Biological parameters of swordfish in the Indian Ocean

used for stock assessment

Growth parameters

• Young, J., and A. Drake. 2004. Age and growth of broadbill swordfish (Xiphias gladius) from Australian waters. Final report for project 2001/014, Fisheries Research Development Corporation, Canberra, Australia. 121 pp.– A preliminary investigation of age and growth

of swordfish, Xiphias gladius, from Western Australian waters using anal fin rays

Growth parameters

• Sampling area

Growth parameters

• Growth parameters (von Bertalanffy)– Female: L = 323.4; K = 0.08148; t0 = -3.413

– Male: L = 260.47 ; K = 0.1096 ; t0 = -3.3808

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Age

LJF

L (

cm)

Female

Male

Sex ratio

• Young, J., and A. Drake (2004)

y = 2E-10x5 - 2E-07x4 + 5E-05x3 - 0.0069x2 + 0.5153x - 14.662

Length-Weight relationship

• Ariz. J., A. Delgado de Molina, M. L. Ramos, and J. C. Santana, 2006. Analyses of sex ratio, by length-class and length-weight relationships for several species of Family Xiphiidae (Xiphias gladius, Linnaeus 1758) and Istiophoridae (Istiophorus platypterus, Shaw 1792) and Tetrapturus angustirostris, Tanaka 1915) caught from experimental cruise on Spanish longliners in the South Western Indian Ocean during 2005. The fifth meeting of the Working Party on Billfish (WPB), Indian Ocean Tuna Commission (IOTC), March 27–31, 2006. Colombo, Sri Lanka. IOTC-WPB-06-10, 14 pp.

Length-Weight relationship

• Sampling area

Length-Weight relationship

• Parameters (W = a L b)– L: LJFL– Female: a = 2.413E-06, b = 3.33727– Male: a = 1.351E-06, b = 3.45674– Combined: a = 1.839E-06, b = 3.39209

Sex ratio

• Ariz. J., A. Delgado de Molina, M. L. Ramos, and J. C. Santana (2006).

Sexual maturity

• Poisson, F., and C. Fauvel, 2009. Reproductive dynamics of swordfish (Xiphias gladius) in the southwestern Indian Ocean (Reunion Island). Part 1: oocyte development, sexual maturity and spawning. Aquat. Living Resour., 22: 45-58.

Sexual maturity

• Sampling area

Sexual maturity

• %mature at length– %Mature females =

100[1/(1 + exp(16.2506 − 0.095342 LJFL))]– %Maturemales =

100[1/(1 + exp(10.1758 − 0.084884 LJFL))]

Sexual maturity

• %mature at length

Sex ratio

• Poisson, F., and C. Fauvel (2009).Y = −1.2×10−11 X6−1.2×10−8 X5 + 5 × 10−6 X 4 − 0.

0011 X3 + 0.1355 X2 − 8.3638 X + 209

Age-length key

• The length distribution for each age group is assumed to be normal distributed with mean and SD.

• Mean length and SD for each age group are estimated based on the parameters and data from Young, J., and A. Drake (2004).

2

, 2

( )1exp

2( )2l

l

L L aa l L L

aa

L LdL

Age-length key

• Length distribution for each age group (probability)

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0 15 30 45 60 75 90 105

120

135

150

165

180

195

210

225

240

255

270

285

300

Length (cm)

Pro

ba

bili

ty

A0

A1

A2

A3

A4

A5

A6

A7

A8

A9

A10

A11

A12

A13

A14

A15

Age-length key

• Proportion that a fish with length X assigned to be a age X (age-length key)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 18 36 54 72 90 108 126 144 162 180 198 216 234 252 270 288

Length (cm)

Pro

pro

tion

A0

A1

A2

A3

A4

A5

A6

A7

A8

A9

A10

A11

A12

A13

A14

A15