318 
Fishery Bulletin 115(3) 
Table 7 
Evaluation of model simulations in which closure location rule 2 was used to examine the influence of area management 
on the Atlantic surfclam ( Spisula solidissima ) stock and commercial fishery in the Mid-Atlantic Bight. Tabulated are the 
proportion of simulations where metrics used to evaluate the Atlantic surfclam population and commercial fishery were 
significantly greater under present-day or alternative management with closure location rule 2 with present-day abundance. 
Rule 2 mandates that the cell with the highest density of small clams (number of clams per square meter) be closed each 
year. There were 9 simulations per percentage. Any fraction over 0.11 (1 significant difference out of 9) is unlikely to occur 
by chance (exact binomial test: a=0.05; Conover, 1980). Size of clams is given as shell length (SL) in millimeters, closure 
duration is measured in years, and LPUE means landings per unit of effort. 
Definition of a small clam 
104 mm SL 93 mm SL 80 mm SL 64 mm SL 
Closure duration (yr) 
357357357357 
Stock density 
Present management 
0.33 
0.11 
0.11 
0.22 
0.00 
0.22 
0.00 
0.11 
0.11 0.33 
0.00 
0.11 
Alternative management 
0.33 
0.44 
0.56 
0.44 
0.33 
0.44 
0.44 
0.67 
0.56 0.22 
0.56 
0.00 
Number of clams per bushel 
Present management 
0.67 
0.89 
0.89 
0.78 
0.89 
1.00 
0.67 
1.00 
1.00 0.33 
0.89 
1.00 
Alternative management 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 0.00 
0.00 
0.00 
LPUE 
Present management 
0.00 
0.11 
0.11 
0.00 
0.00 
0.11 
0.00 
0.00 
0.11 0.11 
0.00 
0.22 
Alternative management 
0.56 
0.67 
0.44 
0.56 
0.44 
0.33 
0.89 
0.67 
0.67 0.56 
0.78 
0.22 
Number of 10' squares fished 
Present management 
0.00 
0.11 
0.44 
0.00 
0.11 
0.22 
0.11 
0.22 
0.44 0.00 
0.33 
0.44 
Alternative management 
0.67 
0.22 
0.00 
0.11 
0.00 
0.00 
0.22 
0.00 
0.00 0.22 
0.00 
0.11 
Total distance traveled 
Present management 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.00 0.00 
0.00 
0.00 
Alternative management 
1.00 
1.00 
0.89 
1.00 
0.89 
0.78 
0.89 
0.89 
0.89 0.89 
0.78 
1.00 
surfclam as a result of increasing bottom water tem- 
peratures in the MAB is understood by both groups 
and has implications not only for the Atlantic surfclam 
population itself but also for the commercial fishery 
supported by the clam stock in this area. The commer- 
cial fishery, which historically extended as far south 
as northern Virginia in the MAB, is now concentrated 
off the New Jersey shore (Cargnelli et aL, 1999; Ja- 
cobson and Weinberg 1 ; NEFSC 2 ). The ongoing increase 
in fishing pressure in this region, as a consequence of 
the range contraction, is already manifesting itself as a 
reduced LPUE and an increasing inability to catch the 
allocated quota. Local overfishing is likely to occur as 
consolidation of fishing pressure in this area increases. 
Barring modifications to the present-day management 
plan or transfer of additional effort northeast to south- 
ern New England and Georges Bank, LPUE will likely 
continue to decline. Because of the location of process- 
ing plants, such a transfer of effort would be extremely 
expensive and therefore represents an economically 
implausible option. The present-day management plan 
offers no responsive option. The need to improve the 
condition of the stock while allowing continued support 
of the historical fishery is a major challenge. 
Area management, such as temporary or permanent 
closures (Walters, 2000; Bloomfield et aL, 2012; Cordo- 
va-Lepe et aL, 2012), has proven to be a useful tool to 
improve shellfish fisheries. The inclusion of fishermen’s 
behavior in area management is essential because the 
response of the fishery to management measures is 
critical in the evaluation of preferred and realistic op- 
tions (Hilborn, 1992; Gillis et aL, 1995; Millischer and 
Gascuel, 2006; Link et aL, 2011). Although this MSE 
model (SEFES) captures the essential components of a 
highly variable system (i.e., the Atlantic surfclam popu- 
lation and fishery), some assumptions are required. The 
lack of knowledge about incidental Atlantic surfclam 
mortality as a result of dredging procedures requires 
an assumption concerning the degree of its importance. 
Fishing gear also can generate incidental shell dam- 
age (Witbaard and Klein, 1994; Gilkinson et aL, 2005; 
Vasconcelos et aL, 2011) that, in the case of bivalves, 
may not be easily repaired (Alexander and Dietl, 2001; 
Moschino et aL, 2003). Consequently, simulations were 
conducted for 0% and 20% incidental mortality of the 
clams encountered but not retained by the dredge with 
the upper value chosen from limited a priori data. An- 
other source of uncertainty is determining the annual 
number and distribution of recruits across the Atlantic 
surfclam population. In order to account for the mean 
annual number and distribution of recruits, simula- 
tions included a range of degrees of patchiness in re- 
