside of Beaufort Inlet) that spans a 40-m 
wide channel between Radio Island and Pivers Island 
(water depth -4 m). Atlantic Ocean water flows into the 
estuary through Beaufort Inlet and approximately 10% 
moves up the channel that provides water to the Radio 
Island-Pivers Island channel (Churchill et al., 1999). 
Species composition and abundance of samples taken 
from Beaufort Inlet are also characteristic of collections 
from surrounding sounds and have potential value as 
predictive measures of year-class strength of estuarine- 
dependent fishes (Lewis and Mann, 1971; Hettler et al., 
1997; Hettler and Hare, 1998; Forward et al., 1999; 
Rice et al., 1999; Taylor et al., 2009). 
Sampling of larvae at ingress 
At Little Egg Inlet, larvae entering the estuary were 
collected with a 1-m diameter, circular plankton net 
(1-mm mesh) fitted with a flow meter. From August 1991 
to 2006, three replicate 30-min sets were made weekly 
with the net deployed to a depth of 1.5 m during night- 
time flood tides. From February 1989 to May 1990 (the 
first year of sampling), five 30-min sets of two concurrent 
plankton nets (one at the surface and one at the bottom) 
were made for a total of 10 sets per sampling date. 
From May 1990 to July 1991, three 30-min sets of two 
concurrent plankton nets (one at the surface and one at 
the bottom) were conducted. Weekly surface and bottom 
data from February 1989 to July 1991 were averaged and 
combined with weekly mid-water data from August 1991 
to 2006 to develop a full time series of larval collections 
(Able and Fahay, 1998, 2010; Witting et al., 1999). 
At Beaufort Inlet, larvae were collected with a 2-m 2 
rectangular plankton net (1-mm mesh) fitted with a flow 
meter. The net was deployed during nighttime flood tides 
and larvae were sampled at the surface (0-1 m depth). 
Four replicate sets were made weekly from November to 
April, 1985-2001. Before 1998, tow duration was nearly 
constant (-5 min), resulting in a variable volume being 
filtered. Since 1998, tow volume has been standard- 
ized (-100 m 3 ) with the use of an electronic flow meter. 
The differences in sampling designs between locations 
resulted from the logistics of net deployment from the 
bridges and the abundance of fishes in the water col- 
