Burchard et at: Maturity indices and field sampling practices for staging Melanogrammus aeglefmus 
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classified as the adjacent histological stage 2.0, 2 ova- 
ries were classified as 3.2, and 5 ovaries were assigned 
as 3.3. One Hl-classified ovary contained early POFs, 
and 5 HI ovaries contained late POFs. In contrast, 2 of 
the 16 samples classified as 3.1 in the laboratory were 
classified as the adjacent D stage with the field index, 
1 sample was classified as H3, and 1 sample was as- 
signed as regressing (S). 
Twenty-one of the 33 ovaries classified as H2 with 
the field index were also classified as the equivalent 
histological stage 3.2 in the laboratory (Table 4). Nine 
H2-classified ovaries were classified as the adjacent 
histological stage 3.3. One ovary contained early POFs, 
and 2 ovaries contained late POFs. In contrast, 4 of 
the 29 ovaries classified as the 3.2 stage in the labo- 
ratory were classified as the adjacent field stages (HI 
and H3), and 4 of those ovaries were classified as S. 
The H3-classified samples were most frequently 
classified as the equivalent histological stage 3.3 (n- 22; 
Table 4). Two H3-classified ovaries were classified as 
the adjacent histological stage 3.2, and 1 ovary was 
classified as 3.1. In contrast, 35 of the 57 ovaries classi- 
fied as the histological stage 3.3 were classified differ- 
ently with the field index, with most ovaries classified 
as H2 (n=9) or RR (n= 17). 
All but 2 of the ovaries classified as RR («=17) in 
the field were classified as the histological stage 3.3 
(Table 4). The 2 remaining ovaries were classified as 
the histological stages 4.2 and 5.0. 
Four of the 12 ovaries classified as S with the field 
index were assigned the equivalent histological stage 
5.0 (Table 4). Four additional ovaries classified as S 
with the field index were classified as the histological 
stage 3.2, and 2 ovaries were assigned as 3.3, 2 ova- 
ries as 3.1, and 1 ovary as 6.0. In contrast, most of 
the 21 ovaries assigned to the histological stage 5.0 
in the laboratory were classified as RE with the field 
index (/? = 16, 76%); however, 1 ovary was assigned as 
H3 (Table 4). 
Twelve of the ovary samples classified as RE with 
the field index were classified as the equivalent histo- 
logical stage 6.0 (Table 4). Sixteen samples classified as 
RE with the field index were classified as the adjacent 
histological stage 5.0 in the laboratory. Two additional 
samples classified as RE in the field were classified as 
histological stage 3.3, and 2 samples were classified as 
1.0, and 1 sample was assigned as 2.0. In contrast, all 
but 1 of the 13 ovaries classified as histological stage 
6.0 in the laboratory were also classified as RE with 
the field index. 
A final composite ovarian maturity index was cre- 
ated on the basis of the findings from this study (Table 
5). Visual characteristics for both the whole ovary and 
tissue sample were emphasized as was similarly done 
by Tomkiewicz et al. (2003) for Altantic Cod in the Bal- 
tic Sea. The final index consists of 7 stages of ovary 
reproductive maturity distinguishable at sea. Table 5 
includes for each maturity stage an image of the whole 
ovary, a photomicrograph of equivalent histological tis- 
sue, and both a macroscopic and microscopic physical 
description of the ovary. Notes are included to aid the 
user in correct macroscopic identification of each stage. 
Sampling techniques for collection of tissue samples 
are also included for problematic stages. On the basis 
of comparison with the histological data, we concluded 
that H3 and RR field stages are identical and grouped 
them together as a single stage (H3). When we used 
this revised H3 field stage, 39 of the 44 ovaries as- 
signed as H3 were assigned the equivalent 3.3 histo- 
logical stage. 
Discussion 
The utility of the field-based staging method for the 
classification of fish reproductive maturity for fisher- 
ies management is dependent on its biological accuracy. 
The findings from this study highlight the problems of 
development of an accurate error-proof field ovarian 
maturity index on the basis of macroscopic observation. 
However, a comparison of field-based and histology- 
based staging methods of Haddock ovaries presented in 
this study revealed the need to revise the field staging 
methods to increase the accuracy of both staging meth- 
ods. Although laboratory staging done on the basis of 
histology is inherently more accurate than any macro- 
scopic field staging method, there was indication that 
field observations can reveal weaknesses in the labora- 
tory approach because samples of the ovary taken for 
histology are not always going to be representative of 
the whole ovary. The strengths and weaknesses of both 
approaches for each maturation stage are discussed 
in the next sections, followed by recommendations for 
correct identification of each stage and a description 
of helpful sampling techniques for collection of tissue 
samples of problematic stages. 
Immature stage 
The I stage in the field index was equivalent to the 
1.0 histological stage (Tables 1 and 2). The only stage 
mistaken for immature in the field was RE (Table 1). 
In both stages, the ovary was small and firm. The RE 
ovary appeared to be a little larger, less transparent, 
and grayer in color in comparison with the pink color 
of an immature ovary. However, in a young mature 
fish or late immature fish, these differences were less 
detectable. The imprecision in separation of immature 
and regenerating mature females also has been en- 
countered in staging Atlantic Cod ovaries (Tomkiewicz 
et al., 2003). Comparison of the current mean length 
at maturity for Haddock with the size of the specimen 
may help support either maturity stage in the field, but 
this criterion should not be relied on because length 
at maturity can change over time (Saborido-Rey and 
Junquera, 1998; Tobin et al., 2010). 
In this study, the smallest Haddock caught was 35.5 
cm FL, larger than the mean length at maturity re- 
