Fish and Fisheries. Ian Cowx Hull international Fisheries Institute

Transcription

1 BioRA Preparation Meeting PART I Office of the Secretariat in Vientiane March 2015 Fish and Fisheries Ian Cowx Hull international Fisheries Institute 1 Outline Characteristics of Mekong fish and fisheries Pressures acting on fisheries in Mekong Indicators 1

2 Characteristics of Mekong fish and fisheries Fisheries production based on household surveys (MRC 2007) Lower Mekong million tonnes Middle Mekong million tonnes Yield = million tonnes Upper Mekong 60,000 tonnes Protein source for 60 million people Plus 1.6 million tonnes from aquaculture mainly in the delta Source: MRC 2

3 Fish species diversity in the 6 main zones of the Mekong River HIGH MOUNTAINS LOW MOUNTAINS 151 species (12% endemics) PLATEAU 140 species (18% endemics) ISLANDS, WETLANDS 191 species (14% endemics) FLOODPLAINS 267 species (16% endemics) DELTA 328 species (11% endemics) Mekong River mainstream is characterized by a gradient of increasing species richness from the headwaters to the sea 484 species (6% endemics) Characteristics of the main fish groups Black fish- Floodplain resident fish, with limited lateral migrations from the river onto floodplains and no longitudinal migrations upstream and downstream. 13% of species richness 50% of capture 3

4 Characteristics of the main fish groups White fish, undertaking long distance migrations, in particularly between lower floodplains and the Mekong mainstream and its major tributaries. 37% of species richness 36% of capture Characteristics of the main fish groups Grey fish: ecologically intermediate between two previous groups, corresponds to fishes that do not spend the dry season in floodplain ponds, but do not undertake long distance migrations either. 50% of species richness 14% capture 4

5 Fisheries of the lower Mekong Basin Total first-sale value is US$7.0 billion per year Per capita consumption average is about 46 kg/person/year 200+ species; 30+ of high commercial importance More than 70% of total fish catch in the lower Mekong basin (about 1.3 million tonnes worth US$2.5 billion) dependent on long distance migrants Fish migrate all seasons of year Spawning migrations all year round Baird and Shoemaker

6 Inland production (tons) Production (tons) Aquaculture production (t x 1000) Smallscale tonguesole Goldfin Tinfoil Barb Spotted algae eater Jullien's Golden Carp Fisheries Baseline Conditions - shifting 200, , , , , ,000 80,000 60,000 40,000 20,000 0 Cà Mau Bạc Liêu Sóc Trăng Hậu Giang Cần Thơ Kiên Giang An Giang Đồng Tháp Vĩnh Long Trà Vinh Bến Tre Tiền Giang Long An Declining inland capture fisheries: Possible cause - disconnection of floodplain for rice production 2,500 2,000 1,500 1, Fish Shrimp Other aquatic species Pangasius - pond Growing aquaculture sector based on intensification 0 Pangasius - cage 6

7 Why so much fish in the Mekong? Ecosystem Productivity Sediment and nutrient loading Floodplains and wetlands Rice fields Large river and tributaries Small streams Multiple habitats Basin scale Fish diversity Hydrological stability FISH YIELD Tropical regime Exceptional abundance of Mekong fish explained by a combination of high fish biodiversity, high productivity linked to high sediment load and flooding Relationship between sediment and fisheries Dai fishery catch as a function of sediment inflow in the Tonle Sap Annual extent of turbidity concentration measured in the Mekong plume impact assessed by mechanistic association 7

8 Pressures on Mekong fish and fisheries Typical fishing pressure in Mekong River, Cambodia Pressures on fisheries in LMB Agricultural development - rice fields Alien species from aquaculture Intense fishing pressure Flood mitigation measures 8

9 Pressures continue. Mining Rubber plantation Gold, copper, tin and zinc mining in Northern Laos A rapid expansions of rubber cultivation in Laos Biggest potential threat is considered hydropower dams 9 planned dams on LMB (mainstream) two under construction. 23 existed dams (> 20 MW) on tributaries Many more tributary dams are projected or under construction Xayaburi (2012) Donsahong (2014) 9

10 It isn t just about damming rivers...! Floodplain & basin connectivity Every dot is a registered water control structure Loss of connectivity = loss of productivity in floodplain/riverine fisheries The MRC water structures map River-floodplain habitats - many dams already built in LMB Rivers fragmented and cut off from floodplains 10

11 Pesticides Fertilizers Impacts of dams Dam creates barrier Interrupts migratory pathways mitigate with fish passage facilities Disruption of downstream passage adults, eggs and larval stages Reduction in species diversity and abundance Problems due to: Loss of species migrating to spawning habitats Impoundment floods spawning and nursery areas Disruption of downstream flows Limited passage over dams, especially for larval stages Reduced flow through reservoirs -Impoundment acts as egg and larval sink Passage through turbines 11

12 Dai catch data ( ). Impact on fisheries Fisheries yield in lower Mekong to reduce fish yield between 25 and 60+% (especially Tonle Sap) Replace by stocking and aquaculture (is it appropriate) Rural livelihoods of 60 million people directly or indirectly affected. Sediment and nutrient delivery to delta areas reduced significantly unknown reduction in coastal fisheries Flooding and nutrient regime of rice production areas altered Fisheries Impacts of sediment reduction Reduced floodplain nutrient loading affecting primary, secondary, and fishery productivity Changes in coastal nutrient loading affecting primary, secondary, and fish productivity in and near plume Coastal erosion Dai catch (t) as a function of Tonle Sap sediment input (t) 35,000 30,000 25,000 20,000 15,000 10,000 5,000 y = x R² = ,000,000 4,000,000 6,000,000 8,000,000 10,000,000 From Koponen et al Mangin and Loisel 2012) 12

13 Indicators Overview Mainstream Hydropower Projects Other exogenous factors Changes in River Flows, Sediment Transport, and Water Quality Obstructions in Fish Migration Routes & Habitat Connectivity Changes in Fish Habitat Quality, Quantity, & Productivity Fish Abundance and Community Composition Yield and Consumption Social & Economic Impacts 13

14 Fisheries Impacts Fisheries Impacts Linkage Between Drivers and Impacts Drivers Causative Factors Components Variations in Seasonal Flows Flows Levels Velocities Inundation Depths Extent of Flooded Areas Timing Tonle Sap Flow Reversals Changes in Habitat Quantity Extent of Salinity Incursions Sediment Loads Channel Erosion Accretion Phosphorus Nitrogen Potassium Channel Morphology In Channel Feature Morphology River Bed Morphology Floodplain Sedimentation Coastal Sediment Plume Ecosystem Productivity Agricultural Productivity Changes in Habitat Quality Changes in Habitat Productivity Linkage Between Drivers and Impacts Drivers Causative Factors Components Changes in Habitat Quantity Habitat Connectivity Physical Barriers Changes in Habitat Quality Migration Routes Changes in Habitat Productivity 14

15 Assessment Indicators Analysis Indicator Fish Habitat Change in extent of habitat inundated and duration Measurement Comments Units Hectares & Connected habitats only number of Correlated with fish species abundance and days/weeks standing crop River flows volumes m 3 /s Correlated with fish yield and species composition Change in extent of salinity intrusion hectares Correlate with species diversity and catch Timing and duration of annual floods onset/offset times Timing and duration of low flow periods onset/offset times Relate to fishery practices and species catch composition Relate to fishery practices and species catch composition Extent of coastal mangrove area hectares Relate to fishery recruitment dynamics Changes in river sediment g/m 2 /day deposition Changes in nutrient loading mg/l Change in habitat inundation depths meters Extent of coastal sediment plume Relate to fisheries productivity Relate to coastal fisheries catches Assessment Indicators linked to fish guilds Analysis Indicator Measurement Units Comment Community Diversity analysis Capture fisheries number of species, diversity and richness indices Correlate with change in flooding extent, amplitude and timing Change in fish guild percent of total by composition weight and number Yield total tonnes Relate to hydrological variables Yield of economically important species tonnes Relate changes in exploitation patterns to hydrological change Relative abundance percent of total catch Determine change in contribution of migratory species and other species guilds Catch per unit effort kg/gear/day Relate change in exploitation patterns to hydrological change Aquaculture Extent of aquaculture hectares area per species group Production by tonnes aquaculture method Relate change in aquaculture production patterns to hydrological change 15

16 Any attempt to change or modify natural flow regimes will have not only negative impacts to Mekong fishery production but also on the livelihoods of people who depend on this resource for their living. what I do for science!!!! 16