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Fishery Bulletin 1 1 1 (1) 
Table 1 
Field index developed and used to stage the reproductive maturity of female Haddock (Melanogrammus aeglefinus ) caught in 
the Gulf of Maine in 2006-07 during this study in which macroscopic methods in the field were compared with histological 
methods in the laboratory. OM=oocyte maturation. 
Stage 
Abbreviation Description 
Immature 
I 
Ovaries small and firm, about 1/8 the volume of the body cavity. Membrane thin and trans- 
parent, gray to pink in color. Contents microscopic: Individual oocytes not visible to the 
naked eye. 
Developing 
D 
Ovaries larger and plump, about 1/3 to 1/2 the volume of the body cavity. Membrane red- 
dish-yellow with numerous blood vessels. Contents visible to the naked eye and consist of 
opaque eggs that give the ovaries a granular appearance. 
Hydration stage 1 
HI 
Ovaries well developed, reddish-yellow in color, at least 2/3 volume of body cavity. Mem- 
brane opaque with blood vessels conspicuous. Contents consist mostly of yellow-looking 
oocytes with <25% of the ovary containing larger translucent oocytes. A batch of oocytes in 
the early stages of OM where oocytes start to hydrate. 
Hydration stage 2 
H2 
Ovaries well developed, reddish-yellow in color, at least 2/3 volume of body cavity. Mem- 
brane opaque with blood vessels conspicuous. Visible surface of the ovary consists of 25- 
50% larger translucent oocytes. Further progression of a batch of eggs in OM. 
Hydration stage 3 
H3 
Ovaries well developed, reddish yellow in color, at least 2/3 the volume of body cavity. 
Membrane opaque with blood vessels conspicuous. Visible surface of the ovary consists 
of 50-75% larger translucent oocytes. Ovaries may appear a little flabby, indicating the 
previous release of batch! es) of eggs. Final stages of the maturation of a batch of oocytes 
before a spawning event. 
Ripe and running 
RR 
Ovaries very large, over 2/3 the volume of the body cavity. Contents consist of mostly large, 
translucent eggs. Eggs running freely with little to no pressure on the abdomen. 
Regressing 
S 
Ovaries soft, and flabby, about 1/4 the volume of the body cavity. Membrane thick and 
tough, purplish in color, and bloodshot. Contents empty, few eggs remain, giving the gonad 
a patchy appearance. 
Regenerating 
RE 
Ovaries small and firm. 1/6 the volume of the body cavity. Membrane thin but less trans- 
parent than an immature ovary, yellowish-gray in color. Contents microscopic, opaque. 
Peterson et al., 2011) on the basis of the percentage of 
hydrated oocytes present (HI, H2, H3; Table 1, Fig. 1). 
During observations of mature female Haddock 
ovaries, we noticed that many of them had varying 
numbers of hydrated oocytes. We did not find an ovar- 
ian maturity index in the literature that categorized 
the progression in percentage of hydrated oocytes in 
a gonad. We were interested in whether the increase 
in percentage of hydrated oocytes was detectable over 
time and whether these stages may aid in examination 
of diel reproductive periodicity (Anderson, 2011). 
Hydration stage 1 (HI) is an ovary where a batch of 
oocytes is in the early phase of OM and when <25% 
of that ovary’s visible surface contains translucent, 
hydrated oocytes (Table 1). 
Hydration stage 2 (H2) is an ovary where a batch of 
oocytes is in the middle phase of OM and when 25- 
50% of that ovary’s visible surface contains translu- 
cent, hydrated oocytes (Table 1). 
Hydration stage 3 (H3) is an ovary with a batch of 
oocytes in a late phase of OM and when 50-75% of 
the visible surface of that ovary contains translu- 
cent, hydrated oocytes (Table 1). 
We hypothesized that HI, H2, and H3 occur with 
each batch of oocytes before it is spawned (Fig. 1). The 
index also includes for each stage: 1) a macroscopically 
derived ratio of ovary volume to body cavity volume, 
similar to the ratio of gonad cavity length to body cav- 
ity length that Robb (1982) included for some stages; 
2) a physical description of the ovary membrane, as 
Homans and Vladykoy (1954) included for some of the 
stages; and 3) a grossly assessed oocyte development 
description, included by Homans and Vladykoy (1954), 
Robb (1982), and Murua et al. (2003) (Table 1). 
The histological staging method was derived inde- 
pendently of the macroscopic ovarian maturity index 
(i.e., during analysis, field-based stages were not used 
by laboratory personnel in development of histological 
stages and vice versa), and it was based on previous 
work of Tomkiewicz et al. (2003), Roumillat and Brou- 
wer (2004), and Brown-Peterson et al. (2011) (Table 2). 
To differentiate the processes of early versus later vitel- 
logenic activity, 2 histological index stages (2.1 or 2.2) 
were used to define developing ovaries (Table 2). Be- 
cause Haddock are classified as possessing determinate 
fecundity (Murua et al., 2003), all oocytes that will be 
spawned during the upcoming season develop during 
these 2 stages, leaving a group of primary oocytes as a 
reserve for the successive spawning season. However, 
the developing stages in the histological index (2.1 and 
