89 
NOAA 
National Marine 
Fisheries Service 
Abstract— Accurate maturity-at-age 
data are necessary for estimating 
spawning stock biomass and setting 
reference points for fishing. This 
study is the first on age at matu- 
rity of female sablefish (Anoplopoma 
fimbria ) sampled in Alaska during 
their winter spawning period, when 
maturity is most easily assessed. 
Skipped spawning, the situation 
where fish that have spawned in the 
past do not spawn during the cur- 
rent season, was documented in fe- 
male sablefish for the first time. De- 
termination of age at maturity was 
heavily influenced by whether these 
fish that would skip spawning were 
classified as mature or immature; 
age at 50% maturity was 6.8 years 
when fish that would skip spawning 
were classified as mature, and 9.9 
years when classified as immature. 
Skipped spawning was more com- 
mon on the continental shelf, and 
rates of skipped spawning increased 
with age through age 15. Estimates 
of age at maturity were similar for 
samples collected in winter and 
summer, when fish that would skip 
spawning sampled during winter 
were classified as mature. When 
fish that would skip spawning were 
considered immature in the sable- 
fish population model for Alaska, 
estimates of spawning biomass de- 
creased. Relative fecundity did not 
change with size and age, verifying 
the assumption made in the Alaska 
sablefish stock assessment that rela- 
tive reproductive output is linearly 
related to female spawning biomass. 
Manuscript submitted 25 November 2014. 
Manuscript accepted 20 November 2015. 
Fish. Bull. 115:89-102 (2016). 
Online publication date: 8 December 2015. 
doi: 10.7755FB.114.1.8 
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. 
Fishery Bulletin 
established 1881 -ft 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Age at maturity, skipped spawning, and 
fecundity of female sablefish (Anoplopoma 
fimbria ) during the spawning season 
Cara J. Rodgveller (contact author) 
James W. Stark 
Katy B. Echave 
Peter-John F. Hulson 
Email address for contact author: cara.rodgveller@noaa.gov 
Alaska Biological Laboratories 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
17109 Point Lena Loop Road 
Juneau, Alaska 99801 
Maturity-at-age data are used in 
stock assessments to estimate repro- 
ductive output of fish populations. 
Commonly, these data are collected 
without the aid of histological analy- 
sis and often during surveys that do 
not correspond with the time of the 
reproductive cycle when maturity 
can be gauged with the greatest ac- 
curacy, the time just before spawn- 
ing (Hunter et ah, 1992). These dis- 
crepancies can result in the misclas- 
sification of maturity and in inaccu- 
racies in estimations of age at ma- 
turity. Misclassifying maturity can 
result in over- or underestimation 
of spawning stock biomass (SSB), 
which is used as a proxy for egg 
production in population models. An 
inaccurate estimation of SSB can af- 
fect management decisions. In some 
cases, egg production is not linearly 
related to SSB, a situation that oc- 
curs when relative fecundity changes 
with age or size (e.g., Hislop, 1988). 
If relative fecundity is not constant, 
incorporating the assumption that 
SSB is linearly related to fecundity 
in population models will lead to 
bias in estimates of productivity. 
Although it is generally assumed 
that marine fish in northern lati- 
tudes reproduce on an annual cy- 
cle, it is not always the case. For 
example, it has been documented 
that a portion of mature Atlantic 
cod ( Gadus morhua) skips spawn- 
ing annually; therefore, the repro- 
ductive cycle for some individu- 
als is longer than 1 year (Marshall 
et al., 2000). In the North Pacific 
Ocean, the Pacific halibut (Hippo- 
glossus stenolepis ) has been thought 
to also skip spawning on the ba- 
sis of their movements during the 
spawning season (Loher and Seitz, 
2008). Skipped spawning, which oc- 
curs when mature fish that have 
spawned in prior seasons do not 
spawn in the current season, is 
likely to be a more common phenom- 
enon than previously thought (Ride- 
out and Tomkiewicz, 2011), hav- 
ing been documented in at least 30 
freshwater and marine fishes (Secor, 
2008; Skjseraasen et ah, 2012). 
Sablefish ( Anoplopoma fimbria) 
are part of a commercially impor- 
tant resource in the North Pacific 
Ocean; the fishery in Alaska is val- 
