320 
Fishery Bulletin 115(3) 
Table 9 
Summary of alternative management strategies for determining the management option that offers 
benefits to both the stock and commercial fishery of the Atlantic surfclam ( Spisula solidissima ) in the 
Mid-Atlantic Bight. Plus signs indicate the management strategy (either present-day or area manage- 
ment through closures) that resulted in the highest values of performance metrics. In situations where 
equivalent proportions of simulations resulted in increases, a plus sign is given to both strategies (i.e., 
landings per unit of effort). 
Rule 1 
(ratio of the number 
Rule 2 
Present-day 
of small clams to 
(number of small 
Performance metric 
management 
market-size clams) 
clams/m 2 ) 
Stock density (number of clams/m2) 
Number of clams per bushel 
+ 
+ 
Landings per unit of effort (bushels/h) 
Number of 10' squares fished 
+ 
+ 
+ 
Total distance traveled (km) 
+ 
are 1) the whole-stock density of clams recruited to the 
fishery (i.e., clams >120 mm SL), and the 2) number 
of clams per bushel. Simulations suggest that imple- 
mentation of closure location rule 1 offers greater im- 
provement to the stock, as measured by an increase 
in whole-stock density or a decrease in the number of 
clams per bushel due to an increase in clam size, in 
comparison with implementation of closure location 
rule 2 (Table 9). That is, closing a 10' square on the 
basis of the proportional abundance of small clams of- 
fers improved outcomes in comparison with the same 
choice that is based on the density of small clams. The 
stock density showed a 4-7% increase under closure 
location rule 1. To put these values in perspective, the 
increase is more than double the fraction of the stock 
removed by the fishery in a given year over the entire 
stock and is very near the exploitation rate for the area 
of highest exploitation, offshore New Jersey. 
Tracking the number of clams per bushel also is 
one way to evaluate the status of the stock. A thriv- 
ing stock will have larger clams and consequently the 
fishery will require fewer clams to fill a bushel. That 
is, landing larger clams results in fewer individuals 
being removed from the population under a specified 
quota, thus conserving stock density. One of the critical 
characteristics of the Atlantic surfclam fishery is that 
fishing economics and fishery management are speci- 
fied in terms of volume, whereas the stock itself is best 
defined in terms of number of individuals. The number 
of clams per bushel is significantly lower under area 
management in an average 31% of 3-year closure dura- 
tion simulations and 100% of the 5- and 7-year closure 
duration simulations, regardless of the definition of a 
small clam. An increase of 4% in the number of clams 
required to fill a bushel under present-day management 
equates to an excess of about 3 clams per bushel when 
compared with alternative management. Three fewer 
clams per bushel translates to around 1 less bushel 
being required to fill a cage (32 bushels=l cage). Annu- 
ally, the equivalent of approximately 4557 cages would 
therefore remain in the fishable stock because these 
animals would not be needed to fill the quota during 
fishing trips. About 81 extra trips of a boat capable of 
carrying 56 cages would be supported. Alternatively, 
these clams increase whole-stock density. 
Influence of area management on the commercial fishery 
Performance metrics used to evaluate the influence of 
area management on the Atlantic surfclam fishery are 
LPUE, the number of 10' squares visited yearly, and 
the total distance traveled by the fishing vessel. Clo- 
sure location rule 1 results in greater opportunities for 
the commercial fishery (Table 9). LPUE is increased 
significantly over all definitions of a small clam in an 
average of 61%, 64%, and 44% of simulations for the 
3-, 5-, and 7-year closures respectively (Table 3). The 
greatest percent increase in LPUE under closure loca- 
tion rule 1 produced enough time saved at sea to enable 
transit for an additional 16.7 km (9 nautical miles), or 
the addition of one 10' square in any direction from the 
port, increasing the fishable area under the dock-to- 
dock time constraint imposed by the rate of spoilage of 
clams on deck. With an increase in incidental mortality, 
the extra time saved by an increase of 15% in LPUE 
would allow the boats to travel to 2 additional 10' 
squares in the same amount of time (approximately 36 
h from the start of fishing to the landing of the clams 
during the warmer months of the year). A 6% increase 
in LPUE would result in a boat that is capable of car- 
rying 56 cages filling all cages about 2 h faster per 
trip, thus permitting more transit time to fish farther 
from home port — 37.0 km (20 nautical miles) for most 
vessels steaming at 5 m/s (10 kn), under the 36-h time 
constraint. A 15% increase in LPUE would equate to a 
reduction of 5 h of fishing time per trip. As fuel use is 
highest while fishing (both the main engine and water 
pump are running), any increase in LPUE exerts an 
