Indian Ocean Tuna Commission

(IOTC): Data needed and

approaches used in Stock

Assessments

Overview

Legal requirements of reporting data

Data types used in Assessments

The Scientific Process / Stock

Assessment Approaches

Summary of IOTC Resolutions

IOTC Resolutions: IOTC and main shark species • IOTC Resolution 10/02 Mandatory statistical requirements for IOTC

Members and Cooperating Non-Contracting Parties (CPC’s) • Minima requirements for the reporting of statistics to the IOTC

• IOTC Resolution 13/08 Procedures on a fish aggregating devices (FADs) management plan • Minima requirements for the collection and reporting of data on FADs,

drifting or anchored, used by Purse seine and pole-and-line fisheries

• IOTC Resolution 13/03 On the recording of catch and effort data by fishing vessels in the IOTC Area of Competence • Minima data requirements for the collection of CATCH-AND-EFFORT

data

• IOTC Resolution 11/04 On a Regional Observer Scheme • Minima requirements sampling of catches in land and at-sea

Summary of IOTC Resolutions (cont.)

IOTC Resolutions: Main sharks and other bycatch species • IOTC Resolution 05/05 Concerning the conservation of Sharks caught in

association with fisheries managed by IOTC • Minima requirements for the reporting of data on sharks caught on

IOTC fisheries

• Other Resolutions on sharks: Ban on catch retention and reporting

requirements for:

• Oceanic whitetip shark: IOTC Resolution 13/06

• Thresher sharks: IOTC Resolution 12/09

• Whale sharks: IOTC Resolution 13/05 (purse seine fisheries)

• IOTC Resolution 10/06 On reducing the incidental bycatch of Seabirds in longline fisheries • Minima requirements for the reporting of interactions with seabirds (longline)

• IOTC Resolution 12/04 On Marine Turtles

• Minima requirements for the reporting of interactions with marine turtles

• IOTC Resolution 13/04 On the conservation of Cetaceans • Minima requirements for the reporting of interactions with cetaceans

Data requirements at a glance

Types of fisheries data for which the Commission has set [data collection] and reporting standards; and data resolution requested by the Commission:

Coastal fleets

EEZ vessels less than 24 m LOA

Active Crafts (FC) Number of fishig craft per boat-gear type category per year

Surface fisheries: CE by

fishery, 1° grid and month

#FADs [Anchored

& Drifting: CE by

1° grid and month

(PS-BB)]

Supply vessels

Purse seine

fishery: Effort 1°

grid and month

Size data (SF)

Scientific observer data Sample of catches in land to cover at least 5% vessel activities

Socio-economic data

Foreign fleets EEZ catch Not applicable

Vessels with LOA ≥ 24 m and all high seas vessels

CE data for foreign licensed fishing vessels (above CE standards)

Sample of catches at-sea to cover at least 5% fishing operations

Individual lengths of IOTC species sampled, by fishery, species, 5° grid, and month

Longline fisheries: CE by fishery, 5° grid and month

Individual vessel data for all fishing ships catching IOTC species

Discard levels IOTC species, sharks, seabirds, marine turtles, Cetaceans per IOTC Area, gear, species and Year (in number of weight)

Nominal catches (weight) of IOTC Species, main species of pelagic sharks, and other bycatch, per IOTC Area, gear, species and Year

No standards have been set as yet

Statistical Requirements

Summary

Catch-and-Effort (CE) CE Data by fishery (type of boat-gear), area and period

Annual catches (NC+DI)

Industrial surface and longline fleets

Applications to gear types

Presentation title | Presenter name

6 |

Coastal Fisheries

Full Compliance: Coastal Fisheries

Reports Fishing Sector

Sampling in

land

Catch-and-

effort (statistical

area, boat-gear,

species, month) Size frequency (statistical area,

boat-gear,

species, month)

Catch-and-

effort

estimation

Nominal Catch (Boat-gear, IOTC

area, Year,

Species)

Aggregatio

n

Catch-and-Effort (boat-gear, Stat

Area, Month,

Species)

Raising

Coverage ≥ 5% vessel

activities (e.g. trips)

Size Frequency (Species, boat-

gear, Stat Area,

Month)

At least 1 fish measured for size per ton of

catch

Socio-

Economic (Various)

Raising &

Aggregatio

n

Fishing Craft (number boats /

size category,

Gear, Year)

[Raising

]

Surface Fisheries

Full Compliance: Surface Fisheries

Catch reports & Logbooks (Fishing Sector)

Sampling in

land

Catch-and-

effort (1°Grid,

boat-gear-fishing

mode, species,

month) Size frequency

(5°Grid, boat-gear-

target, species,

month)

Catch-and-

effort

estimation

Nominal Catch (Boat-gear-

fishing mode-

target, IOTC

area, Year,

Species)

Aggregatio

n

Catch-and-

Effort (boat-gear-

fishing mode-

target, 1°Grid,

Month, Species)

Raising

Size Data (Species,

boat-gear-

target,

5°Grid,

Month)

Socio-

Econ. (Various)

Active

Vessel

List

Sampling at

sea At least 1 fish measured for size per ton of

catch

Size Data

estimation

Total Enumeration

FAD &

Supply [PS+BB]

Discards

Estimation &

Raising

Discards (Boat-gear-

target,

IOTC area,

Year,

Species)

Raising

Coverage ≥ 5% fishing operations

(e.g. sets)

Trip

Report

(1°Grid)

Aggr

egati

on

Longline Fisheries

Full Compliance: Longline Fisheries

Catch reports & Logbooks (Fishing Sector)

Catch-and-

effort (5°Grid,

boat-gear-target

species, month,

species)

Size frequency (Species, boat-

gear-target

species, 5°Grid,

Month) Catch-and-

effort

estimation

Nominal

Catch (Boat-

gear-target,

IOTC area,

Year, Species)

Aggregatio

n

Catch-and-

Effort (boat-

gear-target,

5°Grid, Month,

Species)

Raising

Size Data (Species, boat-

gear-target,

5°Grid, Month)

Socio-

Econ. (Variou

s)

Active

Vessel

List

Sampling at

sea

Coverage ≥ 5% fishing operations

(e.g. sets)

At least 1 fish measured for size per ton of

catch

Size Data

estimation

Total Enumeration

Raising

Discards

Estimation &

Raising

Discards (Boat-gear-

target, IOTC

area, Year,

Species)

Trip

Report

(1°Grid)

Aggregatio

n

Dissection of catch for a Fishing Trip

The IOTC definitions for nominal catches, bycatch, and discards may differ from those used in other areas Catch-and-effort and size data shall be collected for IOTC species and the main species of sharks, as identified by the Commission, from both, nominal catches and discards

Total catch Retained

catch

Dis

ca

rd

s Marketable

(Target)

• Tuna (-like)

• Sharks

• Other finfish

Marketable

(Other)

• Tuna (-like)

• Sharks

• Other finfish

Incidental catch

• Seabirds

• Marine turtles

• Cetaceans

Discards

commercial and

other species

• Tuna (-like)

• Sharks

• Other finfish

NOMINAL CATCH

DISCARDS

BYCATCH

Importance of IOTC fisheries (2008-2012)

Indonesia, Iran, India, and Sri Lanka caught over 50% of the total catches (2008-12)

22%

33

43

52

60

67

71

7579

8285

87 89 90 92 93 94 95 96 97 98 99 100%

0

25

50

75

100

0

500

1000

1500

2000

WS-

Ind

on

esi

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WS-

Iran

, Isl

amic

…

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WS-

Sri L

anka

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ilip

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nya

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riti

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Tim

or

% o

f to

tal c

atch

(ac

cum

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ted

)Me

tric

to

ns

(*1

00

0)

OTHER

Sharks

Billfish

Seerfish

Small tunas

Longtail tuna

Skipjack tuna

Large tunas

%

Tropical Tuna Catch Series

The fishing areas 2006 2010

Purse-

seine

Longline

The fishing areas-Most Recent 2011 2012

Purse-

seine

Longline

Building blocks of Tuna stock assessments

• Catch-and-effort data

• Landed (Nominal) catch (sale slips; sampling)

• Discard levels (observers; logbooks)

• Effort (logbooks; sampling)

• Size/age composition (sampling; tagging)

• Abundance trends

• Fishery CPUE (fine-scale operational data from

logbooks)

• [Size/age/sex composition (logbooks; sampling;

tagging)]

• Exploitation rates (tagging)

• Life history information

• Longevity/natural mortality (tagging; otoliths)

• Growth (tagging; otoliths)

• Maturation (biological samples)

Spatial

and

seasonal

patterns

Routine

Data

Collectio

n

Data

Collection

through

specific

projects

(updated

regularly)

Building blocks of management advice

Slide from R. Method

modified by Joseph E.

Powers

Input files prepared for the assessments

IOTC SECRETARIAT

• Catch [and effort] data by species, time-period (usually quarter),

fishery (groups of Flag-Gear combinations depending on the

selectivity) and areas (depending on the dynamics of the fleets and

species for assessment)

• Number of fish sampled by species, size bin, time-period… (as

above)

• Length-weight, growth, and other functions used for each species

• Life history information

FLAG STATES

• Indices of abundance (from as many fleets as possible); estimated

using fine-scale operational data (logbooks)

Assessment tools and models used by the

IOTC scientific community

Basic indicators

(Catch trends, CPUE, mean size, etc.).

Stock reduction Approaches, Biomass dynamic models (Production models); delay-difference models

ASPIC

Age-structured production models

(ASPM)

Integrated models; catch-at-age or catch-at-size models

(e.g. SS2)

Spatially disaggregated, integrated models

(SS3, MULTIFAN-CL)

Tagging data essential!

Increasing complexity -> better approximation but more data are required!

How do we deal with Uncertainty?

4 Approaches

Parameter Uncertainty (assumptions on

parameter choice).

Data uncertainty (weights, inverse

variance)

Model uncertainty (e.g. Spatial

assumptions, time varying selectivity).

Derived parameter uncertainty, i.e.

estimation error (MCMC Runs).

Projections (Kobe II): So far use the

above framework with deterministic

projections at varying catches.

Skipjack-Parameter

Uncertainty -I

30

S1

0S

10

N3

0N

20E 40E 60E 80E 100E 120E

R1 R2

R3

Skipjack-Parameter

Uncertainty -II

Bigeye-Spatial uncertainty

0 10 20 30 40

0.0

00.0

20.0

40.0

6

Age class (quarter)

Fis

hin

g m

ort

alit

y (

quart

erly)

MSY (1000s mt)

Density

130 140 150 160 170 180

0.0

00.0

10.0

20.0

30.0

4

SB2011/SBmsy

Density

1.2 1.3 1.4 1.5 1.6

01

23

45

6

F2011/Fmsy

Density

0.25 0.30 0.35 0.40

02

46

810

12

Bigeye-

Derived Parameter

Uncertainty using

MCMC

Tunas as a highly migratory species in the

Indian Ocean: the case from tagging

Yellowfin tuna:

• Half the catch from

small-scale and

artisanal fisheries

• Large percentage of

catches from the

high-seas

• Important catches

from FAD’s for purse-

seine

• Distribution of purse-

seine effort less

affected by piracy

than longline

Yellowfin tuna: the history

• Catch history

• CPUE history

0

100,000

200,000

300,000

400,000

500,000

600,000

1950

1954

1958

1962

1966

1970

1974

1978

1982

1986

1990

1994

1998

2002

2006

2010

Catc

h (t

)

FS LS LL LF BB GI HD TR OT

Yellowfin tuna: the history

• CPUE history

• CPUE history

1980 1990 2000 2010

0.0

00.1

00.2

00.3

0

LL 1

1980 1990 2000 2010

0.0

0.5

1.0

1.5

LL 2

1980 1990 2000 2010

0.0

0.5

1.0

1.5

LL 3

1980 1990 2000 2010

0.0

0.2

0.4

0.6

LL 4

1980 1990 2000 2010

0.0

0.4

0.8

LL 5

CP

UE

Yellowfin tuna: the assessment

Model feature MFCL

Population spatial structure / areas

5

Uses Catch-at-length Yes

Tagging data Yes

Age-structured Yes

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

0.0

0.5

1.0

1.5

2.0

SB=SBmsySB<SBmsy SB>SBmsy

SB/SBmsy

F=

Fm

sy

F<

Fm

sy

F>

Fm

sy

F/F

msy

Ove

rfis

hin

g

Overfished

19952000

2005

20102009

2010

Blim Btarg

Ftarg

Flim

Model feature ASPM

Population spatial structure /

areas 1

Uses Catch-at-length Yes

Tagging data No

Age-structured Yes

Catch 2011: 368,663 t

Average catch 2008–2012: 317,505 t

MSY (in thousands): 344 t (290-453)

F2010/FMSY (80% CI): 0.69 (0.59–0.90)

SB2010/SBMSY (80% CI): 1.24 (0.91–1.40)

SB2010/SB1950 (80% CI): 0.38 (0.28–0.38)

The decrease in longline and purse seine effort in recent

years has substantially lowered the pressure on the Indian

Ocean stock as a whole, indicating that current fishing

mortality has not exceeded the MSY-related levels in recent

years. As the security situation in the western Indian Ocean

has improved, a rapid reversal in fleet activity in this region

may lead to an increase in effort which the stock might not be

able to sustain, as catches would then be likely to exceed

MSY levels. Catches increased by 68 Kt in 2012 as compared

to 2011, warranting a new assessment soon.

Yellowfin Summary

Situation of other IOTC species

Neritic Tunas • Essential for the economy of the IOTC coastal States

• Status still unknown for most species, but analyses are progressing

in the past two years.

• Status on Longtail (overfishing) and likely the same for Kawakawa.

Other billfish (Marlins, sailfish and spearfish) • Not targeted by tuna-fishing vessels

• Status unknown although concern exists about apparent declines

Sharks • A growing concern as they are target species for several fleets that

also catch tunas

• Apparent declines in oceanic whitetip and silky sharks

• Thresher under protection but still being caught

IOTC Stock Status Overview

(Tropical and Temperate Tuna)

IOTC Stock Status Overview

(Billfish and Neritic Tuna)

Neritic Tuna

Stock Indicators Advice

Bigeye F2012/FMSY= 0.42 (0.21–

0.80) SB2012SBMSY= 1.44 (0.87–

2.22)

Probably not overfished, and overfishing is

probably not occurring. Probably near full

utilization

Yellowfin F2010/FMSY=0.69 (0.59–0.90)

SB2010/SBMSY= 1.24 (0.91–

1.40)

Probably not overfished, and overfishing is

probably not occurring. Probably near full

utilization

Skipjack F2011/FMSY= 0.8 (0.68-0.92)

SB2011/SBMSY= 1.2 (1.01-1.4)

Highly productive species and robust to

overfishing.

Albacore F2010/FMSY = 1.33 (0.9–1.76)

SB2010/SBMSY=1.05 (0.54–

1.56)

F above MSY levels. Further declines likely due

to effort displacement (piracy). Almost

exclusively LL.

Swordfish F2010/FMSY= 0.79 (0.58-0.84)

SB2010/SBMSY= 1.31 (1.13-

1.46)

The overall stock size and fishing pressure are

estimated to be within acceptable limits

Striped

Marlin

F2011/FMSY= 1.28 (0.95–1.92)

B2011/BMSY= 0.416 (0.2–

0.42)

Stock is overfished, though maybe recovering

due to recent decline in catch levels.

Blue Marlin F2011/FMSY= 0.85 (0.63–1.45)

B2011/BMSY= 0.98 (0.57–

1.18)

The overall stock size is optimal. Fishing rates

are likely below FMSY, though highly uncertain.

Longtail F2011/FMSY=1.11–1.77

B2011/BMSY=1.11–1.25

Increased catches in recent years indicate

that the stock is experiencing overfishing

though is not overfished. This is primarily due

to a change in effort from Tropical to Neritic

Tuna.

Stock status Stocks under IOTC mandate are in relatively good shape (at optimal

utilization), but no room for further fleet expansion.

Current and Future work

Albacore operational model set up for MSE.

Skipjack operational model set up for MSE.

Eventually, have a model that incorporates all

Tropical Tuna Species and develop MSE

procedures simultaneously.

Dialogue initiated on identifying clear

management objectives.