Conrath: Reproductive potential of Sebastes variabilis and 5. polyspinis 
141 
Maturity ogives have been published for both of these 
species (Chilton, 2007, 2010), but little information is 
available about other reproductive parameters. Maternal 
effects, abortive maturity, spawning omission or skipped 
spawning, and spatial disparities in the quantity of broods 
have all been documented for members of this genus 
(Hannah and Parker, 2007; Beyer et al., 2015; Conrath, 
2017). Reproductive potential or the number of viable lar¬ 
vae released by a population at parturition is influenced 
by both the number of developing oocytes (potential fecun¬ 
dity) and the proportion of adults that have incomplete 
spawning (partial reproductive failure) or fail to spawn 
(total reproductive failure or skipped spawning). The objec¬ 
tive of this project was to assess the reproductive potential 
of light dusky and northern rockfish at 2 different sites 
within the Gulf of Alaska by examining a variety of repro¬ 
ductive parameters, including development of oocytes and 
embryos within the ovary, gonadosomatic indices, potential 
annual fecundity, annual rates of reproductive failure, and 
maternal effects. Values for these parameters will be pro¬ 
vided to stock assessment scientists for the management of 
these and other rockfish species in this region. 
Materials and methods 
Two research cruises were conducted in May (spring) and 
December (winter) 2014. During each cruise, 2 sites in the 
central Gulf of Alaska were sampled: one at 49 Fathom 
Pinnacle and one on Snakehead Bank (Fig. 1). Both sites 
are located offshore of Kodiak Island near Middle and 
Southern Albatross Bank. We collected samples from 
female northern and light dusky rockfish at the site at 
49 Fathom Pinnacle. Adult light dusky rockfish also were 
captured at the site at Snakehead Bank (Table 1). Each 
fish was measured for fork length (FL) and total weight, 
and the ovary was removed and preserved in a solution of 
10% neutral buffered formalin. 
A sample removed from the center of one lobe of the 
ovary from each specimen was embedded in paraffin and 
thin sectioned to 6 pm. Standard histological techniques 
were used to stain these tissue samples with hematoxy¬ 
lin and eosin (Sheehan and Hrapchak, 1980). These sam¬ 
ples were used to examine the development of oocytes 
and embryos within the ovary, with stages defined on 
the basis of the terminology of Bowers (1992) (Table 2). 
Each sample was examined to determine which oocyte 
or embryo stages were present by using a compound 
microscope. The most advanced oocyte or embryo stage 
within the section was identified. In addition, the sec¬ 
tion was examined for the presence of atretic oocytes. 
Alpha atresia was characterized by the disintegration of 
the nucleus, irregularly shaped oocytes, disintegration of 
yolk, and the dissolution of the zona radiata. Beta atresia 
was characterized by oocytes having a compact structure 
composed of disorganized granulosa cells. Delta atresia 
was characterized by a dark yellow or brown pigment 
within the granulosa cells (Hunter and Macewicz, 1985a). 
156°0'0"W 154°0'0"W 152°0'0"W 150°0’0"W 
Figure 1 
Map of the 2 sites where northern rockfish (Sebastes polyspinis) and light 
dusky rockfish (S. variabilis) were sampled off Kodiak Island near Middle and 
Southern Albatross Bank in the central Gulf of Alaska in May and December 
2014. Female northern and light dusky rockfish were collected at the site on 
49 Fathom Pinnacle (1). Adult light dusky rockfish were also captured at the 
site on Snakehead Bank (2). 
