Walden et al.: Measuring change in productivity of a fishery with the Bennet-Bowley indicator 
281 
Year 
= Bottom quartile 2008 
m 2nd quartile 2008 
V 3rd quartile 2008 
■ Top quartile 2008 
Figure 1 
Bennet-Bowley (BB) productivity indicator values unadjusted for biomass 
change during 2008-2013 and shown by quartile (where the “top quartile” rep- 
resents vessels with the highest degree of productivity in 2008). The BB indica- 
tor was used to measure a change in productivity before and after the imple- 
mentation of a catch share system in 2010 in the northeast groundfish fishery. 
quotas on several species. During the catch share era 
(2010-2013), negative productivity gains occurred for 
these vessels in all 4 years. Unlike procedures of the 
precatch share era (2008-2009), the inability to con- 
tinue fishing because of concerns about the proportion 
of bycatch in relation to target species in catches, and 
a lack of ACE for key species, may be hindering the 
ability of fishing crews to post productivity gains. Over 
time, these vessels may again be leaders in productiv- 
ity gain, but it may take time for new trading arrange- 
ments and other institutional changes to allow these 
gains to occur. 
Changes in outputs and inputs 
Vessels could also improve their productivity by chang- 
ing their input use, or switching their output targets, 
and harvesting a different mix of species. The output 
and input portions of the BB indicator can be exam- 
ined separately, and doing so showed that, in both 
2008 and 2009 before catch shares were implemented, 
the output indicator increased, whereas the input in- 
dicator decreased (Table 2). The years 2008 and 2009 
were years before catch shares were implemented, and 
all vessels were under an input control system. The 
ability to reduce input use and increase outputs led 
to productivity gains during that time period. In the 
first year of the new management regine (2010), both 
the output and input indicators decreased. In the fol- 
lowing year, 2011, the input indicator increased, and 
this year was the only one in the time series when this 
increase occurred. This gain is consistent with gain in 
the data seen in Table 1, where both days at sea and 
the number of trips increased in 2011, along with an 
increase in the average size of vessels operating in the 
fishery. Generally, in years where both the output indi- 
cator and input indicator declined, the declining use of 
inputs was not enough to offset the declining outputs, 
and productivity declined. 
One possible reason for the continuing decline in 
the output indicator could be deterioration of the fish 
stock biomass. Because the biomass indicator devel- 
oped above is an additive measure, it can be used to 
both adjust the productivity metric and to examine 
trends in the species-specific components of overall 
biomass. A negative value in the biomass indicator in- 
dicates reduced fish biomass. Between 2008 and 2013, 
the biomass indicator was negative in all years (Table 
2). The year 2010, which was the first year of the catch 
share plan, showed a particularly large drop in the VI 
(-0.27). 
Although the biomass indicator is used to adjust 
the BB indicator, it does not give a complete picture of 
how biomass is impacting vessel output. Specifically, if 
there are species interactions among the various stocks 
where they are caught jointly, the most constraining 
stock would likely be limiting catches of other stocks. 
Availability of species may also change if there is a 
spatial shift in the distribution of species. For example, 
species may shift more offshore to deeper colder water 
because of environmental changes. With a catch share 
system where quotas can be “unbundled” and leased 
on a species basis, it may be possible for quotas to be 
traded in a manner such that vessels that are special- 
ists in one species can lease or buy quota that will not 
constrain their activities. The trading arrangements 
which would facilitate “unbundling” of quotas, however, 
may take some time to evolve. 
