North and South Atlantic albacore (Thunnus alalunga) stocks assessment

ICCAT WG ALB, 26 Sept., 2007

Ex. Report ALB SCI-017

Multifan Inputs for ALB Assessment, March 2007 SCI-030 /2007

Detail Albacore stock assessment, July 2007- SCI-036 /2007

ALB- Atlantic Biology

• Stock structure for assessment: North and South stocks in the Atlantic ocean separated at 5º and Mediterranean stock. Intermingling of Indian and Atlantic oceans needs research.

• Present knowledge on habitat distribuition by size, spawning areas, maturity based on limited studies mostly from past years.

• Revised vB growth equation was estimated for South Atlantic stock based on aging dorsal fin ray section

• Vertical distribution: immature at sub-surface above thermocline in summer. Adult distribution at wider range from surface to ~ 300m depth.

ALB - Spatial distribution based on average catch

2000 - 2005 period

Catch trend Northern stock ALB1930-2005 years

BB

LL

TROL

0

10000

20000

30000

40000

50000

60000

70000

1930

1932

1934

1936

1938

1940

1942

1944

1946

1948

1950

1952

1954

1956

1958

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

ALB: North Atlantic

ca

tch

es

(t)

Other surf.

Troll

Traw l

Bait boat

Longline

1975 VPA

Fisheries indicators in North Atlantic

BB

LL

TROL

• Targeting immature and sub-adults (50- 90 cm FL) by surface fisheries in the North Eastern Atlantic from Azores Is. to northern lalitude (SW Ireland) and Bay of Biscay areas, during spring, summer and autumn.

• Targeting immature and adult albacore (60-130 cm FL) by longline fisheries in Central and Western Atlantic waters all year round.

• Catch was extended back to 1930 after revision for stock assessment.

• Trend: declining began in 1986 due to reduction of traditional surface fleets (Troll and Baitboat) and longline fleets. Stabilization observed in the 90´s due to incorporation of new fleets (drifnets & mid-water pair pelagic trawl). Maximun catch of 38,063 t registered in 1993. Followed by the lowest on record of 22,685 t in 2002. Since then and steady increase until reaching a peak of 36,077 t in 2006.

Overall description

Surface Fisheries

BB

LL

Longline Fisheries

• Gears: troll, baitboat, mid-water pair pelagic trawl (MWPT).

• Main fleets involved: EC (Spain, France Portugal and Ireland)

• In 2006 the surface fishery represented the 86 % of total catch in North stock

• EC-France MWPT reported the highest catch of recent years in 2005, but decreased the 30 % in 2006.

• EC-Ireland MWPT catch has decreased since 2002.

• EC-Spain increased the baitboat catch by 49% respecting 2005 catch and the troll catch in 2006 was similar to 2005 level.

• Longline catches decreased in 2006, due to a decrease of landings by Chinese-Taipei fleet of 60% compared to 2005 caused by decline in fishing effort.

Catch trend Southern stock ALB1956-2005 years

BB

LL

LL

BBLL

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

1950

1952

1954

1956

1958

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

ALB: South Atlantic

ca

tch

es

(t)

Other surf.

Bait boat

Longline

Traw l

Fisheries indicators in South Atlantic

BB

LL

TROL

• Targeting immature and sub-adults (70- 90 cm FL) by surface fisheries in the South Eastern Atlantic in coastal waters of Namibia and South Africa from October to May.

• Targeting adult albacore (> 90 cm FL) by longline fisheries in Northeast coast off Brazil (5ºS-20º S) and over the South Atlantic area by longline fleet from Chinese-Taipei Central all year round.

• Trend: total reported catch in 2006 was 24,375 t , an increase of about 5,000 t respect 2005. The Chinese –Taipei catch increased in 2006 to 12,293 t. As for Brazilian catches, the Chinese –Taipei vessels (incluidng Belize and St. Vincent flagged boats ) stopped fishing for Brazil in 2003, then albacore was only caugth as by-catch in the SWO and Trop target longline fisheries, reaching 267 t.

• The decreased of albacore in 2006 in inshore waters of South Africa and unfavorable foreign currency has caused a reduction in number of active baitboat vessels.

Overall description

Catch trend Mediterranean stock ALB1964 -2005 years

BB

LL

LL

BBLL

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

19

50

19

52

19

54

19

56

19

58

19

60

19

62

19

64

19

66

19

68

19

70

19

72

19

74

19

76

19

78

19

80

19

82

19

84

19

86

19

88

19

90

19

92

19

94

19

96

19

98

20

00

20

02

20

04

20

06

ALB: Mediterranean

catc

hes

(t)

Troll

Purse seine

Other surf.

Longline

Bait boat

• Reported catches in 2006 were 5,874 t, an increased with respect to 2005.

Longline

Other Surf

Main Fleets

Assessing the State of Atlantic stocks

BB

LL

LL

BBLL

Background

• Thorough revision of North and South Atlantic stock data: Task I and Task II, was done and more robust method was implemented to analyse Catch-at-Size (CAS) information.

• Historical Catch for North Atlantic stock was recovered and incorporate to the analyses up to 1930.

• Catch rates analyses were reviwed and new model applied for some longline fleets resulting in better fit to data.

• Substantial work was undertaken to implement new methods which do not assume that CAA is known whitout error, to assess the albacore stocks.

• This new implemented method provided the opportunity to evaluate a range of hypothesis:

- how the fisheries operated over time and their impact in the population ?

ALB- North stock. Total Catch-At-Age (CAA)

1 to 8+ age group

Bubble size proportional to number of fish

ALB-AN (Total)

0

1

2

3

4

5

6

7

8

9

year

ALB- North stock. Catch-At-Age (CAA) by Fishery

1 to 8+ age group

Bubble size proportional to number of fish on each fleet

ALB-AN (LL_USA)

0

1

2

3

4

5

6

7

8

9

year

ALB-AN (LL_ J PN)

0

1

2

3

4

5

6

7

8

9

year

ALB-AN (LL_TAI)

0

1

2

3

4

5

6

7

8

9

year

LONGLINE FLEETS By-catch By-catch USA

SURFACE FLEETS

ALB-AN (BB_ESPcant)

0

1

2

3

4

5

6

7

8

9

year

Target BB ESPALB-AN (TR_ESPcant)

0

1

2

3

4

5

6

7

8

9

year

Target TR ESP Target OTHERALB-AN (Others)

0

1

2

3

4

5

6

7

8

9

year

By-catch JPN Target Ch-TAI

ALB- North CPUE time series

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1925 1935 1945 1955 1965 1975 1985 1995 2005

Rel

ativ

e C

PU

E

Historic Troll CompositeSpain TR Age 2Spain TR Age 3France TR early ages 2-3France TR late ages 2-3

CPUE scaled to each series mean

0

0.5

1

1.5

2

2.5

3

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

Japan LLUSA LLTaiwan LLJapan LL EarlyJapan LL Transition

Surface

TR fleet

Longline

Taiwan LL target

ALB-N- Recruitment and Spawning stock

0

5,000,000

10,000,000

15,000,000

20,000,000

25,000,000

1925 1935 1945 1955 1965 1975 1985 1995 2005

Re

cru

itme

nt (

Ag

e 1

)

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

1925 1935 1945 1955 1965 1975 1985 1995 2005

Sp

aw

nin

g S

tock

(T

)

Age 1- recruit

MFCL model

2005 high but uncertain

1930- 2005

MFCL model

SSB ~ ¼ Max in 40´s

ALB- N- Relative F, SSB and status stock relative to MSY

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1925 1935 1945 1955 1965 1975 1985 1995 2005

Ra

tio

B/BMSY

F/FMSY

ALB- North State of stock

• SSB has decreased to one fourth of the SSB in the highest level in the 40´s

• Recruit decreased from the 60´s until 2004. In 2005 the estimated recruitment is high ~ 60´s, but magnitude is uncertain.

• The stock rebuild to levels near BMSY (SSB 20% below MSY) vs 2000 assessment when SSB 50% below MSY

• Current F is 50% above F msy

• Estimates of MSY varied over time as a combination of surface and longline fisheries with changing selectivity pattern over time period.

• MSY for 3 recent years ~ 32.000 t , but over time ranged from 26.000 t to 34.00 t.

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4SSB/SSBmsy

F/F

msy

1930-2005

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2SSB/SSBmsy

F/F

msy

1990-2005

ALB- North Atlantic

Fishing trajectory and 2005 status

1930-2005 evolution of relative biomass and fishing mortality estimated trajectory relative to MSY

status in 2005

ALB- North Atlantic

Uncertainty of 2005 status determination

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2

B/Bmsy

F/Fmsy

2005 status

F/Fmsy =1.5

B/Bmsy = 0.81

ALB- N- Projections

0

2

4

6

8

10

12

14

1975 1985 1995 2005 2015

SS

B/S

SB

msy

26K t

30K t

32K t

34.5K t

38K t

36K t

20K t

25K t

0

0.5

1

1.5

2

2.5

3

2002 2004 2006 2008 2010 2012 2014 2016 2018 2020

26K t 30K t32K t 34.5K t38K t 36K t20K t 25K t

VPArelative SSB (SSB/SSBMSY) for scenarios of cte catch 2008 -2020

TAC of 34.500 t

2006 CATCH of 36.000 t

32.000 t

Projected Current catch for 2006 & 2007

ALB- N- VPA Projections scenariosassuming strong year class

relative SSB (SSB/SSBMSY) for scenarios of cte catch 2008 -2020

Projected Current catch for 2006 & 2007

34.500 t TAC

32.000 t TAC

ALB- South stock. Total Catch-At-Age (CAA)

1 to 8+ age group

Bubble size proportional to number of fish

ALB-AS (Total)

0

1

2

3

4

5

6

7

8

9

year

ALB- South stock. Catch-At-Age (CAA) by Fishery

1 to 8+ age group

Bubble size proportional to number of fish on each fleet

LONGLINE FLEETS By-catch JPN Target and By-catch BRATarget Ch-TAI

SURFACE FLEETS Target BB SA Target BB NAM Target OTHER

ALB-AS (LL_ J PN)

0

1

2

3

4

5

6

7

8

9

year

ALB-AS (LL_TAI)

0

1

2

3

4

5

6

7

8

9

year

ALB-AS (LL_BRA)

0

1

2

3

4

5

6

7

8

9

year

ALB-AS (BB_ZAF)

0

1

2

3

4

5

6

7

8

9

year

ALB-AS (BB_NAM)

0

1

2

3

4

5

6

7

8

9

year

ALB-AS (Others)

0

1

2

3

4

5

6

7

8

9

year

ALB – South CPUE time series

0

2

4

6

8

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Taiwan LLBrasil LLJLL earlyJLL TransitionJLL Bycatch

0

1

2

1959 1964 1969 1974 1979 1984 1989 1994 1999 2004

South Africa Baitboats Early

South Africa Baitboats Late

Longline

Taiwan

Target

Surface

Baitboat

0

0.5

1

1.5

2

2.5

3

0 0.5 1 1.5 2 2.5

Current biomass/Biomass at MSY

Catc

h/R

ep

lacem

en

t yie

ld

1970

2005

ALB- South Atlantic

Fishing trajectory and 2005 status

ALB- South Atlantic

Uncertainty of 2005 status determination

2005 status

F/Fmsy =0.63

B/Bmsy = 0.9

ALB- South State of stock

• Last assesmment was done in 2003

• Longline CPUE ´show a declining trend at the begining of time series, less marked in the recent period. Thos indices traget adult albacore.

• Surface CPUE´s (Baitboat) target mostly immature albacore and no trend is seen.

• Current SSB has declined 25% from unfished SSB.

• Accordingly it is likely that in 2005 SSB is about 90% of Bmsy and F is 40% below F msy

• Estimates of current MSY is around 33.300 t and Replacement yield is around 29.000 t, current catch 24.460 t is below.

ALB- S- Projections

0

50000

100000

150000

200000

250000

300000

350000

1956

1960

1964

1968

1972

1976

1980

1984

1988

1992

1996

2000

2004

2008

2012

2016

Sp

awn

ing

bio

mas

s in

to

nn

es

BMSY

10 years projections

SSB over time trend and 80% confidence bounds

Projected cte catch = 25.000 t

ALB- N MANAGEMENT Rec.

ALB- S MANAGEMENT Rec.

• Current TAC is 34.500 t

• 2005 and 2006 catches have been above

• Projections indicate that stock will not recover from overfished state if catch level remain > 30.000 t

• If strong year class enters the fishery the stock would recovered faster

• Current TAC is 29.900 t

• 2Recent catches have been below

• Projections indicate that catches at 2006 level will recover the stock from overfished state

• Current management scheme is sufficient for recovery of South stock

THANKS