190 
National Marine 
Fisheries Service Fishery Bulletin 
NO A A ^ es ^ a ^ s ^ e ^ * n i88i *<r> 
Spencer F. Baird 
First U.S Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
The effect of reduced data on the ability to monitor 
rebuilding of overfished fish stocks 
Chantei It Wetzel (contact author) 1 
Andre E. Punt 2 
Jason M Cope 1 
Email address for contact author: chantei.wetzel@noaa.gov 
1 Fishery Resource Analysis and Monitoring Division 
Northwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
2725 Montlake Boulevard East 
Seattle, Washington 98112-2097 
2 School of Aquatic and Fishery Sciences 
University of Washington 
1122 NE Boat Street 
Seattle, Washington 98105-6770 
Abstract-Several rockfish stocks 
off the U.S. west coast are below 
target biomass and are managed 
under rebuilding plans that severely 
limit the allowable harvest. Limited 
harvest, however, reduces the oppor¬ 
tunity to collect fishery-dependent 
data, which are the primary source 
of information on changes in abun¬ 
dance for species poorly sampled by 
fishery-independent methods. A sim¬ 
ulation study was conducted by us¬ 
ing an operating model to evaluate 
the effect of reduced data on estima¬ 
tion of spawning biomass and bio¬ 
logical parameters during rebuilding 
of a stock. Decreased availability of 
data during rebuilding resulted in 
increased among-simulation varia¬ 
tion in estimates of spawning bio¬ 
mass. Additionally, decreased data 
resulted in reduced average catches 
and increased interannual variation 
in catches during rebuilding com¬ 
pared with averages of and variation 
in catches when data collection was 
maintained at higher levels. The 
presence of time-varying parameters 
in the operating model that were not 
accounted for within the estimation 
method resulted in increased among- 
simulation variability in spawning 
biomass than with the time-invari¬ 
ant case, and the largest increase 
in variability occurred during stock 
rebuilding when data were reduced 
or eliminated. Retaining data col¬ 
lections at historical levels allowed 
improved parameter estimation dur¬ 
ing rebuilding, resulting in reduced 
variability in estimated stock size, 
increased average catches during re¬ 
building, and in reduced frequency 
of stocks being prematurely estimat¬ 
ed as rebuilt. 
Manuscript submitted 22 June 2017. 
Manuscript accepted 9 February 2018. 
Fish. Bull. 116:190-206 (2018). 
Online publication date: 7 March 2018. 
doi: 10.7755/FB.116.2.8 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
In the United States, federally man¬ 
aged stocks that fall below a mini¬ 
mum stock size threshold (MSST) are 
declared overfished and are mandated 
to be rebuilt to target biomass levels 
in the shortest amount of time, ac¬ 
counting for present biological and 
environmental conditions (Sustain¬ 
able...1996; National...2016). In the 
absence of an unexpected run of good 
recruitment, rebuilding overfished 
stocks requires a reduction in fish¬ 
ing mortality to a level that allows 
stock biomass to increase and there¬ 
fore leads to substantial reductions in 
fishing effort in relation to historical 
levels. The severity of management 
restrictions during rebuilding can, for 
some stocks, lead to a situation where 
the ability to collect data becomes 
limited when the stock is under a re¬ 
building plan, a period when manag¬ 
ers are likely most concerned about 
stock size and trends in biomass. 
Overfished rockfish species off the 
U.S. west coast have experienced 
large reductions in harvest during 
rebuilding. One example, yelloweye 
rockfish (Sebastes ruberrimus), was 
declared overfished in 2002 (Methot 
and Finer 1 ). Similar to other rockfish 
species off the U.S. west coast, catch¬ 
es of yelloweye rockfish were unsus¬ 
tainable during the 1980s and early 
1990s. Catches of yelloweye rockfish 
decreased dramatically in relation 
to historical catches after the over¬ 
fished declaration, and the allowable 
catch during the first year of rebuild¬ 
ing fell to approximately 10% of the 
catch from 4 years earlier (Stewart 
et al. 2 ). Yelloweye rockfish is one no¬ 
table example of an overfished west 
coast rockfish species that has expe¬ 
rienced similar large reductions in 
harvest during rebuilding. Other ex¬ 
amples include the cowcod (Sebastes 
levis ; Dick and MacCall 3 ), canary 
1 Methot, R., and K. Finer. 2002. Re¬ 
building analysis for yelloweye rockfish: 
update to incorporate results of coast¬ 
wide assessment in 2002, 11 p. Pacific 
Fishery Management Council, Portland, 
OR. [Available from website.] 
2 Stewart, I. J., J. R. Wallace, and C. Mc- 
Gilliard. 2009. Status of the U.S. yel¬ 
loweye rockfish resource in 2009, 235 
p. Pacific Fishery Management Coun¬ 
cil, Portland, OR. [Available from web¬ 
site.] 
3 Dick, E. J., and A. MacCall. 2014. Sta- 
