Monitoring landings of Taiwanese tuna longliners at Penang Harbour

P.E. Chee
Fisheries Research Institute
Department of Fisheries Malaysia
11700 Gelugor, Penang, Malaysia

Sok Kean Khoo
70 Lorong Ipoh
11600 Penang, Malaysia

ABSTRACT

Foreign fishing boats, particularly Taiwanese tuna longliners, are attracted to Penang because of her strategic location in the Straits of Malacca and the support of good port and communication facilities. Monitoring of the total landings of tuna by Taiwanese tuna longliners began in 1990. From mid-1992 until the end of 1993, the monitoring of tuna landed and transshipped through Penang was done more systematically with the financial support of the Indo-Pacific Tuna Development and Management Programme (IPTP). From this monitoring programme information on total catch, species composition, and size information of the major tuna species, i.e., yellowfin tuna was compiled. The seasonality of fishing activities, fishing grounds and fishing vessel information were documented. The increase in longlining for yellowfin in the eastern Indian Ocean may cause possible interactions among tuna fisheries in other parts of the Indian Ocean. The information collected from this monitoring programme is important since without this documentation, a good part of the information relating to the exploitation of the tuna resources in the Indian Ocean will not be known.

1. INTRODUCTION

During the 1960s, Penang served as a landing and transshipment port for foreign tuna fishing vessels. This activity ceased in the 1970s but had resumed since the mid-80s. The number of Taiwanese tuna fishing vessels discharging their catch at Penang Harbour has increased since the mid-80s due to Penang's strategic location, good support facilities, good international air and sea linkages, and the presence of similar cultures (Mohamad, 1993).

The Taiwanese started tuna longline fishing in the Indian Ocean in 1963. Initially their main target was albacore (Thunnus alalunga), but two years later switched to yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus) (Hsu and Liu, 1991).

The tuna longliners that land at Penang Harbour are generally small vessels averaging 50 GRT and are powered by engines of about 400 hp. These vessels operate for a duration of up to one month at sea. The fishing grounds in the Indian Ocean lie mainly between 0-10°N latitudes and to 80-95°E longitudes. Each vessel has 7-10 crew members. Fishing is usually carried out at depths between 45-70 m. A description of the fishing vessels, their gear and mode of operation was documented earlier (Khoo and Chee, 1994). The bulk of the tuna is exported to Japan in the chilled form for the sashimi market. Second-grade tuna are sold in the frozen form both to local and foreign canneries.

2. TOTAL LANDINGS

The total recorded landings of tuna in Penang from 1990 to September 1994 are shown in Figure 1. For the four year period, a clear seasonality in landings was observed. Landings of tuna peak in December/January annually while the lowest recorded landings were in the middle of the year. Total landings ranged from 136 tonnes per month to 2,040 tonnes per month over the period covered from 1990 to September 1994. It is of interest to note that the highest landings corresponded with the highest demand of the Japanese sashimi market which occurs during the New Year period.

Figure 1. Berthings and landings, 1990-94 (data from Penang Port Commission).

3. TOTAL NUMBER OF BERTHINGS

Figure 1 also shows the number of berthings recorded by the Penang Port Commission. The highest number of berthings were recorded also during the months of December of one year and January of the following year. There is a close correlation between the number of berthings and the quantity of tuna landed.

4. SPECIES COMPOSITION

Table 1 shows the species composition of sampled landings by month for 1992 and 1993. It is clear that yellowfin tuna (Figure 2) always made up the highest proportion of the landings; bigeye were landed in smaller amounts. Marlins (Makaira indica, M. mazara and Tetrapturus audax), swordfish (Xiphias gladius), sailfish (Istiophorus platypterus), skipjack tuna (Katsuwonus pelamis), wahoo (Acanthocybium solandri), barracudas (Sphyraena), and a few species of sharks were also landed.

Table 1. Composition of Taiwanese longline landings (kg) at Penang Harbour, 1992-93.

Year	Month	Yellowfin	Bigeye	Martins	Swordfish	Sharks	Others	Total
1992	Jan.	424852	32176	19035	7992	7318	5996	497369
	Feb.	228311	36614	10985	6548	3434	2536	288428
	March	126324	20417	6256	1922	1967	1566	158452
	April	37029	6403	2759	1099	492	1352	49134
	May	69163	7637	4938	4862	1387	3464	91451
	June	20384	2133	1956	246	542	137	25398
	July	34389	7586	7787	4533	7310	5989	67594
	Aug.	13805	1055	993	1589	6345	1172	24959
	Sept.	58797	17452	8980	8817	3637	8660	106343
	Oct.	60357	7622	7484	4790	4754	5610	90617
	Nov.	122033	20907	9555	2978	3880	3825	163178
	Dec.	371523	80470	27579	6235	2945	4329	493081
1993	Jan.	317381	52654	19200	5808	4823	4194	404060
	Feb.	276376	61624	10101	3296	2864	7168	361429
	March	206259	89623	6957	3352	1853	5003	313047
	April	140353	38189	1449	1417	596	5582	187586
	May	158014	24116	18613	1261	632	4209	206845
	June	66223	10259	7718	2043	1886	5500	93629
	July	35378	12827	5337	3004	581	3548	60675
	Aug.	47141	15980	6944	6838	1408	7205	85516
	Sept.	124643	25293	8711	7702	3509	8271	178129
	Oct.	46806	8746	8753	2680	1372	3503	71860
	Nov.	68578	32719	19247	10411	6093	14265	151313
	Dec.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.

Figure 2. Species composition of Taiwanese longline landings at Penang Harbour, 1992-93.

5. SIZE COMPOSITION

The average gilled-and-gutted weight of yellowfin and bigeye tuna sampled by month in 1992 and 1993 is shown in Figure 3. For both yellowfin and bigeye tuna, the average gilled-and-gutted weights, were low during the third quarter of the year. This shows that more large fish were caught during the time of peak fishing activity. However from Figure 4, it can be seen that the weight of fish landed per berthing (or per fishing trip), appears to be rather consistent, i.e., approximately 10 tonnes per berthing. This quantity of fish is possibly limited by the size of the fish hold of the vessel as well as by the saturation time of handling of the fish on board to maintain the quality desired for export to the Japanese sashimi market.

6. HANDLING

6.1 Tuna for Sashimi

On board the fishing vessel, tuna directed to the sashimi market are killed, dressed and chilled immediately after capture. The fish are also to be handled gently, yet quickly, to prevent bruises and the condition called "yake niku" or burnt flesh. Fish in this condition cannot be sold for sashimi because of their unpleasant appearance, acidic flavour and metallic after-taste (Putro, 1990). Fish that are not dressed on board are gilled-and-gutted at the landing site. Sashimi-grade tuna are chilled with crushed ice. Fish for export are packed in cartons with dry ice while second-grade tuna are usually frozen and sold to local canneries or exported.

Figure 3. Average gilled-and-gutted weight of yellowfin and bigeye tuna.

Figure 4. Landings per berthing recorded at Penang Harbour, 1990-94 (data from Penang Port Commission).

6.2 Other Bycatch

Almost all the bycatch are killed and eviscerated and the heads and fins are cut off before being stored in deep freeze. However some prime quality marlins are also chilled and sold for sashimi as well. Swordfish are usually exported to European markets for fish steak.

6.3 Possible Interactions

The increase in longlining for yellowfin in the eastern Indian Ocean may affect the present fishing activities in the western part of the Indian Ocean. In the western Indian Ocean, fishing primarily by Spanish and French purse seiners catch yellowfin in addition to skipjack (Lablache, 1991). Thus interaction may arise from the fishing of the same species but at different life cycle stages since purse seiners generally catch smaller size fish from surface schools. Fishing in parts of Indonesia, which also uses the longline, may be affected, e.g., in areas to the west of Sumatra, where a similar fishery targeting for sashimi-grade tuna has recently developed (Naamin and Bahar, 1994).

7. DISCUSSION

Penang has benefitted from the transshipment activities of the Taiwanese tuna longliners. Besides accruing revenue directly from the fishing activities, several activities associated with the transshipment business have been initiated, e.g., development of milkfish farms to supply live bait for tuna longliners. These activities will increase and will continue to support the fishing operations for oceanic tuna in the Indian Ocean if the resources are sustained. Since yellowfin are reported to move extensively, it would be desirable to continue the collection of these data to examine possible interaction issues related to the yellowfin resource in the eastern Indian Ocean to support the proper management of these oceanic tuna resources.

8. REFERENCES CITED

Hsu, C.C., and H.C. Liu. 1991. Taiwanese longline and gillnet fisheries in the Indian. Paper presented at the Expert Consultation of Stock Assessment of Tunas in the Indian Ocean, 2-6 July 1990, Bangkok, Thailand. Coll. Vol. Indo-Pac. Tuna Dev. Mgt. Programme 4: 244-258.

Khoo, S.K., and P.E. Chee. 1994. A study of the Indian Ocean tuna longline fishery based in Penang, Malaysia. Proceedings of the Fisheries Research Conference, Department of Fisheries Malaysia IV: 210-218.

Lablache, G. 1991. Tuna fishing trends in the western Indian Ocean. Paper presented at the Expert Consultation of Stock Assessment of Tunas in the Indian Ocean, 2-6 July 1990. Coll. Vol. Indo-Pac. Tuna Dev. Mgt. Programme Vol. 4: 478-488.

Mohamed, Z. 1993. Penang now the top fish jetty. The Star Publications Sdn. Bhd., Penang, 22 April 1993, 16 p.

Naamin, N., and S. Bahar. 1994. Interaction in the yellowfin tuna fisheries of the eastern part of the Indonesian waters. In: Shomura, R.S., J. Majkowski and S. Langi (eds.). Interactions of Pacific tuna fisheries. Proceedings of the First FAO Expert Consultation on Interactions of Pacific Tuna Fisheries, 3-11 December 1991, Noumea, New Caledonia. Vol. 1: Summary report and papers on interaction. FAO Fish. Tech. Pap. (336/1): 199-212.

Putro, S. 1990. Handling and processing of tuna for sashimi. INFOFISH Technical Handbook 1. 26 p.