Burchard et al. : Maturity indices and field sampling practices for staging Melanogrammus aeglefmus 
93 
Immature 
Regenerating 
Regressing 
H3 
* 
A 
\ 
H2 
J 
> 
Oocyte maturation 
(OM) 
HI 
Batch 2 J 
* H3 -_ H2 
Interbatch period 
OM re-occurs with 
every batch before 
a spawning event = Spawning event 
Figure 1 
The maturation cycle of the female Haddock ( Melanogrammus aeglefinus), including 3 
hydration stages and an interbatch period, introduced and used during this study of meth- 
ods for staging the reproductive maturity of Haddock sampled in the southwestern region 
of the Gulf of Maine in the spring of 2006 and 2007. Hydration stage 1 (HI), hydration 
stage 2 (H2), and hydration stage 3 (H3) represent early-to-late progression of final oocyte 
maturation (OM) of a batch of oocytes, based on the percentage of hydrated oocytes pres- 
ent. *=spawning event. 
2.2) were grouped together as one developing stage 
(2.0) when the histology results were compared with 
the field results because those stages could not be dif- 
ferentiated by macroscopic examination. Three phases 
of spawning-capable (SC) ovaries were assigned in the 
histological index as 3.1, 3.2, and 3.3 to differentiate 
the process of early, middle, and late phases of OM: 
early germinal vesicle migration (GVM) and germinal 
vesicle breakdown (GVBD) (Table 2). The gross assess- 
ments of HI, H2, and H3 are based on morphologically 
distinct criteria that are corroborated by the histologi- 
cal sections that effectively separate these stages from 
each other (Table 2). Two histological index stages (4.1 
and 4.2) were defined to categorize SC ovaries that 
showed evidence of recent ovulation with the presence 
of recent (4.1) or old (4.2) postovulatory follicles (POFs; 
Alekseyeva and Tormosova, 1979; Saborido-Rey and 
Junquera, 1998). POFs are ruptured empty oocyte cas- 
ings left in the ovary after a spawning event (Table 2; 
Alday et al., 2010; Saborido-Rey and Junquera, 1998). 
If a sample contained POFs but also exhibited char- 
acteristics of another stage, the alternative stage was 
assigned with a note that the sample contained POFs 
(e.g., if a sample primarily contained oocytes in stage 
3.1 but also contained POFs, it was assigned to the 3.1 
stage). 
Field sampling 
Commercial fishing vessels were chartered for 25 dedi- 
cated survey trips in the spring of 2006 (15) and 2007 
(10) to collect biological samples of Haddock in the 
southwestern Gulf of Maine (National Marine Fisher- 
ies Service Statistical area 514; Fig. 2). Surveys were 
based on a fixed station design with sampling where 
Haddock aggregations were known to previously exist. 
Sampling was conducted during the known spawning 
season of Haddock in the Gulf of Maine, between Janu- 
ary and June (Brown, 1998). Haddock were identified 
in the manner used bj' Collette and Klein-MacPhee 
( 2002 ). 
Longlining was the preferred collection method 
for samples because few discards would result. Ap- 
proximately 19 m of longline was set and retrieved 
3 times at each sampling location over a 12-h period 
with the objective of having 2 consecutive trips repre- 
sent sampling over a 24-h period (0100-0000 h; Table 
3). Sets were conducted within specific 4-h time bins 
