Tuna Fishery

Tuna Fishery in the Western and Central Pacific Ocean (including the Philippines)

I. Introduction

Based on Grolier International Encyclopedia (1991). tunas are among the largest and most commercially important of all fishes. Seven species, making up the genus Thunnus of the tuna and mackerel family Scombridae, are found in temperate and tropical oceans around the world and account for a major proportion of the U.S. fish catch and U.S. fish imports. The two dominant species of tuna in western and central Pacific Ocean are skipjack tuna and yellowfin tuna whose distribution and spawning areas are shown in Map 1 below.

Tunas typically have cigar-shaped, streamlined bodies with two dorsal finlets—a narrow tail region, and a large, deeply forked tail. They vary extensively in size, color, and fin length. Along with the mackerel sharks, tunas are unique among fishes in having a body temperature higher than that of the surrounding water—a result of a complex circulatory system and continuous sustained activity. Fast swimmers, traveling at more than 48 km/hr (30 mph), they typically migrate long distances and appear only seasonally in any one location. Tunas occur both in surface waters and at great depths, where their large eyes help them to see in the dark. They feed on other fishes and on squid.

The larget species, a highly prized sport fish, is the bluefin, Thunnus thynnus, found worldwide. Some specimens exceed 4.2 m (14 ft) and weigh more than 680 kgs (1,500 lb). Other important species include the albacore, T. alalunga, a small fish , often less than 18 kg (40 lb), which is famed for its tasty while meat, the large yellowfin, T. albacares; and the deep-water bigeye, T. obesus.

The tuna fishery is controlled by international agreements limiting how much fishers may take and where they may fish—limits that not always observed. Another major problem is created by the method used to harvest tuna (as well as salon and squid): huge nets are stretched across kilometers of ocean, capturing sea birds, seals, porpoises, and dolphins and dolphin kill has been huge, constituting a threat to their populations.

Map 1. Distribution and Spawning Grounds in the World

Philippines

Distribution and Spawning Areas of Skipjack

Philippines

Distribution and Spawning areas of Yellowfin tuna

Geographic Distribution

Major Tuna Species of the World

Table 1 shows that the top 3 tuna species: skipjack, yellowfin, and big-eye are mainly caught in the following countries: Southeast Asia (Philippines, Thailand, Indonesia), Micornesia (Samoa), Cental/South America (Mexico, Venezuela, Colombia, Ecuador), Africa (Senegal and Ivory Coast), and Europe (Spain and Italy).

Table 1. Showing the Pictures of the Different Tuna Species and Certain Data

Life Cycle

3 yearsmaximum

4 – 7 years

5 – 7 years

5 yearsmaximum

10 – 25 yearsmaximum

At least 12 years

1 – 2 years

Distribution of Catches of Tuna in the Western and Central Pacific Ocean

It is in the western and central Pacific ocean which has the highest concentration of tuna population of the following species: yellowfin and big-eye tuna as shown in Map 2.

1

2 3

4 5

1

1 1

2 3

3 5

2 3 2 3

4 54

5

Map 2 Distribution of yellowfin (top left), bigeye (top right), albacore (bottomleft) and broadbill swordfish (bottom right) catches in the western and central

Pacific Ocean [Source: Secretariat of the Pacific Community]

Ecological Importance of Western and Central Pacific Ocean (WCPO)

The WCPO is characterized by the presence of islands as shown in Map 3.

Map 3. Showing the island countries in the WCPO

The ecological characteristics of WCPO indicates the following:

1. The presence of several humdreds of islands which surrounded by shallow waters and coral reefs make it very rich in primary productivity and fishery productivity.

2. The vast expanse of the area with several thousand miles in length (west to east) and few thousand miles in width (north to south) makes the area ideal for a) habitat, b) shelter and b) spawning and nursery grounds for oceanic large pelagic migratory species of fish like tuna

Migration of Tuna (yellowfin and big-eye) from WCPO to Southeast Asian waters and North/South America

It has been observed through research (the tagging method) that yellowfin and Big-eye tuna that are found in the WCPO migrate towards westward (Indonesia and Philippines) and eastward (North and Central America) as shown in Map 4; likewise, tuna from north and central america migrate towards the WCPO. This indicates that there is only stock of said species of tuna in the whole Pacific Ocean.

Map 4. Showing the Direction of Migration of Tuna

Pacific Ocean

Pacific Ocean

Long-distance (>1,000 nmi) movements of tagged Yellowfin tuna

Long-distance movements of tagged Big-eyed Tuna

Australia

ChinaJapan

Taiwan

But in the case of yellowfin tuna being distributed throughout the tropical and sub-tropical waters of the Pacific Ocean, there is some indication of restricted mixing between the western and eastern Pacific based on analysis of genetic samples and tagging data. Adults (larger than about 100 cm) spawn, probably opportunistically, in waters >26C, while juvenile yellowfin are first encountered in commercial fisheries (mainly surface fisheries in the Philippines and eastern Indonesia) at several months of age.

Tuna migration in the Philippines

Map 5 shows the direction of migration of tuna from the Philippine waters. It has been suggested that juvenile yellowfin start to migrate out of Philippine waters at 30 cm size, and that most of these juvenile yellowfin are gone from the region by the time they reach 60 cm in length. Yellowfin larger than 110 cm are caught by hook-and-line fishers coming from the Philippines (General Santos City, Sarangani, and Davao) in the northern Celebes Sea which is part of the territorial water of Indonesia.

Map 5. Indicating Migration of Tuna from Higher to Lower Latitude

Map 6 below shows the frequented fishing grounds for tuna being located near the equator within the latitude 5o North and 5o South of the Equator, although tuna can be caught at higher latitudes

Northern Celebes Seawhere yellowfin tuna1.1 meter long (fork length) are caugh by hook& line fishers

Yellowfin tuna migrate out of the Philippine waters at30 cm in fork length

But there are large tuna that arecaught in the Pacific side outsideof Municipal water but within the EEZ

0o

5o

10o

15o

Direction of migration is towards the warmer watertemperature of the equatorial region as Autumn approaches(Nov-December-January) or When tuna reaches 30 cm or6 months old from spawningTime (summer/early spring)

( 6 months old)

5o

Most of this surface tuna catch is made by fleets of large purse-seinersin the equatorial band (5oN-5oS).

during certain months of the year particularly during summer/spring months when temperature is relatively warmer.

Map 6. Showing Tuna Concentration near the Equator

Food Requirement of Tuna

Based on the Food Web as illustrated below, tuna primary food are herrings, sardines, anchovy, and squids. Certain species tend to become cannibalistic.

Figure 1. Food Web in Tropical Regions

LargeSharks

MarlinMedium-sized

Sharks

Lancetfish(e.g. swordfish)

Tuna/

Mesopelagic Fishes(200m-1km depth)

SnakeMackerel

squid Dolphin

Vertically-migratingMesopelagic fishes

Flying fish

HyperiidAmphipods(small crustaceans)

Lanternfish

Oceansunfish

Copepods(zooplanktons

ShrimpsEuphausiids(zooplanktons)

Coccolithopores(phytoplanktons)

Dinoflagellates(phytoplanktons)

Top predators

Predators

Filterers

Herbivores

Algae

FOOD WEB OF THE TROPICAL SEA

SardinesFlying fish

Copepods/diatoms

SardinesHerringanchovy

5

-5

Austrialia

California

Pacific Ocean

Fishing Grounds of Tuna as indicated by dots

The reason for the fact that most species of tuna particularly skipjack and yellowfin are usually caught in the latitude 5o North and 5o South is that, it is in this area where primary production and small pelagic fish production (as the main food of tuna) are highest as compared with those of the higher latitudes.

II. Status of Tuna Fishery

A. Biomass and Recruitment

1. Initially, most of the biomass is estimated to have occurred in the tropical regions 2 and 3. Recently, biomass has increased in both the northern (region 1) and southern (region 5) regions.

2. Overall, biomass increased strongly in the late 1970s and 1980s driven by the increased recruitment, but has been in decline since the mid-1990s. The recent decline has been particularly marked in regions 2 and 3. Despite these recent declines, current total biomass is estimated to be at similar levels to the 1960s and 1970s.

3. Figure 2 presents the following: Region 1 highest recruit comes from Region 2 at 50%, followed by Region 1 itself at 32%; Region 2 highest recruit comes from Region 2 itself at 74%, followed by Region 3 at 18%; Region 3 highest recruit comes from Region 3 itself at 58%, followed by Region 2 at 25%; Region 4 highest recruit comes from Region 2 at 43%, followed by Region 4 itself at 27%; Region 5 highest recruit comes from Region 5 itself at 80%, followed by Region 2 at 12%; Regions 2,3, and 5 with highest recruits coming primarily from within are also receiving certan levels of recruits.

Figure 2. Showing Tuna Recruits from Different Regions

B. Fishing Pressure (Tuna Production)

1. Tuna Production (Worldwide)

Total annual world tuna production in the year 2000s is 3.159 million metric tons. Catch of skipjack tuna, yellowfin tuna, and big-eye tuna represent 50-55%, 35%, and 8% of the total tuna catch, respectively.

1

2

35

4

5 5 5

5

3

2

2

1

11

333

1

2

3

2

a. The western and central Pacific Ocean (WCPO) currently supports the largest industrial tuna fishery in the world, with total annual catches from 1991 to 1994 of approximately 1,000,000 mt. The three gear types accounting for most of the catch in the area are longline, purse seine and pole-and-line. Large-mesh drift-net, handline and trolling gear have been utilised in some areas, but not to the extent of the above-mentioned gear types. The primary target species are skipjack, yellowfin, bigeye and albacore. Skipjack is the most important of the four major tuna species in the fishery, accounting for 67 per cent of the catch by weight in 1992, followed by yellowfin (24.5%), bigeye (5%) and albacore (3%). Purse seine gear was responsible for 80 per cent of the total catch, with pole-and-line gear accounting for 7 per cent, longline gear 12 per cent and troll gear 1 per cent.

b. Nearly 70% or 2 million ton of the world’s annual tuna harvest, currently (2000s) 3.2 million tons, comes from the Pacific Ocean

c. Skipjack tuna (Katsuwonus pelamis) dominate the catch. Although skipjack are distributed in the surface mixed layer throughout the equatorial and subtropical Pacific, catches are highest in the western equatorial Pacific warm pool, a region characterized by low primary productivity rates that has the warmest surface waters of the world’s oceans.

2. Tuna Production (Philippines)

a. In the Philippines, the 2000 catch of big-eye tuna and yellowfin ccategorized as “tambakol” catch) skipjack, and bonito was 243,000 m.t. or 7.7% of world production (see Graph 1 below).

Graph 1. Philippine Marine Fish Catch (BAS Fisheries Statistics 2000)

3. Comparison of Tuna Production (Philippines, Indonesia, and Malaysia)

Philippine Marine Fish Catch

256 200.5113 112.2 92.9 90.3 79.6 71.4 67.3 53.7 46.8 40 36.3 29.5 26.8

355.5

1,316.60

1,740.30

0200400600800

100012001400160018002000

Gal

ungg

ong

Tam

ban

Gul

yasa

n

Tul

inga

n

Tun

soy

Tam

bako

l

Dilis

Mat

angb

aka

Sap

sap

Alu

mah

an

Pus

it

Oce

anic

Bon

ito

Alim

asag

Bis

ugo

Has

ahas

a

Tot

al fo

r T

una

Tot

al (

15 s

peci

es)

Phi

lippi

nes

Species

Cat

ch (

x000

m.t.

)

Skipjacktuna

Frigatetuna Big-eye and

Yellowfin tuna Katchorita

Skipjack - 113,000 m.t.Yellowfin/Big-eye - 90,000Oceanic Bonito - 40,000 m.t

243,000 m.t.

a. Durng the period 1981-1991, top tuna producers among the ASEAN countries were the Philippines and Indoneisa (see Graph 2 below). It is estimated that Indonesia (also facing the Pacific ocean) which is closer to the tuna-rich equatorial region and the fact that yellowfin tuna and big-eye are considered already overfished in the western and central Pacific Ocean has surpassed now the Philippines in tuna production.

b. Malaysia, the Philippines, Indonesia, and Thailand use purse seine, longline and vertical handlines to fish for tunas in the region; the same oceanic and neritic tuna species are also taken.

c. In the Philippines the marked increase in growth of the tuna fishery has been attributed to the use of FADs (called payaos in the Philippines). Yellowfin tuna, skipjack, and frigate tuna (Auxis thazard) are the principal species caught in the Philippines. Purse seines, ring nets, and handlines catch juvenile yellowfin ranging in size from 16 cm to 55 cm. Since few yellowfin between 60 cm to 200 cm are caught by the Philippine tuna fishery, it has been suggested that juvenile yellowfin start to migrate out of Philippine waters at 30 cm size, and that most of these juvenile yellowfin are gone from the region by the time they reach 60 cm in length. Yellowfin larger than 110 cm are caught by hook-and-line fishermen in the northern Celebes Sea. Catches reported by the national authorities in Indonesia have been used in this assessment, but further validation is required. Increased purse seine catches using FAD sets in region 3 have also contributed to the increase.

Graph 2. Comparison of Tuna Production among 4 ASEAN countries

d. In Indonesia the yellowfin tuna and skipjack are the dominant species in the catch. The use of FADs (called rumpons in Indonesia) also play an important role in the development of the Indonesian tuna fishery. Presently tuna are caught by a variety of gears including purse seines, handlines, troll lines, and longlines.

92 93 94 95 96 97 98 99 2000 01

Philippines

Indonesia

400

450

Philippines

Thailand

Malaysia

YellowfinSkipjackFrigate TunaBig-eye

Long-tailFrigate tunaYellowfin

Indonesia tuna catch increasing

Philippines

SkipjackBig-eye/YellowfinFrigate TunaBonito Tuna

C. Catch by gears - WCPO

1. Since 1990, the yellowfin tuna catch in the western and central pacific oecean (WCPO) has varied between 320,000 m.t. (1990) and 485,000 m.t. (1998) as shown in Graph 3 but starting 1998 total volume of catch had decreased Graph 3. Showing the WCPO Yellowfin Catch by Gears

2. Yellowfin tuna are harvested with a diverse variety of gear types, from small-scale artisanal fisheries in Pacific Island and southeast Asian waters to large, distant-water longliners and purse seiners that operate widely in equatorial and tropical waters. Purse seiners catch a wide size range of yellowfin tuna, whereas the longline fishery takes mostly adult fish

3. Purse seiners harvest the majority of the yellowfin tuna catch (49% by weight in 1996–2000), with the longline and pole-and-line fisheries comprising 15% and 3% of the total catch, respectively. Yellowfin tuna are often directly targeted by purse seiners, especially as unassociated schools.

4. Longline catches in recent years (56,000–73,000 t) are well below catches in the late 1970s to early 1980s (which peaked at 117,000 t), presumably related to changes in targeting practices by some of the larger fleets.

5. Catches in the ‘Other’ category are largely composed of yellowfin tuna from the Philippines and eastern Indonesia. These catches come from a variety of gear types (e.g. ring net, gillnet, handline and seine net) and have increased steadily over the past decade. Based on catch data provided by those countries, recent catches represent approximately 35% of total WCPO yellowfin tuna catches.

Catch by Gears – Philippines (Northern Samar)

1. Map 7 shows that beyond the 15-km limit municipal water in all municipalities, there is large area for tuna fishing. Yellowfin tuna and skipjack (gulyasan or budlis) are caught through “payao” fishing using hook & line outside of the 15-km limit. It has been reported that the size of tuna caught in said area is much more smaller than those caught in the offshore of Gamay by commercial fishing boats coming from as far as General Santos City.

Me

tric

To

ns

Map 7 Northern Samar indicating the tuna fishing ground

2. The catch of tuna is all-year round, but the peak season is during the period of “habagat” that covers the months of May to October. Graph 4 shows that Frigate Tuna or “tulingan” was caught in big quantity in August by Dona Lucia fishers but within the nearshore water, while Budlis and yellowfin were the main catch by Chitongco fishers in May (Graph 5) and by Bugko fishers in April and May (Graph 6) all in the fishing grounds beyond the 15-km limit.

Graph 4. Showing the Hook & Line Catch of Brgy Dona Lucia

mud

rocky

mud

sand

coral

coralsand

rock

sand

0 5 10 15 kms

1000 fathoms

100 fathoms

50 fathoms (90 meters)

20 fathoms

BiriIsland

Camongon Island

Catarman

Mondragon

San Roque

RosarioSan Jose

ToCatubig

Pambuhan

Laoang

KahayaganIsland

Laoang Island

BatagIsland

LaoangBay

BantayanBay

CatubigRiver

2,500 has

AMIHANNOV-APR

CauhaganIsland

N o r t h e r n S a m a r

San Bernardino Strait

15 k

m d

ista

nce

from

mai

nlan

d sh

orel

ine

DonaLucia

ChitongcoBugko

PAYAOBugko

PAYAOOther group

PAYAOOther Group

Bugko Payao

25 kms from shore

Drifted by strongcurrent/waveslast July 2004

PatingDolphinSibubogBudlisYellowfinlamadangpayao

payao

10050

Smallerr Yellowfin Tuna towards shallow waterof San Bernardo Strait

Gamay

Palapag

Laoang

MondragonCatarman

San Jose

Bobon

Rosario

Graph 5. Showing Fisch Catch of Brgy Chitongco Fishers using Hook % Line

Graph 6. Showing Fish Catch of Brgy Bugko Fishers Using Diff. Gears

During the months June to August N. Samar was frequented by typhoons and bad weather when deepsea “payao” fishing could not be possible, hence fishers confined their fishing activities within the nearshore water.

D. Effect of fishing to total biomass

1. The greatest impacts of tuna fishing have occurred in regions 2 and 3, where the “actual” BIOMASS has DECREASED between the period 1962-1998/2000) as shown in the Graph 7. This result would suggest that there has been a significant DEPLETION OF SUB-POPULATIONS in these regions, primarily by the domestic fisheries of the Philippines and Indonesia and the combined purse seine fishery. But the BIOMASS (or sometimes called the standing stock biomass) is computed based on several data subjected to computer program which only experts can be able to do.

Graph 7. Showing the Decreasing Biomass of Yellowfin Tuna and Exploitable Abundance versus Actual Catch Per Unit Effort (CPUE)

2. Graph also shows that there was too much fishing mortality or higher fishing pressure directed at the juveniles than that of adult yellowfin tuna.

3. Aside from biomass level, an indicator of overfishing can also be gleaned from the comparative data between the actual catch per unit of fishing effort (CPUE) and the Exploitable

Exploitable abundance isHigher than the CPUEBetween 1990-2000

Exploitable abundance islower than the CPUEBetween 1990-2000

Exploitable abundance islower than the CPUEBetween 1990-2000

Exploitable abundance islower than the CPUEBetween 1990-2000

Exploitable abundance isHigher than the CPUEBetween 1980-2000

Abundance of tuna in each region as shown in above Graph 7 which show that it is in Regions 2 and 3 and to a certain extent Region 4 where the actual CPUE is more than the Exploitable abundance. Therefore, Graph 7 (on biomass change) is validated by the Graph 7 (on CPUE vs. Exploitable Abundance).

E. Effect of Fishing on the Size of Fish Population (Length-Frequency)

1. The Graph 8 below shows the length-frequency of the catch by the different fishing gears. Longline used in the 5 Regions have yellowfin tuna catch of larger size; catch of purse-seines in Regions 2 and 3 using fish aggregating devices (FADs) and Logs consist mostly of smaller size groups; the catch in the Philippines using ring net and handline and Indonesia both countries being part of Region 2 consists of smaller size group; and Ring net used in the Philippines has catch of yellowfin tuna of the smallest size group.

Graph 8. Showing the length-frequency of yellowfin of the different fishing gears in different Regions of WCPO.

45 cm (fork length) catch of yellowfin in Northern Samar (May-Aug) in “payao” area

0.5 of maximum size ofyellowfin

2. There is a pattern that yellowfin tuna and other species are found in the Philippines and Indonesian waters during the early years of their life cycle and then migrate towards deeper waters as they grow in size.

Length-weight-age relationship

1. The Length-frequency data are used to determine the status of the fishery species. The information needed are the relative size or the ratio of the average size of fish caught and the attainable maximum size of the fish. Based on the available data on yellowfin tuna, the Graph 9 below is constructed.

Graph 9. Showing the Weight-Length-Age Relationship

Graph 10. Showing the Attainable Max.Size and half-max size of Yellowfin tuna

Growth Rate of Yellowfin Tuna

0 3.4

63.5

176 176 176 176

0

20

40

60

80

100

120

140

160

180

200

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

Age (years)

Ind

ivid

ua

l We

igh

t (kg

s)

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.6 6.0 6.5 7.0

18 cm (Fork length) = 20 kgs (2.5 years)

2.1 meters

1.9-2.1 meters (fork length); max 7 years= 176 kgs

kgs3.4 Kgs=(1.5 years)

63.5 kgs=4 years

Maturity age120 cm forklength

= 2 - 3 yrs

20 kgs =2.5 yrs

47-67 or60 cm ave.

90-125cm or110 cm ave.

115-150cm or130cm ave.

120-165mc or140cm ave.At 30 cm fork length

(1 kg) Yellowfin tuna Starts to move out of Philippine waters; a significant number largerthan 30 cm are stillcaught within Philippinewaters

Length-Weight Relationship of Yellowfin Tuna

0

20

40

60

80

100

120

140

160

180

200

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Fork Length (cm)

Wei

ght (

kgs)

Fork LengthMax.=190 cm

Fork length½ max.=95cmor 20 kgs

Fork lengthMax.= 180cmor 176 kgs

2. Based on Graph 10 above, the half-maximum size of yellowfin is 96 cm or 20 kgs. Average of size of yellowfin catch below this size (length and weight) is considered overfished.

3. Based on the preceeding item no. 2, the status of yellowfin may be characterized as follows:

a. It is in Regions 2 and 3 where the length-frequency has modal point value less than half the maximum size of the fishery species. If the maximum of yellowfin tuna is 1.9 meters, its half value is 95 cm (or 20 kgs) which is just 0.5 the maximum length which means that the specie is at the boundary between overfished and high-yielding status. Graph above shows that yellowfin tuna is already overfished in regions 2 and 3 and the fishing gears that contributed to their conditions are purse-seines and ring nets with fish aggregating device. The use of long line in Regions 1, 2. 3, 4, 5 resulted to the catching of large size yellowfin which is more than 0.5 of the maximum observed length. This means that longline is a more sustainable gear.

b. In the case of Northern Samar, Philippines which is part of Region 2, Graph 11 shows that the size of yellowfin ranges from 30 cms to 45 cms which is less than half the maximum sizes of the specie indicating that yellowfin is being overfished. But it has been yellowfin caught in the offshore water of Gamay are of the big size which is more than half the maximum size of the specie. On the other hand, skipjact tuna or “budlis” catch has average size of 40 cm (standard length) or 42.5 cm (fork length) whish is more than half the usual maximum size (80 cm) showing that this specie is still high-yielding in the Philipiine waters.

c. But considering the western and central Pacific Ocean as a whole, it is only in the Philippine and Indonesian water that undersize yellowfin and big-eye tunas are caught. The main reason is that these species stay in the Philippine-Indonesian water in the early stage of their life cycle and migrate towards the deeper and warmer waters as they grow in size.

Graph 11. Catch data on yellowfin and budlis caugh by fishers of Brgy Chitongco

.

Weight Frequency

Catch data on Yellowfin by Chitongco Fishers per day

2.5 2 2.25 2.25 1.5 2.5 2.51.25 2 2.5

4543

45 45

38

30

39

45 45

39

0

5

10

15

20

25

30

35

40

45

50

April AugustMonth (2004)

Invi

divi

dual

wei

ght a

nd s

tand

ard

leng

th (

cm)

Individual weight (kg)

Standard length (cm)

Catch data on Budlis per day per fisher

2 1.5 1.25 1.90.75 0.9

31.5

43

3840 41

30

45

40 40

0

5

10

15

20

25

30

35

40

45

50

April August

Months

Wei

ght (

kg)

and

Sta

ndar

d le

ngth

(cm

)

individual weight (kg)

Standard length (cm)

Yellowfin becomes Sexually Mature at 120 cm (FL) or 2-3Yrs of age; othersmature at 50-60 cm

or 1-1.25 yrs.old)

Skipjack between 41-87cm (FL) can disperse between 80,000 and 2,000,000 eggs per season

(April-June)Payao

Payao (April-June)

1. Weight-frequency is similar to length-frequency. Instead of length, the weight data are used to determine the change over time or comparing the weight composition of a given specie caught in different Regions or catch of said specie by different gears in the same Region.

Graph 12. Showing that Longline weight-frequency catch

2. The correctness of the constructed length-weight data of yellowfin is confirmed by the weight-frequency of the yellowfin caught by longline as presented in Graph 13 below. The half-

Half-maximum length rf 95 cm or 20 kgs

maximum length as shown in the length-frequency graph which is located to the left of the distribution curve as in the case of longline is also the same point in the distribution curve of the weight-frequency curve. This means that both the length-frequency and weight frequency can be used in determining the status of the fishery. Longline fishing does not contribute to overfishing.

Graph 13. Showing the Longline weight-frequency catch during 1997-2001

3. The above Graph indicates that since 1997 until 2001, longline fishing has been consistent to be contributing to sustainable fishing.

1 year

1 year

1 year

1 year

Half-maximumSize of yellow fin

Tuna Producing Area and Tuna Fishing Operation

1. Map 8 shows that the Philippines and Indonesia are near the equatorial region and facing the tuna-rich WCPO. For being so, the said countries have the highest tuna production among ASEAN countries.

Map 8. Showing the Major Tuna Producing Countries in Asia and Tuna Fishing Grounds

The following Table 2 presents 2002 tuna fish catch in the western and central Pacific Ocean (WCPO), by fishing gears, by what nationality, and the status of tuna species:

Table 2. Showing WCPO tuna fishery dataSpecies Fishing Gears

Large Tuna-rich is

hing

Ground ( longlin

e,

purse-seine)

INDONESIA

MALAYSIA

THAILAND PHILIPPINES

General Santos/DavaoTranshipment Placefor Tuna caught in thePacific Region

Major Tuna ProducingCountries in Asia:

PhilippinesIndonesiaThailandMalaysia

Japan, South Korea, a

nd Taiwan

Catching tuna w

ith la

rge Fishing

Fleet

Relatively Less

Population of la

rge

tuna species

Purse-seineCatch (m.t.) %

Pole & LineCatch (m.t.) %

LonglineCatch (m.t.) %

Troll gearsCatch (m.t.)

Status

Sipjack-66%

962,233 83 281,322 85

- -

-

2002 level of stocks are high and catch levels are easily sustainable

Yellowfin- 22%

176,175 15

16,548 5

82,252 34 -

2002 not being overfished and current level of exploitation is sustainable; any future increases in fishing mortality would not result in any long-term increase in yield and may move the yellowfin stock to an overfished state

Big-eye- 6%

21,696 2

3,309 1

82,252 34 -

Stocks not in an overfished state although overfishing is occurring and the current level of exploitation appears not to be sustainable in the long term, unless the high recent recruitment is maintained in the future.  

Albacore Tuna –6%

- 29,787 77,412 -The impact of the fishery on the overall stock is estimated to be small, and higher levels of catch could likely be sustained.

TOTAL 1,160,104 58 330,968 17 241,917 11 4,477

REMARKCatches for the Korean and Taiwanese fleet increased in 2002 while Japan catch decreased

Atlantic tuna is caught by Japanese coastal and offshore fleet

Caught by large vessel and distant water fleet of Japan, Korea, and Taiwan

also other variety of artisanal gears mostly in eastern and southern Philippines;lower effort of USA fleet

2. Skipjack tuna (Katsuwonus pelamis) contributes 66% in total tuna catch in the WCPO (see Table 2), 70% of the total tuna catch in the Pacific Ocean, and 50-55% of the world tuna catch, but the largest catches are taken from the warm-pool in the western equatorial Pacific. U.S. purse-seine fishing vessels catch skipjack tuna and based on the analysis of catch and effort data, it was found out that one of the most successful fishing grounds is located in the vicinity of a convergence zone between the warm (>28-29° C) low-salinity water of the warm-pool and the cold saline water of equatorial upwelling in the central Pacific

3. Yellowfin tuna constributes 22% of total tuna catch in WCPO, 35% of the total world tuna catch and is being harvested by smalls-cale artisanal fisheries in Pacific Island and southeast Asian waters to large, distant-water longliners and purse seiners that operate widely in equatorial and tropical waters. Purse seiners catch a wide size range of yellowfin tuna, whereas the longline fishery takes mostly adult fish.

4. Bigeye tuna (Thunnus obesus) contributes 6% of the total tuna catch in WCPO and is considered an important component of tuna fisheries throughout the Pacific Ocean. They are the principal target species of the large ‘distant-water’ longliners from Japan and Korea and of the smaller ‘fresh sashimi’ longliners based in several Pacific Island countries. Bigeye tuna are fundamental to the economic survival of the longline fishery in the western and central Pacific Ocean.

5. Purse-seine tuna catch in the WCPO is the highest at 58%, followed by pole % line at 17%, longline at 11%, and troll line with other artisanal gears mostly in eastern Indonesia and the Philippines at 14%. A typical high-tech purse-seine fishing vessel is shown in Figure 3.

6. The western and central Pacific Ocean (WCPO) currently supports the largest industrial tuna fishery in the world The three gear types accounting for most of the catch in the area are longline, purse seine and pole-and-line. Large-mesh drift-net, handline and trolling gear have been utilised in some areas, but not to the extent of the above-mentioned gear types. The primary target species are skipjack, yellowfin, bigeye and albacore.

7. The foreign tuna fishing vessel operators have been doing transshipment of their tuna catch at General Santos City or Davao City so that they can economize in their cost of operation and continue fishing operation. However, in the process certain volume of tuna with lower quality (particularly caught by purse-seine and ring net) are marketed in the country at lower price than those large tuna caught by small Filipino fishers in the tuna-rich northern Celebes Sea using handline. This results to the lowering of the market price of tuna caught by the handline fishers. Therefore, the good quality tuna are marketed abroad possibly through Japanese/Korean outlets at lower price ensuring them high profit.

Figure 3. Typical Purse-seine fishing vessel and purse-seine operation

Conclusions

1. There is the harvesting of the same tuna stock(s) by countries fishing in the same region. Using the most efficient fishing gear (Filipino-owned or joint venture with Japanese, Taiwanese, Koreans, and U.S.), each country harvests the tuna at a particular size and at a particular point in the migration route. Thus, the harvest of tuna by one country impacts the present and future catches of the same stock(s) of tuna by countries which harvest these resources later on in the migratory route of the tuna.

2. Based on item no. 1, there is an urgent need to study interactions among fisheries nationally and regionally. Without a coordinated and directed approach to gather, document,

Purse-seine

Service boatused in tugging the other end of the net while Mother boat moves in circular manner as to encircle the school of fish

RadarHauling of seine net (mechanized boom)Boom

Trappedfish

Surface line floaters

Bottom line with sinkers enclosed forming purse

analyse, and interpret the relevant data, the tuna fishery resources in the southeast Asia region cannot be assessed and managed effectively to ensure sustained harvests.

3. Fishing mortality for juvenile yellowfin tuna has increased strongly since about 1992, partly as a result of catchability increases in the purse seine fisheries. But a significant component of the increase is attributable to the Philippines and Indonesian fisheries, which have the weakest catch, effort and size data. This is of continuing concern. There has been recent progress made in the acquisition of a large amount of historical length frequency data from the Philippines and regular sampling operations are now in place there. However, uncertainty with the total catch and size composition data for the Indonesian fishery continues to be a problem.

4. The overall impact of fishing on stock biomass is estimated to be in the vicinity of 35% in recent years. The impact is differentially high in the tropical regions (around 50%) compared to the subtropical regions. This means that the tropical regions which are the most productive in fishery are also the most exploited fishing grounds. However, the level of yellowfin biomass in the MCPO areas is not yet in the critical condition (or being overfished or in an overfished side).

5. The Philippine waters and Indonesian waters have the most productive tuna fishery among the ASEAN countries being both facing the WCPO areas found to be thickly populated with yellowfin tuna and big-eye tuna. However majority of the tuna biomass in said countries are composed of juveniles indicating that this part of the WCPO serves as the tuna habitat in their 1 st

few months of their life cycle. And it is towards the winter months that yellow fin and big-eye tuna (about 30 cm in fork length) migrate out of the Philippine waters towards the equatorial region at less than 5o latitude. However, large size tuna can be caught in large quantities off Samar island outside of the municipal water.

6. Based on item no. 5 above and the fact that tuna fishery (yellow fin and big-eye) in the WCPO areas are still not considered overfished particularly the skipjack tuna, the smallscale and artisanal fishers should be provided with incentives to engage in tuna fishing through the use of FAD using handlines or ring net for periodic total harvest.

7. The transshipment scheme of foreign tuna fishing vessel operators to dump tuna catch of poorer quality being caught by purse-seines in the southern Philippines’ fish landing areas (General Santos City – tuna cannery in the Philippines) for the purpose of lowering down the price of qood quality tuna caught by the Filipino tuna handliners must be exposed and opposed.

REFERENCE CITED

BAS Fisheries Statistics

Chee, P.E. Tuna fisheries interactions in Malaysia. Fisheries Research Institute, Dept of Fisheries Malaysia, 11700 Gelugor, Penang Malaysia.

Grolier International Enclopedia. 1991

Hampton, J, Langley, A., Williams, P. The Western and Central Tuna Fishery 2002.

Hampton, John. Stock assessment of yellowfin tuna in the western and central Pacific Ocean.SCTB15 Working Paper, Oceanic Fisheries Programme, Secretariat of the Pacific Community; Noumea, New Caledonia

Hampton J., Bigelow, K., Labelle, M. A summary of current information on the biology, fisheries and stock assessment of bigeye tuna (Thunnus obesus) in the Pacific ocean, with recommendations for data requirements and future research. Oceanic Fisheries Programme, Secretariat of the Pacific Community (SPC).

Lehodey P., Andre J-M, Bertignac M., Hampton J., Stoens A., Menkes C., Memery L., Grima N. Predicting skipjack tuna forage distributions in the equatorial Pacific using a coupled dynamical bio-geochemical model. Oceanic Fisheries Programme, Secretariat of the Pacific Community (SPC).

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