P.E. Chee
Fisheries Research Institute
Department of Fisheries Malaysia
11700 Gelugor, Penang, Malaysia
ABSTRACT
Neritic small tuna species including longtail tuna (Thunnus tonggol), kawakawa (Euthynnus affinis), and frigate tuna (Auxis thazard) have traditionally been caught in Malaysia at subsistence levels by fishermen using a variety of fishing gears. However, with implementation of the Exclusive Economic Zone, Malaysia has joined other nations in exploring waters beyond their immediate shores for commercially important pelagic finfish species such as yellowfin tuna and skipjack tuna. For Malaysia these new fishing grounds are mainly in the South China Sea off the east coast of Peninsular Malaysia and off the States of Sabah and Sarawak.
With the introduction of larger fishing boats and modern fishing gear, the fishery for tuna in Malaysia is expected to shift from the subsistence level to a commercial operation. Thus, management of these tuna resources need to be addressed so catches can be maintained at optimum sustained levels. Since it is acknowledged that these tuna resources are likely to be shared by the countries in the region, the management of these resources should be implemented on a regional basis. A study of tuna interactions of these fisheries within Malaysia and within the region should provide the basis for formulation of management measures that will ensure the proper development and exploitation of these tuna resources.
1. INTRODUCTION
Pelagic fisheries have contributed significantly to the diversified fisheries of Malaysia. Prior to the introduction of the trawl, the purse seine was the major gear exploiting the fishery resources in Malaysia. The purse seine, together with other smaller seines and the drift gillnet have been the principal gears which have contributed the bulk of the commercial marine fish landings in Malaysia up to the present time. The species that form the bulk of the commercial pelagic fish catch are mainly the scombrids (Rastrelliger kanagura, R. bachysoma, Euthynnus affinis, Auxis thazard, Thunnus tonggol) and carangids (Decapterus spp., Auxis mate, Selar spp., Megalaspis cordyla). Other gears used by artisanal fishermen to catch pelagic species include handlines, troll lines, and barrier nets.
The major gears used to catch tuna are the purse seine in the Malacca Straits area and the troll line, purse seine, and drift gillnet in the South China Sea area (Figure 1).
2. DEVELOPMENT OF PURSE SEINE TUNA FISHERY IN MALAYSIA
During 1987 and 1988 experimental purse seine fishing trials for tuna were conducted in Malaysia's Exclusive Economic Zone (EEZ) of Pulau Layang-Layang (Figure 1) by a research vessel (Gambang and Chong, 1988) as well as a commercial purse seiner (Johari, 1989). Fishing was conducted in conjunction with fish aggregating devices (FADs). An average catch rate of 14 mt per haul was recorded by the commercial purse seiner. In mid-1994, the vessel (K.L. PAUS) of the Malaysian Fisheries Training Institute conducted fishing trials in conjunction with FADs; the average catch was 15.5 mt per haul. It was noted that the aggregation of tuna by FADs varied with time of year and the sea surface condition (Johari, 1989, Gambang, in press). More fish seemed to aggregate under FADs between the months of March to June. Aggregations by FADs may also vary with the migration pathways of the tuna.
The experimental fishing carried out in the Pulau Layang-Layang area gave some interesting results. Fishing with vertical handlines at depths ranging from 200 m to 300 m yielded 90% yellowfin tuna (Thunnus albacares) and 10% skipjack tuna (Katsuwonus pelamis). The yellowfin ranged in size from 1 kg to 60 kg. There is a possibility that some small bigeye tuna (Thunnus obesus) were caught, but were misidentified as yellowfin tuna. Purse seine catches consisted of 85% skipjack tuna weighing between 1 to 4 kg per fish; the remaining 15% of the catch consisted of yellowfin tuna. Fishing with vertical longlines and purse seines were carried out in conjunction with FADs. It was also reported that more fish were caught around FADs set in deep trenches (Johari, 1989). Fishing with the longline yielded mainly bigeye tuna; individuals ranged between 20 kg and 70 kg (Gambang, in press).
Following the experimental fishing trials, commercial tuna fishing in Malaysia commenced with the purse seine and vertical handline gears as the principal fishing gears used.
3. OTHER TUNA FISHERIES IN THE REGION
Similar to 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. 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 (Aprieto, 1989).
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 (Anon., 1993)
The development of the Thai tuna fishery was catalysed by the development of the canned seafood industry in the early 1980s (Bhatia et al., 1989). Prior to this development, the target species of the marine fishery were the small pelagics; tunas were considered as bycatch of the pelagic fishery. With the increased demand for tuna, the purse seine fishery in Thailand began to target small tunas including the longtail (Thunnus tonggol), kawakawa (Euthynnus affinis), and frigate tuna (Auxis thazard). The bulk of the catch was directed to the canneries. The purse seine and gillnet fisheries have contributed very impressively to the increased tuna landings in Thailand (Anon., 1993).
4. TUNA LANDINGS IN THE REGION
The total landings of tuna in Malaysia show a steady increase from around 6,000 mt in 1970 to a high of 35,000 mt in 1992 (Figure 2). The bulk of the tuna landed came from the east coast of Peninsular Malaysia; the west coast of Peninsular Malaysia contributed only small quantities of tuna. Until 1991 the tuna catch recorded in the states of Sabah and Sarawak were very small; however, in 1991 and 1992 these states recorded the highest tuna catch for all of Malaysia. Landings for both states together totalled 13,000 mt and 19,000 mt for 1991 and 1992, respectively. The major increase in tuna landings came from the expansion of the commercial tuna fishery into the EEZ waters of Malaysia, mainly around Pulau Layang-Layang area in the South China Sea. It expected that the tuna production in Malaysia will continue to show substantial growth in the future.
Figure 3 shows the landings of tuna and tuna-like fishes (this category includes billfish and seerfish) by countries in the Southeast Asia region. The two countries with the highest recorded tuna landings are the Philippines and Indonesia, followed by Thailand and Malaysia.
Figure 2. Tuna landings in Malaysia, 1971-92.
Figure 3. Tuna, billfish and seerfish caught in Area 71, by country, 1981-91.
5. INTERACTION BETWEEN THE TRADITIONAL TROLL FISHERY AND THE COMMERCIAL PURSE-SEINE FISHERY IN MALAYSIA
Traditionally the troll line operators of Kuala Terengganu on the east coast of Peninsular Malaysia targeted tuna and Spanish mackerel. Trolling is carried out on small boats using about four lines per boat. The number of hooks per line ranges from 2 to 25; the number of hooks per line is increased if fishing success is high. These boats usually perform trips of 3-4 days duration; the operation of these trollers has been described by Chee (1989). Landings by these trollers were reported to be the highest relative to other gears used to catch tuna (Figure 4).
Since late 1987, a fleet of 40 purse seiners has fished in the South China Sea mainly for tuna. With the introduction of this purse seine fleet, the small tuna resources of this area has been shared by troll vessels and purse seiners. With the introduction of the purse seine fishery a number of interaction problems arose. Initially these purse seiners intended to fish for free-schooling small tuna in the South China Sea; however, in actual fishing operations spot-lights were used by these vessels to aggregate fish. The purse seiners, thus, caught the larger free-swimming tunas and also small pelagics which aggregated in response to the spot-light (Chee, 1992). With the influx of the purse seiners, the catches of the trollers were expected to decline; this decline was observed (Figure 4). It was noted that while the purse seiners are capable of ranging over a wide fishing area, the trollers by virtue of their small size and type of gear were limited to the traditional fishing grounds in the vicinity of the oil rigs off Terengganu in the South China Sea. It appears that a direct interaction exists between the purse seine fleet and the troll fishery; it was also noted that the drift gillnet fishery may also be affected.
Figure 4. Tuna landings in east coast peninsular Malaysia, by gear, 1979-92.
The catch by gear of the tuna fisheries of Malaysia are shown in Figure 4. Except for 1986 and 1987, the catch of the troll fishery show a gradual decline in catch from 1983; increased landings were noted for 1986 and 1987. The drift gillnet fishery also shows a gradual decline in catch which started in 1984. Unlike the troll and drift gillnet fisheries, the purse seine fishery shows an increase in landings from 1982; the 1988 catch was unusually high.
While interaction between the purse seine fishery and the traditional troll and drift gillnet fisheries may be a factor contributing to the decline in catches of the latter two fisheries more detailed studies of the dynamics of the fisheries need to be carried out in order to verify and quantify this interaction. As noted earlier the increase in the catch of the purse seine fishery may be due to the movement to newer and more productive grounds further offshore.
6. INTERACTION IN THE HARVEST OF TUNA BY COUNTRIES IN THE REGION
As early as 1989, a decrease in size of longtail tuna was reported from the monitoring of the troll fishery at Terengganu. The average size of longtail tuna caught by trollers increased from 1983 to 1987 from 35.2 cm to 36.6 cm. In 1988 the mean size declined to 33.2 cm and still smaller size to 32.6 cm in 1989. General declines in the mean size of longtail tuna caught by the Thai purse seine and gillnet fisheries were also observed in 1989 relative to earlier years (Yesaki, 1994). The mean size of kawakawa also decreased in 1989 (Yesaki, 1994). However, the mean size of frigate tuna showed an increase in 1987 and a decrease in 1989 (Yesaki, 1994).
The decreases in mean size could result from increased exploitation rates of these tuna species by Malaysian fisheries as well as other countries fishing in the region. Since this inference was made on the basis of fishery-related information, more evidence should be gathered from further monitoring of these stock(s) in the region. More biological information on the migration and distribution of the tuna stock(s) also need to be collected. Some studies of this nature have been initiated in Malaysia; these studies include tagging of small tuna to study their migration and distribution in the region (Raja Bidin, 1990). In an effort to identify unit stock, a study of the distribution of tuna larvae was initiated (Liew, personal communication); similarly, the use of parasites as biological indicators of stocks was also attempted (Faizah, et al., 1988).
7. A REGIONAL APPROACH IN STUDYING INTERACTIONS OF TUNA FISHERIES
From the above discussion, it appears likely that interactions exist among the tuna fisheries of neighbouring countries in southeast Asia. The harvesting of tuna at a particular time, age, and size by one country will definitely affect the catch of another country if common resources are involved. Thus, the size segregation of tuna species by gear and fishing grounds needs to be studied.
Conspicuous shortcomings in the available documentation of the biology of tuna species of the region is the lack of information on the distribution and migration of the several species involved and the virtual lack of stock structure information. Solution to these basic problems cannot be achieved without the concerted effort of all parties involved with the fisheries. While biological information is being collected independently by countries fishing in the region, the information is not readily available; in many instances the information is inadequate for proper assessment. It appears a coordinated regional approach is necessary to gather the appropriate data and to carry out the analyses and interpretation of the data that could lead to effective management. Therefore, effort should be undertaken to establish a regional approach to research and management of the resources in the region. Recognizing this need, a few regional projects directed toward management of shared stocks have been proposed for implementation by the Southeast Asian Fisheries Development Center (SEAFDEC), in Kuala Terengganu, Malaysia (Raja Bidin, 1994). These projects include the collection and documentation of catch and effort data and biological data, the latter includes carrying out spawning ground surveys and tuna tagging programmes.
8. CONCLUSION
Interaction in the tuna fisheries of Malaysia relate mainly to resource allocation by fishing gear used within the country. The problem of resource allocation also arises out of the harvest of the same tuna stock(s) by countries fishing in the same region. Using the most efficient fishing gear, 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.
Recognising this, there is an urgent need to study interactions among fisheries nationally and regionally. Without a coordinated and directed approach to gather, document, 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.
9. REFERENCES CITED
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