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Atlantic surfclams are distributed in length-based 
size classes. Average wet weights (W) are calculated 
with an allometric relationship of the form (Marzec et 
ah, 2010): 
W = aL\ (1) 
where L = the length in millimeters. 
Parameter values come from Marzec et al. (2010). 
Growth and mortality rates vary latitudinally and 
across-shelf for each 10' square. The growth rate of 
Atlantic surfclam is calculated from a von Bertalanffy 
growth curve (with a growth rate ( k ) that increases in 
the northern and eastward direction) by using the fol- 
lowing equation: 
L a = LSI - e~ kA ), (2) 
where L = length in millimeters; and 
A = age in years. 
Parameters are based on Munroe et al. (2016) and 
NEFSC 2 . Natural mortality is imposed by using a con- 
stant mortality rate across all size classes consistent 
with the presently accepted stock assessment model 
(NEFSC 2 ) and the analysis of Weinberg (1999) and 
is specified to increase from northeast to southwest 
across the domain to reduce Atlantic surfclam abun- 
dance at the southern and inshore extremes of the 
range as observed. 
A survey of the simulated clam population is con- 
ducted annually on 1 November and includes the most 
recent recruitment event. The true clam density for 
each 10' square is used for this survey and samples 
are taken from every 10' square in the domain. Re- 
sults from the survey are then used to set the annual 
quota based on a quota cap established by the fish- 
ery management plan (FMP) for the Atlantic surfclam 
(MAFMC 8 ), the presently accepted biological reference 
points (NEFSC 2 ), and the allowable biological catch 
control rules. The annual quota biomass is then con- 
verted to bushels of clams. In practice, the Atlantic 
surfclam allowable biological catch has always been 
above the FMP quota cap. The stock has never been 
overfished and overfishing has never occurred. Conse- 
quently, in these simulations, the total allowable catch 
remained stable at the FMP quota cap of 3.5 million 
bushels. Thus, simulations address management op- 
tions for a fishery in which overfishing does not occur 
and for which the stock is not overfished — simulations 
consistent with the conditions present throughout the 
2000 to 2012 period as documented in the most recent 
federal assessment (NEFSC 2 ). 
For the current FMP for Atlantic surfclams, an indi- 
vidual transferable quota system is used that allocates 
a number of cage landings to each of the shareholders 
8 MAFMC (Mid-Atlantic Fishery Management Council). 1986. 
Amendment #6 to the fishery management plan for Atlantic 
surf clam and ocean quahog fisheries, rev. ed., 102 p. Mid- 
Atlantic Fishery Management Council, Dover, DE [Avail- 
able from website.] 
(McCay et al., 1995; MAFMC 9 ; NEFSC 2 ). In practice, 
these shares are amassed through direct ownership 
or lease by processing plants and quotas are issued to 
the vessels each of which fishes exclusively for specific 
processing plants. That is, the fishery is vertically inte- 
grated with processing plants holding quotas that they 
distribute to vessels that land catch only at designated 
ports. Within this model, the current FMP is imple- 
mented and area management is added to the manage- 
ment plan. Each processing plant distributes its frac- 
tion of the total quota to its vessels weekly. The weekly 
quota is limited to twice the vessel hold size serving 
to limit the number of trips per vessel to 2 trips/week, 
a number consistent with industry practice. During 
each simulation, a vessel harvests clams on the basis 
of the captain’s decision and memory of fishing areas 
and according to imposed harvest quotas. The vessels 
fish to capacity if possible, given the constraint that 
time at sea is restricted during the warmer months to 
limit deterioration of the catch because Atlantic surf- 
clam vessels have no or a limited capacity for refrigera- 
tion. Captains’ memories are updated after each fish- 
ing trip. Harvest rates are calculated from tow speed, 
dredge width, dredge efficiency, the size selectivity of 
the dredge, and the skill of the captain. Tow speed, 
dredge width, dredge efficiency, and the size selectivity 
of the dredge are based on federal survey program data 
reported from 2011 (e.g., NEFSC 2 ) and data received 
in 2013 from vessel owners and captains on standard 
operating conditions for harvesting Atlantic surfclam. 
Simulation experiments 
The essential elements of an MSE include management 
objectives, performance metrics, and management op- 
tions (Smith, 1994). The primary management objective 
is to insulate both the Atlantic surfclam stock and the 
commercial LPUE from further decline. The evaluation 
of alternative management procedures for both the en- 
hancement of the Atlantic surfclam stock and the eco- 
nomics of the industry is based on statistical analysis 
of performance metrics. The performance metrics are 
rooted in interviews with representatives from process- 
ing plants, industry trade organizations, and vessel 
captains to ensure appropriateness. The performance 
metrics chosen are important in that they provide met- 
rics that allow commercial stakeholders to evaluate the 
results of each management procedure based on their 
business model. A total of 5 performance metrics were 
used. Two of these metrics are used to measure the popu- 
lation: clam whole-stock density, which is the number 
of clams >120 mm SL per square meter (the fishable 
stock is defined as clams >120 SL mm [NEFSC 2 ]), and 
the number of clams per bushel. Three metrics were 
used to measure the effect of area management on the 
9 MAFMC (Mid-Atlantic Fishery Management Council). 
2013. Atlantic surfclam information document, 9 p. Mid- 
Atlantic Fishery Management Council, Dover, DE. [Avail- 
able from website, accessed September 2014.] 
