Diel%20Reproductive%20Periodicity%20in%20Haddock%20in%20the%20Southwestern%20Gulf%20of%20Maine

1
Diel Reproductive Periodicity in Haddock in the
Southwestern Gulf of Maine Katie A. Anderson,
Francis Juanes and Rodney Rountree University of
Massachusetts Amherst, USA
METHODS Commercial fishing vessels were
chartered for 25 dedicated survey trips in the
spring of 2006 (15) and 2007(10). Long lines were
set and hauled in each of six time bins
(0100-0500 h, 0500-0900 h, 0900-1300 h, 1300-1700
h, 1700-2100 h or 2100-0100 h) over a one to two
week period to obtain representative 24 hour
sampling. Sex, fork length and reproductive
maturity of approximately 2000 haddock were
recorded at sea. The presence and percentage of
hydrated oocytes in each ovary was noted.
(Fig.1). In the laboratory the ovaries of a
subsample of female haddock selected from each
haul were excised and weighed to determine the
gonad somatic index (GSI Gonad Weight/ (Body
Weight-Gonad Weight) x 100). Preserved oocyte
samples were sent to and independent laboratory
of William Roumillat (South Carolina Department
of Natural Resources) for histological
examination to determine the accuracy and
consistency of our field observations of ovarian
macroscopic maturity stages.
Figure1. Hydration indices created and used in
the field when determining the maturity stage of
haddock ovaries. A) Developing ovary (no hydrated
oocytes) B)Oocyte recruitment has seized,
oocytes maturation has begun with lt25 oocytes
hydrated C) 25-50 oocytes hydrated D) Late
final oocyte maturation stage with gt50 oocytes
hydrated.
RESULTS ltgtlt Comparisons made between
macroscopic predictions of maturity stage made in
the field with histology analysis showed
an 80 overall agreement . Thus our
macroscopic field methods appear to reliably
determine early and late final oocyte
maturation (FOM). ltgtlt GSI was very highly
significantly influenced by time of day and
appear to take the form of a quadratic
polynomial response, indicating a decline in GSI
in the early morning hours (Fig.2).
ltgtlt Percentage of female haddock in ripe and
running reproductive maturity stage was
significantly influenced by time of day in both
years with a significant day/night
difference (Fig.3). ltgtlt Catch Per Unit Effort
CPUEnumber of haddock caught/(number of hooks
fished x length of time gear soaked) of
spawning female took a very different form then
the remaining reproductive maturity
stages.
ACKNOWLEDGEMENTS Funding MIT Sea Grant
Program, Degree advisers Francis Juanes and
Rondey Rountree, Committee members Cliff Goudey
and Steve Cadrin. FishermanTom Hill, Phil Powell
and John Montgomery, Histology work Wiilliam
Roumillat. Many gracious field volunteers.