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DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Reproduction
Jewfish Jewfish Workshop Workshop
20062006
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Establish the reproductive strategy of black jewfish.
Aim
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
1. Determine the spawning season and the relevance of the annual aggregations.
2. Establish the size of sexually mature black jewfish (minimum and I50).
3. Document the current size/age structure of black jewfish landings.
Objectives
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
• Over a two year period, 70 fish per month were measured, weighed and sampled.
• Fish sourced from commercial fishers and fishing tour operator landings.
• Additional fish (<50 cm & >130 cm) sourced from commercial and rec. fishers.
General Methods
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Reproduction Study Methods
• Gonad sampling: – Individual lobes
weighed; section of one lobe preserved.
• Gonad processing:– Sectioned and stained;
Classified based on oocyte stages.
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Classification SystemStage Most advanced oocyte Other key criteria
F1 Immature Chromatin nucleolar or perinucleolar
Thin gonad wall; Brown bodies not present; Compact, well packed lamellae; May have atretic cortical alveoli oocytes.
F2 Developing Cortical alveoli (yolk vesicle)
May have atretic oocytes; May also have post-ovulatory follicles and brown bodies.
F3 Developed Yolk globule May have atretic oocytes; May also possess brown bodies.
F4 Pre-spawning Migratory nucleus Ovary appears disorganised; Brown bodies may be present; May have post-ovulatory follicles if fish has spawned already.
F5 Spawning Hydrated Ovary appears disorganised; Post-ovulatory follicles, brown bodies and atretic oocytes may be present.
F6 Spent Atretic vitellogenic Lammellae disrupted and disorganised; Vasculated in late spent stage; Brown bodies generally present.
F7 Resting Chromatin nucleolar or perinucleolar
Thick gonad wall; Brown bodies common but not always present; Lammellae not compact, often vaculated.
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Mea
n G
SI
0
1
2
3
4
5
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Mea
n G
SI
Relative gonadosomatic index and standard deviation for females (n = 529).
Spawning Season
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
F2 – Developing gonads
Histological Results
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
F3 – Developed gonads
Histological Results
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
F4 & F5 – Near spawning gonads
Histological Results
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
Histological ResultsF6 – Spent gonads
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
F7 – Resting gonads
Histological Results
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
F2 Developing (July)
F3 Developed (October)
F6 Spent (February)
F7 Resting (May)0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
0
1 0
2 0
3 0
4 0
5 0
J a n F e b M a r A p r M a y J u n J u l A u g S e p O c t N o v D e c
Nu
mb
er
F4-5 Near Spawning (November)
Histological Results
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Spawning Size
Size at first maturity
• Minimum size of maturity = 85 cm
• Maximum size of immaturity = 100 cm
• I50 estimate = ~90 to 95 cm.
• Need to run logistic model.
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Size StructureLength/weight of black jewfish harvested near Darwin, 2004-06 (n = 1490).
y = 5 E - 0 5 x 2 .6 2 8 5
R 2 = 0 . 7 5 8 7
02468
1 01 21 41 61 82 02 22 4
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0
L e n g t h ( c m )
We
igh
t (k
g)
Length (cm)
Wei
ght
(kg)
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Size StructureLength/weight of black jewfish harvested near Darwin, 2004-06 (n = 1490).
y = 5 E - 0 5 x 2 .6 2 8 5
R 2 = 0 . 7 5 8 7
02468
1 01 21 41 61 82 02 22 4
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0
L e n g t h ( c m )
We
igh
t (k
g)
Length (cm)
Wei
ght
(kg)
Mature Fish
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Length/weight of black jewfish harvested near Darwin, 2004 (n = 415).
Length (cm)
Wei
ght
(kg)
Length (cm)
y = 5 E - 0 5 x 2 .6 2 8 5
R 2 = 0 . 7 5 8 7
02468
1 01 21 41 61 82 02 22 4
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0
L e n g t h ( c m )
We
igh
t (k
g)
Size Structure
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Length/weight of black jewfish harvested near Darwin, 2005 (n = 636).
Length (cm)
y = 5 E - 0 5 x 2 .6 2 8 5
R 2 = 0 . 7 5 8 7
02468
1 01 21 41 61 82 02 22 4
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0
L e n g t h ( c m )
We
igh
t (k
g)
Length (cm)
Wei
ght
(kg)
Size Structure
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Length/weight of black jewfish harvested near Darwin, 2006 (n = 438).
Length (cm)
y = 5 E - 0 5 x 2 .6 2 8 5
R 2 = 0 . 7 5 8 7
02468
1 01 21 41 61 82 02 22 4
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0
L e n g t h ( c m )
We
igh
t (k
g)
Wei
ght
(kg)
Length (cm)
Size Structure
DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES
Summary• GSI indicates extended spawning = Aug to Jan.
• GSI and histology suggests serial spawning.
• Minimum size = 85 cm; I50 = ~90-95 cm.
• No apparent difference in size between years.
