presented by : michael ballón

Trends in relative investment of energy in growth and/or reproduction by Peruvian hake Merluccius gayi peruanus from

1972 – 2004:an issue of length dependence

Authors: Michael Ballón, Claudia Wosnitza-Mendo, Arnaud Bertrand, Jacqueline Palacios, Humberto Olivera, and Renato Guevara-Carrasco

Presented by: Michael Ballón

Instituto del Mar del Peru,

Project INCOFISH

OVERVIEW

Introduction

Objective

Materials and Methods

Results and Discussion

Conclusions

Significance of hake• Distribution

Main factors that have affected the hake population

•sardine and anchovy regime•El Niño•Overfishing 40 cm 25 cm

Current situation•New regulations (2002) were set up based on a single species approach (IMARPE)•The stock still far from recovery•Why?

Introduction

82° W 80° W 78° W 76° W

12°S

10°S

8°S

6°S

4°S

Paita

C him bote

C allao

Objective

Main question: How has hake reacted physiologically to the fishing pressure and the physical environment?

Clarifying the effects.

Reducing uncertainty about:

Natural Mortality and Recruitment Success

Hake physiological responses

Materials and MethodsBiological data:

52106 Female hakes sampled from 1971-2004 from Paita port

Total body weight (W) Total length (L)Gonad weight (Wg) Stomach weight (Ws)

Biological Indices

Fulton's condition factor K = W.L-3

Gonadosomatic index GI = Wg.W-1

Fullness index FI = Ws.W-1

Physical environment and time

Paita sea surface temperature anomaly (SSTA) Year-Month (YM)

Time series (1971-2004)Condition factor Gonadosomatic index

0.004

0.024

0.044

0.064

0.084

0.104

0.124

0.144

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

years

mea

n co

nditi

on fa

ctor

0.005

0.0055

0.006

0.0065

0.007

0.0075

0.008

0.0085

0.009

0.0095

mea

n go

ndos

omat

ic in

dex

GI K

Results and Discussion…time series

0.004

0.024

0.044

0.064

0.084

0.104

0.124

0.144

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

years

mea

n co

nditi

on fa

ctor

0.005

0.0055

0.006

0.0065

0.007

0.0075

0.008

0.0085

0.009

0.0095

mea

n go

ndos

omat

ic in

dex

GI K

Long term

Upward trend in condition factor

Downward trend in reproduction activity

Results and Discussion…time series

Short term

Negative impact of El Niño

In both: Fish condition and reproduction

Results and Discussion…?

What are the factors that influence fish condition and maturation proccess?

Materials and MethodsBiological data:

52106 Female hakes sampled from 1971-2004 from Paita port

Total body weight (W) Total length (L)Gonad weight (Wg) Stomach weight (Ws)

Biological Indices

Fulton's condition factor K = W.L-3

Gonadosomatic index GI = Wg.W-1

Fullness index FI = Ws.W-1

Physical environment and time

Paita sea surface temperature anomaly (SSTA) Year-Month (YM)

Generalized Additive Model GAM (1980 -2004) Large hakes (35-50

cm) Small hakes (20-35 cm)

Condition factor K according to GI+FI+SSTA+YMGonadosomatic index GI according to K+FI+SSTA+YM

0.00 0.07 0.14 0.21 0.28 0.35

Fullness IndexFullness index

Results and Discussion…GAM models

Condition factor: K according to GI+FI+SSTA+YM

Large hake (35-50cm)Small hake (20-35cm)

0.00 0.05 0.10 0.15 0.20 0.25

Gonadosomatic Index

-0.0

005

0.00

10"C

ondi

tion

Fact

or"

Gonadosomatic index

“Con

diti

on f

acto

r”

Gonadosomatic Index: GI according to K+FI+SSTA+YM

0.0040 0.0055 0.0070 0.0085 0.0100Condition Factor

-0.0

60.

000.

06"G

onad

Inde

x"

0.0 0.1 0.2 0.3Fullness Index

During the spawning season there is a starving process.

Fecundity depends more on the initial condition factor than on the food intake during the spawning season.

Better condition

More food

Better condition

Higher FecundityStarving

-2 -1 0 1 2 3 4-0.0

012

-0.0

008

-0.0

004

0.00

00

-1 0 1 2 3 4

-0.0

15-0

.010

-0.0

050.

000

Results and Discussion…

“Con

ditio

n F

acto

r”

“Gon

ados

omat

ic in

dex”

Poor condition + spawning high mortalityLarge hake invest more energy in reproduction than small hakeLarge hake disappeared during the El Niño 1992-93 and 1997-98

Large

Small

Large

Small

SSTAnomaly SSTAnomaly

EL Niño

_

+

RESULTS and DISCUSSION…long term

1980 1985 1990 1995 2000 2005

Y M

-0.0

00

40

.00

00

0.0

00

4

s(Y

M)

-0.0

10

.00

0.0

10

.02

s(Y

M)

“Con

ditio

n fa

ctor

”

“Gon

ados

omat

ic in

dex”

Large hake (35-50 cm)

-0.0

15

-0.0

10

-0.0

05

0.0

00

0.0

05

s(Y

M)

1980 1985 1990 1995 2000 2005

Y M

-0.0

00

40

.00

00

0.0

00

4

s(Y

M)

Small hake (20-35 cm)

“Gon

ados

omat

ic in

dex”

“Con

ditio

n fa

ctor

”

?

Why small hake spent their energy reserves in reproduction and large hake do not, although the latter has a higher condition factor ?

RESULTS and DISCUSSION…long term

• Low reproduction could be expected when biomass is close to the carrying capacity level

HOWEVER

•hake biomass has been at a low level from the late 1990s onwards

•Size at first maturity has reduced in the last decades (recovering SSB)

AND at the same time large hake has reduced reproduction activity

That is not a logical density-dependent effect

Is this a density-dependent effect?

RESULTS and DISCUSSION…long term

0.0

0.2

0.4

0.6

0.8

1.0

89 91 93 95 97 99 01 03 05

0.0

0.2

0.4

0.6

0.8

1.0

80 82 84 86 88 90 92 94 96 98 00 02 04

0.0

0.2

0.4

0.6

0.8

1.0

95 97 99 01 03 05

35 +_ 2 cm

+_ 2 cm25

+_ 2 cm20

Fem

ale

prop

orti

on

Years

Female propotion estimated

from commertial landings Paita

•Sex proportion from 80% males to 80% females

•Lack of males for large hake ( >35 cm)

•Low fertilization rate

•Low stimulation for the spawning act

Conclusions