Walden et a! : Measuring change in productivity of a fishery with the Bennet-Bowley indicator 
279 
Table 2 
Bennet-Bowley (BB) productivity indicators, biomass volume indicator, and bio- 
mass-adjusted BB productivity indicator for the period 2007-2013. The BB indica- 
tor is based on 2 years of data; therefore, the values for the row labeled 2008, for 
example, are results for the time period 2007-2008. 
Year 
Output 
indicator 
Input 
indicator 
BB 
indicator 1 
Biomass 
indicator 
Biomass- 
adjusted 
BB indicatior 
2008 
0.30 
-0.07 
0.37 
-0.07 
0.44 
2009 
0.11 
-0.06 
0.17 
-0.21 
0.38 
2010 
-0.94 
-0.16 
-0.79 
-0.27 
-0.52 
2011 
0.09 
0.08 
0.01 
-0.06 
0.07 
2012 
-0.79 
-0.04 
-0.75 
-0.36 
-0.39 
2013 
-0.25 
-0.07 
-0.18 
-0.09 
-0.09 
BB indicator >0 indicates improvement, whereas a value <0 indicates decline. 
fishery if the vessel operated part of the year in other 
fisheries (Fare et al., 2015). 
In addition to fuel, labor, and capital, the quantity 
of ice used per trip was also included as an input cat- 
egory. Vessels that used longline gear included one ad- 
ditional input category, which was bait. Total bait cost 
was obtained from observer data, but it was only an 
aggregate cost with no price or quantity data. In order 
to include the quantity of bait, an average cost per day 
at sea for bait was calculated from sea sampling trips. 
Bait cost was then multiplied by days spent at sea (as 
recorded in the vessel logbooks) to obtain the total cost 
of bait for each trip. In the bait price and quantity 
components, days at sea were used as the quantity in- 
put, and the cost per day at sea for bait was the price 
component. 
Results 
The constructed BB indicator is shown with its com- 
ponent parts, namely the output indicator and input 
indicator, in Table 2. These are all normalized values 
($ 1000s) where the normalization factor was the 2007 
value of the overall quota (TAG) for most of the ground- 
fish species (Table 2). 4 The 2007 TAG value was picked 
as a normalization factor so that both the BB indicator 
and the VI used to measure changes in biomass would 
be normalized by the same factor. The BB indicator 
is based on 2 years of data, consequently when inter- 
preting the results in Table 2, the row labeled 2008 
provides results for the time period 2007-2008. Unlike 
a ratio-based index number, the BB indicator can be 
4 The species and stock areas included in the TAG value were 
Georges Bank Atlantic cod, Gulf of Maine Atlantic cod, Gulf 
of Maine haddock, southern New England yellowtail floun- 
der, Gulf of Maine yellowtail flounder, American plaice, witch 
flounder, Georges Bank winter flounder, southern New Eng- 
land/mid-Atlantic winter flounder, white hake, and pollock. 
either positive, or negative, with positive values indi- 
cating productivity increase and negative productivity 
decline. 
The biomass-adjusted BB indicator showed increas- 
es in both 2008 and 2009, before dropping sharply in 
2010, which was the first year of the new catch share 
system (Table 2) 5 . The drop-off was expected because 
the management system adopted strict catch limits 
and accountability measures for all participants. It was 
also consistent with the trend seen in the previously 
published Lowe index that was calculated for the an- 
nual performance report for this fishery (Murphy et al, 
2015). 6 Although the Lowe index and BB indicator are 
not directly comparable, overall the trends were gen- 
erally consistent with one another. Between 2011 and 
2013, the biomass-adjusted BB indicator continued to 
decline. 
Entry and exit 
As the BB indicator has been constructed, vessels that 
exit the fishery and do not fish in a year will always 
contribute negatively to the overall indicator, whereas 
entering vessels will always contribute positively. Ves- 
sels continuing within the fishery may either contribute 
positively or negatively to the indicator. Results show 
that productivity changes in any year are primarily 
being driven by vessels continuing withing the fishery 
(Table 3). Only in 2011 did entering vessels contribute 
5 The species included in the biomass indicator were Georges 
Bank Atlantic cod, Gulf of Maine Atlantic cod, Gulf of Maine 
haddock, southern New England yellowtail flounder, Gulf of 
Maine yellowtail flounder, American plaice, witch flounder, 
Georges Bank winter flounder, southern New England/mid- 
Atlantic winter flounder, white hake, and pollock. 
6 The productivity estimates in the annual groundfish report 
were based on a 2007 base year, and were converted to an- 
nual changes to be consistent with the Bennet-Bowley indi- 
cator method. 
