Rodgveller et al.: Age at maturity, skipped spawning, and fecundity of female Anoplopoma fimbna 
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Table 1 
Microscopic (histological) and macroscopic (visual) descriptions of oocyte stage and ovarian maturity of female sablefish 
C Anoplopoma fimbria ) sampled before spawning in the central Gulf of Alaska during December 2011. For the histological 
classification of ovarian maturity, the most advanced stage of oocytes present is described followed by the maturity stage of 
the ovary. The stages that were observed are marked with an X. 
Structures defining maturity 
Oocyte stage 
Maturity 
Observed 
Microscopic classification of ovarian maturity 
Oocytes with multiple nucleoli or perinucleolar; 
thin ovarian wall. 
Primary growth 
Immature 
X 
Oocytes with multiple nucleoli or perinucleolar; 
thick ovary wall; thick stroma; blood vessels present. 
Primary growth 
Mature; 
skipped spawning 
X 
Yolk accumulated within eosinophylic spheres (vitellogenesis). 
Secondary growth 
Mature 
X 
Yolk spheres have coalesced and yolk has fused. 
Oocyte maturation 
Mature 
X 
Ovulatory follicles remain in the ovary after ovulation. 
Postovulatory follicle 
Mature 
Macroscopic classification of ovarian maturity 
Ovaries thin and tubular; no oocytes visible. 
Ovaries tubular in shape, contain transparent oocytes, 
which appear indistinct through ovary wall. 
Ova opaque, white, and clearly discernible through 
Immature 
Immature 
X 
the distended, transparent ovary wall. 
Mature 
X 
Ovaries engorged with free-flowing, translucent eggs. 
Ovaries large, flaccid, and may be bloodshot. 
Mature; spawning 
Spent 
X 
Ovary small, flaccid; oocytes not discernible. 
Mature; 
skipped spawning 
X 
Ovarian tissues were embedded in paraffin, sectioned 
at 5-6 pm, stained with hematoxylin, and counter- 
stained with eosin. 
Histological slides were examined microscopically 
by 2 readers, and maturity was classified according to 
the most advanced ooctye stage or structure contained 
in the ovary, as well as other features (Table 1) (e.g., 
Hunter et al., 1992; Stark, 2007). Ovaries with pri- 
mary growth oocytes as the most advanced stage were 
classified as immature. However, if ovaries had 1) pri- 
mary growth oocytes accompanied by a thick stroma 
and structural reorganization (loose structure of oo- 
cytes with tissue surrounding oocytes), 2) blood ves- 
sels within the lamellae, and 3) a thick tunica (ovarian 
wall), the ovaries were classified as resting. Because 
sampling was conducted immediately before spawning, 
fish with resting ovaries were classified as fish that 
would skip spawning in the current spawning season. 
The presence of thick tunica and stroma before the 
spawning period has been used as criteria for identify- 
ing skipped spawning in multiple fish species, includ- 
ing winter flounder (Pseudopleuronectes americanus 
[Burton and Idler, 1984]) and Atlantic cod (e.g.. Burton 
et al., 1997; Rideout et al., 2000, 2005; Rideout and 
Tomkiewicz, 2011). Mature females that had vitellogen- 
ic oocytes, hydrated oocytes, or postovulatory follicles 
were characterized as females that were expected to 
spawn in the current spawning season. Ovarian wall 
widths were measured on images taken from the slides 
used for histological examination. Five measurements 
were taken and averaged for each fish. 
Macroscopic determination of maturity during summer 
Macroscopic determination of maturity has been com- 
pleted and accompanying otoliths have been collected 
for aging annually since 1996 during AFSC summer 
longline surveys, which are conducted from the end of 
May through the end of August. Sampling stations are 
spaced systematically 35-55 km apart along the conti- 
nental slope of the Gulf of Alaska, the eastern Bering 
Sea, and the Aleutian Islands (Sasaki, 1985). At each 
station in the Gulf of Alaska, 7200 hooks are set. For 
this study, we examined only samples collected in the 
central Gulf of Alaska (17 stations) for comparison with 
samples collected during the winter survey. The fish 
were collected by using a random, systematic method 
so that samples were taken from all depth strata (100- 
200-m intervals from depths of 200-1000 m). 
During the summer, fish are classified as immature, 
or juvenile, if ovaries are string-like or are slightly en- 
larged and are clear or pink and contain no visible oo- 
