Climate change impact assessment on capture and culture of lobster in ninh hai district, ninh thuan province

MINISTRY OF EDUCATION AND TRANNING NHA TRANG UNIVERSITY --- NGUYEN HONG TRUONG CLIMATE CHANGE IMPACT ASSESSMENT ON CAPTURE AND CULTURE OF LOBSTER IN NINH HAI DISTRICT, NINH THUAN PROV

MINISTRY OF EDUCATION AND TRANNING

NHA TRANG UNIVERSITY

-

NGUYEN HONG TRUONG

CLIMATE CHANGE IMPACT ASSESSMENT ON CAPTURE AND CULTURE OF LOBSTER IN NINH HAI DISTRICT,

NINH THUAN PROVINCE

MASTER THESIS

KHANH HOA – 2017

MINISTRY OF EDUCATION AND TRANNING

NHA TRANG UNIVERSITY

-

NGUYEN HONG TRUONG

CLIMATE CHANGE IMPACT ASSESSMENT ON CAPTURE AND CULTURE OF LOBSTER IN NINH HAI DISTRICT,

NINH THUAN PROVINCE

MASTER THESIS

and Climate Change

Code:

Decision on establishing the

Suppervisors:

Prof AKHMAD FAUZI

Chairman:

Faculty of Graduate Studies:

KHANH HOA – 2017

iii

UNDERTAKING

I undertake that the thesis entitled: “Climate change impact assessment

on capture and culture of lobster in Ninh Hai district Ninh Thuan province”

is my own work The work has not been presented elsewhere for assessment

until the time this thesis is submitted

Nha Trang, date 2nd May, 2017 Nguyen Hong Truong

iv

ACKNOWLEDGMENTS

I want to express my sincere grateful to the following organizations and persons for their invaluable support, help and encouragement to me in conducting this study:

Marine Ecosystem based Management and Climate Change in Norhed program for giving me the opportunity to study and conduct this master thesis

on Marine Ecosystem based Management and Climate Change

I would like to express special appreciation to my supervisor, Assoc.Prof.PhD: Ngo Dang Nghia and Prof.PhD: Akhmad Fauzi who I have learned a lot from his guidance, useful advices and valuable comments throughout the study period

I would you like to thank Locals and Agencies in Ninh Thuan for their helps on collecting primary and secondary data

Finally, I would like to express my sincere gratitude to my small family (my wife, daughters), friends, classmates and colleagues for their love, encouragement and help

Nha Trang, date 2nd May, 2017

Nguyen Hong Truong

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LIST OF CONTENTS

UNDERTAKING iii

ACKNOWLEDGMENTS iv

LIST OF CONTENTS v

LIST OF SYMBOLS vii

LIST OF TABLES viii

LIST OF FIGURES ix

ABSTRACT xi

INTRODUCTION 1

CHAPTER 1: OVERVIEW 3

1.1 An overview of aquaculture and capture of lobster Ninh Thuan province 3

1.2 Role of capture and aquaculture of lobster in Ninh Thuan province 6

1.3 Equipment and tools 7

1.4 The main factors influence lobster development 11

1.4.1 Depth factor 11

1.4.2 Sea-bottom topography (Seabed structure): 12

1.4.3 Sea water temperature 13

1.4.4 Salinity factor: 14

1.4.5 Wild feed source 15

1.4.6 Storm 16

1.4.7 Wave level and wind 17

1.5 General of study area 18

1.5.1 Actual state of natural conditions 18

1.5.2 Actual state of Climate 19

1.5.3 Actual state of livelihood of local people 30

CHAPTER 2: RESEARCH METHODOLOGY AND DATA COLLECTION 32

2.1 Research targets and objectives 32

2.2.1 Research targets 32

2.2.2 Research objectives and scope of the research 32

2.1 Research methodology 33

2.2 Study area 34

2.3 Data collection 35

vi

2.3.1 Observation method, station's equipment and instrument and method of data

processing 35

2.3.2 Secondary data 39

2.4 Data analysis 39

2.4.1 Lobster aquaculture data 39

2.4.2 Climatic factors data 39

2.4.3 Data processing methods 40

CHAPTER 3: RESULTS AND DISCUSSIONS 41

3.1 Assessment of natural conditions and socio - economic in Ninh Thuan province 41

3.1.1 Assessment of natural conditions 41

3.1.2 Statistics of socio – economic conditions 41

3.1.3 Economic growth 42

3.1.4 People's literacy levels and education 42

3.2 Variations in capture and culture of lobster production 43

3.2.1 Variability in culture of lobster production 43

3.2.2 Climatic events 45

3.3 Relationship between climate events variations and annual quantity of lobster 46

3.3.1 Annual sea water temperature and quantity of lobster 46

3.3.2 Annual average salinity and quantity of lobster 49

3.3.3 Annual average sea level rise and quantity of lobster 51

3.4 Relationship between climatic events and annual average number of lobster captured per household 54

3.4.1 Annual sea water temperature and number of lobster caught 54

3.4.2 Annual average salinity and number of lobster caught 55

3.4.3 Annual average sea level rise and number of lobster caught 56

3.5 Discussions 57

CHAPTER 4: CONCLUSIONS AND SUGGESTIONS 60

4.1 Conclusions 60

4.2 Suggestions 61

REFERENCE 62

vii

LIST OF SYMBOLS

IPCC Intergovernmental Panel on Climate Change

SPSS Statistical Package for Social Sciences

viii

LIST OF TABLES

Table 1.1: Annual average sea water temperature 13

Table 1.2: Annual average sea water salinity 14

Table 1.3: Annual average air temperature in Ninh Thuan 20

Table 1.4: Fluctuation of precipitation in Ninh Thuan province 21

Table 1.5: Annual average relative humidity in Ninh Thuan province 24

Table 1.6: Number of storm effect on in Ninh Thuan province 25

Table 1.7: Frequency of prevailing wind directions in Ninh Thuan province 27

Table 1.8: Mean monthly wind speed in Ninh Thuan province 29

Table 1.9: Mean speed of major wind directions in different months 29

Table 1.10: Maximum speed of major wind directions in different months 29

Table 2.1: Location of stations in Ninh Thuan provinve 35

Table 2.2: Observation equipment of stations 38

Table 3.1: Population situation in Ninh Thuan province and Ninh Hai district, 2015 41

Table 3.2: Labor situation in Viet Nam and Ninh Thuan province 42

Table 3.3: Gross domestic product ( GDP) in Ninh Thuan province, 2015 42

Table 3.4: Statistics education level of lobster farmer 43

Table 3.5: Total lobster production in Ninh Thuan province 44

Table 3.6: Total lobster capture in Ninh Thuan province 44

Table 3.7: Environment factors in Ninh Hai, Ninh Thuan province 46

Table 3.8: Total number of lobster aquaculture in Ninh Hai district 54

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LIST OF FIGURES

Figure 1.1: Catching lobster by gillnet (Binh Son, Ninh Hai district) 7

Figure 1.2: Catching lobster by diving (Source: Tan,2013) 8

Figure 1.3: Catching lobster by trap (Source: Tan, 2013) 9

Figure 1 4: Aquaculture by floating cage 10

Figure 1 5: Aquaculture by dimension of fixed cage 10

Figure 1.6: Aquaculture by submerged cage 11

Figure 1.7: The depth of seafloor at sea area in Ninh Thuan province 12

Figure 1.8: Average sea water temperature in Ninh Thuan province 14

Figure 1.9: Average sea water salinity in Ninh Thuan province 15

Figure 1.10: Wave level map at East sea in December 17

Figure 1.11: Wave level map at Southwest sea in August 18

Figure 1.12: Annual average air temperature in Ninh Thuan province 20

Figure 1.13: Annual rainfall, dry season and rainy season in Ninh Thuan 22

Figure 1.14: Annual average relative humidity in Ninh Thuan province 24

Figure 1.15: Frequency of Annual wind speed in Ninh Thuan province 28

Figure 2.1: Commodity lobster aquaculture activities in Vinh Hy bay 33

Figure 2.2: Research content block diagram 34

Figure 2.3: Topography and study area map in Ninh Thuan province 35

Figure 2.4: Map of Net work Hydro-Meteorological in Ninh Thuan 36

Figure 2.5: Observer implemented observations in Phan Rang station 37

Figure 2.6: Observer implemented observations at 7 am, Tri Thuy station 38

Figure 3.1: Fluctuation in lobster production in study area in recent 16 years 44

Figure 3.2: Fluctuation in number of lobster per household in study area 45

Figure 3.3: Variations in Sea water temperature 47

Figure 3.4: Correlation between SWT and lobster production 48

Figure 3.5: Fluctuations of both lobster quantity and sea water temperature 48

Figure 3.6: Variations in salinity in study area during 2000 to 2015 49

Figure 3.7: Fluctuations of both lobster quantity and salinity in study area 50

x

Figure 3.8: Correlation between lobster quantity and Salinity 50

Figure 3.9: Changes in sea level in study area during period 2000 to 2015 51

Figure 3.10: Fluctuations of lobster quantity and SLR 52

Figure 3.10: Correlation between lobster quantity and SLR 52

Figure 3.12: Average sea level rise and salinity in study area during 53

Figure 3.12: Correlation between salinity and sea level rise during study period 54

Figure 3.14: Average sea water temperature and lobster caught 55

Figure 3.15: Correlation between Annual SWT and number of lobster caught 55

Figure 3.17: Correlation between annual salinity and lobster caught 56

Figure 3.18: Annual average sea level rise and number of lobster caught 57

Figure 3.19: Correlation between annual average sea level rise and number of lobster caught 57

Developing from 1995s, lobster farming generates super profit and high internal rate of return in investment As a small lobster culture region of Ninh Thuan province, lobster farming career in Vinh Hy bay used to create a number

of jobs for not only farmers, but also for fishers and other locals related to this farming In recent years, after the disease outbreak occurred in 2006 and the storm happened in 2010, there is a phenomenon that farmers in Vinh Hy bay limit their cages for lobster culturing and transform gradually to culture marine finfish and other jobs

By a SPSS statistic analysis model, the role of parameters such as climatic parameters, lobster production, number of lobster capture per household, culture time, number of cages, etc

Salinity affected of lobster production and number of lobster captured with high correlation coefficients (r = 0.674; p=0.05) For suggestion to farmers should rational exploitation and structure of sustainable lobster farming in context to respond with climate change in Ninh Hai district

The statistical and analysis method are employed for the analysis climatic factors to find out what factors influence on aquaculture and captured of lobsters

in Ninh Hai district We demonstrate that aquaculture and capture of lobster has been both positively and negative influencing on economic well-being of the people community, but negatively impacted climate change recently years

Key words: Climate change, lobster production, cage lobster, diving, Sea

level rise, salinity, Sea water temperature, extreme events, Vinh Hy bay

1

INTRODUCTION

Climate change is globally considered to be a serious threat, especially for populattion in coast areas of Viet Nam The coast is one of themost vulnerable areas to potential impacts of climate change, particularly because of anticipated future sea-level rise (Wong et al., 2014) The coastal zone is an important natural resource system, which provides space, as well as living and non- living resources for human activities

The human living near the coast is advantageous for aquaculture and fisheries, especialy culture and capture of lobster activities in Ninh Hai district impacts which are exacerbated by climate change, with elevated water levels becoming more frequent and severe due to intensively aggregated human activities There is a need, there- fore, to assess to impacts of climate change on culture lobster and wild caught lobster

With a coastline of 3,260 km and an Exclusive Economic Zone (EEZ) of more than one million km2, Viet Nam has great potential for aquaculture and fisheries development In 2010, the total annual seafood production was 5.2 million tonnes wet weight, of which 2.5 million tonnes were from the marine capture fisheries and 2.7 million tonnes from aquaculture (Nguyen Minh Duc 2011) Even though the Vietnamese authorities built plans to develop the marine fisheries, catches landed today may be close to the maximum sustainable yield (Ministry of Agriculture and rural development, 2005) Therefore, the future growth of the seafood industry must rely on the development of aquaculture The objective of the Vietnamese national plan is to produce 2 million tonnes of aquaculture seafood by 2020 (Ministry of Agriculture and rural development, 2014) The plan focuses particularly on developing aquaculture species with a high export value In addition to generating foreign exchange earnings, the aquaculture industry is of vital importance for the livelihood of the population in rural and coastal areas The development of coastal and marine farming is crucial to creating new jobs for fishers leaving the captured fisheries due to the over-exploitation of fish stocks

Many areas in the coastal zone of Vietnam are suitable for seacage culture, with more than 4,000 islands and many lagoons and bays giving

The main species cultured is Green lobster (Panulirus ornatus), Ornate

spiny lobster, among others such as Rock lobster (Panulirus Homarus) and

Red lobster (Panulirus Longipes) etc (Tuan et al 2000; Tuan and Mao 2004)

Lobster aquaculture production increased markedly between 1999 and 2006, and reached a peak of approximately 1,142 tonnes in 2006 However, due to ‘milky disease’ that appeared in late 2006, lobster production has since declined about

863 tonnes

CHAPTER 1: OVERVIEW 1.1 An overview of aquaculture and capture of lobster Ninh Thuan province

Global situation:

Growout lobster aquaculture on the world first appeared very early at North American, Australia, New Zealand and Southeast Asia, but its actual development started from 1984 to now In Australia, lobster source (natural capture and culture of lobster) is a very important fishery Lobster culture also bring significantly profits in New Zealand (Institute No3, 2015)

In countries of Southeast Asia, the lobster farm experiment have been established since 1970s untill 1990s the lobster farming was thrives in this

country Main lobster species as: Green lobster (Panulirus ormatus), Red lobster (Panulirus longipes) In Philippines, the lobster farm experiment have

been established since 1970s, but the first year of 1990s the growout lobster (commodity lobster culture) was thrives (Institute No3, 2015)

In Taiwan, seed of lobsters was conducted in the pond of 200 cubic metre (m3), average weight was 25grams/individual, lobster weight was 330grams, rate of survival was 80% after 6 months The food of lobster is crab, squip, abalone, mussel, etc (Institute No3, 2015)

Domestic situation:

Lobsers farming in Viet Nam began during the last 1980s The first year

of 1990s, some of fishermen of Viet Nam have preserved, upgraded small lobster to commodity lobster culture Although farming has just culture and accumulated experience, but the early result showed that Green lobster

(Panulirus Ornatus) and Rock lobster (Panulirus homarus) have good

growth and thrive in the captivity and this profession has given substantial profits (Institute No3, 2015)

In the past, lobster farming mainly used lobster cages under bottom substrate fixed pin, focus culture at the shallow waters, 100 to 500 metres far

away from the shore Many problems such as algae, wastes, pollution, accumulation of feeds, etc have changed lobster pin cages by the floating cages

Profits from commodity lobster culture allows lobster farmers to invest more larger cages, with good and durable material

The process of traditional culture techniques has been applied to feeding lobster with fresh feed: low value fish, snail, molluscs, crustaceans and feed conversion ratio (FCR) often exceeds 20 showing a large amount of organic material released into the aquatic animal Besides, appeared more and various diseases with affected survival rate, growth and quality produce Dangers still exist and lobster farming still suffer problems of diseases, especially as milk disease in 2006, reduced lobster significantly, less than 1,000 tonnes in season

Nowadays, juvenile lobster resource which provides commodity lobster still depend on natural exploitation High profits brought from juvenile lobster

so farmers captured frequently, continuoul and this caused negative impacts on the quality of inshore water sources Effect other breed aquatic species, especially breed lobster production Besides, used equipment, rudimentary tools, small size to brought danger exhausted breed lobster resouses in the future

Grow seedling:

Collected or direct selling for commodity lobster culture, some farmers sell grow seedlings in province or other localities In recently, the province has ten household specialized grow seedling in My Tan, My Hiep village, Thanh Hai commune with approximately 300 cages and 30 household grow seedling

by commodity lobster produce cages The main season of grow seedling lobster capture was from December to April next year The grow seedling scale depend on size of cages but range from 500 to 600 individuals/cage

After grow seedling, the seed lobsters sold for culture households at localities and Khanh Hoa, Phu Yen, Binh Dinh and Quang Ngai province

Commodity lobster:

Lobster culture activities in Ninh Thuan region appeared for long time and focus on two main culture areas, such as: Phan Rang Bay, Vinh Hy Bay Species popular is Rock lobster, Green lobster and Red lobster; mainly cultured by water cages with side 3 x 4 x 4metres, make up a raft floating on the water with each raft has from 12 to 30 cages

Feeds used in commodity lobster culture activities is fresh food, wastes accumulate bottom substrate has been showed sign of organic pollution in the culture area for long time For example, by 2008, this region has only 60 cages

of lobster culture At this time, several farming households began to experiment commodity lobster culture in Phan Rang bay

After the effectiveness of lobster culture period, so lobster farming has gradually extended the scale with relatively large number of lobster cages When commodity lobster farm development has brought about some action development, other service such as net cages, jobs, increased incomes and improved livelihoods for coastal communities in Ninh Hai district

Ninh Thuan has more than 450 facilities to seed lobster and approximately 70 facilities to seed snail In recent years, the situation of these

breeding objects has become more difficutly and unstable Therefore, requiring another object of contributing to the diversity of commodity species as well as the economic development in Ninh Thuan province is required (Institute No3, 2015)

Besides, Ninh Thuan is one of the province has relatively large natural resource exploitation of lobster annual production of 300,000 to 500,000

units/year, mostly rock lobster (Panulirus homarus) But natural lobster

resource exploitation sharply decrease since 2014 to now (2015)

1.2 Role of capture and aquaculture of lobster in Ninh Thuan province

Describe the potential location for developing culture and capture of lobster in recent decade

Since 1995, in Ninh Thuan, commodity lobster has been cultured in Vinh Hy Bay region (Vinh Hai - Ninh Hai district) bring high economic efficiency In 2008, the number of cages have 300 cages at Vinh Hy Bay, but now reduce only to 60 cages The period of year 2010 - 2012, lobster activities have been increased again, however, until early 2013 reduced the number of cages compared to 2012

The reason is that farmer used fresh food sources should environment culture areas in sea region of Vinh Hy Bay, Mi Tuong village and Binh Tien caused heavily pollutions Specifically, date: from 5 to 7, May 2012, the lobster appear some illness and milk disease caused heavy damage to the lobster farmers

Ninh Thuan is one of the localities with favorable conditions for the development of aquaculture breed production Ninh Thuan province has always been one of the leaders in terms of yield and quality of brackish water shrimp (prawn, white shrimp) of the country with over breed production 450 facility

Ninh Thuan is also one of the provinces with the seed lobster resource exploitation annual natural relatively large (over 500,000 units/year), which is largely green lobster Ninh Thuan has also grow seedling vocational formation

served commodity lobster culture, but only in the feed form by cage sinking in waters close to the wind, rate of survival low, advantages time for this vocational activities in the short and occur diseases is also very large (Institute No3, 2015)

1.3 Equipment and tools

Catching by gillnet:

The fishing gear is seine net with 5 mm mesh size (2a = 5 mm) The size

of the seine nets depends on exploitation scale of the fishermen, but typically the net length varies from 100 metres to 150 metres, with a 4 – 6 metres height Netting operation is conducted during night time with a 1000 - 2000 W fluorescent light placed at the entrance of the seine net The net is released at around 8:00 pm and after 4 -5 hours (around 12:00 -1:00 am), it is hauled into the boat and puerulus lobster is gathered The net is then released again and collected around 4:00 am for the second harvesting

Figure 1.1: Catching lobster by gillnet (Binh Son, Ninh Hai district)

Netting operation terminates at around 5:00 am of the next day The size

of the collected puerulus are very similar They are about 7 - 8 mm in total length, are transparent and weigh about 0.25 - 0.35 gram The surveyed data on catching by seine net at some of the bays and gulfs during three years in Ninh Thuan province showed that prejuvenile numbers have increased and green

lobster (Panulirus ornatus) is the dominant species of puerulus/prejuveniles of green lobster (Panulirus ornatus) caught

Catching by diving:

Diving to catch the prejuvenile is the most traditional method of collecting prejuvenile lobster by fishermen in central coastal Viet Nam This method results in larger juveniles being caught, from 12 - 15 mm carapace length and 7

- 9 grams body weight, and these have the best survival during culture However, the maximum catch is only 100 -150 prejuveniles for a boat with five divers for 10 days of operation during the main fishing season1

Figure 1.2: Catching lobster by diving (Source: Tan,2013)

Catching by trap:

Traps are often made of nets of about 60 cm in length and about 40 cm

in diameter Gap drilled coral is used for the trap, the size of the coral pieces used varies according to what coral is locally available

Most of the coral pieces are coral blocks of 2 - 5 kg in weight The surface holes are drilled at 10 -15 cm intervals and are 2 - 2.5 cm in diameter Wooden traps are drilled to make holes in the same way as those of the coral

1

Current Status and Exploitation of Wild Spiny Lobsters in Vietnamese Waters Nguyen Thi Bich Thuy and Nguyen Bich Ngoc, 2004.

ones In November every year, the time when lobster prejuveniles are expected

to be found, traps are set into water at a depth of about 4 - 5 metres

Figure 1.3: Catching lobster by trap (Source: Tan, 2013)

After 3 - 5 days of being placed, every morning fishermen collect the lobster pre-juveniles by shaking the traps so that the lobster fall into a ringnet Alternatively, in shallow water, the prejuveniles can be manually picked from the drilled holes

The collected prejuveniles vary from 7.5 - 10 mm in carapace length and 0.3-1gram in body weight During the peak collection period of January - February, as many as 50 - 200 individuals might be taken by one fisherman

Aquaculture by floating cage

The bag of the floating cage is normally supported by a frame with buoys and commonly located in waters with a depth of 10 - 20 metres Although the initial investment for this kind of cage is high because of the frame construction, the sustainability of these cages is high with the using time up to 6 - 10 years This lobster cage is popularly used in the Vinh Hy bay and Phan Rang Bay in Ninh Thuan Province ( see figure 1.4)

Figure 1.4: Aquaculture by floating cage Aquculture by Fexed cage

The framework is made of salt-resistant wood Wooden stakes with 10 -15 cm diameter and 4 - 5 metres length are embedded every 2 metres so as

to create a rectangular or square shape The bottom area of a farm is normally 10 - 20 metres square, but may be as large as 200 - 400 metres square The cage size also varies Each cage normally has a cover The cage may be on or off bottom A fixed off-bottom cage is about 0.5 metre above the seabed A fixed on- bottom cage is lined with a layer of sand This kind

of cage is suitable for sheltered bays and behind islands where there is shelter from big waves and typhoons This cage is no commonly used in the Vinh Hy bay in Ninh Thuan province ( see figure 1.5)

Figure 1.5: Aquaculture by dimension of fixed cage

Aquaculture by Submerged cage:

The framework is made of iron with a diameter of 15 - 16 mm The bottom shape is rectangular or square with an area normally between 1 and

16 metres square The height is 1.0 - 1.5 metres The cage has a cover and a feeding pipe This kind of cage is common for nursing juveniles in Mi Tuong village of Ninh Hai, Ninh Thuan province It is very flexible for moving from this area to another area when the storm or bad weather happened (see figure 1.6)

Figure 1.6: Aquaculture by submerged cage

The materials for making cages, such as wood, iron, net, etc., are available in Vietnam The marine cages are often of a small size suitable for

a family-scale operation That is why the number of cages has increased significantly in recent years While individual developments may have no significant impact on the environment or society A large number of developments, however, may have significant impacts on the wider social and economic environment, and on each other (Heen K & Le A T., 2007)

1.4 The main factors influence lobster development

1.4.1 Depth factor

The depth impact of the distribution of the wild lobster species

l At the juvenile stage of lobster, they distributed at a depth of 1 to 5 metres water, but at the adult stage of lobster, most of species of lobster distributed at depth of 5 to 100 metres water, particularly at depth of 180 to

400 metres water as lobster species

Research by authors show that, in the central coast of Viet Nam, Juvenile of lobsters caught in depth 0,5 to 5 metres water However, in the same area but different species lived in different depths For example: green lobster

(Panulirus ornatus), rock lobster (Panulirus homarus), red lobster (Panulirus

longipes) lived in depth of 4 - 6 metres water Therefore, when nursery lobters

should attention to the depth of the cage, usually 2 to 3 metres water

Adult stage of lobster distributed at the depth of 10 to 50 metres water, usually coaral reef, coastal areas and islands

1.4.2 Sea-bottom topography (Seabed structure):

See figure 1.8 show that Sea-bottom topography is one of the most

important environment factors which decide the distribution of the lobster, particularly juvenile stage of lobster Lobster often focused in the cave: rock, coral, mud, etc

Figure 1.7: The depth of seafloor at sea area in Ninh Thuan province

Particularly, green lobster (Panulirus ornatus), rock lobster (Panulirus homarus), red lobster (Panalirus longipes) and lotus lobster (Panulirus versicolor) often live in caves and caves rock small has flashlight Bamboo

lobster (Panulirus polyphagus) prefer to buried themselves under the sand so

species distributed in the seabed sand and pebbles with algae growth

1.4.3 Sea water temperature

The sea water temperature level is one of the most importance ecological parameters, decide the distribution seeds of lobster species The temperature is factor to direct impact of natural environmental temperature In summer, dry and drought climate, the atmosphere temperature is relatively high, a direct impact on sea water temperature In Winter, wet and rainy, the air temperature

is low than 1-2oC Results of monitoring the sea water temperature in the recorded and survey ranged from 27.1 - 29.8oC, average sea water temperature about 28.70C ( see Table 1.1) ( Kevin C Williams, 2009)

Generally, sea water temperature maintained ranges from 27 - 29oC suitable for the growth and development of lobster However when sea water temperature has increased from 29.5 - 30oC, lobster has an expression to decreased prey Sea water temperature suitable for the growth and development

of lobster is in the range of 25 - 300C, however, prolonged rising temperatures may be cause disease outbreaks (According to Booth, J.D Kenway, M (2002)

Table 1.1: Annual average sea water temperature

Unit: 0C Factors 1 2 3 4 5 6 7 8 9 10 11 12

TMean 27.1 27.3 28.0 29.2 29.8 29.6 29.1 29.0 29.1 29.1 28.9 28.1

TMax 30.8 30.3 31.3 32.4 32.5 32.2 32.0 31.2 32.0 33.0 31.4 31.0

TMin 24.3 25.2 25.8 25.0 26.6 25.3 26.7 26.8 27.0 26.5 25.7 22.9 (Source: Central Region South HydroMeteorological station, 2016)

Figure 1.8: Average sea water temperature in Ninh Thuan province

1.4.4 Salinity factor:

Salinity is one of the factor impacted on the lives of lobsters, particularly juveniles of lobster (seeTable 1.2)

The Salinity recorded ranged from 31 - 35 ‰ (mean: 33.7‰) According

to surveyed data, the sea area in central Vietnam showed that adult lobsters are living at the depth of 10 meters offshore waters, salinity ranges fluctuated from

30 - 35‰ Therefore, the salinity conditions in sea region of Ninh Thuan province fixed on the threshold of growth and development of lobster

Table 1.2: Annual average sea water salinity

Unit: Parts per thousand

Mean 30.8 30.5 30.7 28.2 30.5 30.5 30.6 30.3 29.5 29.1 28.6 29.8 Max 33.5 33.6 33.6 33.6 33.9 33.8 34.2 33.9 33.8 33.5 33.5 33.5 Min 25.2 23.7 23.2 18.5 26.8 25.2 25.5 25.6 25.6 24.5 25.6 25.6 (Source: Central Region South HydroMeteorological station, 2016)

Figure 1.9: Average sea water salinity in Ninh Thuan province

The survey data show that salinity ranges around 33 - 34 parts per thousand, in summer salinity of 33.6 - 34.2 parts per thousand and 33.5 - 33.8 parts per thousand in winter The salinity sudden change from 5 to 15 parts per thousand, so juveniles of lobster will catch bait decreased from 30 - 90%, when the salinity reduced to 20 - 25 parts per thousand and prolonged 3 to 5 days would cause status of the juveniles lobster die slowly (Kevin C.Williams, 2004)

Lobster species were affected catch bait activities by the salinity water, ability to regulate the osmotic pressure of the juvenile lobster, from which the adverse change or extend the time molting or death of us

1.4.5 Wild feed source

Lobsters are seen as of general predators main lived in bottom organism marine systems They catch bait with abundant food on the reefs areas at night and direct impact on general structure of ecosystem or ecological region, including species composition and abudence of organisms is their bait (prey)

In our country, the study of authors showed that animals and plants composition often seen at lobster distribution areas, include: the animal of small crustaceans (shrimp, crab), mollusk (clams, mussels, snails), sea stars, seaweed, moss, etc

1.4.6 Storm

Storm season in Ninh Thuan is almost simultaneous with rainy season, from September to the end of December During these months, most storms and tropical depressions directly affect Ninh Thuan region occur (about 9 storms or tropical depressions for a cycle of 10 years)

Temperature and salinity caused by storms affect lobster activities Lobsters are extremely tolerant of abrupt temperature changes and within certain ranges can survive rapid increases of 18°C and decreases of 20°C However, smaller temperature changes may be important environmental cues that trigger certain behavioral and/or physiological responses (McCleese & Wilder 1958), including the well-documented seasonal migrations of lobsters (Kanciruk & Herrnkind 1978) In contrast, the low salinities which resulted from the hurricane were potentially lethal in some areas and it is likely that lobsters either moved to deeper, more coastal waters where the salinity was higher, or died Although we have no mortality data, we believe that it is likely that some lobsters, particularly those near molting which extends from September through December in this area, died as a result of the storm The observed general downstream movements of lobsters provides evidence that at least some individuals attempted to avoid the low salinities resulting from the storm This is consistent with our laboratory studies showing that lobsters actively avoid low salinity water before it reaches levels that are potentially lethal (Steven H Jury etc, 1995)

The effect of environmental disturbance caused by storms may be more pertinent to the life history of estuarine and coastal in tropical In the Ninh Hai district the average precipitation was 1039 mm (Central Region South HydroMeteorological station, 2016)

However, in this 10 year span there were 5 instances when the precipitation

in any one winter month was more 120 mm During these months the salinity in the Ninh Hai district estuary reduced significantly and may have triggered movement similar to those reported in this study Thus, these relatively

common environmental disturbances are likely to have both a short-time and long-term impact on the distribution and/or recruitment of estuarine and nearshore and they should be considered more thoroughly in future studies (Central Region South HydroMeteorological station, 2016)

1.4.7 Wave level and wind

Wave level and wind are main factors impact of farming activities causing break the cage, loss of revenue, damage to farmers and fishermen

Analysis result of height wave map and real wind data of 4 stations, including: Truong Sa, Phu Quy, Quy Nhon, Phan Rang We can give several remarks:

- In Winter monsoon (Northeast season), The north and northeast wave often occurred in September, October, November, December, January, February These months of winter, coastal region of South central province often better shielded, large waves rarely affected inshore area This period is very convenient (advantage) for culture and capture of lobsters in Ninh Thuan province (see Figure 1.11)

Figure 1.10: Wave level map at East sea in December

- In Summer monsoon (Southwest season), The south and southwest wave often occurred on May to August, the period southwest wind increased strongly causing break the cage, loss of revenue, effect to livelihood of local peoples (see Figure 1.12)

Figure 1.11: Wave level map at Southwest sea in August

1.5 General of study area

1.5.1 Actual state of natural conditions

Ninh Thuan is coastal provice in South Central Region; Ninh Thuan’s topography is the followed from West to East, from North to South The latitude prolonged from 11018’14"N to 12009’15"N and longitude prolonged from 108009’08" E to 109014’25" E, with a coastalline about 105 km length The sea area and the territorial waters in Ninh Thuan are 18,000 km2 large

Topography of Ninh Thuan is very diverse and complex, the province has territorial mountainous, midland and coastal delta

The high of topography mountainous account for 60% total natural area, with elevation prolonged from rezo to 1000 metres height (compare with above sea water level) In this region, Chon mount has the highest point about 1978 metres height in Phuoc Binh commune, the Ca Na mount has 1528 metres height and Nui Chua mount has 1040 metres height ( Ninh Hai district)

The midland area, the total natural area account for 20% These small hilly

is mixed with flat areas, natural ground level from 30 to 200 metres height

The coastal area, the total natural area account for 20%, main distributed along river downstream of Cai river and Lu river This area is a relatively flat area, flat of concentration, natural ground level from 30 to 200 metres height

1.5.2 Actual state of Climate

a) Thermal Regime and Air Temperature:

The thermal regime varies temporally with following temperature characteristics Day circulation of direct radiation intensity is as following: at night, direct radiation intensity is zero; the intensity is gradually increasing from early morning, reaching its maximum at noon, then decreasing gradually

in the afternoon Therefore, generally, the minimum temperature is recorded at the end of night or at early morning (from 5 am to 7 am); the maximum is recorded after noon (from 1 pm to 3 pm) The thermal regime also varies according to environmental differences, especially between sea and land, delta and mountainous areas Based on data of the days with extreme temperature values, we can see that: sea area is airy with moderate temperature, which is less affected by dry and hot Western wind than is the inland area Day temperature amplitude (the gap between the maximum temperature and the minimum temperature of the day) in Ninh Thuan is big (more than 6oC), so it is classified as tropical climate

Air temperature: The mean air temperature: Annually, mean monthly air temperature reaches its maximum in May or June and its minimum in December or January Annual air temperature reaches about 27 oC and tends to decrease from East to West The gap in mean air temperatures between the hotexperiment month the coldest month in Ninh Thuan is only from 4.0 – 4.1oC; it fits with a criterium of tropical climate (below 6oC) The absolute maximum air temperature usually occurs in May or June The absolute maximum air temperature recorded in Ninh Thuan is 40.5 oC at Nha Ho Meteorological Station on 6th June 1983; 39.40C at Phan Rang on 23rd May

1998 The abslolute minimum temperature recorded in Ninh Thuan is 16.1 oC

at Phan Rang Meteorological Station on 25th December 1999 Hot season in low areas: If hot season is defined by the time with mean daily temperature stable and above 25oC and the cold season is the time with the stable mean

daily temperature of below 20oC and the cool season the time between the two formers, the hot season in Ninh Thuan lasts more than 11 months and the cool season contains the small number of rest days; the cold season does not appears

at all (see Table 1.3)

Table 1.3: Annual average air temperature in Ninh Thuan

Unit: 0C Month

T Mean 24.8 25.5 26.6 28.1 28.7 28.9 28.6 28.5 27.8 26.9 26.2 25.2

TMax 33.1 33.8 35.7 37.4 39.4 38.8 37.6 38.6 37.0 34.7 33.9 32.7

T Min 17.0 17.8 18.1 21.0 22.1 22.6 23.2 17.5 22.0 21.0 17.8 16.1 (Source: Central Region South HydroMeteorological station,2016)

In dry season In Rainy season Annual air temperature

Figure 1.12: Annual average air temperature in Ninh Thuan province

b) Rain Regime: during the rainy season and summer

Rain characteristics are indicators of unstability of monsoon weather Usually, rain occurs when there is dynamical oscillation in wind season regime caused by convergence zone, trough and depression etc

However, the characteristics depends greatly on features of rain (medium rain on large scale or light rain; long time or short time rain) and the time of rain period; these features determine the effectiveness of rain for production and living For example, a rain spell without large rainfall but with high intensity may still cause flood and inundation; the same rainfall at the time of late dry season floods will impose quite different effects compared to that occurs in rainy season

In Summer (Dry season) in Ninh Thuan usually lasts from January to the middle of September annually However, dry season comes earlier and ends later compared to many years average in some years due to the effect of climate change (Typically, in 2004, the dry season ended in December) The rainfall in dry season accounts for about 30% to 40% of total annual rainfall

Table 1.4: Fluctuation of precipitation in Ninh Thuan province

Annual rainfall Precipitation in dry season Precipitation in rainy season

Figure 1.13: Annual rainfall, dry season and rainy season in Ninh Thuan

Frequencies of months with minimum rainfall: Months with minimum rainfall are the three beginning months of dry season (from January to March) However, the monthly minimum rainfall may occur in any months of dry season, even in rainy season

Rainy season in Ninh Thuan usually lasts from September to the middle

of December The rainy season includes consecutive months with monthly rainfall accounting for 8.3% of annual rainfall and with frequency of equal or more than 50% The rainy season in Ninh Thuan varies at different regions For the whole province, rainy season is defined to last from September to December (when there is rainfall of at least 100 mm) The rest time of year is dry season

The maximum daily rainfall does not necessarily occur in the location with maximum annual rainfall Statistics show that, the maximum daily rainfall

in Nha Ho is 323.2 mm which is greater than that in Tan My (236 mm); while the maximum annual rainfall in Tan My is greater than that in Nha Ho In addition, the maximum daily rainfall of a year does not necessarily to occur in rainy season In Ba Thap, the maximum daily rainfall in a data string occured

in dry season

The percentage of rainy season rainfall in total annual rainfall at different locations in Ninh Thuan is approximately 60 - 70% and decreases from East to West The decrease is caused by that in higher mountainous areas, the rainfall in dry season is bigger than that in delta region and rainy season lasts longer and moves toward summer months

Frequency of months with maximum rainfall: Months with maximum rainfall usually belong to rainy season, especially September, October and November However, they may be in dry season, then causing floods in dry season (late-dry-season floods occur in May and June annually)

Mean of raining days: The number of raining days is the number of the days with recorded rainfall of at least 0.1mm In Ninh Thuan, annual mean of raining days, according to recorded data, is from 41 to 94 days of which the raining days in rainy season are from 28 to 55 days

Late-dry-season rain: In Ninh Thuan, as well as other Southern Central provinces, in middle months of dry season, there are usually heavy rain-spells called dry season rain The rainfall from such spells is precious water at the middle of dry time In some years, at some locations, the dry-season rain lasts till rainy season; in some other years there is no dry-season rain

The rainfall regime in this area is characterized by the monsoons of Asia It has two main seasons: summer (also known as the dry season) and the rainy season:

During the summer (dry season): Rainfall regime is mainly affected by the cold air alone from January to March every year From April to August, rainfall is mainly caused by the Southwest monsoon and the influence of topography, therefore, nightfall and night which often appears the heavy rainfalls and rainfall period usually lasts no more than 3 hours per day Rainfall during the summer (8 months) is only about 30 to 40% of the annual rainfall and the average number of rainy days is less than 10 days/month

During the rainy season: Rainfall regime is mainly affected by the weather patterns such as storm, tropical depression, reinforcing cool air, intertropical

convergence zone, etc that caused rainfall in Ninh Thuan area from September to December and rainfall period usually lasts from 1 to 3 days Rainfall during the rainy season was 60 to 70% of the annual rainfall and rainfall increases from plain area to mountainous area Number of rainy days in the months of the rainy season

is from 4 to 15 days/month

c) Relative humidity

Relative humidity: Beside variations among years, relative humidity varies in daily circulation and annual circulation Daily variation of humidity contrasts with that of temperature Relative humidity is high at night and reaches its maximum at early morning; it is low during daytime and reaches its minimum

at noon, the hotexperiment time of day Humidity varies seasonally and depends

on rainfall In rainy season, humidity is high and it is low in dry season

The mean relative humidity in Ninh Thuan in dry season is from 72 to 77%; in rainy season, it is from 79 to 80% (see Table 1.5)

Table 1.5: Annual average relative humidity in Ninh Thuan province

Figure 1.14: Annual average relative humidity in Ninh Thuan province

On average, annually, the days with relative humidity of less than 75% only accounts for 25%; however 75% of days are with humidity of from 75%

to 80%

Nonetheless, relative humidity does not completely reflect humidity condition; we use absolute minimum humidity to assess humidity potential d) Storm and Tropical depression

Storm and tropical depression are regulated by the same mechanism and cause the same effects They are formed by counter-clockwise whirling effect around a deep low-pressure center; the cyclones move from South China Sea

or Pacific Ocean to Ninh Thuan with strong wind, heavy rain and negative weather lasting for some days to about one week

The laws of storms in Ninh Thuan according to many-years statistics:

- Law of Season

Storm season in Ninh Thuan is almost simultaneous with rainy season, from September to the end of December During these months, most storms and tropical depressions directly affecting Ninh Thuan region occur (about 9 storms

or tropical depressions for a cycle of 10 years) However, there are some exceptions; for example, in March 2006, a tropical depression weakened to be a low area that hit Ninh Thuan and in March 1991 there was a storm hiting Binh Binh, another storm hit Khanh Hoa in February in 1982 ( see Table 1.6)

Table 1.6: Number of storm effect on in Ninh Thuan province

- Law of weather effect

Storm is a dangerous natural disaster due to its weather effects such as strong wind with changing directions, air pressure drop, storm surge and long lasting heavy rain

How serious the real effects are depends on topography

The frequency of storms making landfall in Ninh Thuan province is very little because this area is surrounded by high mountains Generally, active storms on the East Sea and when it goes around mainland, then they are often weakened into a low pressure area, therefore, they are low impact to works and property of people

In Ninh Thuan, the weather effects are weaker than those in other coastal provinces in Southern Central region, especially wind effect During all recorded storms, wind speed has not surpassed 35 m/s, much smaller than record wind speed of storms hiting Northern land (maximum wind speed in Hai Phong is 80 m/s) The reason is that storms hitting Ninh Thuan are all at the end of storm season so that they are weak (the storms are active at the recession time of summer monsoon)

Beside strong wind, storms usually cause long-lasting heavy rain When storms hit Ninh Thuan, they cause rainfall of more than 100mm, even more than 500mm, during 2 to 4 - 5 days That means the rain lasts long after the storms dissolve and leave a local low trench A record rainfall in 24 hours caused by storm in Ninh Thuan is 323.2 mm in Nha Ho (on 16th November, 1979); 365.8

mm on 13rd November 2003 in Quan The and 410.6 mm in Nhi Ha

Since all rivers and their tributaries originate from the east side of Truong Son range, and they are high sloping, storm rain usually cause flash floods in mountainous area

In downstream region, when floods are caused by storm rain come, they combine with high tides and block retreat ways to sea of water, triggering serious inundation