CHANGES IN THE SPECIES COMPOSITION OF DEMERSAL FISH TRAWL SURVEYS IN THE EAST COAST OF I'ENINSULAR MALAYSIA

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2 CHANGES N THE SPECES COMPOSTON OF DEMERSAL FSH TRAWL SURVEYS N THE EAST COAST OF 'ENNSULAR MALAYSA Ahmad Adnan bin N uruddin Fisheries Research nstitute Batu Maung Penang Demersal fish resource surveys using bottom trawl nets have been carried out in the east coast of Peninsular Malaysia since 1970 with the latest survey being conducted in The trawling stations are mostly conducted in waters between 10 to 60 metres in depth with a few in waters deeper than 60 metres. The major species or fish groups composition of these surveys are reviewed and compared to determine any changes in their degree of dominance. Comparisons are made for the whole survey region as weu as by depth-zones. The parameters used in the comparisons are the percentage catch by weight of commercial sized fish and their rankings in terms of dominance. A number of species or fish groups showed major changes in their degree of dominance. Among these are the sciaenids which were third in terms of dominance in 1970 but almost negligible in ] 995. SqUids which were ranked 14 in 1970 became the most dominant group in Thus from 1970 to 1995 a number of changes have occurred in the species or fish groups composition of the demersal fish resource surveys in the east coast of Peninsular Malaysia. Survei sumber ikan demersal dengan menggunakan pukat tunda dasar telah dijalankan di pantai timur Semenanjung Malaysia sejak tahun 1970 dan yang terbaru sekali ialah pada tahun Kebanyakan stesen menunda dijalankan di antara 10 hingga 60 meter kedalaman air dan beberapa stesen lagi di perairan melebihi 60 meter. Komposisi spesis atau kumpulan ikan yang utama dari survei-survei ini di bandingkan untuk menentukan sarna ada berlaku apa-apa perubahan pada tahap dominan mereka. Perbandingan dibuat untuk keseluruhan kawasan survei dan juga mengikut zon kedalaman air. Parameter yang digunakan di dalam perbandingan adalah peratusan berat tangkapan ikan-ikan yang bersaiz komersial dan kedudukan mereka dan segi dominan. Beberapa spesis atau.kumpulan ikan telah menunjukkan perubahan yang besar di dalam tahap dominan mereka Di antaranya ialah ikan Gelama (SCAENDAE) yang merupakan kumpulan ketiga paling banyak pada tahun 1970 tetapi hampir tidak:. terdapat pada tahun Cumit-cumit (LOLGODEA) yang merupakan kumpulan yang ke empat belas dari segi dominan pada tahun 1970 menjadi kumpulan yang paling dominan pada tahun Oleh itu dari tahun 1970 hingga tahun 1995 terdapat beberapa perubahan yang berlaku kepada komposisi tangkapan spesis atau kumpulan ikan yang diperolehi dari survei sumber ikan demersal di pantai timur Semenanjung Malaysia. The fisheries resources in the coastal waters of Peninsular Malaysia have been subj ected to intense fishing pressure from the various fishing gears operating in those waters. Among the more dominant gears in operation are the bottom trawls purse seines and driftjgillnets. Demersal fish resource surveys have been periodically carried out in the waters off the west and east coasts of Peninsular Malaysia in order to monitor the status of these resources. The average catch rates obtained from these surveys indicate that the demersal fish resources in the east coast of Peninsular Malaysia have declined from 1970 to the present day. The overall average catch rate of the

3 1970 survey was kg/hr (Pathansali et al. 1974). The 1971 survey showed a drastic drop il'\ the overall average catch rate with kglhr (Jothy et a. 1975) before improving in the next survey in 1972 with kg/hr (Lam et al. 1975). The overall average catch rate subsequently showed a declining trend up to the 1988 survey which had a figure of 71.8 kglhr. The next two surveys conducted in 1990 and 1991 each had similar values for the overall catch rates thus suggesting that these rates had stabilised. However the latest survey carried out in 1995 showed a drastic drop to only 29.3 kglhr. This paper discusses the changes in the species composition of the major species or species group found during the demersal fish resource surveys conducted off the east coast of Peninsular Malaysia. This discussion may lead to a better understanding of the effect of fishing pressure on the available resources in these waters. Results from previous surveys conducted in the coastal waters off the east coast of Peninsular Malaysia were compared. These results were obtained from both published reports i.e. Pathansali et ai 1974; Jothy et al. 1975; Lam et al. 1975; Lamp and Shaari 1976; Ahmad Adnan 1990' as well as internal reports of th~ Fisheries Rese~rch nstitute. The surveys consdered in this analysis were from the first demersal fish survey conducted by the Fisheries Research nstitute off the east coast of Peninsular Malaysia in 1970 to the most recent survey in the same area conducted in The surveyed region of the these surveys is shown in Figure 1. Comparison of the results of these surveys was possible because of the standardisation of the survey methodology.each surveyused bottom trawl nets of the same design. The trawling speed was fixed at between. 2.8 to 3.0 knots while the trawling duration was also fixed at one hour. The catch of each haul was also processed in the same way for each of the surveys. For the analysis the species composition of the surveys were used. Only species or fish groups recorded in the commercial fish category i.e. commercial species which have attained marketable size were considered as data on these types of fish were available. The percentage catch by weight was used as an indicator of the degree of dominance of the various species or species groups caught. Thus for each survey conducted the species or species groups were ranked based on their percentage catch. The first 15 most dominant species or species groups in the first survey conducted in 1970 were used as a base for comparison purposes. The rankings of these species or species groups in subsequent surveys were obtained. As the rankings of some of these species or species groups fell below the top 15 the other species or species groups which replaced them in the list were also noted. To ascertain whether changes in dominance for the whole surveyed region were due to changes related to depth of water further analyses were carried out. The percentage catch according to depth zones of all the species or species groups listed in the first phase of the analysis for all the

4 surveys conducted were obtained. The depth of water were categorised.as 10-30m 31-50m and 51-70m zones.. The ranking of the dominant species or species groups for each of the demersal fish surveys off the east coast of Peninsular Malaysia is shown in Table 1. The corresponding percentage catch by weight for the same species or species groups for each survey is shown in Table 2. t should be noted that these percentages are heavily influenced by the percentage composition of the trash component of the total catch. Thus although a high ranking may be achieved by a particular species or species group the corresponding percentage composition may be relatively low due to a high percentage catch of trash fish. The percentage catch by weight of the selected species for the la-30m depth zone is given in Table 3a for the 31-50m depth zone in Table 3b and for the 51-70m depth zone in Table 3c. During the first survey conducted in 1970 the most dominant fish were the threadfin breams of the genus Nemipierus which contributed 6.3% of the total catch from the whole surveyed region. From 1970 to the late 1980s this genus had always been the most or second most dominant group landed (Figure 2). They contributed between 5.8% to 9.4% of the total catch of each survey during this period. However from the 1990 survey to the most recent survey conducted in 1995 this group appeared to have declined slightly in terms of dominance. During the three surveys conducted in the 1990s this genus had dropped to fourth or fifth place in terms of abundance. n 1995they contributed only 2.5% of the total catch..the percentage catch by weight of the nemipterids also appeared to be declining in the la-30m depth zone particularly for the period between 1988 and n 1995 they contributed only 0.5% of the total catch in this depth zone. n the 31-50m depth zone this genus showed a sharp increase in percentage contribution from 1971 to 1974before experiencing a sharp drop in From 1983 to 1995 their contributions showed a slight but gradual decline from 8.9% to 4.6%~ which was still better than the la-30m depth zone. However they still appeared to be well represented in the deeper waters as their percentage composition in the 51-70m depth zone duj1ngthe 1995 survey' was 12.5% thu.s making them one of the most dominant groups in this zone. Their percentage composition in this depth zone appeared to fluctuate without any clear trend. The CARANGDAEwhich is a family made up of many species was the second most dominant group in 1970~ during which time their contribution towards the total catch was 5.6% (Figure 3). n the next survey i.e. in 1971 the carangids became the most abundant or dominant group with a percentage catch of 6.9%. Subsequently this group showed a declining trend in terms of abundance for the next two surveys before recovering in terms of dominance until the 1988 survey. They then again showed a declining trend for subsequent surveys until the most recent survey. n 1991 and 1995 they were ranked only eighth in terms of dominance with percentage catches of 3.7% and 1.2%respectively.

5 This family also showed declining trends in all the three depth zones from the 1980s surveys. For the 10-30m depth zone their percentage contribution declined from 8.8% in 1981 to 1.3% in 1995 although there was an increase between 1983 to Their declining trend in the 31-50m depth zone started in 1988 with 7.6% to 1995 with 2.5%. For the 51-70m depth zone their decline also started in 1988 with 6.0% to 1991 with 1.0%. However they registered a slight increase to 1.3% in The croakers or sciaenids which ranked third in terms of abundance in the 1970 survey showed a dramatic declining trend in their degree of dominance (Figure 4). During the first few surveys they showed great fluctuations in their ranking. From their third placing in 1970 with 3.0% contribution they dropped to tenth position in terms of abundance in 1971 with 1.4%. n the next survey i.e. in 1972 they were the most dominailt group with 14.5% but then dropped to ~fifteenth position in 1974 with 0.5% contribution. Subsequently they showed some recovery in the next two surveys in 1981 and 1983 with rankings of twelfth and eleventh respectively. From the 1984 survey to the 1995 survey this group dropped to less than fifteenth in terms of dominance with percentage catches ranging from 0.26% to 0.01% thus becoming one of the lesser groups in the total catch. This group inhabits shallower waters and thus their percentage catches in the~e waters will greatly influence ther overall percentage catches for the whole surveyed region. Their percentage catch in the 10-30m depth zone followed the same pattern shown for the Whole surveyed region i.e. in"espectiveof depth of water. n 1970 their contribution was 3.8% but this dropped to 0.14% in 1971 before surging to 33.1% in n 1974their percentage composition dropped greatly to 0.8% but increased gradually to 3.7% in From 1984 to 1995 their percentage catch ranged from 0.36% to 0.03%. n the 31-50m depth zone this group experienced a jump from 2.1% in 1871 to 11.0% in However between 1974 to 1990 their perc.entage contribution towards the tot'll catch ranged from 0.2% to 0.03%. They were negligible in this depth zone in the 1991 and 1995 surveys. As was suggested earlier this group did not appear to favour deeper waters. n the 1970 survey they contributed 0.6% to the total catch in the 50-70m depth zone. However in subsequent surveys their contributions were less than O.1% of the total catch from this depth zone. Goatfish or mullids which ranked fourth in 1970 had been quite consistent in their degree of dominance (Figure 5). Their lowest ranking was sixth in 1972and their highest was first in For the past two surveys they were ranked second in terms of dominance. Their percentage composition of the total catch showed a generally increasing trend from 1972 with 2.7% to 1988 with 10.3%.For the nexi three surveys their percentage composition fluctuated with the 1995 survey registering a contribution of 4.5% towards the total catch. Their catch composition in the shallower waters i.e. the 1O-30mdepth zone had generally shown a slight but gradually increasing trend with some fluctuations. n the 1974 survey they contributed 1.0% of the total catch in this depth zone and in the 1991 survey this had increased to 7.7%. Their contribution in this depth zone in the

6 latest survey had dropped to 4.68%. A similar situation was observed in the 3 l-50m depth zone where they contributed 2.1% of the total catch at this depth during the 1972 survey. This increased to 8.9% during the 1995 survey. This figure which had also been achieved during the 1988 survey was the highest percentage contribution of this group for this depth zone throughout all the surveys. Mullids apppeared to be more dominant in the deeper waters. Their percentage composition in the 51-70m depth zone was always higher than those for the other two depth zones except for the and 1995 surveys. Their percentage composition in this depth zone showed fluctuations throughout the surveys. They ranged from 4.6% in 1991 to 30.7% in 1974 with the latest survey i.e. in 1995 registering a value of 8.0%. The marine catfish or the tachysurids which were.fifth in terms of percentage catch by weight during the 1970 survey had not shown any clear trends in their degree of dominance (Figure 6). Their rankings fluctuated from one survey to the next ranging from being the most dominant in 1974 to the fourteenth in 1984 and They were ranked ninth in Their percentage composition too showed fluctuations over the years ranging from 0.5% in 1981 to 17.3% in During the 1995 survey they contributed LO% of the total catch. This group appeared to be present in all three depth zones and did not seem to favour any of these zones. Their percentage contribution in the 10-30m depth zone fluctuated from survey to survey ranging from 0.5% during the 1981 and 1984 surveys to 4.9% during the 1971 survey with the exception of the 1974 survey when they contributed 27.0% of the total catch. Their contribution in this depth zone during the 1974 survey appeared to have greatly influenced their high ranking and high overall percentage composition for the whole surveyed region. Their percentage composition also fluctuated in the 31-50m depth zone ranging from 0.3% during the 1981 survey to 9.8% during the 1983 survey. They appeared to have been quite consistent in their contributions for this depth zone during the last three surveys i.e. ranging from 1.5% to 1.2%. This group appeared to be quite consistent in their percentage catch by weight for the 51-70m depth zone between 1970 and 1990 ranging from 0.6% in 1983 to 2.9% in Their percentage composition in this depth zone appeared to have increased during the last two surveys i e. 4-4% in 1991 and 3.4% in The ponyfish or leiognathids were ranked sixth in the 1970 survey. Their ranking dropped to fifteenth during the 1971 survey and greater than fifteenth during the subsequent surveys with the exception of the latest survey when they were ranked twelfth. From the 1972 survey to the 1995 survey their contributions had never exceeded 0.9% of the total catch. Their catch composition during the 1974 and 1981 surveys were also negligible. Since this group had only appeared thrice in the top fifteen most dominant fish groups throughout the surveys it was thus considered as one of the lesser groups in this area and was not discussed in detail. The snappers or lutianids were ranked seventh in the t 970 survey_this family had been quite consistent in their degree of dominance since they had always been ranked between fifth and eighth with the exception of the 1974

7 and 1981' surveys during which they were ranked tenth and more than fifteenth respectively (Figure 7). 1'heir percentage composition increased from 1.9% in 1970 to 3.3% during the next survey in They then showed a declining trend until the 1981 survey with a contribution of 1.3% before showing an increasing trend to reach 4.4% in Between 1984 and 1991 this group had always contributed between 4.0% to 5.0% of the total catch with the exception of the 1990 survey when their contribution was 3.2%. However their percentage composition dropped to 2.2% during the 1995 survey. This family appeared in all three depth zones and they did not appear to show distinct differences' in their percentage compositions in these zones. n the 10-30m depth zone the lutianids showed an increasing trend from 0.5% in 1974 to 5.4% in 1984 before declinin~ to 0.7% in Other than the and 1984 surveys their percentage composition in this depth zone had always less than 1.5%. n the 31-50m depth zone> they showed a declining trend from 3.3% in 1970 to 1.0% in Subsequently their percentage composition had shown an increasing trend to reach 7.5% in 1995 thus indicating that they were becoming more dominant in this depth zone. For the 51-70m depth. zone they appeared to show an increasing trend from 1.5% in 1974 to 11.2% in However their contribution in this depth zone dropped drastically to 1.5% m 1995 The next most dominant group during the 1970 survey was the genus Scolopsis which was ranked eighth in terms of percentage catch by weight. From the 1970 survey to the 1984 survey they were consistently ranked seventh to tenth in terms of dominance (Figure 8). However they subsequently showed a declining trend in ranking from the 1988 survey when they were placed eleventh and dropped further to fifteenth position during the next survey in During the 1991 survey their ranking was more than fifteenth. They appeared to have recovered during the 1995 survey when they achieved an eleventh placing in terms of dominance. Their percentage catch by weight however showed only a slightly declining trend particularly from the 1974 survey when they contributed 2.0% of the total catch to 1995 when their contribution was 0.6%. Within the 10-30m depth zone this ge:nus had shown relatively consistent contibutions towards the total catch.. Their percentage composition for this depth zone generally ranged from 1.0% which was obtained during the 1995 survey to 2.5% during the 1988 survey. The exception to this was during the 1981 survey when they reached a peak of 6.5% and the 1974 survey when their percentage composition of the total catch was only 0.6%. For the 31-50m depth zone their contribution fluctuated between the 1970 survey to the 1984 survey. However from the 1984 survey when their contribution was 2.7% they showed a declining trend in percentage contribution until the 1991 survey when their contribution was 0.5%. During the 1995 survey this genus increased their contribution to 1.0%. Their percentage composition in the 51-70m depth zone had generally been lower than the other two depth zones throughout the surveys thus suggesting that this genus was less dominant in deeper waters. Their contribution towards the total catch in this depth zone did not show any considerable

8 changes and were always less than 1.0% with the exception of the 1970 and 1972 surveys when.they contributed 1.2% and 2.1% respectively. The next most abundant group during the 1970 survey was the rays which ranked ninth in terms of dominance. During the next survey i.e. in 1971 they became the third most abundant group and until the 1988 survey their rankings were quite consistent ranging from second to fifth (Figure 9} From their fifth position in 1988 the rays improved to become the most dominant group during the next survey i.e. in However their ranking dropped sharply to seventh during the 1991 survey while during the 1995 survey they were sixth ranked. Their percentage composition of the total catch had shown an increasing trend from the first survey carried out in 1970 with 1.5% to the 1990 survey with 10.3%. However their contribution towards the total catch appeared to declining for the last two surveys carried out in 1991 and 1995 ' with 4.7% and 1.9% respectively. The rays appeared to be more dominant in the shallower waters of the survey region. The percentage composition of this group in the 10-30m depth zone appeared to be increasing from 1.1% during the 1974 survey to 17.4% during the 1988 survey. During the subsequent surveys i.e. in and 1995 their contribution dropped greatly to between 3.8% and 5.3%. n the 31-50m depth zone their percentage composition also appeared to be on an increasing trend starting from the earlier surveys. During the 1970 survey they contributed 2.1% of the total catch and by the 1990survey this value had reached 18.4%. Howeverthis bjfoup appeared to have declined sharply in dominance since the last two surveys when their contributions were 5.1% in 1991and 1.1% in n the 51-70m depth zone their percentage composition appeared to be fluctuating from one survey to the next and therefore no clear trends could be observed. Their contribution within this depth zone ranged from 0.1% in 1983to 3.5% in The tenth most dominant group during the 1970 survey was the family GERRDAE. Subsequently their ranking dropped to fourteenth during three surveys and less than fifteenth during the other surveys. Throughout the surveys the contribution of this family never exceeded 1.2% of the total catch which was achieved during the 1970 survey. Since this family did not appear to be a major group throughout the surveys it was not discussed in detail here. Sharks were ranked eleventh in terms of percentage catch by weight during the 1970 survey. Their ranking appeared to be fluctuating over the smveys and did not exhibit any clear trends (Figure 10). Their ranking dropped to less than fifteenth during three of these surveys two of which were the 1991 and 1995 surveys. Their percentage composition also appeared to be fluctuating although there seemed to be an increasing trend from 1981 with 0.3% to 1990 with 3.4%. However their contribution towards the total catch dropped to 1.1% during the 1991 survey and 0.3% during the 1995survey. Sharks appeared in all depth zones and did not seem to be particularly dominant within a specific depth zone. Within the 10-30m depth zone their contribution appeared to exhibit a

9 decreasing trend from 2.2% in 1971 to 0.2% in However their percentage composition showed a big jump to 2.6% in 1988 and 3.7% in 1990 before experiencing a big drop to 0.1% and 0.2% for the 1991 and 1995 surveys respectively. n the 31-50m depth zone the catch composition of sharks appeared to fluctuate without demonstrating any clear trend. Their catch composition in this depth zone ranged from as low as O.1% during the 1981 survey to 3.4% which was achieved during the following survey i.e. in n the 51-7m depth zone their catch composition appeared to to be on an increasing trend from the 1971 survey with 2.2% to the 1983 survey with 0.2%. Subsequently they showed an increasing trend until the 1990 survey when they registered a catch composition of 4.8% before declining sharply to 0.7 % and 0.5% during the and 1995 surveys respectively. t appeared that the high overall catch composition achieved in 1990 was the result of the relatively high catch composition in each of the three depth zones. The pentapods were ranked twelfth during the 1970 survey. However during the other surveys they registered a ranking of better than fifteenth for only four times. These were from the 1972 to 1981 surveys and during 1991 survey. Their highest ranking ever was eighth which was achieved during the 1972 survey. Their catch composition wa~ also relatively low throughout the vanous surveys. Their presence was negligible during the 1988 and 1990 sw:eys while for the other surveys ther percentage composition ranged from 0.3% during the 1995 survey to ~.2 ~oduring the 1972 survey. As this famtly. appeared not to be a major group t was not discussed in detail. The next most dominant group during the 1970 survey was the lizardfish or the synodontids which was ranked thirteenth in terms of percentage contribution by weight. The ranking of this family appeared to undergo an increasing trend from 1970 to the 1981 suvey when they were ranked sixth (Figure 11). During the next few surveys their rankings fluctuated and declined to eleventh position during the 1990 survey. However during the next two surveys they appeared to one of the more dominant groups when they achieved rankings of fourth and third for the 1991 and 1995 surveys respectively. Their percentage composition also followed a similar trend to that of their ranking. From a contribution of only 0.9% during the 1970 survey they reached a percentage composition of 4.4% during the 1984 survey. Their percentage composition dedined to 1.6% during the next survey in 1988 before increasing again until the 1991 survey with 5.6%. Although they achieved a percentage composition of 3.2% during the 1995 survey they were still among one of the most dominant groups landed The synodontids appeared to be slightly more dominant in the deeper waters of the survey area. Within the ]0 30m depth zone their percentage composition appeared to be gradually illl;::reasingfrom 0.5% during the 1970 survey to 5.9% during the 1984 survey. Their contribution subsequently dropped to 1.6% for the 1988 and 1990 surveys before recovering to 5.6% during the ]991 survey. Their contribution again dropped drastically to 0.6% for the 1995 survey. Their contributions in the 31-50m depth zone appeared to be gradually increasing throughout the surveys i.e. from ].3% during the 1970 survey to 7.0% during the 1995 survey although there were a

10 few minor fluctuations over the years. They appeared to be generally more dominant in the metres depth zone. From a percentage composition of 2.3% during the 1971 survey their representation within this depth zone increased gradually to 7.0% during the 1981 survey. Subsequently they experienced a declining trend over the next three surveys to reach 1.7% contribution during the 1988 survey before again increasing to 5.3% and 5.4% during the 1990 and 1991 surveys. During the 1995 survey their contribution shot up to 13.0%. The squids of the genus Loligo S. another group which showed a dramatic increase in their representation in the total catch (Figure 12). During the 1970 survey they were ranked fourteenth in terms of percentage catch by weight. They then improved their rankings over the next few surveys to reach third and fourth placing during the 1974 and 1981 surveys respectively. The next survey i.e. in 1983 saw their representation dropped to eighth. However their rankings improved over the next surveys and during the 1990 survey they were the second most dominant group while during the 1991 and 1995 surveys they were the most dominant group caught. The trend shown by their percentage composition was also very similar to that shown by their ranking. During the 1970 survey they contributed only 0.8% of the total catch but by the 1974 survey they had increased this to 5.6%. Their contribution then dropped to between 3.0% to 4.0% over the next three surveys before increasing again increasing gradually to 11.9% during the 1991 survey. Their contribution during the 1995 survey when they were the mo&tabundant group caught was 7.8%. The percentage composition of squids in the total catch for the 10-30m depth zone appeared to be gradually increasing from 05% in 1970 to 9.0% in The 1991 and 1995 surveys saw their representation dropping to 5.7% and 3.2% respectively. Within the 31-50m depth zone their contributions increased from 1.1% in 1970 to 9.1% in 1974before dropping to 2.7% and 2.8% for the 1981 and 1983 surveys respectively. Their representation within this depth zone then showed an increasing trend to reach 13.4% and 20.1% for the 1991 and 1995 surveys respectively. The trend of their representation in the 51-70m depth. zone was very similar to that which was shown for the 31-50m depth zone. From a contribution of 2.5% in 1970 they increased their representation to 12.3% in 1974 before decreasing over the next three surveys to reach 2.2% in The next four surveys saw them increasing their percentage composition to 10.6% and 18.2% for the 1991 and 1995 surveys respectively. Thus it may be suggested that their high ranking in terms of percentage catch by weight for the whole surveyed was due mainly to their high percentage compositions in the deeper waters i.e. the 31-50m and 51-70m depth zones. The fifteenth most dominant group during the 1970 survey was the sweetlips or Diagramma punctatum. However their rankings during the subsequent surveys had always been relatively low. Their highest ranking ninth was achieved in 1971 and in five of the surveys their degree of dominance was less than fifteenth. As this group was considered as one of the minor groups caught it was not discussed in detail.

11 Table 1 also showed other species or species group which at one time or another achieved a ranking of at least fifteenth in terms of dominance. However their appearances in the list were quite sporadic and inconsistent and did not show any clear trends. The exception to this was the genus Priacanthus. From 1910 to 1981 it did not appear in the fifteen most dominant group. However from the 1983 survey to the latest survey in 1995 it had achieved a relatively high degree of dominance; ranging from eighth in 1984 to third in They were ranked seventh during the 1995 survey. Their percentage composition ranged from 1.3% during the 1995 survey to 7.0% during the 1991 survey. The priacanthidsappeared to favour the deeper waters of the survey area. Within the 31-50m depth zone their contribution from 1983 to 1995 ranged from 3.0% in 1984 to 8.3% in For the 51-70m depth zone th.eir contribution Within the same period ranged from 4.2% in 1995 to 13.6% in 1983 while in 1990 their contribution was negligible. n contrast their contribution in the 1O-30mdepth zone for the same period ranged from O.1% in 1995to only 2.5% in 1988 with their contribution in 1990 being negligible. Species composition is not expected to change within short periods such as annually. Changes in species co~position will occur over longer penods as a result of heavy fishing on the preferred species as well as the spread of new fishing teetmology that are of ~nterest (Gulland1983). The above dscussionhad shown that while so~e.species or species group did not exhibt any c ear c h anges m. then. degree of dominance throughout the surveys others however had shown that their degree of dominance had greatly increased or decreased. The sciaenids had shown a very clear decline in dominance. From being one of the major components of the total catch in the earlier surveys they had become almost negligible in the later surveys. Since they had shown preference for the shallower waters it may be suggested that intense fishing pressure in the waters had greatly reduced their abundance. On the other hand the squids in particular and the lizardfish to some extent had shown marked increases in dominance. Both these groups had shown a higher percentage composition in waters deeper than 30m. The increase in the dominance of squids might indicate a reduction of their predators. This might have arisen through heavy fishing pressure on these predators. Another group which had also shown a major increase in their degree of dominance particularly since the 1980s was the priacanthids' This group also showed increases in dominance in the deeper waters... Therefore the analysis made in this paper had shown that there had been changes in the species composition of the demersal fish trawl surveys in the east coast of Peninsular Malaysia. As had been mentioned earlier such changes were probably due to heavy fishing pressure on targeted species as well as the spread of new technology. ncreases in fishing pressure could have occurred even if the nwnber of fishing vessels remained constant. Such increases could have come from the utilisation of more efficient fishing '.gears and fishing vessels. Further analyses 0.[ the data by taking into consideration the food web involving

12 theother'resources in these waters the trophic levels of the species of interest and the predator-prey relationship of these species may produce an even clearer picture of the status of these resources. The author would like to thank the Director General Department of Fisheries Malaysia Y. Bhg. Dato' Shahrom bin Haji Abdul Majid for his kind permission to present this paper. Thanks are also due to the Director of Research Fisheries Research nstitute Mr. brahim bin Saleh and the Head of the Resource Branch Ms. Chee Phaik Ean for their encouragement during the preparation of this paper. The author is also grateful for the assistance rendered by En. Abdul Rahman bin Abdul Majid and his colleagues in the preparation of this paper. 20th September 1972). Fisheries Bulletin No. 9. Ministry of Agriculture and Rural Development Malaysia: 1-19 Lamp F. and Mohd. Shaari bin S.A.Latiff (1976): Demersal fish resources in Malaysia waters Fourth trawl survey of the coastal waters off the east coast of Peninsular Malaysia (13th July - 12th August 1974). Fisheries Bulletin No. 12. Ministry of Agriculture Malaysia: 1-25 Pathansali. D. G. Rauck A A Jothy Mohd. Shaari bin S.A.Latiff and T.BCurtin (1974): Demersal fish resources in Malaysia waters - 1. Trawl survey of the coastal waters off the east coast of Peninsular Malaysia. Fisheries Bulletin NO.1. Ministry of Agriculture and Rural Development Malaysia: Ahmad Adnan bin Nuruddin (1990). Demersal fish resources in MalayRia waters Fifth trawl survey of the coastal waters off the east coast of Peninsular Malaysia (June-July 1981). Fisheries Bulletin No 60 Ministry of Agriculture Malaysia GuUand.A (1983). Stock Asse:ssment: Why? FAO Fisheries Circular No 759: 18pp. Jothy AA G. Rauck Mohd. Shaari bin S.A.Latiff Ong Kah Sin Liong Pit Chong and L.Carvalho (1975). Demersal fish resources in Malaysia waters - 3. Second trawl survey of the coastal waters off the east coast of Peninsular Malaysia (March-May 1971). Fisheries Bulletin NO.4. Ministry of Agriculture and Rural Development Malaysia: Lam Wah Chang W Weber Lee Aik Kean Dng Kah Sin and Liong Pit Chong (J 975>- Demersal fish resources in Malaysia wators rd trawl survey of the coastal n'dters off the east coast of Peninsular jvf. lc1ysia (14th August-

13 Table 1. Ranking of dominant species from demersal fish surveys East Coast Peninsular Malaysia. Survey year No. of hauls Main Species/Fish groups of first survey; Nemipterus spp CARANGDAE SCAENDAE MULLDAE TACHYSURDAE LE!OGNATHDAE LUTANfDAE Scolopsis spp Rays GERRDAE ' - 14 Sharks PENTAPODDAE SYNODONTDAE LOLGODEA Diagramma punctatum Changes in dominant species Aba/istes stel/aris Pomadasys spp 7 10 SEPODEA Thenus orientalis Brachyura 14 CAESODDAE 10 SERRANDAE Priacanthus spp Sphyraena spp. 14 Others Siganus spp. 13 Lethrinus spp. 9 Rachycentron csnadus ALUTERDAE 15 - indicates a ranking of> 15 in terms of dominance Vol Vol

14 ẉ l:>- Table 2. Percentage catch by weigh! of dominant species from demersal fish surveys East Coast. Peninsular Malaysia. Survey year No. of hauls Main Species/Fish groups of first survey: Nemipterus spp CARANGDAE SCAENDAE MULLlDAE TACHYSURDAE LEOGNATHDAE LUTANDAE Scoiopsis spp Rays GERRDAE Sharks PENTAPODDAE SYNODONTDAE LOLlGODEA Diagramma punctatum Changes in dominant species Aba/istes stel/aris Pomadasys spp SEPODEA Thenus orienta lis Brachyura 0.57 CAESODDAE 0.69 SERRANDAE Priacanthus spp Sphyraena spp. 093 Others Siganus spp Lethrinus spp Rachycentron canadus ALUTERDAE 1.19

15 Table 3a. Percentage catch by weight of dominant species from metre depth zone demersal fish surveys East Coast Peninsular Malaysia. Survey year No. of hauls; Species/Fish group: Nemipterus spp CARANGfDAE SCAENDAE MULLfDAE H.B TACHYSURDAE LEOGNATHDAE O.g4 LUTANDAE Sco/opsis spp Rays GERRDAE :50 Sharks PENTAPODDAE SYNODONTDAE % LOLGODEA Diagramma punctatum '7 Changes in dominance Aba/istes stel/aris Pomadasys spp SEPODEA '7 Thenus orienta/is Brachyura 0.42 CAESODDAE 3.08 SERRANDAE Priacanthus spp Sphyraena spp. J 0.11 Others Siganus spp 2.31 Lethrinus spp Rachycentron canadus 0.18 ALUTERDAE 008 w Vl

16 w 0\ Table 3b. Percentage catch by weight of dominant species from metre depth zone demersal fish surveys East Coast Peninsular Malaysia. Survey year No. of hauls: Specie sf Fish group: Nemipteros spp CARANGDAE SCAENDAE MULLDAE TACHYSURDAE leogt-jathroae 0.70 '1'l LUTANOAE Sc%psis spp Rays GERRDAE Sharks PENT APODrDAE ':1 SYNODONTDAE b.% LOLGODEA i Diagramma punctatum Changes in dominance Aba/istes stelfaris Pomadasys spp SEPODEA Thenus orienta/is Brachyura 0.98 CAESOOOAE 0.21 SERRANOAE Priacanthus spp Sphyraena spp..' 057 Others Siganus spp. 128 Lethrinus spp Rachycentron canadus 2.07 ALUTERDAE 1.17

17 Table 3c. Percentage catch by weight of dominant species from metre depth zone demersal fish surveys East Coast Peninsular Malaysia Survey year No. of hauls: Species/Fish group: Nemipferus spp CARANGDAE SCAEN/OAE MULL/OAE i TACHYSUROAE LEOGNATHOAE LUTJANDAE Sc%psis spp Rays GERROAE ' 0.00 Sharks PENTAPODOAE SYNODONTOAE '~5 LOLGOOEA Diagramma punctatum '32 Changes in dominance Aba/istes stellaris Pomadasys spp SEPODEA & Thenus orienta/is Brachyura 0.03 CAESODDAE 0.01 SERRANDAE Priacanthus spp Sphyraena spp Others Siganus spp. 026 Lethrinus spp. Rachycentroncanadus ALUTERDAE 4.21 w-...l

18 103 E -J 7N 1

19 N " ~ ~ ~./ ~ 6 "'percentage catch EO c..... " 5.00 u.. ex: Qj 8.. ll " " sn Survey year a). Ranlting and percentage catch from the whole surveyed region C " ".. /\ ' m " ~ y... \ ~ ~ ".. " " /.. \ /.. \ '\ / - '\./ """" t r ll m & Survey year b). Percentage catch of different depth zones Fig. 2: Changes in the dominance of Nemipterus spp.

20 . 7 c:. «8 7: 4.00 ~ :. percentage catch Survey year

21 ~ 7 c 0:: 8 i: 8.00 u Qj > \....\' percentage catch Survey year /\ / \ \ m Fig 4: Changes in the dominance of SCAENDAE

22 ~.... c '".. c: a:: l: " percentage catch ' Survey year a). Ranking and percentage catch from the whole surveyed region " 1.. " ""

23 >< 7 c. a: C a.. ~ /\31-50m / \.r:....>""; V~-- / \ ~. b). Percentage catch of different depth zones Fig. 6: Changes in the dominance of T ACHYSlJ RDAE

24 percentage catch 2 ' " 4 " " 3.50 :'/ 5 " 6 " C "" c: l:! a:: 8 10 Ranldng 2.50 l \ \ Survey year a). Ranking and percentage catch from the whole surveyed region " l:! 6.00 l ~ " ~.. ~ - " " ;; " / / ' / '" "31-50 m Fig. 7: b). Percentage catch of different depth zones Changes in the dominance of LUTANDAE

25 percentage catch >< 7 i: <:: u a: 8 i; 9 10 " " " " " Survey yur a). Ranking and percentage catch from the whole surveyed region ~ m n ~ b). Fig. 8: Changes in the dominance of Scolopsis spp.

26 8.00 '" 7 c: ~ 8 C 6.00 ~ 11. ~ percentage catch \ \ \ \ \ \ \

27 percentage catch c:. ~ e Q( Survey year 1.50 ll" a). Ranking and percentage catch from the whole surveyed region m ' \ - ' DCA Fig. 10: Changes in the dominance of Sharks

28 ~ percentage catch 1 \ C 3.00 ~ J.'. 1/

29 '\ 1 '\ 2 '\ '\ 3 '\ '\ >< 7 a: " 8 '... 3 " ' percentage catch \ a). Survey year Ranking and percentage catch from the whole surveyed region m A / '\ '\ " //31-50m '/ \.. \ m Fig. 12: Changes in the dominance of Loligo spp.