104 
Fishery Bulletin 111(1) 
Noting the apparent longevity of POFs helped us un- 
derstand the duration and cyclical process of OM in 
this species and potentially other boreal or cold-water 
fishes. Because reproductive maturation occurred over 
a prolonged period of time, OM occurred throughout 
3 distinct field stages (HI, H2, and H3) and histol- 
ogy stages (3.1, 3.2, and 3.3). This finding supports 
the conclusion of Alekseyeva and Tormosova (1979) 
that Haddock exhibits asynchronous maturation of in- 
dividual groups of oocytes. We believe that the asyn- 
chronous maturation of oocytes in a batch results in 
heterogeneous ovaries during early phases of OM and 
can lead to misclassification of HI ovaries as D stage 
in the field. However, Robb (1982) and Templeman et 
al. (1978) previously reported that Haddock ovaries 
are homogeneous in structure throughout all phases of 
maturity. Studies of follicle size-frequency distributions 
throughout OM are needed to confirm our observation 
of apparent heterogeneity of ovaries during early matu- 
ration to clarify how future studies should be modified 
to ensure accurate staging in the field and laboratory. 
Additional work should be focused on differentiation 
of a regenerating ovary from an immature ovary. This 
differentiation is the most important distinction in de- 
termination of maturity or reproductive dynamics of a 
stock because of the use of these numbers in estima- 
tion of spawning stock biomass. 
The timing of the sampling in this study, although 
restricted, was focused around the known spawning 
season of Haddock in the Gulf of Maine. This focus 
likely increased the reliability of staging SC fish be- 
cause the closer in time to the spawning season the 
more developed the ovary becomes, as was observed 
by Tomkiewicz et al. (2003). Alternatively, reliability 
in staging SC fish in the fall and winter is tenuous 
because ovary development is just beginning (Tomkie- 
wicz et ah, 2003). Therefore, the optimal time to collect 
data to be used to estimate spawning stock biomass 
should span across the spawning season, and we cau- 
tion against the use of SC data collected off season in 
estimation of spawning stock biomass. 
It is anticipated that the revised ovarian maturity 
index (Table 5) presented in our study will be useful 
to Haddock resource managers. The H2 and H3 stages 
appear to be useful indicators of spawning readiness 
for Haddock ovaries in the field. We suspect that the 
progression of OM is detectable in other boreal spe- 
cies with the same reproductive traits as Haddock and 
that the later stages could also be used to examine diel 
periodicity in these species. Although this index was 
developed for studies on diel reproductive periodicity, 
we feel it would also be useful for study of other short- 
term temporal reproductive patterns related to tidal, 
lunar, or solar zenith cycles. The revised field index in- 
cludes pointers to help users stage ovaries and take ap- 
propriate samples (Table 5). Although this revised field 
index will improve accuracy in the determination of the 
maturity stage of Haddock in the field, evidence has 
shown that field indices alone may not be enough to 
correctly classify a fish in problematic stages. However, 
the observations in our study also demonstrate that de- 
termining the maturation of an ovary by histological 
examination alone may not always be accurate, high- 
lighting the importance of field staging. In addition to 
field staging with the index presented here, appropri- 
ate tissue samples should be collected and analyzed 
microscopically or histologically to verify problematic 
stages, especially when field data are used in assess- 
ment and management of ^a fish stock. 
Acknowledgments 
This publication is the result of research spon- 
sored by The Massachusetts Institute of Technol- 
ogy Sea Grant College Program, under National Oce- 
anic and Atmospheric Administration grant number 
NA060AR4170019 and project number 2005-R/RD-29. 
The authors thank the cooperative work and generos- 
ity of fishermen T. Hill, P. Powell, and J. Montgomery. 
We also thank C. Goudey, S. Cadrin, and R. McBride 
for project advice and support. The assistance of vari- 
ous volunteers in the field and laboratory work is 
appreciated. 
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