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eISSN: 2575-906X

Biodiversity International Journal

Research Article Volume 2 Issue 2

Biological environmental survey in Cat Ba Island

Doan Quang Tri,1,2 Tran Hong Thai2

1Ton Duc Thang University, Vietnam
2Vietnam Meteorological and Hydrological Administration, Vietnam

Correspondence: Doan Quang Tri, Sustainable Management of Natural Resources and Environment Research Group, Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Vietnam

Received: December 04, 2017 | Published: March 28, 2018

Citation: Tri DQ, Thai TH. Biological environmental survey in Cat Ba Island. Biodiversity Int J. 2018;2(2):123–133. DOI: 10.15406/bij.2018.02.00054

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Abstract

Cat Ba Island has a significant biodiversity value as it is home to a number of rare and endangered species of plants and animals, with the world’s rarest primates the Golden-headed Langur. According to the study results, Cat Ba place have listed 2,380 species of animals and plants including: terrestrial plants 741 species; living animals in the forest area 282 species; mangrove plants 30 species; seaweeds 79 species; phytoplankton 287 species; plank tonic animals 98 species; sea-fish 196 species; corals 154 species. It is identified as one of the areas of highest biodiversity importance in Vietnam and is recognized as a high priority for global conservation.

Keywords: mangrove, seagrass, coral reef, phytoplankton, cat ba island

Introduction

Biosphere reserves Cat Ba Island has been recognized as a UNESCO World on December 02nd, 2004. It is the 4th world’s biosphere reserve in Vietnam. Biosphere reserves Cat Ba archipelago including great majority of Cat Ba Island in Cat Hai district, Hai Phong city, Vietnam. Cat Ba Island is considered the richest marine biological system because of its diversity in the North of Vietnam. On the previous study,1 they found the Langur distribution and forest cover in Cat Ba Island (Figure 1). The objective of this study was shown the distribution of mangrove, seaweed/seagrass, coral reefs and phytoplankton in Cat Ba Island.

Figure 1The white-headed langur (Trachypithecus poliocephalus), an endemic species from Cat Ba Island.1

Materials and methods

Description of the study area

Cat Ba is the largest of 336 islands in the Cat Ba Archipelago, and also the second largest limestone island (200 km2) in the coastal zone of Vietnam.2 It is located in the north-east of Vietnam in the northern section of the Tonkin Gulf and adjacent to Ha Long Bay (the world natural heritage site) (Figure 2). The total natural land area of Cat Ba Archipelago Biosphere Reserve is 26,240 ha, of which land area (island) is 17,040 ha and 9,200 ha of sea. Cat Ba Island is considered the richest marine biological system because of its diversity in the North of Vietnam.3‒7

Figure 2Cat Ba Island.

Methods of field survey

Mangrove: All mangrove species that were identified in the survey sites were recorded. Also to obtain quantitative data, a 10m x 10m quadrate was set at a location that was representative of the site, and the following information was recorded: species composition, canopy height (highest and lowest), stem diameter (3 m from ground) and density (No. of stems/100 m2).

Seaweed/seagrass: All seaweed/seagrass species that were identified in the survey sites were recorded. Samples were collected and preserved in a 10% formalin solution for further analysis at IMER’s laboratory. Except sites AL11, survey was conducted only along the shoreline (underwater survey was not possible due to very low water visibility). Sites AL11 was surveyed by scuba diving.

Coral Reefs: Coral survey was conducted by squba diving at sites AL11. Species composition and live coral coverage were recorded at 5m interval along a 100 m line transect.

Phytoplankton: The qualitative Phytoplankton samples were collected by towing a plankton net (mesh size: 20μm, diameter: 20cm) several times in the vertical direction. Quantitative samples were collected from the surface by collecting 1L of surface water in the PVC bottle. All samples were preserved in 3ml Lugol solution for further analysis at IMER’s laboratory.

Demersal fish: Demersal fish was collected with a trawling net (mesh size: #15, width: 5m). Each trawl was conducted for 15 minutes at a speed of approximately 2 miles/hour. All collected species were measured (total length) and weighted, then preserved in 10% formalin solution for further analysis at IMER’s laboratory.

Results and discussion

Diversity of the species composition

According to previous studies, a total of 2,380 species have been recorded in Cat Ba Island. Among of them 1,053 species are terrestrial species occupies 51.7% of the total species while the marine species occupies 48.3% with 985 species (Table 1). High biological diversity of the species included in the Cat Ba Island will be a very important basis for the exploitation of natural resources to serve different purposes of human. On the other hand it provides great significance in scientific research: evolution, ecology, environmental indicators along with a wide range of species likely to play an important role in the provision of ecosystem services such as disaster prevention and source of raw materials for the chemical industry and medicine production.

Taxon

Number of species

Taxon

Species

Terrestrial plant

741

Zooplankton

79

Terrestrial animal

282

Marine fishes

196

Mangrove plant

30

Coral

154

Phytoplankton

287

Zoobenthos

538

Seaweed

79

 

 

 

 

Total: 2,380 species

Table 1 The species composition recorded in Cat Ba Island8

Diversity of major marine ecosystem

Coral reefs: Coral reefs are mainly distributed at the surrounding waters in the southeast of Cat Ba Island such as Cong La, Ang Tham, Ba Trai Dao, Van Boi, Cong Hip, Tung Ngon, and Coc Cheo. The coral reefs areas are the major fishing grounds for reef fisheries due to high values of the coral reef fishes and associated reef species (Figure 3). The coral reefs in Cat Ba - Ha Long area are represented for the fringing reef types and two addition types of islands connectivity and the unofficial atoll. Generally, along the limestone islands of Cat Ba have coral distribution at a depth of 3, 6, 9 and 11 meters. Morphology of the reef is determined mainly by the morphology of the ground slopes and partly by carbonate sediments originated from organisms on the reef. Due to changes of the environmental conditions under the impact of natural and human, coral reefs are now greatly reduced in terms of area and the level of diversity of the groups living together. The percentage of the live coral coverage occupies by less than 40%, meaning classification of medium and low level by the UNESCO criteria for assessment of the coral reef health.

Figure 3Locations of the field survey sites (mangrove, seaweed/seagrass and coral reef).3 Note 1 Coral was surveyed only at sites AL11; Site AL8 was not surveyed as the area was under construction activities.

Table 2 shows the hard coral species identified through the field survey. Twenty-eight species and 58 species were identified at the sites AL11 respectively. The diversity at site AL11 was lower probably due to relatively turbid conditions. Within the identified species, 4 species are listed in the Vietnam Red Book namely: Porites lobata, Acropora aspera, Acropora formosa and Acropora nobilis; which are all classified as “Vulnerable”. Porites lobata was found at the AL11 site.

 

Survey site

Family

Genus/species

Status in vietnam
red book

1

AL11

Acroporidae

Acropora pulchra

Not listed

2

Poritidae

Porites lobata

Vulnerable

3

Porites lutea

Not listed

4

Goniopora columna

Not listed

5

Goniopora lobata

Not listed

6

Agariciidae

Pavona decussata

Not listed

7

Oculinidae

Galaxea astreata

Not listed

8

Galaxea fascicularis

Not listed

9

Pectiniidae

Pectinia lactuca

Not listed

10

Echinophyllia aspera

Not listed

11

Mycedium elephantotus

Not listed

12

Fungiidae

Lithophyllon undulatum

Not listed

13

Sandalolitha robusta

Not listed

14

Mussidae

Lobophyllia hattaii

Not listed

15

Lobophyllia hemprichii

Not listed

16

Symphyllia. agaricia

Not listed

17

Merulinidae

Merulina ampliata

Not listed

18

Faviidae

Favia maritime

Not listed

19

Favia matthaii

Not listed

20

Favia lizardensis

Not listed

21

Favia maxima

Not listed

22

Favites abdita

Not listed

23

Goniastrea pectinata

Not listed

24

Goniastrea favulus

Not listed

25

Cyphastrea serailia

Not listed

26

Echinopora lamellose

Not listed

27

Platygyra daelalea

Not listed

28

Dendrophylliidae

Turbinaria peltata

Not listed

Table 2 List of hard coral species identified through the field survey (EIA, 2011).

Seagrass: Seagrasses are mainly distributed in Cat Ba Island in the narrow range like leopard style on tidal marshes (with the carpet of mangroves) in Gia Luan and in aquaculture ponds in Phu Long. A small area of seagrass distributes in the island of Long Chau (offshore) and Van Boi (Southeast of Cat Ba Island) where there are coral reefs with live coral cover is relatively high (Figure 4). There were only two species of seagrass have been identified in the island of Cat Ba such as Ruppia Maritima and Halophila beccarii. However, both species are not included in the Red Data Book of Vietnam, although the species of Halophila beccarii is classified at the level of “danger threatened” in the IUCN red list of threatened species, 2011.

Figure 4Distribution map of the seagrass area at Cat Ba islands.3

Table 3 shows the seaweed species identified through the field survey. Seventeen species belonging to 9 families were identified. Chaetomorpha capillaris and Enteromorpha compressa were the most common species. Some species such as Asparagopsis taxiformis, Colpomenia sinuosa, and Cladophoropsis membrannacea were identified at only specific sites. None of the identified species are included in the Vietnam Red Book. Some species in the Ulvaceae family are harvested for food stuffs in certain areas of Vietnam. Table 2 shows the seagrass species identified through the field survey. Only two seagrass species Ruppia maritima and Halophila beccarii were identified, which were found at sites AL10 and AL11 respectively. Halophila beccarii was record for the first time in the surveyed area. Although both species are not included in the Vietnam Red Book, Halophila beccarii is classified as “Vulnerable” in IUCN Red List.

 

Family

Genus/species

Status in vietnam red book

Identified survey sites

1

Ceramiaceae

Bostrychia binderi

Not listed

AL3, AL5, AL7, AL10

2

Polysiphonia sertularioides

Not listed

AL1, AL2, AL10

3

Delesseriaceae

Caloglosa ogasawaraensis

Not listed

AL2, AL3, AL7

4

Dictyotaceae

Padina australis

Not listed

AL11

5

Cladophoraceae

Chaetomorpha capillaris

Not listed

AL1, AL03, AL5, AL7, AL10, AL11

6

Ch. linum

Not listed

AL1, AL10

7

E. compressa

Not listed

AL1, AL3, AL5, AL7, AL10, AL11

8

E. kylinii

Not listed

AL1, AL10

9

E. flexuosa

Not listed

AL1

10

Ulva conglobata

Not listed

AL5

11

Ruppiaceae

Ruppia maritima

Not listed

AL10

12

Hydrocharitaceae

Halophila beccarii

Not listed

AL11

Table 3 List of seaweed species identified through the field survey (EIA, 2011).

Mangrove forest: The mangrove forest and the coral reefs are the invaluable natural resources of the tropical countries in general and Cat Ba in particular. They play as the sources of genetic reservation, increasing of the natural biomass and stabilization for the shoreline. Most of the mangrove forests maintain high cover in the western side of Cat Ba Island (Phu Long Natural Reserve). In near future, the fight campaign for climate change will lean much on these green corridors (Figure 5).

Figure 5Distribution map of the mangrove area at Cat Ba islands.3

Most of the mangrove areas distribute in Phu Long Commune with high relative density. The total area is 775.98 ha of mangrove forest is divided into two types: mangrove distribution outside the farming area (224.74 ha), mangrove distribution in ponds (551.24 ha) (Figure 6). Because mangrove forests in farming systems are relatively large so the long-term master plan and conservation of mangroves will be difficult due to satisfactorily resolve the relationship of private-public ownership. Table 4 shows the mangrove species identified through the field survey. Eleven species belonging to 9 families were identified. Rhizophora stylosa and Avicennia marina were the most common species in the survey area. None of the identified species are included in the Vietnam Red Book.

Figure 6Mangrove distribution in Cat Ba Island.3

No.

Family

Genus/species

Status in vietnam
red book

Identified survey sites

1

Sonneratiaceae

Sonneratia caseolaris

Not listed

AL10

2

Rhizophoraceae

Rhizophora stylosa

Not listed

AL1, AL2, AL3, AL5, AL7

3

Kandelia obovata

Not listed

AL5, AL10

4

Bruguirea gymnorrhiza

Not listed

AL1, AL3, AL7

5

Aviceniaceae

Avicennia marina

Not listed

AL1, AL2, AL3, AL5, AL7

6

Myrsinaceae

Aegiceras corniculatum

Not listed

AL1, AL3

7

Pteridaceae

Acrostichum aureumh

Not listed

AL10

8

Verbenaceae

Cleodendrum inerme

Not listed

AL2, AL10

9

Euphorbiaceae

Excoecaria agallocha

Not listed

AL3, AL5

10

Malvaceae

Hibiscus tiliaceus

Not listed

AL5

Table 4 List of mangrove species identified through the field survey.

Phytoplankton: Phytoplanktons are the keystone species in this habitat type, providing basic food items for the zoobenthis and fish that are the key targets of the capture fishery (Figure 7). Table 5 and Table 6 show the phytoplankton species identified through the dry and wet season surveys respectively. In the dry season, a total of 134 species were identified (Table 5). The genus Chaetoceros was found in many survey sites, which play an important role as food sources for fish and other marine species, in particular at the early stages of their life cycle. Some of the identified dinoflagellate species such as Ceratium fusus, Prorocentrum micans and Dinophysis caudate are known to cause red tide and harmful algae bloom when at high density. In the rainy season, a total of 136 species were identified (Table 6). The density of the phytoplankton has been driven by some dominante species such as Skeletonema costatum with the cell density is approximate 103 up to 4,104 cell/L; next to the Chaetoceros spp. with the density from 103 - 56,103 cell/L; Ceratium furca has the density from 2.103 to approximate of 104 cell/L (EC9 site); Oscillatoria sp.2 103 cell/L and Bacteriastrum spp. reaches 47,103 cell/L.

Figure 7Locations of the field survey sites (phytoplankton, zooplankton, zoobenthos, demersal fish and other zoobenthos).3

Table 5 to Table 6 shows the number of phytoplankton species and cell density at each survey site. For the dry season, the number of species ranged between 32 and 57 species. While there was no clear spatial trend in the cell density, relatively high levels were recorded at the EC4 and EC8 sites. The seasonal variation shows a clearly trend of reduction both interm of species composition and cell density. However, the number of species is slightly lower in rainy season while the cell density rapidly reduces up to 98.42% at the EC8 site to 22.3% at the EC11 site.

No.

Scientific name

No. of identified survey sites

No.

Scientific name

No. of identified survey sites

No.

Scientific name

No. of identified survey sites

No.

Scientific name

Phylum- Bacillariophyceae

Phylum- Bacillariophyceae

Phylum - Dinophyceae

Phylum - Dinophyceae

1

Paralia sulcata

1

42

Chaetoceros lorenzianus

11

83

Ceratium macroceros

4

124

Pyrophacus horologicum

2

Hyalodiscus stelliger

1

43

Chaetoceros paradoxus

3

84

Ceratium massiliense

4

 

Phylum - Dictyochophyceae

3

Cyclotella striata

3

44

Chaetoceros rostratus

9

85

Ceratium asymmetricum

2

125

Dictyocha fibula

4

Cyclotella comta

6

45

Chaetoceros subtilis

3

86

Ceratium tripos

3

126

Dictyocha speculum

5

Cyclotella sp.

1

46

Biddulphia regia

2

87

Prorocentrum micans

10

Phylum - Cyanophyceae

Phylum- Bacillariophyceae

47

Biddulphia reticulum

3

88

Prorocentrum rhathymum

1

127

Trichodesmium erythraeum

6

Coscinodiscus asteromphalus

12

48

Odontella mobiliensis

1

89

Prorocentrum sp.

2

128

Oscillatoria sp.

7

Coscinodiscus oculus-iridis

6

49

Hemiaulus sinensis

1

90

Dinophysis caudata

10

Phylum – Chlorophyceae

8

Coscinodiscus radiatus

1

50

Cerataulina bergonii

1

91

Dinophysis mitra

1

129

Pediastrum simplex v. simplex

9

Coscinodiscus granii

1

51

Cerataulina compacta

1

92

Dinophysis cf. rotundata

1

130

Pediastrum duplex v. duplex

10

Coscinodiscus cf. subtilis

3

52

Ditylum brightwellii

1

93

Noctiluca scintillans

4

131

Pediastrum sp.

11

Coscinodiscus sp.

1

53

Eucampia zoodiacus

6

94

Gonyaulax sp.

4

132

Scenedesmus sp.

12

Lauderia borealis

5

54

Climacodium biconcavum

3

95

Gonyaulax polygramma

9

133

Scenedesmus quadricauda

13

Skeletonema costatum

8

55

Palmeria hardmaniana

5

96

Gonyaulax spinifera

1

134

Staurastrum sp.

14

Leptocylindrus danicus

3

56

Thalassionema frauenfeldii

12

97

Gonyaulax scrippsae

2

 

 

15

Guinardia flaccida

8

57

Navicula membranacea

7

98

Gonyaulax verior

1

 

 

16

Guinardia striata

12

58

Navicula cancellata

2

99

Gonyaulax rotundata

2

 

 

17

Bacteriastrum varians

5

59

Tropidoneis lepidoptera

1

100

Gonyaulax diegiensis

4

 

 

18

Bacteriastrum hyalinum

5

60

Pleurosigma affine

4

101

Protoperidinium steinii

5

 

 

19

Thalassiosira eccentrica

2

61

Pleurosigma angulatum

1

102

Protoperidinium conicum

10

 

 

20

Thalassiosira lineata

6

62

Pleurosigma sp.1

7

103

Protoperidinium crassipes

8

 

 

21

Thalassiosira sp.

2

63

Pleurosigma sp.2

1

104

Protoperidinium divergens

6

 

 

22

Arthrospira platensis

2

64

Pleurosigma naviculaceum

4

105

Protoperidinium depressum

1

 

 

23

Rhizosolenia robusta

3

65

Pleurosigma pelagicum

4

106

Protoperidinium elegans

3

 

 

24

Rhizosolenia setigera

2

66

Amphiprora alata

1

107

Protoperidinium oceanicum

3

 

 

25

Rhizosolenia hyalina

4

67

Nitzschia lorenziana

6

108

Protoperidinium ovum

9

 

 

26

Proboscia alata

9

68

Nitzschia longissima

2

109

Protoperidinium pellucidum

11

 

 

27

Proboscia alata f. indica

1

69

Nitzschia longissima v. reversa

1

110

Protoperidinium pentagonum

1

 

 

28

Proboscia alata f. gracillima

1

70

Nitzschia sigma

4

111

Protoperidinium leonis

2

 

 

29

Proboscia alata f. genuina

1

71

Nitzschia sigma v. intercedens

1

112

Protoperidinium spinulosum

1

 

 

30

Chaetoceros affinis

12

72

Pseudonitzschia sp.1

8

113

Protoperidinium sphaeroides

6

 

 

31

Chaetoceros affinis v. willei

1

73

Pseudonitzschia sp.2

2

Phylum - Dinophyceae

 

 

32

Chaetoceros abnormis

5

74

Surirella ovalis

5

114

Protoperidinium sp.

8

 

 

33

Chaetoceros curvisetus

4

75

Surirella gemma

2

115

Peridinium quinquecorne

2

 

 

34

Chaetoceros compactus

3

76

Campylodiscus echeneis

3

116

Scrippsiella sp.

1

 

 

35

Chaetoceros compressus

7

77

Campylodiscus undulatus

1

117

Alexandrium sp.

2

 

 

36

Chaetoceros constrictus

12

Phylum - Dinophyceae

118

Alexandrium pseudogonyaulax

4

 

 

37

Chaetoceros decipiens

1

78

Ceratium breve

3

119

Goniodoma polyedricum

5

 

 

38

Chaetoceros denticulatus

3

79

Ceratium furca

11

120

Diplopsalis sp.

5

 

 

39

Chaetoceros distans

2

80

Ceratium deflexum

2

121

Diplopsalopsis sp.

2

 

 

40

Chaetoceros dydimus

1

81

Ceratium fusus

11

122

Zygabikodinium sp.

1

 

 

41

Chaetoceros lauderii

1

82

Ceratium trichoceros

10

123

Oblea sp.

2

 

 

Table 5 List of phytoplankton species identified through the field survey (in dry season)

No.

Scientific name

No. of identified survey sites

No.

Scientific name

No. of identified survey sites

No.

Scientific name

No. of identified survey sites

Bacillariophyceae (Diatoms)

Bacillariophyceae (Diatoms)

Bacillariophyceae (Diatoms)

1

Paralia sulcata

2

46

Eucampia cornuta

1

91

Protoperidinium pellucidum

6

2

Melosira granulata

2

47

Eucampia zoodiacus

2

92

Protoperidinium pentagonum

2

3

Melosira granulata v. angustissima

6

48

Climacodium biconcavum

1

93

Protoperidinium punctulatum

1

4

Cyclotella comta

11

49

Palmeria hardmaniana

4

94

Protoperidinium spinulosum

6

5

Coscinodiscus asteromphalus

11

50

Thalassionema nitzschioides

5

95

Protoperidinium sphaeroides

1

6

Coscinodiscus oculus-iridis

4

51

Thalassionema frauenfeldii

11

96

Protoperidinium sp.

1

7

Coscinodiscus jonesianus

1

52

Pleurosigma affine

2

97

Protoperidinium sp.1

2

8

Coscinodiscus jonesianus v. commutata

12

53

Pleurosigma sp.

2

98

Peridinium sp.

1

Bacillariophyceae (Diatoms)

54

Pleurosigma sp.1

1

99

Alexandrium sp.

1

9

Coscinodiscus marginatus

1

55

Nitzschia lorenziana

3

100

Goniodoma polyedricum

1

10

Coscinodiscus cf. subtilis

1

56

Nitzschia longissima

1

101

Lingulodinium polyedra

5

11

Asteromphalus cleveanus

1

57

Pseudo-nitzschia sp.1 (P. cf. pungens )

3

102

Diplopsalis sp.

2

12

Thalassiosira eccentrica

3

58

Campylodiscus echeneis

1

103

Diplopsalopsis sp.

2

13

Thalassiosira lineata

12

59

Ceratium breve

2

104

Zygabikodinium sp.

1

14

Thalassiosira sp.

2

60

Ceratium deflexum

1

105

Pyrophacus horologium

1

15

Lauderia borealis

11

61

Ceratium extensum

1

106

Pyrophacus sp.

7

16

Skeletonema costatum

11

62

Ceratium falcatum

1

107

Podolampas bipes

1

17

Guinardia flaccida

5

63

Ceratium furca

11

Cyanophyceae (Cyanobacteria)

18

Guinardia striata

2

64

Ceratium fusus

4

108

Trichodesmium erythraeum

2

19

Dactyliosolen mediterraneus

2

65

Ceratium trichoceros

6

109

Oscillatoria limosa

3

20

Bacteriastrum varians

8

66

Ceratium massiliense

1

110

Oscillatoria raciborskii

3

21

Bacteriastrum hyalinum

1

67

Ceratium tripos

3

111

Oscillatoria sp.1

6

22

Pseudosolenia calcar-avis

3

68

Ceratium sp.

1

112

Oscillatoria sp.2

2

23

Rhizosolenia cylindrus

1

69

Dinophysis miles

3

113

Oscillatori princeps

2

24

Rhizosolenia robusta

1

70

Dinophysis caudata

11

114

Lyngbya sp.

1

25

Chaetoceros affinis

8

71

Dinophysis hastata

1

115

Arthrospira platensis

9

26

Chaetoceros abnormis

5

72

Dinophysis doryphorum

1

116

Anabaena sp.

4

27

Chaetoceros curvisetus

10

73

Dinophysis sp.

1

117

Anabaena cf. viguieri

1

28

Chaetoceros coarctatus

2

74

Ornithocercus magnificus

1

118

Microcystis cf. wesenbergii

7

29

Chaetoceros compressus

3

75

Histioneis costata

1

119

Microcystis sp.

7

30

Chaetoceros constrictus

2

76

Amphisolenia bidentata

3

Chlorophyceae (Chlorophyte)

31

Chaetoceros crinitus

1

77

Gymnodinium sanguineum

1

120

Pediastrum simplex v. simplex

9

32

Chaetoceros diversus

3

78

Gonyaulax sp.

3

121

Pediastrum boryanum v. boryanum

1

33

Chaetoceros distans

1

79

Gonyaulax polygramma

3

122

Pediastrum duplex v. duplex

8

34

Chaetoceros lorenzianus

7

80

Gonyaulax rotundata

5

123

Pediastrum sp.

3

35

Chaetoceros subtilis

9

81

Protoperidinium abei

1

124

Pediastrum tetras

4

36

Biddulphia regia

11

82

Protoperidinium cf. brochii

3

125

Scenedesmus sp.

3

37

Biddulphia dubia

1

Bacillariophyceae (Diatoms)

126

Scenedesmus quadricauda

6

38

Biddulphia reticulum

1

83

Protoperidinium conicum

11

127

Scenedesmus carinatus

1

39

Odontella mobiliensis

4

84

Protoperidinium claudicans

4

128

Scenedesmus acuminatus var. acumin

1

40

Bellerochea horologicalis

1

85

Protoperidinium crassipes

3

129

Scenedesmus javanensis

2

41

Hemiaulus sinensis

3

86

Protoperidinium divergens

1

130

Staurastrum sp.

8

42

Hemiaulus indicus

1

87

Protoperidinium elegans

1

131

Palmella sp.

1

43

Cerataulina bergonii

1

88

Protoperidinium oceanicum

6

132

Eudorina elegans

1

44

Cerataulina compacta

1

89

Protoperidinium ovum

1

133

Eudorina sp.

4

45

Ditylum sol

11

90

Protoperidinium thorianum

1

 

 

 

Table 6 List of phytoplankton species identified through the field survey (in rainy season)

Demersal fish: Table 7 shows the demersal fish species identified through the dry and rainy season surveys respectively. In the dry season, in general, fish diversity and abundance were significantly higher in the shallow coastal survey sites (e.g. EC1, EC2, EC4, and EC7) compared to the deeper offshore survey sites. Within the identified species, two species are listed in Vietnam Red Book namely, Bostrichthys sinensis and Anodontostoma chacunda, which were found in the shallow coastal survey sites EC1 and EC2 respectively. Bostrichthys sinensis and Anodontostoma chacunda are classified as “Critical” and “Vulnerable” respectively. In the wet season, the similar trend in term of fish diversity and abundance has been found among sampling sites (shallow sites are more abundance than the off shore sites). However there are differences in the species composition of the economic species with the distribution of the family Sciaenidae to occur in 9/11 sampling sites. This family also contributes for higher biomass of the total catch at the sampling sites of EC8, EC9 in the rainy survey.

Survey site

Family

Genus/species

No. of individuals

Total and ave. wet weight (g)

Average length (cm)

Status in vietnam red book

In dry season

EC1

Sparidae

Sparus latus

1

6

6.5

Not listed

Taenioididae

Trypauchen

2

Total: 12.97

9

Not listed

vagina

Ave. : 6.5

 

Eleotridae

Bostrichthys

1

23

13

Critical

 sinensis

Sillaginidae

Sillago sihama

1

15.4

12.5

Not listed

Eleotridae

Butis butis

1

4.5

5

Not listed

Platycephalidae

Rogadus asper

1

12.5

11

Not listed

Platycephalidae

Cociella

1

5

5.5

Not listed

 crocodila

Cynoglossidae

Symphurus

1

4.5

3.5

Not listed

 orientalis

EC2

Cynoglossidae

Symphurus

1

11

9.5

Not listed

 orientalis

Soleidae

Heteromycterus

1

13

8

Not listed

japonica

Sillaginidae

Sillago sihama

1

12.5

14.9

Not listed

Clupeidae

Anodontostoma

5

Total: 60

15.3

Vulnerable

chacunda

Ave: 12

Sciaenidae

Nibea albiflora

1

26

23.5

Not listed

In rainy season

EC1

Muraenesocidae

Muraenesox

1

36

25

Not listed

cinereus

Taenioididae

Trypauchen

2

Total: 25.4

13

Not listed

vagina

Ave. : 12.7

Eleotridae

Bostrichthys

1

Total: 42

12.5

Critical

 sinensis

Ave: 14

Sciaenidae

Nibea soldado

26

Total: 93.37

7.2

Not listed

Ave: 3.59

Siganidae

Siganus

1

7.5

8

Not listed

fuscescens

EC2

Bagridae

Cranoglanis

9

Total: 400

22.3

Not listed

sinensis

Ave: 44.4

Bothidae

Arnoglossus

3

Total: 3.13

5

Not listed

tenuis

Ave: 1.04

Clupeidae

Anodontostoma

2

Total: 30

16.7

Vulnerable

 chacunda

Ave: 15

Sciaenidae

Nibea albiflora

3

Total: 17.04

3.5

Not listed

Ave: 5.68

Table 7 Results of demersal fish survey

Diversity of terrestrial animals

Cat Ba National Park is tropical moist forest on limestone, which harbors a number of endemic and rare species, foremost of which is the endemic Cat Ba Langur Trachypithecus poliocephalus poliocephalus.9‒11 These led to the discovery of new species of Goniurosaurus12 (Figure 8) and Sphenomorphus.13 Among the 40 reptile species recorded from Cat Ba Island, two species are listed in the IUCN Red List (2008), seven species are listed in the Vietnam Red Data Book,14 four in the CITES appendices (2008), and five species are protected by governmental law (Decree No. 32/2006/ND-CP) (Table 8).

Figure 8(1) Cuora mouhotii¬. (2) Acanthosaura lepidogaster. (3) Pseudocalotes brevipes. (4) Goniurosaurus catbaensis. (5) Gekko gecko. (6) Gekko palmatus. (7) Hemidactylus frenatus. (8) H garnotii. (9) Eutropis multifasciatus. (10) Plestiodon quadrilineatus. (11) Scincella reevesii. (12) Sphenomorphus tonkinensis.12

Scientific name

IUCN

VNRB

CITES

Dec. 32

2008

2007

2008

2006

Physignathus cocincinus

 

VU

 

 

Gekko gecko

 

VU

 

 

[Varanus salvator]

 

EN

II

IIB

[Python molurus]

LR/nt

CR

I

IIB

Coelognathus radiatus

 

EN

 

IIB

Ptyas korros

 

EN

 

 

Bungarus multicinctus

 

 

 

IIB

Naja atra

 

EN

II

IIB

Cuora mouhotii

EN

 

II

 

Table 8 List of threatened reptile species recorded from Cat Ba Island13

Notes: IUCN: IUCN Red List, VNRB: Vietnam Red Data Book: CR: critically endangered, EN: endangered, VU: vulnerable, LR/nt: near threatened; CITES: I, II = Appendix I and II; Dec. 32: Governmental Decree No. 32/2006/ND-CP: IB = Group IB (prohibited exploitation and use for commercial purpose), IIB = Group IIB (limited exploitation and use for commercial purpose); []: Only photographic record or observation.

Conclusion

In this study, there are occurrences of three main key habitats: mangrove, coral reefs, and seaweeds/seagrass. These contribute for species diversity and abundance of the natural marine resources available for the local people to exploit. The distribution trends of the living resources are higher abundance in the near shore sites, lower abundance at the offshore sites. These may relate to the biological/physical driven factors such as the available of substrate/habitat, natural food resources or water current. The coastal sites provide the nursery grounds for the economic species where the mangrove forests remain as the shelters.

Acknowledgements

We would like to thank the National Hydro-meteorological Service (NHMS) for their assistance in the collection of topography map and data for this paper. We are thankful to the NHMS for this research opportunity and providing permission for using their facilities to perform the study.

Conflict of interest

The authors declare that there are no competing interests regarding the publication of this paper.

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