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463 
sential habitat for juvenile marine migrant Atlantic 
sturgeon can broadly be defined as coastal waters <20 
m depth, and it is concentrated in areas adjacent to es- 
tuaries such as the Hudson River-NY Bight, Delaware 
Bay, Chesapeake Bay, Cape Hatteras, and Kennebec 
River. This narrow band of shallow water appears to 
represent an important habitat corridor and potential 
migration path. There are likely additional hotspots 
along the migration corridor, but greater temporal and 
spatial sampling effort is required to identify them. 
Other authors have reported concentrations of Atlantic 
sturgeon in Long Island Sound (Bain et al., 2000; Savoy 
and Pacileo, 2003) and NC (Laney et al., 2007), and 
Stein et al. (2004a) reported several concentrations of 
Atlantic sturgeon in Massachusetts Bay, RI, NJ, and 
DE. However, Stein et al. (2004a) used bycatch data in 
areas where captures were lowest during the summer 
months while the fishing rates were highest. However, 
this change in fishing effort may influence the observed 
distributions. 
The reason(s) for aggregations of Atlantic sturgeon 
migrants are not understood, nor are their movements 
to and from aggregation areas. Concentrations identified 
by Stein et al. (2004b) led the authors to suggest that 
temperature, bathymetry, geomorphic formations, food 
habits, and the sampling gear type used may contrib- 
ute to observed movements and aggregation of Atlantic 
sturgeon. Complex water circulation patterns are also 
a potential reason for observed concentrations of At- 
lantic sturgeon (Wilk and Silverman, 1976; Savoy and 
Pacileo, 2003). Hatin et al. (2002) found that Atlantic 
sturgeon concentrated within the St. Lawrence estu- 
ary had large numbers of nematodes and oligochaetes 
within their stomachs, which would indicate that these 
habitats are feeding areas. Known seasonal migra- 
tions often involve energetic demands related to food 
availability, environmental factors, and reproductive 
activity (Roff, 2002). Because the majority of captures 
are juveniles, reproductive activity is not a likely cause 
for movement, although causal mechanisms influencing 
traits under selection are difficult to identify because 
life-history stages are often linked through long-term 
fitness (Taborsky, 2006). We hypothesize that migra- 
tions are depth restricted and aggregations are related 
to food availability, and that seasonal cues, temperature 
in particular, drive movement. 
Current and future management of Atlantic sturgeon 
Current knowledge indicates that the majority of Atlan- 
tic sturgeon populations have been extirpated and that 
the Hudson River stock is one of the largest remaining 
populations (Waldman et al., 1996; van Eenennaam et 
al., 1998; Savoy and Pacileo, 2002; Secor et al., 2002). 
Three fishery management tools commonly used to help 
restore depleted populations are 1) minimum size limits, 
2) temporary closures of the fishery, and 3) marine 
reserves (Nowlis, 2000). Management of Atlantic stur- 
geon has been accomplished by minimum size limits 
since the early 1990s, followed directly by a 40-year 
complete closure of the fishery beginning in 1998. Cur- 
rently, after 10 years of the fishery closure, recruitment 
within the Hudson River still remains at historic lows 
(Kahnle et al., 2007). 
Because previous Atlantic sturgeon management has 
not resulted in significant improvements to popula- 
tions, recovery efforts should now focus on establish- 
ing marine reserves or implementing area closures 
to protect essential habitat and to reduce fishing 
mortality on juveniles (Collins et al., 2000). Specifi- 
cally, Sandy Hook (NJ), Rockaway (NY), and Ken- 
nebec (ME), which are hotspots of Atlantic sturgeon 
captures, as identified by this study, should be pro- 
tected. Although sturgeon are not as abundant in the 
Kennebec region in ME as in NY and NJ waters, this 
region represents a unique hotspot. It is of particular 
importance because Atlantic sturgeon captured in ME 
river systems have been shown to represent a separate 
discrete population segment (Grunwald et al., 2008). 
The genetic origins of the Atlantic sturgeon captured 
within marine waters of ME are unknown, but they 
are likely to originate from multiple stocks. Because 
of the proximity of ME river systems, it is probable 
that the majority of these Atlantic sturgeon are part of 
this discrete population segment. If our recommended 
habitat protection were to occur, the total amount of 
closed area within these locations would be relatively 
small — totaling 85.47 km 2 within NJ (Fig. 9A), 106.19 
km 2 within NY (Fig. 9A), and 209.79 km 2 within ME 
(Fig. 9B). In addition, although Atlantic sturgeon are 
highly migratory, primary juvenile habitat and migra- 
tions are limited to narrow corridors in waters less 
than 20 m deep. The presence of Atlantic sturgeon in 
such narrow bands of water indicates a seasonal or 
permanent closure to gillnet and trawl fisheries could 
be successful. By focusing immediate efforts on the 
protection of these hotspots and corridor pathways, 
bycatch mortality will be reduced effectively through 
protection of habitat. Further efforts should also be 
made to protect important areas within other systems 
and to conserve the several discrete population seg- 
ments defined by ASSRT 3 and Grunwald et al. (2008) 
and to promote genetic diversity among Atlantic stur- 
geon populations. 
By understanding the time periods of localized ag- 
gregations and movements of Atlantic sturgeon, plans 
could be developed that minimize the extent and length 
of closures that are concentrated within narrow cor- 
ridors. Some states already restrict inshore trawling 
which limits fishery interactions with Atlantic stur- 
geon, such as NJ (3.22 km limit), MD (1.61 km limit), 
DE (no trawling), and NY (various no trawl zones in 
marine waters). Any spatial closures require proper 
enforcement and substantial community-level support 
for successful implementation (Sumaila et al.. 2000). 
Although broad-scale movement patterns are becoming 
clearer, work is required to understand the finer scale 
movements of Atlantic sturgeon such that any spa- 
tial management plans could be minimized while still 
achieving adequate protection. Current plans toward 
