DEPARTMENT OF PRIMARY INDUSTRY, FISHERIES AND MINES Reproduction

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

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4 0

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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

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F3 – Developed gonads

Histological Results

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

0

1 0

2 0

3 0

4 0

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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

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F4 & F5 – Near spawning gonads

Histological Results

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

0

1 0

2 0

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Histological ResultsF6 – Spent gonads

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

0

1 0

2 0

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4 0

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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

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F7 – Resting gonads

Histological Results

DEPARTMENT OFPRIMARY INDUSTRY, FISHERIES AND MINES

0

1 0

2 0

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4 0

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0

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F2 Developing (July)

F3 Developed (October)

F6 Spent (February)

F7 Resting (May)0

1 0

2 0

3 0

4 0

5 0

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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.