Probable effects of Climate Change on Freshwater Aquaculture in Noakhali district.

Introduction:

Aquaculture, also known as aqua farming, is the farming of aquatic organisms such as fish, crustaceans, mollusks and aquatic plants. It has two types, freshwater aquaculture and salt-water aquaculture. Climate change is now widely recognized as the major environmental problem facing the globe.

Rainfall & Noakhali District

Climate change

Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors that include oceanic processes (such as oceanic circulation), biotic processes, variations in solar radiation received by Earth, plate tectonics and volcanic eruptions, and human-induced alterations of the natural world; these latter effects are currently causing global warming, and "climate change" is often used to describe human-specific impacts.

Freshwater Aquaculture

Aquaculture involves cultivating freshwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the harvesting of wild fish. Broadly speaking, finfish and shellfish fisheries can be conceptualized as akin to hunting and gathering while aquaculture is akin to agriculture.

Noakhali District

Noakhali District (CHITTAGONG division) with an area of 3600.99 sq km, is bounded by COMILLA district on the north, the Meghna estuary and the BAY OF BENGAL on the south, FENI and CHITTAGONG districts on the east, LAKSHMIPUR and BHOLA districts on the west. Annual average temperature: maximum 34.3°C, minimum 14.4°C; annual rainfall 3302 mm. Main rivers are Bamni and MEGHNA.

Noakhali (Town) Noakhali Sadar upazila town (Maijdi) consists of 9 wards and 36 mahallas. It has an area of 12.61 sq km. The town has a population of 74585; male 51.50%, female 48.50%; population density per sq km 5915. Literacy rate among the town people is 60.7%. The ancient name of Noakhali Sadar was Sudharam. In 1948 when the upazila headquarters were extinct by the erosion of the Meghna River, it was shifted 8 km to the north to its present place at Maijdi. The town has five dakbungalows.

Current climate condition in Noakhali:

Noakhali has a humid, warm, tropical climate as other place in Bangladesh, mostly alike the areas in coastal zone. Its climate is influenced primarily by monsoon and partly by pre-monsoon and post-monsoon circulations. The south-west monsoon originates over the Indian Ocean and carries warm, moist, and unstable air. The monsoon has its onset during the first week of June and ends in the first week of October, with some inter-annual variability in dates. Besides monsoon, the easterly trade winds are also active, providing warm and relatively drier circulation. In Bangladesh there are four prominent seasons, namely, winter (December to February), Pre-monsoon (March to May), Monsoon (June to early-October), Post-monsoon (late-October to November).  

The general characteristics of the seasons are as follows:  

• Winter is relatively cooler and drier, with the average temperature ranging from a minimum of 7.2 to 12.8°C to a maximum of 23.9 to 31.1°C. The minimum occasionally falls below 5oC in the north though frost is extremely rare. There is a south to north thermal gradient in winter mean temperature: generally the southern districts are 5oC warmer than the northern districts.

  

Figure 2 Temperature changes per degree C

•  Pre-monsoon is hot with an average maximum of 36.7°C, predominantly in the west for up to 10 days, very high rate of evaporation, and erratic but occasional heavy rainfall from March to June. In some places the temperature occasionally rises up to 40.6°C or more. The peak of the maximum temperatures are observed in April, the beginning of pre-monsoon season. In pre-monsoon season the mean temperature gradient is oriented in southwest to northeast direction with the warmer zone in the southwest and the cooler zone in the northeast. 

• Monsoon is both hot and humid, brings heavy torrential rainfall throughout the season. About four-fifths of the mean annual rainfall occurring during monsoon. The mean monsoon temperatures are higher in the western districts compared to that for the eastern districts. Warm conditions generally prevail throughout the season, although cooler days are also observed during and following heavy downpours. 

• Post-monsoon is a short-living season characterized by withdrawal of rainfall and gradual lowering of night-time minimum temperature. Probable effect of Climate Change on Freshwater Aquaculture: 

In this assignment, we will try to learn about the probable effect of climate change on freshwater aquaculture in Noakhali district.

Probable effects of Climate Change on Freshwater Aquaculture: 

Future effect of climate change on freshwater aquaculture in Noakhali will be so vulnerable. Some of probabilities are denote here:

 Fluctuation in Temperature:

1) Increasing temperature may create a problematic adaptation in native freshwater fish life cycle. (feeding, breeding, growth etc)

2) Increasing temperature may decrease the water level under soil lyre and made the irrigation system harder. 

3) Increasing temperature may degrade the soil quality & texture from fertile to dry or burn soil.

4) Increasing temperature can made some freshwater fish endangered and put them in venerable condition.  

5) Increasing temperature can make the aquaculture critical for available species in that environment.

6) Increasing temperature may reduce the activity of different medicine and antibiotics for freshwater aquaculture.

7) Increasing temperature may make the production of fish feed difficult and costly for farmers and industrialist also.

Sea level rising at Noakhali coastal zone

1) Sea level rising may submerge the shore area of Noakhali coastal area, specially the islands of Noakhali scatters in Bay of Bengal.

Figure 3 Flooded area of Noakhali in 1998

2) Sea level rising may increase the salinity of water and soil; make the fresh & clean drinking water extinct below normal availability level.

3) Sea level rising may enhance the occurrence of shore erosion by increasing tidal range & activity at inter tidal zone in the coastal area of Noakhali.

4) By rising salinity soil fertility will loss for normal agriculture and crop production as well as the production of fish feed.

5) Freshwater species cannot adapt with salt water so freshwater aquaculture will tough and venerable for this region in future.

6) Sea level raising will backflow Meghna the river water and increase the estuary and broadcast the higher salinity to lower salinity area and will pressed the freshwater species migrate to more northern area. As a result Noakhali will be emptied about freshwater fish species in future.

7) Sea level rising may also have a potentiality in increasing cyclones, flood etc natural disaster by decreasing coastal defense.

8) By raising sea level, loss of land and loss of marine and freshwater ecosystem may introduce in coastal area. 

For example, Water from lower aquifer in Noakhali is needed to be refined by chemical to remove salt and air oxidation for removing iron load in it. 

Rainfall & Noakhali District:

1) Modest rainfall seems in Noakhali district through the year but recently its reveled that rainy season is out of rainfall as previous.

2) Climate change may cause late or early rainfall in here.

3) Increasing temperature or sudden evaporation may causes heavy rainfall in anytime of the year in here due to the geographical position of Noakhali at coastal area.

4) Over rainfall may causes flood, water stagnancy, disease outbreak etc

5) Rainfall not in time may have a great impact on local crop production in Noakhali. 

6) It may also have a negative effect on freshwater aquaculture in here.

7) Seasonal fish species may late in their breeding time and fry production may decline.

8) Fish may also deny adapting themselves in this late rained environment and their growth may decline as well.

9) Rainfall irregularity may also make a non-suitable environment for the production of fish feed and also make rotten when in preservation.

10) Seasonal ponds and wetlands may not fulfill due to irregular and insufficient rainfall and aquaculture in there remain difficult and in some case it becomes impossible in here. 

11) Soli may get harden due to not raining and water level may decrease due to not sufficiently discharge by rain water. 

Natural Disaster & its impact on Freshwater Aquaculture in Noakhali

1) Due to Sandy clay soil type flood is not much effective in Noakhali but in 1998 some of its area chatkhil, Begumganj, Senbagh etc were flooded. At that time, vast aquaculture system was demolished and system loss at a time. So, huge money and resource loss were happened. 

2) At coastal zone, due to sea level rising, coastal defense system may breakdown and it is known well that there is no forest like sundarban in Shatkhira are here to protect Noakhali from cyclone and hurricanes. Thus aquaculture ot coastal area may decline as well.

3) Sudden evaporation may occur due to temperature rising in a place and make heavy rainfall and flood which is very venerable to freshwater aquaculture: 

Impacts of natural disaster in Freshwater Aquaculture:

1) Fish may escape the pond, wetland of cultivated area by flood.

2) Fish may get stressed and deny to take food.

3) Death of fish may increase due to outbreak of various diseases by mixing waste water through storming. 

4) Freshwater aquaculture infrastructures may demolish by heavy storm surge and also lost its durability.

5) Freshwater may get salted by flood or hurricanes from oceanic side and freshwater aquaculture may disrupted by this occurance. 

Mitigation Measurements

For reducing the future effect of climate change on freshwater aquaculture, we can follow this chart for better understanding:

By answering these questions, we may easily determine our duties for the mitigation of those venerable effects of climate changes on freshwater aquaculture in Noiakhali.

Although here is some efficient recommendations for this issue: 

1) We may produce adaptive and stress tolerable species of freshwater fish and broadcast them in Noakhali.

2) Tree plantation like mangrove forest, mainly at coastal area of Noakhali (chairman ghat, boyar char, at the bank of sandwip channel etc) can protect the access of natural resources and ecosystems also from natural disasters and predation.

3) Making extra water reservoir and apply wetland management at various important place of Noakhali.

4) Water refining plant and Deep-well water propagation may also solve the freshwater unavailability partially.

5) Well drainage system and non-blocking the natural flow of water or non-filling the natural water pond or wetlands in Noakhali for proper water circulation.

6) New invented or proposed sustainable technique for freshwater aquaculture should be tested and broadcast throughout every sector of Noakhali fish farmer community.

7) Moreover, Local government should aware and take steps according to world climate change summit in Copenhagen.  

Conclusion:

Future is unpredictable. But from the past climate analysis, we may get a partial scenario about probable effect of climate change on freshwater aquaculture in Noakhali. Whether, it needs more to get some concrete recommendations but till then we need some manageable steps and mitigation measures to initiate against negative impact of climate change and use the positive part of climate change for the betterment of freshwater aquaculture. All attached institutions and other governmental and nongovernmental organization should take appreciation and conduct a scientific study to determine the probable impacts of climate changes and its relevant measure for a better & sustainable freshwater aquaculture system in Noakhali.

References:

1) H. Neil , Climate change impacts on aquaculture and the use of GIS, Institute of Aquaculture, University of Stirling, UK.

2) K. Soheila Yazdi and B. Shakouri, The Effects of Climate Change on Aquaculture, International Journal of Environmental Science and Development, Vol.1, No.5, December 2010, ISSN: 2010-0264.

3) FAO, Climate Change For Fisheries And Aquaculture, Technical background document from the expert consultation held on 7 to 9 april 2008.

4) Banglapedia, Noakhali district section.