Reprint:
JURNAL ILMU-ILMU PERAIRAN DAN PERIKANAN INDONESIA
ISSN 0854-3194 Desember 2007, Jilid 14, Nomor 2 Halaman 137 – 150
Characteristics of Chondrichthyan Diversity in Western Indonesia (Karakteristik Keanekaragaman Jenis Ikan Bertulang Rawan di Indonesia) Mohammad Adrim and Fahmi
Alamat Penyunting dan Tata Usaha: Departemen Manajemen Sumberdaya Perairan, Fakultas Perikanan dan Ilmu Kelautan, Institut Pertanian Bogor - Jl. Lingkar Akademik, Kampus IPB Darmaga, Bogor 16680, Wing C, Lantai 4 - Telepon (0251) 622912, Fax. (0251) 622932. E-mail :
[email protected] Berdasarkan Keputusan Direktur Jenderal Pendidikan Tinggi, Departemen Pendidikan Nasional No. 55/DIKTI/Kep./2005 tanggal 17 November 2005 tentang Hasil Akreditasi Jurnal Ilmiah Direktorat Jenderal Pendidikan Tinggi Tahun 2005, Jurnal Ilmu-ilmu Perairan dan Perikanan Indonesia (JIPPI) diakui sebagai jurnal nasional terakreditasi.
CHARACTERISTICS OF CHONDRICHTHYAN DIVERSITY IN WESTERN INDONESIA1 (Karakteristik Keanekaragaman Jenis Ikan Bertulang Rawan di Indonesia) Mohammad Adrim2 and Fahmi2 ABSTRACT A total of 27 837 individual sharks and rays (chondrichthyans), from 124 species and 29 families was observed during the study at twenty six fish landing sites of twenty provinces in Sumatra, Java, Kalimantan, Bangka, Bali, and Lombok Islands. The study was conducted from June 2003 to November 2005. Those locations were grouped into two main regions, Sunda Shelf and the Indian Ocean regions. In general, rays contributed more to the species composition of each landing site in the Sunda Shelf, Dasyatid was the commonest group. Conversely, sharks contributed more than rays in the Indian Ocean region, representing by carcharhinid and sphyrnid. Dasyatis kuhlii (Dasyatidae) was the commonest chondrichthyan species occurred in both regions overall. Keywords: Chondrichthyan, diversity, shark, ray.
ABSTRAK Sebanyak 27 837 individu ikan hiu dan pari (ikan-ikan bertulang rawan), mewakili 124 jenis yang ditempatkan pada 29 suku telah dijumpai selama penelitian di 26 lokasi pendaratan ikan (Tempat Pendaratan Ikan (TPI), pasar-pasar ikan, dan pusat konsentrasi nelayan terkait) yang tersebar di 20 propinsi di Pulau Sumatera, Jawa, Kalimantan, Bangka, Bali, dan Lombok, sejak Juni 2003 hingga November 2005. Lokasi-lokasi tersebut dikelompokkan ke dalam dua wilayah utama, yaitu Paparan Sunda dan Samudera Hindia. Secara umum, ikan-ikan pari yang didominansi oleh suku Dasyatidae memegang peranan yang lebih besar dalam komposisi jenis ikan di tiap lokasi pendaratan di wilayah Paparan Sunda, sedangkan ikan-ikan hiu yang diwakili suku Carcharhinidae dan Sphyrnidae memberikan kontribusi yang lebih besar dalam komposisi jenis ikan-ikan bertulang rawan di wilayah Samudera Hindia. Secara keseluruhan, Dasyatis kuhlii (Dasyatidae) merupakan jenis yang paling umum dijumpai di kedua wilayah perairan tersebut. Kata kunci: Ikan bertulang rawan, keanekaragaman jenis, hiu, pari.
adaptations to a benthic life style (Last and Compagno, 2002).
INTRODUCTION Chondrichthyan diversity varies with depth and geography. Some species may occur in shallow waters and others in deeper waters. Some cartilaginous fishes may occur in the continental shelf from 0 to 200 m depth, on the continental slope from 200 m to more than 2,000 m depth, free living as oceanic fishes, or occupying a variety of habitats according to their adaptations and life styles (Compagno, 2002; Last & Compagno, 2002). Hydrography is an important factor influencing the “diversity and commonality” of chondrichthyan fish faunas (Compagno, 2002). Sharks have a wide habitat range and occur in almost all habitat categories, while rays have lesser habitat ranges. Most rays prefer to live in benthic habitats because of their strong 1
Diterima 8 Maret 2007 / Disetujui 4 Juni 2007.
2
Pusat Penelitian Oseanografi, Lembaga Ilmu Pengetahuan Indonesia, Ancol, Jakarta.
As an archipelago, Indonesia is surrounded by seas and oceans. There are three main hydrographic regions in Indonesian waters. The first is a broad continental shelf with water up to 60 m depth, which includes the Sunda Strait, Karimata Strait, Malacca Strait, Java Sea and the lower part of Makassar Strait. The second is the Indian Ocean off the southern part of the country, with depths ranging from 20 to 7000 m. The third region is the enclosed waters where depths vary between 200 and 3000 m, i.e. the upper part of Makassar Strait, Sulawesi Sea, Molucca Sea, Banda Sea, Ceram Sea, Bali Sea and Flores Sea. The first two regions are in western Indonesia while the third region is in eastern Indonesia. Indonesian waters have a very high diversity of cartilaginous fishes with different communities in the different regions.
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Unfortunately, there is a lack of data about elasmobranch diversity in Indonesia. Even though several studies mention the occurrence of sharks and rays in Indonesian waters, information about elasmobranch diversity was only a minor component. The exact number of elasmobranch species in Indonesian waters is unknown. Many studies of shark diversity, biology and fisheries have been conducted in several Asian countries. At least 63 species of sharks, 67 batoids and three chimaeroids have been recorded in Malaysia (Ali et al., 2004). In Thailand waters, 74 sharks, 70 batoids and one chimaeroid are known to occur (Vidthayanon, 2002). Twenty shark species have been confirmed in Philippine waters (Barut & Zartiga, 2002), and at least 136 species of sharks, 103 batoids and four chimaeroids occur in the South China Sea and adjacent areas (Compagno, 2002; Last and Compagno, 2002). A major study of the species composition and diversity of Indonesian chondrichthyans was commenced in 2003. It focused mainly on 26 fish landing sites in two regions: Sunda Shelf and the Indian Ocean. The main aim of the present study was to build a database of chon-
drichthyan diversity and provide assessment of the species composition and relative abundance of the chondrichthyan fishes of western Indonesia. The degree of characterization of species composition between these two regions and among sites was analyzed to test a hypothesis that there are no significant differences between chondrichthyan species composition in the two regions in western Indonesia.
MATERIALS AND METHODS Data collection
Chondrichthyan diversity in western Indonesia was determined from several main fish landing sites and markets, which represent most of the western regions of Indonesia. This study was conducted from May 2003 to November 2005. Nine sites in Sumatra, 13 sites in Java and four sites in Kalimantan were chosen for “sampling” (Figure 1). Then, those sites were grouped into two main hydrographic regions (Table 1). Each landing site was generally visited for between two and seven days at the peak fish landing time, depending on accessibility and budget constraints (Table 2).
Figure1. Location of the 26 Chondrichthyan fish study sites observed in Western part of Indonesia.
The peak landing fish time was varied among locations but generally it began at around six o’clock in the morning and finished at around mid day. Data were collected from fish landings and fish markets at each site by determining the species that were present on
that day, recording the numbers and biomass (kg) of each species and also collecting some general fisheries information. Each species was identified using the keys in Compagno (1984a; 1984b; 1999b; 1999a;
Adrim, M. And Fahmi, Characteristics of Chondrichthyan Diversity in Western Indonesia
2001), Compagno and Last (1999), Last and Stevens (1994) and Last et al. (2005). Undetermined species (for several reasons such as rotten, cut, finned or unidentified) were identified to the level of genus and provided with a temporary name. Unidentified species thought to be new species were purchased and preserved
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with 10% formalin (when the size of the specimen made such collection practical). Larger specimens, which were impractical to collect in this way, were photographed using a digital camera (CANON A95 with five and NIKON Coolpix 4500 with four mega-pixels resolution) for further identification and description.
Table 1. Chondrichthyan Sampling Sites and Their Fishing Region Grouping in Indonesia.
Main region Fishing Region Sunda shelf Java Sea
Region West North Java (WNJv)
Sampling site Muara Angke (MAng) Muara Baru (MBr) Java Sea Central North Java (CNJv) Batang (Btg) Pekalongan (Pkl) Java Sea East North Java (ENJv) Rembang (Rmb) Brondong (Brdg) Sunda Strait Sunda (Snd) Labuan (Lbn) Malacca Strait North East Sumatra (NESmt) Belawan (Blw) Tanjung Balai (TjBl) Malacca Strait East Sumatra (ESmt) Tembilahan (Temb) Kuala Tungkal (KlTkl) North Karimata Strait East South Sumatra (ESSmt) Pangkal Pinang (PkPng) South Sumatra, North Sunda Strait South Sumatra (SSmt) Labuhan Maringgai (LbMgr) North Karimata Strait, Natuna West Kalimantan (WKal) Sungai Kakap (WKal) South Kalimantan waters, Java Sea South Kalimantan (SKal) Muara Kintab (SKal) South Kalimantan waters, Java Sea Central Kalimantan (CKal) Sampit (CKal) Makassar Strait East Kalimantan (EKal) Manggar (EKal) Indian Ocean Indian Ocean West Coast Sumatra (WSmt) Sibolga (Sbg) Tiku, Padang (Pdg) Bengkulu (Bkl) Indian Ocean West South Java (WSJv) Binuangeun (Bngn) Palabuhanratu (PlRt) Pameungpeuk (Pmpk) Indian Ocean East South Java (ESJv) Sadeng (Sdg) Prigi (Prg) Bali Strait, Indian Ocean East Java (EJv) Muncar (Mcr)
Data Analyses In order to facilitate analysis, sampling sites were grouped into two main hydrographic regions (Sunda Shelf (shallow waters) and Indian Ocean groups (deep waters)). The Sunda Shelf group consisted of sites which have fishing grounds in the Sunda Shelf area in depths less than 200 m, while the Indian Ocean group consisted of sites which have fishing grounds in the Indian Ocean in depths between 20 and 3000 m (Table 1). Non-metric multidimensional scaling (MDS) analysis (PRIMER v.5.2.4) was used to
assess patterns among sites in chondrichthyan species diversity from each location. This analysis has ability to plot data in a “map” and puts samples that have high rank of similarity close each other, and it is easy to interpret by users (Clarke & Warwick, 1994). MDS is based on the similarity matrix and has some benefits because the plots can be scaled, located rotated or inverted. The user also can choose a configuration of points which minimizes the degree of stress or distortion between similarity rankings and the corresponding distance in the ordination plot (Clarke & Warwick, 1994).
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The number of elasmobranch species landed at each location per day and the proportion of the number of each species in the total species landed in one location were analyzed using MDS. Because of the differences in the number of sampling days among locations, the mean values of the number of species from each location and relative abundance values were employed to plot the ordination of the sites. Prior to ordination, the average numbers of spe-
cies per site were fourth root transformed to reduce the influence of abundant species and also some rare species that only occurred in one or two locations. Data transformation was applied to weight the contribution of both common and rare species in the non-parametric analysis (Clarke and Warwick, 1994). The Bray-Curtis index was used to obtain similarity ranks among locations to derive a similarity matrix for plotting MDS configuration plots.
Table 2. Number of Species and Total Individual of Elasmobranch Species per Site in Indonesia from June 2003 to November 2005. Total Number Number Days number of of of sampling individuals Species Families Muara Angke 4 6649 34 12 Muara Baru 4 434 25 9 Binuangeun 4 450 36 17 Labuan 4 395 34 15 Pamengpeuk 3 31 15 7 Palabuhanratu 7 315 36 20 Batang 7 12544 34 12 Pekalongan 3 96 17 6 Rembang 4 356 16 6 Sadeng 3 46 13 10 Brondong 2 1017 37 13 Prigi 4 101 16 10 Muncar 3 343 27 15 Belawan 3 1445 10 4 Tanjung Balai 4 521 12 3 Sibolga 3 266 31 13 Padang 2 29 8 6 Tembilahan 3 22 9 1 Kuala Tungkal 3 51 9 3 Bengkulu 4 66 22 9 Labuhan Maringgai 4 190 21 8 Pangkal Pinang 7 669 30 12 Muara Kintab 7 180 21 7 Sungai Kakap 7 860 41 13 Sampit 7 272 23 8 Manggar 7 489 25 7 Site
A number of arrangements of the data were taken to get good representation of the species composition ordination in MDS configuration plots, indicated by the lowest stress value. Data from percentage compositions of each species per site were also ordinated using the MDS technique to be compared with other ordination results. Due to the large number of sites (samples) plotted in multidimensional scaling ordination, sites were grouped based on
their fishing regions (Table 1). This gives simpler MDS plots with lower stress value. According to Clarke and Warwick (1994), the lowest stress value means the least misinterpretation is likely in the multi dimensional representation. One-way analysis of similarities was used to test the significant difference of species composition among sites and among regions (Clarke, 1993). Also similarity percentages (SIMPER) were determined to find out the species that in-
Adrim, M. And Fahmi, Characteristics of Chondrichthyan Diversity in Western Indonesia
fluenced the dissimilarity among sites and typified particular locations or regions (Somerfield and Clarke, 1997).
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4 4
Chondrichthyan data were collected from each fish landing sites between two and seven days. Seven days trip was presumed as the ideal number of sampling because it can represent the condition of the market in each day in a week. Regarding to the mean contribution of the number of day sampling of seven locations, the three days sampling at fish landings gathered about 71.1 % of data collecting in seven days sampling (Figure 2).
species
U
RESULTS
Pl Batan Pk Wka Ska Cka Eka
3 2 2 1 1 5 0 0
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2
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4
5
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7
Day
Figure 3. The cumulative number of chondrichthyan species from day-1 to day-7 at seven landing sites in western Indonesia
Chondrichthyan diversity
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0 0
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5
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Fig. 2. The Mean Proportion of the Cumulative Number of Species from Day-1 to Day-7 Sampling at Seven Different Fish Landings in Western Indonesia. The Error Bars Re0present Standard Deviation Values.
The more homogenous of fishing methods and the regularity of fishing operations in one landing site, the number of day sampling can be shortened to reach the asymptote value of the number of species. For instance, the fishing activities at the Muara Kintab, South Kalimantan was homogenous all the time by using the same fishing method and fishing location. This situation made the number of species at this particular site did not change anymore from the day-4 until the day-7 (Figure 3). This also happened to the Batang landing site where reached its asymptote on the day-5 of sampling. On the other hand, other sites those were more heterogeneous in their fishing methods and fishing areas, have not reached the asymptote yet after the 7-days sampling.
A total of 27 837 individual chondrichthyans, from 124 species and 29 families was recorded from 26 landing sites during the study in the western region of Indonesia from June 2003 to November 2005 (Table 2). This total consisted of 65 species of shark representing 16 families and 58 species of rays (including sting rays, eagle rays, devil rays, shark ray, shovelnose rays and guitar fishes) representing 11 families and a single species of holocephalan. Dasyatidae and Carcharhinidae were the most common families recorded during the study in terms of the number of individuals and species. Both families were represented by 27 species. Dasyatidae comprised about 82.88 % of the total individuals recorded, while carcharhinids were only 8.34%. The family rank based on the abundance and number of species and cumulative percentage of chondrichthyan fishes in western Indonesia is shown in Table 3. The most abundant species were Dasyatis kuhlii, Himantura gerrardi and Himantura walga. These three species contributed about 55.10 %, 15.9 % and 4.1 % of the total abundance of chondrichthyans recording during the study. Species Composition Between Two Main Regions
Sampling sites in western Indonesia were segregated into two main regions: Sunda Shelf and Indian Ocean. The number of species recorded at landing sites in the Sunda Shelf region was almost equal with the number of spe-
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cies recorded at landing sites in the Indian Ocean region, but the total number of individu-
als in the Sunda Shelf region was much higher than in the Indian Ocean region (Table 4).
Table 3. Family Rank of Chondrichthyan Fishes Recording from 26 Fish Landing Sites in the Western Indonesia. Family Dasyatidae Carcharhinidae Gymnuridae Sphyrnidae Hemigaleidae Rhynchobatidae Myliobatidae Hemiscyllidae Rhinobatidae Triakidae Potamotrygonydae Squalidae Mobulidae Stegostomatidae Alopiidae Rhinidae Hexanchidae Orectolobiidae Rhinopteridae Centrophoridae Rajidae Scyliorhinidae Chimaeridae Somniosidae Plesiobatidae Dalatiidae Squatinidae Ginglymostomatidae Pseudocarcharhiidae Total
Number of Abundance Species 27 23071 27 2321 3 501 3 346 4 290 3 233 7 213 3 154 4 137 5 130 2 112 6 104 4 72 1 34 2 23 1 19 1 15 1 15 2 11 4 10 4 8 3 8 1 3 1 2 1 1 1 1 1 1 1 1 1 1 124 27 837
Table 4. Number of Species and Total Individual of Elasmobranch Species in Two Main Regions of Indonesia from June 2003 to November 2005. Total individuals Sunda Shelf 26190 Indian Ocean 1647
Number Number of of species Families 87 18 90 29
The two dimensional result from multidimensional scaling (MDS) ordination based on the Bray-Curtis similarity coefficient also indicated the segregation of samples collected from
Percentage of Abundance 82.879 8.338 1.800 1.243 1.042 0.837 0.765 0.553 0.492 0.467 0.402 0.374 0.259 0.122 0.083 0.068 0.054 0.054 0.040 0.036 0.029 0.029 0.011 0.007 0.004 0.004 0.004 0.004 0.004 100.00
Cumulative Percentage 82.879 91.217 93.016 94.259 95.301 96.138 96.903 97.457 97.949 98.416 98.818 99.192 99.450 99.573 99.655 99.723 99.777 99.831 99.871 99.907 99.935 99.964 99.975 99.982 99.986 99.989 99.993 99.996 100.000 100.000
sites in Sunda Shelf and Indian Ocean regions (Figure 4). Samples from the Indian Ocean region tended to plot to the left of the horizontal axis whereas those from the Sunda Shelf region plotted to the right. The stress value of the MDS plot, which is 0.16, shows a good presentation of the ordination of samples on the plot. According to Clarke and Warwick (1994), a stress value less than 0.2 gives a good representation of the sample relationships with minor interpretation.
Adrim, M. And Fahmi, Characteristics of Chondrichthyan Diversity in Western Indonesia
Figure 4. Two Dimensional Result from MDS Ordination of Chondrichthyan Landing Sites in the Wwestern Indonesia. The Two Different Symbols Indicate Segregation of Samples Collected from Sunda Shelf and Indian Ocean Regions According to Their Species Compositions.
Landing data from the Sunda Shelf region comprised 37 species of sharks and 50 species of rays, while the Indian Ocean region consisted of 55 species of sharks, 34 rays and one species of holocephalan. In general, rays contributed more to the species composition of each landing site in the Sunda Shelf region except for the Muara Baru (WNJv) and Manggar (EKal) landing sites. In contrast, sharks contributed more than rays to the species composition in the Indian Ocean region (Figure 5). Dasyatidae contributed most to the species composition of chondrichthyans in the Sunda Self region. This family comprised 29.99% of the total number of species documented in the region and about 85.91% of the total individuals. Carcharhinidae was the second highest contributor in the number of species (25.29%), but contributed only 7.28% of the total abundance. Conversely, carcharhinids contributed 23.33% of the total number of species recorded in the Indian Ocean, followed by dasyatids (11.11%). However, Dasyatidae was the most abundant family contributing about 34.73% of the total abundance, while the Carcharhinidae comprised 25.20% of the total number of chondrichthyans recorded in Indian Ocean region. A one way ANOSIM using the average number of species per site was performed to test the significance of the difference in species composition between these two main regions and showed that there were significant differences in overall species compositions (R = 0.496; p = 0.001). The SIMPER analysis showed the spe-
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cies that distinguished the two main regions (Table 5). Species with large differences in the average abundance and dissimilarity, contributed most to the differences between the two regions and among sites in the ordination plot of chondrichthyans in western Indonesia. Samples from Sunda Shelf region were correlated with the higher average abundance of dasyatids such as Dasyatis kuhlii, Himantura gerrardi and H. walga and carcharhinids Carcharhinus sorrah and C. dussumieri, while samples from Indian Ocean regions were associated with the higher abundance of Sphyrna lewini and Carcharhinus brevipinna.
Figure 5. The Species Composition of Sharks, Rays and Holocephalan in Sunda Shelf Region (Upper Chart) and Indian Ocean Region (Lower Chart).
Species Composition among Fishing Regions
Twenty six fish landing sites in western Indonesia were grouped into 16 fishing regions. Each fishing region has a specific area in Indonesian waters. The grouping of sites was not based on the distance and locality of each site, but on the locality of fishing grounds of fishers who landed or unloaded their catches at each site. The most abundant chondrichthyan landings were recorded in the Central North Java region (CNJv), comprising 45.41 % of the total chondrichthyans recorded during the study.
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Dasyatis kuhlii and Himantura gerrardi were the dominant species in terms of number of
individuals and contributed most to the abundance of chondrichthyan fishes in this region.
Table 5. Species Contributions for Typifying Chondrichthyans Between Two Regions in Western Indonesia, Based on the SIMPER Analysis (Cut Off for Low Contributions at 50% of the Cumulative Percentage Contribution). Group Sunda Group Indian Shelf Ocean Average Dissimilarity/ Species dissimilarity SD Average Average abundance abundance Dasyatis kuhlii 191.56 5.64 5.27 0.94 Himantura gerrardi 54.35 3.39 5.19 1.16 Himantura walga 12.87 4.06 3.28 0.79 Carcharhinus brevipinna 1.60 3.88 3.08 0.76 Sphyrna lewini 1.72 6.24 2.98 0.84 Himantura uarnacoides 4.49 0.00 2.87 0.77 H. sp. cf. gerrardi (no spot) 0.97 1.42 2.45 0.83 Carcharhinus sorrah 7.55 1.09 2.43 0.72 Carcharhinus falciformis 1.35 2.27 2.23 0.82 Himantura jenkinsii 3.15 0.58 2.03 0.81 Mobula japanica 0.05 1.55 1.82 0.66 Carcharhinus dussumieri 6.15 0.03 1.68 0.67 Chiloscyllium punctatum 1.58 0.42 1.65 0.67 Himantura uarnak 2.26 0.24 1.61 0.68 Gymnura poecilura 1.33 0.03 1.55 0.54 Taeniura lymma 0.86 0.64 1.50 0.54 Squalus sp.3 0.10 2.24 1.50 0.50 Rhynchobatus australie 2.36 0.24 1.47 0.66 Table 6. List of Ten Species Based on the Most Abundant Fishes in the Sunda Shelf and the Indian Ocean region. Sunda Shelf
Percentage of Abundance
The Indian Ocean
Percentage of Abundance
Dasyatis kuhlii Himantura gerrardi Himantura walga Dasyatis zugei Carcharhinus sorrah Carcharhinus dussumieri Aetoplatea zonura Himantura uarnacoides Himantura jenkinsii Scoliodon laticaudus
57.05 16.78 3.83 3.19 2.24 1.83 1.47 1.34 0.93 0.90
Sphyrna lewini Dasyatis kuhlii Himantura walga Carcharhinus brevipinna Himantura gerrardi Carcharhinus falciformis Squalus sp.3 Pteroplatytrygon violacea Mustelus sp.2 Mobula japanica
12.51 11.35 8.14 7.77 6.80 4.55 4.07 3.34 3.22 3.10
The MDS ordination revealed a separation between Sunda Shelf and Indian Ocean groups (Figure 6). The horizontal axis of the plot shows the geographical pattern and habitat grouping. The Sunda Shelf group was plotted on the left side of the ordination while the Indian Ocean group was on the right. Also, fishing regions with fewer species were plotted further from the centre. East South Java region is typified by deep water habitat (Indian Ocean region) and East Sumatra region by shallow water
habitat (Sunda Shelf region) with large dissimilarities in species composition. SIMPER analysis showed that the species which typified the differences between East South Java and East Sumatra regions were Himantura gerrardi, Squalus sp.3, Carcharhinus brevipinna and Rhino-batos sp.1 with dissimilarity contributions of 16.01%, 13.52%, 8.43% and 8.24%, respectively. Squalus sp.3, C. brevipinna and Rhinobatos sp.1 typified the East South Java region, while Himantura gerrardi the East Sumatra region. The over-
Adrim, M. And Fahmi, Characteristics of Chondrichthyan Diversity in Western Indonesia
lap among fishing regions in the Sunda Shelf group with the Indian Ocean group on the horizontal axis was due to the presence of some chondrichthyan species in both groups. For instance, the similarity in species composition between East Kalimantan (EKal) and West Sumatra regions (WSmt) was large expressed by the closeness in the plot, due to the occurrence of some shark species typifying the deeper waters habitat in East Kalimantan region. The ANOSIM test showed that East Kalimantan was different from West Sumatra even though the R-value was not quite good (R-value = 0.326, p = 0.003). The SIMPER test addressed the similarity between East Kalimantan and West Sumatra in the difference in the abundance of Paragaleus tengi, Dasyatis kuhlii and Carcharhinus brevipinna. P. tengi was the most abundant of shark species at the Manggar landing site, East Kalimantan, contributing of 25.56% to the total chondrichthyan landing at this site. This species was also recorded at other sites in the Sunda Shelf region such as at Labuhan Maringgai (SSmt),
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Muara Baru (WNJv) and Brondong (ENJv) and also at Bengkulu landing sites (WSmt), but in low abundance. The vertical axis shows a separation based on the dissimilarity of the species compositions among the regions and the species diversity. Less diverse sites were plotted further from the central and sites with different species composition were plotted on the separate side. The ordination plot based on the Bray Curtis index of similarity shows a marked difference in species composition between sites in West Sumatra (WSmt) and sites in South Java. SIMPER showed that the species that differentiated the West Sumatra and West South Java region (WSJv) were Sphyrna lewini, Himantura walga and H. gerrardi with a contribution of dissimilarity 14.62%, 9.30% and 8.91%, respectively. While West Sumatra and East South Java (ESJv) were differentiated by Sphyrna lewini, Squalus sp.3 and Himantura gerrardi with contributions of 15.20%, 8.39% and 8.29%, respectively.
Figure 6. A Two Dimensional Result of Multidimensional Scaling Ordination Plot of Fourth Root Transformed Data on the Average Number of Species per Site. Symbols Correspond to Fishing Regions and Dashed Line Indicates Segregation of Samples Between the Sunda Shelf (left) and the Indian Ocean Region (right).
A one way ANOSIM based on the fourth root transformation of species data per site per day detected a significant difference among fishing regions (p = 0.0001; Global R = 0.52). From 120 pairwise comparisons among fishing regions, 11 sets of pairwise comparisons did not differ significantly (p > 0.05). Chondrichthyan species which contributed significantly to the
discrimination of fishing regions were identified by SIMPER analysis (Table 7). Sunda Shelf region Chondrichthyan fishes recorded from fish landing sites in the Sunda Shelf region were caught from enclosed waters and the upper continental shelf with depths between 3 and 200 m.
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Dasyatis kuhlii and Himantura gerrardi were the most abundant species recorded in this region, comprising about 57.05 % and 16.78 % of the total individuals recorded in Sunda Shelf region. D. kuhlii was recorded in large numbers at the Batang (Central North Java) and Muara Angke landing sites (West North Java), com-
prising about 28.14% and 23.07% of total species abundance in the Sunda Shelf region. Another dominant species, H. gerrardi was recorded in large numbers only at Batang, comprising about 28.10% of the total abundance at that landing site or about 13.35% of total species abundance in the Sunda Shelf region.
Table 7. SIMPER Result of Top Three Species which Typified Each Fishing Region in Western Indonesia. Fishing region West South Java East South Java East Java West Sumatra North East Sumatra East Sumatra East South Sumatra South Sumatra Sunda West North Java Central North Java East North Java South Kalimantan Central Kalimantan West Kalimantan East Kalimantan
Himantura walga Carcharhinus brevipinna Carcharhinus brevipinna Sphyrna lewini Himantura gerrardi Himantura gerrardi Dasyatis kuhlii Carcharhinus brevipinna Sphyrna lewini Dasyatis kuhlii Dasyatis kuhlii Himantura walga Himantura walga Himantura uarnacoides Himantura gerrardi Paragaleus tengi
Carcharhinus falciformis Squalus sp.3 Dasyatis kuhlii Dasyatis kuhlii Carcharhinus sorrah Himantura sp. cf. uarnacoides Himantura uarnacoides Dasyatis kuhlii Mustelus sp.2 Himantura gerrardi Himantura gerrardi Dasyatis kuhlii Himantura gerrardi Himantura gerrardi Rhynchobatus australie Carcharhinus brevipinna
Batang and Muara Angke were the largest chondrichthyan landing sites in the Sunda Shelf region. Both sites contributed about 47.89% and 25.39% of the total individuals recorded in the region during the study. On the other hand, the Brondong landing site (East North Java) has the greatest species richness of chondrichthyan fishes, i.e. 37 species. The most abundant species at this site was Dasyatis kuhlii, comprising about 36.87% of the total number of chondrichthyans recorded at this site during the study. Carcharhinus sorrah was the most abundant shark species in Sunda Shelf region, comprising of 2.24% of the total abundance of chondrichthyans in this region (Table 6). Tanjung Balai landing site (North East Sumatra) contributed most for the abundance of this species in the region (66.99%). According to the species occurrence data, the ten most common chondrichthyan fishes in Sunda shelf region were led by Himantura gerrardi (Table 8). Indian Ocean region
Chondrichthyan fishes recorded from fish landing sites in the Indian Ocean region were
Mobula japanica Rhinobatos sp.1 Himantura jenkinsii Dasyatis kuhlii Himantura uarnacoides Taeniura lymma Himantura gerrardi Carcharhinus dussumieri Himantura gerrardi Gymnura poecilura Himantura cf. pastinacoides Himantura uarnacoides Dasyatis kuhlii
caught from the coastal waters to the open sea of the Indian Ocean with depths between 10 and 2000 m. Sphyrna lewini and Dasyatis kuhlii were the most abundant species recorded in this region, comprising respectively about 12.51 % and 11.35 % of the total numerical abundance recorded in the Indian Ocean region. S. lewini was recorded in large numbers at Binuangeun (West South Java), comprising about 58.25% of the abundance of the species in the Indian Ocean region, while D. kuhlii was abundant at Muncar, East Java (43.85%). The Binuangeun and Palabuhanratu landing sites (West South Java) were the most species rich, with 36 species of chondrichthyans recorded. Even though Sphyrna lewini and Dasyatis kuhlii were the most abundant species recorded in this region, Carcharhinus brevipinna was recorded as the most common species in the Indian Ocean region according to species occurrence data (Table 9). C. brevipinna was abundant at Muncar landing site, comprising about 74.22% of the total abundance of the species in Indian Ocean region.
Adrim, M. And Fahmi, Characteristics of Chondrichthyan Diversity in Western Indonesia
Table 8. Rank List of the Ten Most Common Chondrichthyan Fishes Based on Their Occurrence at 17 Landing Sites of the Sunda Shelf Region. Species
Occurrence
Himantura gerrardi Dasyatis kuhlii Himantura sp. cf. gerrardi (no spot) Himantura uarnacoides Himantura walga Himantura uarnak Chiloscyllium punctatum Dasyatis zugei Gymnura cf. poecilura Carcharhinus dussumieri
17 14 14 14 13 12 12 10 10 10
Percentage of Occurrence 100.00 82.35 82.35 82.35 76.47 70.59 70.59 58.82 58.82 58.82
Table 9. Rank List of the Ten Most Common Chondrichthyan Fishes Based on Their Occurrence at Nine Landing Sites of the Indian Ocean Region. Species
Occurrence
Carcharhinus brevipinna Carcharhinus falciformis Carcharhinus sorrah Sphryna lewini Dasyatis kuhlii Mobula japanica Himantura gerrardi Himantura sp. cf. gerrardi (no spot) Himantura jenkinsii Himantura uarnak
7 6 6 6 6 6 5 5 5 5
Percentage of occurrence 77.78 66.67 66.67 66.67 66.67 66.67 55.56 55.56 55.56 55.56
SPECIES IDENTIFICATION During the study, some species could not be identified to species level and were given temporary names based on their genus name. Other species were named based on the “suggested” species name. Twelve species have been observed since 2001 in a previous study in the eastern Indonesia (ACIAR project) and their temporary names are used here (Table 10). Nineteen species which have been recorded during this study were named with the appropriate genus. Some of them were named using the suggested names. Pastinachus solocirostris sp. nov. is a new dasyatid species that occurs in the Indo-Malay archipelago (Last et al., 2005). During the study, three individuals were recorded at Tembilahan
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(ESmt), five at Sungai Kakap (WKal) and one individual at Sampit (CKal). Atelomycterus sp. is a cat shark species, which was only recorded at the Binuangeun landing sites (WSJv). During the study, only two individuals of this species were found at size between 330 and 475 mm in total length. A female of the species (475 mm TL) was collected for further identification to find out the possibility of being an endemic or even a new species.
DISCUSSION As the biggest families in the sub class of Elasmobranchii, Dasyatidae and Carcharhinidae contributed significantly to species composition of chondrichthyan landings in western Indonesia. Some species become the most abundant in particular areas and others in different ones. Dasyatis kuhlii was recorded as the commonest chondrichthyan species in this study. This species was the commonest small ray in tropical Indian and western Pacific Ocean waters. D. kuhlii is commonly found on sandy substrates in inshore areas with depths less than 90 m (Compagno, 1998). Due to the biology of D. kuhlii, which live in large groups, this species often get caught in large numbers. D. kuhlii was not only abundant in the landings in the Sunda Shelf region, but was also in large numbers in the Indian Ocean region. Some landing sites had a large number of chondrichthyan landings and had a high species diversity, but for other sites only one or two species were recorded. There are some particular factors that likely cause particular sites to have a large number of chondrichthyan landings, i.e. location, facility and accessibility, target of fishing, fishing grounds, gear, size and number of boats and days of trip. Species composition between main regions
The MDS ordination plot detected segregation between the Sunda Shelf and the Indian Ocean region. The Sunda Shelf region was typified by some common dasyatids and inshore sharks and the Indian Ocean region by large and deep water sharks. However, some medium to large shark species often occurred in the Sunda Shelf region during the study. The segregation between the Sunda Shelf and the Indian Ocean regions were mainly caused by the differences in species abundances. The spottail shark, Car-
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chrahinus sorrah, was recorded in large abundance in the enclosed water fishery. This species is quite common in inshore waters especially as juveniles, while the larger sizes usually occur in the offshore and are widely distributed. Nine of 17 sites in the Sunda shelf region recorded landings of C. sorrah indicating the common-
ness of this species in the region. This species was caught mostly from Malacca Strait, South Sumatra waters and south eastern Kalimantan all of almost equal size (less than 1 m in total length). Even though C. sorrah was also found in the Indian Ocean region, they were less abundant and had a different size composition.
Table 10. The Unidentified Species and Temporary Species Name List for Some Chondrichthyans that Have Been Recorded in Western Indonesia During the Study. The (*) Symbol Indicates the Size was Measured Using the Disc Width (DW). Species ACIAR Project’s name
Rhinobatos sp. 1 Rhinobatos sp. 2 Dipturus sp. 1 Dasyatis sp. 1 Himantura sp. cf. gerrardi (no spot) Himantura sp. 1 (long snout) Centrophorus cf. granulosus Squalus sp.1 Squalus sp.3 Orectolobus sp. cf. maculatus Hemitriakis sp. Mustelus sp. 2 Hydrolagus cf lemures
Locality (region) observed
Size (mm TL)
Snd, WSJv, CSJv Snd, ENJv, EJv WSJv WNJv, WSJv, ESJv Snd, WNJv, CNJv, NESmt, ESmt, ESSmt, SSmt, SKal, CKal, WKal, WSmt, WSJv, ESJv ESmt, WKal, CKal WSmt WSJv, CSJv WSJv, CSJv, ESJv ESJv WSJv, EJv Snd, ESJv, EJv, WSmt, WSJv, EJv
This study
Rhynchobatus sp cf. laevis Rhynchobatus sp. Okamejei cf. powelli Raja (Dipturus) sp.2 Dasyatis sp. cf.. kuhlii (no spot) Dasyatis sp.2 (cf. akajei) Himantura sp. cf. pastinacoides Himantura sp.cf. uarnacoides Rhinoptera cf. neglecta Squalus sp. cf. megalops Squalus sp.A Squalus sp.B Squatina sp. Atelomycterus sp. Mustelus sp.black fins Carcharhinus sp. Glyphis sp.
CNJv, ENJv, ESSmt, CKal, EKal, ESJv, SSmt, ESSmt, WSmt Snd, WSJv ESJv CNJv, NESmt Snd NESmt, ESmt, WKal, CKal CNJv, ENJv, ESmt WKal ESJv, WSmt WSmt WSmt WSJv WSJv Snd, CNJv, WSJv ESSmt, SSmt CKal
Species composition among fishing regions
The MDS separated the Sunda Shelf and Indian Ocean landings. However, the separation was not a straight vertical line. Some fishing regions overlapped and are not obviously sepa-
rated into two main regions. Moreover, some sites from different fishing regions were closer each other than to other sites in the same fishing region. However, fishing ground is not the only reason for differences in the species composition among sites in the region. It is likely that
Adrim, M. And Fahmi, Characteristics of Chondrichthyan Diversity in Western Indonesia
gear selectivity and fishing method also contributed. In general, the Indian Ocean region was typified by the occurrence of some medium to large sharks while the Sunda Shelf region was typified by some small to medium rays. The occurrence of some shallow water species in the Indian Ocean region indicates the distribution of species that occur not only in the enclosed waters, but also in coastal waters adjacent to the Indian Ocean. Himantura gerrardi is the most common species in Indonesian waters because it was recorded at 17 sites in the Sunda Shelf region and at five sites in the Indian Ocean region. Dasyatis kuhlii was the second most common species during the study, occurring at 20 out of 26 landing sites that were sampled in western Indonesia. As well as D. kuhlii, H. gerrardi is a medium size of ray which can be found in the inner continental shelf and distributed widely in the Indo-Pacific waters (Compagno, 1998). This species is also often caught in large quantities in coastal areas and muddy substrates ranging in depth from 3 m to 60 m.
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ing for instance, and makes that particular species the most abundant species at that site; (b) The number of sampling days was insufficient. In order to get representative data for a population, sufficient replicates are required. There is a particular species that has become a target for local fishers in a particular area. This situation may raise the presence of that species at particular landing sites as the consequence of the catch intensively. This usually happens with species that have high economic value (e.g. Rhynchobatus spp., Rhinobatos typus and Himantura gerrardi).
CONCLUSIONS The presence of Dasyatis kuhlii and Himantura gerrardi in large numbers on every occasion and also location made both species the most common and dominant chondrichthyan species in western Indonesian waters. Therefore, the occurrence and abundance of those species in western Indonesian fishery could provide an indicator for sustainability of chondrichthyan stocks in this region.
Species diversity
ACKNOWLEDGEMENT
Species richness and diversity of particular habitats could not be measured by the abundance and diversity of species at particular fish landings or sites. The differences of fishing ground, method, gear, time and condition of each site including facilities, technology and socio economics, renders measures of species diversity incomparable. However, if species diversity is analyzed from where the species are captured (i.e. fishing ground), then the values can be compared with all contributing factors above. In this study, sites were grouped into 16 regions and each region has a specific fishing area (Table 1).
This study was funded by Census Marine Life Program, Indonesian Institute Sciences. We also thank to Dr. Ian Tibbetts the University of Queensland for his advice this paper.
The relative abundance of chondrichthyans from each region detected the dominance of a particular species through the steepness of the species composition values. The dominance of particular species and the steepness in the species rank of average relative abundance at particular sites may be caused by the following factors: (a) A particular species may be abundant at a landing site in only one or two days sampling. This number influences the average species composition of seven days sampl-
of of of to
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