Climatic and anthropogenic factors changing spawning patternand production zone of Hilsa fishery in the Bay of Bengal

M. Shohidullah Miah n

College of Agricultural Sciences IUBAT—International University of Business Agriculture and Technology, 4 Embankment Drive Road,Uttara Model Town, Sector 10, Dhaka 1230, Bangladesh

a r t i c l e i n f o

Article history:Received 5 February 2014Received in revised form29 December 2014Accepted 14 January 2015Available online 30 January 2015

Keywords:Hilsa (Tenuolosa ilisha) spawningCatch per unit effort (CPUE)Maximum sustainable yield (Msy)Optimum yield per recruit (Y/R)Climate change

a b s t r a c t

Hilsa (Tenualosa ilisha Hamilton) as a single species accounts 12% for more than half of the total marinecatches. About 2% of the entire population of the country is directly or indirectly engaged with Hilsafishing. Hilsa has a wide geographical distribution in Asia from the Persian Gulf to the South China Sea.Particularly large stocks are found in Upper Bay of Bengal (BoB) region sustained by the large riversystems. The global Hilsa catch is reported 75% from Bangladesh water, 15% from Myanmar, 5% fromIndia and 5% from other countries such as Thailand and Iran. Hilsa is a highly migratory and anadromousfish with the same migratory and same breeding behavior as that of Atlantic Salmon fish (Salmo sp.). Dueto various anthropogenic activities, climate change effect, increased siltation and rising of the riverbasins, the migratory routes as well as spawning grounds of Hilsa are disturbed, displaced or evendestroyed. During last two decades hilsa production from inland water declined about 20%, whereasmarine water yield increased about 3 times. Major Hilsa to catch has been gradually shifted from inlandto marine water. Hilsa fish ascend for spawning migration from sea into estuaries. It has been found thatthe major spawning areas have been shifted to the lower estuarine regions of Hatia, Sandwip and Bhola.At the spawning ground of Hilsa, the fishing level F¼1.36 yr�1, where in the river Meghna theFmsy¼0.6 yr�1 and exploitation rate E¼0.70 is (Emsy40.5). Oceanographic changes viz. high turbidityincreased flooding, more tidal action and changes of salinity etc. have accelerated the change ofmigration patterns of spawning, growth and its production. Hilsa fecundity ranges from 1.5 to 2.0 millioneggs for fish ranging in length from 35 to 50 cm. Hilsa fecundity is declining in different areas due toclimate change and the declining fecundity impacting greatly on Hilsa production. Due to shifting of thespawning ground at the lower zone, the survival rate of juvenile Hilsa is seriously affected.

& 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1102. Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103. Environment of Bay of Bengal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1104. Fishing grounds in the Bay of Bengal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1115. Marine fish resources in the Bay of Bengal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1116. Hilsa is a major marine fish resource in the Bay of Bengal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1117. Spawning behavior of Hilsa fishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1128. Hilsa population characteristics at the spawning ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1129. Climate change impacts on reproductive behavior of Hilsa fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

10. Sea level raise and water temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11411. Adaptation to climate change and Hilsa fishing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11412. Traditional adaptation for Hilsa fishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Contents lists available at ScienceDirect

journal homepage: www.elsevier.com/locate/wace

Weather and Climate Extremes

http://dx.doi.org/10.1016/j.wace.2015.01.0012212-0947/& 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

n Tel.: þ880 1748190474.E-mail address: drshohidullah@iubat.edu

Weather and Climate Extremes 7 (2015) 109–115

13. Stock discrimination for sustainable management of Hilsa fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11414. Policy adaptation for marine fisheries development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11415. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

1. Introduction

Marine fisheries sector plays an important role in the economyof Bangladesh in terms of nutrition, income, employment andforeign exchange earnings. Marine fish production increased 1.12million tons (from 3.79 million tons to 4.87 million tons) from2001 to 2007, but per capita fish consumption decreased becauseof increase in population (Hussain and Hoq, 2010). The marinefisheries provide a livelihood for millions of people in the Bay ofBengal (BoB) region but the coral reefs are quite limited in the BoBdue to high river discharge and turbidity. Alteration of marineecosystem due to climate change has direct and indirect adverseeffect on fish flora for their reproduction, migration and survival.Reproduction of fish is regulated by various exogenous andendogenous conditions. The reproductive cycle is a harmoniousprocess interlinked with environmentally mediated routine ofvarious aquatic ecosystems. Therefore, any adverse environmentalconditions may affect the natural reproductive process of themarine fish population and ultimately hinder the recruitmentprocess to the stock through spawning and hampered the migra-tion process. The BoB is a world’s largest deltaic shape as shown inFig. 1.

The marine total catch contributes around 20% of fish produc-tion in Bangladesh. Hilsa (Tenualosa ilisha) as a single speciesaccounts for more than half of the total marine catches. Inquantitative terms, Hilsa catch is 12% of the total fish productionin Bangladesh and 2% of entire population engaged with thisfishery. The average annual production of Hilsa is around 2.4 mil-lion tons. Hilsa (Fig. 2) has a wide geographical distribution in Asiafrom the Persian Gulf to the South China Sea. Particularly large

stocks are found in Upper BoB region sustained by the large riversystems. At present 75% of the global Hilsa catch is reported fromBangladesh waters, 15% from Myanmar, 5% from India and 5% fromother countries such as Thailand, Iran, etc. This paper will predictthe further management strategy for obtaining the maximumsustainable catch of Hilsa from the BoB.

2. Methodology

This study was conducted using the information from differentscientific research and grey literature published in different formseither in peer reviewed journals or periodicals, news media andlocal traditions as well as from own research publications. Infor-mation was also collected visiting marine and fisheries researchinstitutes, Bangladesh Fisheries Development Corporation, Direc-torate of Fisheries and meteorological stations. Information wascollected directly from the stakeholders, administrative bodies,fishermen communities, Non-Government Organizations (NGOs),women and youth communities of the coastal region. Electronicmedia was also an important source for information.

3. Environment of Bay of Bengal

The sedimentation loads from rivers entering into the BoB haveincreased hundred times in the last century (SRDI, 1998). The largevolume of discharge of untreated industrial wastes, pesticideresidues and fertilizer leakages-all are dangerous to the marineenvironment. Destruction of marine habitats has also been causinggreat concern for the future of marine fisheries. Over exploitationof the marine living resources and the environmental impact onmariculture are the major concerns for sustainable management.Three of the main rivers of the subcontinent the Ganga, Brahma-putra and Meghna drain from vast areas of India, Bangladesh,Nepal and the Himalayas. These rivers and their tributariesconverge in Bangladesh, carrying approximately 85% of the totalwater volume which reaches the BoB from Bangladesh. Thisfreshwater runoff is a dominant feature that influences thedynamics of the coastal and marine environment. The dischargesshow distinct seasonal fluctuations. Freshwater runoff can reachup to 195,000 m/s in the monsoon period (Mahmood, 1994).Seasonal variation in precipitation and in the intensity and amountof discharge causes the flood flow in Bangladesh. Compared topast, the intensity of water flow has tremendously been reduced inBangladesh due to Farakka barrage. Thus the migration routes of

Fig. 1. The geographical location of the BoB (Mome and Arnason, 2007). Fig. 2. Anadromous Hilsha (Tenualosa ilisha) (Halder, 2005).

M. Shohidullah Miah / Weather and Climate Extremes 7 (2015) 109–115110

Hilsa in the river basin of Bangladesh have been affected seriouslyas the water-flow from India into Bangladesh has been reducedduring the dry summer.

4. Fishing grounds in the Bay of Bengal

In the BoB within the territorial waters of Bangladesh there arefour major fishing grounds which include: (i) South patches, (ii)South of south patches that lies between 201500N to 211400Nlatitude and 911000E to 911500E longitude covering an area ofabout 6200 km, (iii) The Middle Fishing Ground is situatedbetween 201500N to 211200N latitude and 901000E to 911000Elongitude that covers an area about 4600 km, (iv) Swatch of NoGround that lies between 211000N to 211210N latitude and 891000Eto 901000E longitude which covers an area of about 3800 km(Shahidullah, 1983) which shown in Fig. 3.

5. Marine fish resources in the Bay of Bengal

The marine capture fisheries are exploited under multi-speciesstrategy from the BoB and about 100 species are being exploited(White and Khan, 1985). The major species are finfish, shrimp,crabs, lobster, mollusks, starfish, cuttlefish, squid, snakes, turtles,crocodile and mammals (Khan, 2002; DOF, 2008). The most

abundant groups are catfishes (Ariidae) which account for11.99%, croakers (Sciaenidae) for 10.37% and threadfin bream(Nemipteridae) for 9% (Khan, 2002). The marine catch is subdividedinto industrial and artisanal fisheries. The industrial fishery is basedon trawl (shrimp trawl and fish trawl) fishery. Out of the total 127trawlers, 45 are shrimp trawlers and the remaining are finfishtrawlers DOF (Department of Fisheries) (2008). The fish species-wise catch production and % compositions are shown in Figs. 4 and 5.

The year-wise total catches production (MT) of fish from theBoB and the Catch per Unit Effort (CPUE) pattern are shown inFigs. 6 and 7, respectively.

The catch per unit effort (CPUE) is decreasing steadily and theCPUE has been decreased up to 50% and the biodiversity has alsobeen declined although the overall production has improved. Cur-rently 299 trawlers are licensed for fishing in the BoB for deep seafishing and the GoB has given license to 25 more trawlers for deepsea fishing (Bangladesh Newspaper, Daily Star, 30 July, 2013). The twoorganizations, the Bangladesh Fisheries Development Corporation(BFDC) and the Bangladesh Jatyo Matshyajibi Samabaya Samity(BJMSS) have started the process of mechanized fishing in the BoB.

6. Hilsa is a major marine fish resource in the Bay of Bengal

Average annual production of Hilsa is about 2.8 million tons.At present 75% of global Hilsa catch is reported from Bangladesh

Fig. 3. Fishing ground of marine fishes in the BoB (Mome and Arnason, 2007).

M. Shohidullah Miah / Weather and Climate Extremes 7 (2015) 109–115 111

waters, 15% from Myanmar, 5% from India about 5% from othercountries. Hilsa fishery plays an important role in Bangladeshsociety in terms of protein supply, employment generation andearning of foreign currency. Historically Hilsa used to migrate upto 110–150 km to the upper reaches of the main rivers ofBangladesh, India and Myanmar. Hilsa has a particular spawningground in the open water system in Bangladesh, where the adultHilsa return year after year for the spawning. Hilsa gets mature forspawning in a year. Due to high economic value, many fishermenare engaged with the Hilsa fishing but for getting sustainable Hilsaproduction, the fishing level should be reduced by 25% of theexisting fishing level (Amin, et al., 2002; Ahmed, 2007). There isvery limited information found on Hilsa fishery in Myanmar.Catching of Hilsa commences from the juvenile stage. The juvenileHilsa is caught by jagat-ber-jal (large beach seine net) and thecatch trends of juvenile Hilsa have increased significantly. Thenumber of fishing boats and gears has increased four times.Marine catch of Myanmar has also increased. The sex ratio ofmigrating Hilsa population was recorded from various landinglocations of Bangladesh such as Goalanda—male:female—1:0.45

(Upper stream); Chandpur—1:0.57 (Upper stream); Chittagong—1:1.4 (Lower stream) and Khulna—1:0.98 (Lower stream) (Miahet al., 1999). The data revealed that male Hilsa migrate more to theupper stream than the female Hilsa.

7. Spawning behavior of Hilsa fishes

Marine fish spawn in the area where salinity ranges between1 and 26% and stay for a few months and return to the sea duringmonsoon (Department of Fisheries (DoF), 2006). Juvenile ofmarine fishes migrate for feeding in the lower zone of estuariesduring monsoon period where as Hilsa breed at the upper reachesof the fresh waters. Hilsa fecundity ranges from 1.5 to 2.0 millioneggs for fish ranging in length from 35 to 50 cm. Hilsa fecundity isdeclining in different areas. This declining of fecundity has naturalimpact on Hilsa productivity. During breeding season plenty offully ripe and oozing male and female Hilsa were found and theirratio was 1: 1.6 at the spawning ground (Miah et al., 1999). About80% of the female fish were found ready for egg realizing conditionat the spawning ground. Major spawning is held during the fullmoon and new moon with high river flow the peak of spawningperiod in September and October (Miah, et. al., 1997). Due tovarious anthropogenic activities, climate change effect, increasedsiltation and rising of the river basins, the migratory routes as wellas spawning grounds of Hilsa are disturbed, displaced or evendestroyed. It has been found that the major spawning areas havebeen shifted to the lower estuarine regions of Hatia, Sandwip andBhola in Southern region of Bangladesh. Oceanographic changesviz. high turbidity, increased flooding, more tidal action andchanges of salinity, etc. have accelerated the change of migrationpatterns of spawning, growth and its production. Movementpattern of Hilsa are shown in Fig. 8.

8. Hilsa population characteristics at the spawning ground

The population characteristics of Hilsa at the spawning groundare as follows: asymptotic length Lα¼61.5 cm; asymptotic weightWα¼2.98 kg; curvature parameters¼0.35 yr�1; age at first cap-ture Tc¼1.7 yr (31 cm in length), Fishing level F¼1.36 yr�1(wherethe Fmsy¼0.6 yr�1) and exploitation rate E¼0.70 (Emsy40.5). Thedata on exploitation rate indicate that the Hilsa population is in

12.8

11.6

4.43.3

3

2.92.5

2.52.11.91.1

0.90.8

0.80.7

0.6

0.5

0.2

4.2

43.2

Croakers (12.8%) Cat fishes (11.6%) Threadfin (4.4%) Jack & Scads (3.3%)Goat fishes (3%) Lizard fishes (2.9%) Ribbon fishes (2.5%) Pony fishes (2.5%)Grunters (2.1%) Serdines (1.9%) Tunas (1.1%) Bullseyes (0.9%)Pomfrets (0.8%) Squid (0.8%) Anchovies (0.7%) Silverbiddies (0.6%)Bombayduck (0.5%) Snappers (0.2%) Skates, rays (4.2%) Hilsa plus others (43.2%)

Fig. 5. The percentage compositions of fishes in the Bay of Bengal (World Fish Center, Report, 2008).

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

CroakersCat fishesThreadfin

Jack, ScadsGoat fishes

Lizard fishesRibbon fishes

Pony fishesGruntersSerdines

TunasBullseyesPomfrets

SquidAnchovies

SilverbiddiesBombayduck

SnappersSkates, rays

Hilsa plus others

20,67018,729

7,1175,0394,8114,6634,0433,9983,4153,109

1,8361,4331,3481,2961,082959783356

6,71469,679

Production in (t)

Fig. 4. The fish species-wise catch production (World Fish Center, Report, 2008).

M. Shohidullah Miah / Weather and Climate Extremes 7 (2015) 109–115112

over exploitation level and the fishing level is double than the Fmsy

at the spawning ground (Miah et al., 1999, 1997, 1998). Therefore,in the long run the Hilsa population will affect the maximumsustainable yield (MSY) from the BoB. It migrates from the BoB toupstream rivers: the Ganges (Padma), Meghna and other rivers ofthe country for breeding; they grow in the fresh water and returnback to the BoB. Hilsa breeds throughout the year but the peak isfrom September to October. Hilsa matured at one year of age. Fishspawned throughout the country year round in low or zero salinitywaters. There were two periods of more intense spawning thatcoincided with the main monsoon (July–November) and thespring warming (February–May). Spawning occurred in coastalareas and in the northern Bay of Bengal during the monsoonseason when river flow was greatest. Fish fecundity was high(800,000–1 Millions eggs) but declining in many areas. Thisreduction in fecundity was shown to be impacting on hilsaproductivity.

The data also reveal that the catch per unit effort (CPUE) hasbeen reduced significantly in the recent years. Thus, the liveli-hoods of the fishermen have been affected seriously. The fisher-men harvest Hilsa by using the traditional small mechanized andnon-mechanized boats with the net called Chandijal (drift gill net)or Konajal (modified dyke-net) which resulted in declining CPUE.Since the Hilsa of Bangladesh, India and Myanmar belong to the

same stock, for its conservation and maximum sustainable yield(MSY), better understanding of the population dynamics areneeded through stock assessment, maintaining an optimum fish-ing level (Fmsy), optimum yield per recruit (Y/R) pattern, higheststeady yield year after year. The DOF of Bangladesh, Fisheriesdepartment of India and Myanmar are jointly working for themanagement of the fishery.

9. Climate change impacts on reproductive behavior of Hilsafish

Climate change has direct and indirect adverse effect on theirreproduction, migration and survival. Reproduction in fish, as oneof their important life history trait, is regulated by variousexogenous and endogenous conditions. Therefore, reproductivecycle is a harmonious process interlinked with environmentallymediated routine of various aquatic ecosystems. In such case anyadverse environmental condition might affect the natural repro-duction process of marine fish population and ultimately hinderthe recruitment in a stock through spawning.

All the essential exogenous semi-saline or freshwater ecologicalparameters trigger the reproduction of Hilsa parental stocks.The river water nurses the millions of larvae where they growand revert to juvenile and adult Hilsa. At that stage they againmigrate towards the sea. But the recent siltation problem on the

Jatka

Fresh WaterSpawning

Brackish Water

Sea WaterAdult-premature

Adult-Mature

Fig. 8. Movement pattern of Tenualosa ilisha (Hilsa) into different habitats (Halder,2005).

0

100

200

300

400

500

600

2002 2003 2004 2005

Catch/day/boat (kg)

Fig. 7. Catch per unit of effort of Hilsa in the riverine area (World Fish Center,Report, 2008).

Fig. 6. Year-wise total catches production (MT) of Hilsa from the BoB (www.boblme.org, 2012).

M. Shohidullah Miah / Weather and Climate Extremes 7 (2015) 109–115 113

upstream part of Padma and other river systems affected thenormal course of spawning and migration of the fish. Recent studyrevealed that availability of Hilsa stock is gradually declining in thePadma and Megna river catchment areas. As a result, the trend ofHilsa production in the rivers has been decreased and alterna-tively, the production trend in marine water as mentioned abovehas comparatively been increased. Similar conditions might occurfor other potential marine fish/shrimp species although no definitestudy had yet been carried out in Bangladesh.

10. Sea level raise and water temperature

The sea level raise (SLR) is another critical variable due toclimate change (Ota Agarawala, et al., 2003). World Bank report(2000) revealed that 10 cm, 25 cm and 1 m SLR by the year 2020,2050 and 2100 respectively, will result in loss of land area to thesea at the rat e of 2%, 4% and 17.5%, respectively. Due to SLR,salinity is decreasing in the coastal region and thus seriouslyaffecting the breeding of marine fishes (SRDI, 1998). Surface watertemperature varies in different months from 22.80 to 32.901 C. Thehighest sea surface temperature is reported in September and thelowest during January and February ( Mahmood, 1994).

11. Adaptation to climate change and Hilsa fishing

In 2005, the Government of Bangladesh launched its NationalAdaptation Programme of Action (NAPA), in partnership with otherstakeholders, which highlights the main adverse effects of climatechange and identifies adaptation needs. The Climate Change Cell inDepartment of Environment (DoE) under the Ministry of Environ-ment and Forests supports the mainstreaming of climate change intonational development planning. DoE has recently launched thepreparation of the Climate Change Policy and Action Plan forBangladesh (CCPAP). This Plan will take a holistic, inclusive andcomprehensive approach involving all stakeholders toward under-standing climate risks and vulnerabilities and then respondingthrough concerned sectors, agencies and stakeholders.

12. Traditional adaptation for Hilsa fishing

The Hilsa fishing is greatly depending on localities, occupa-tional groups and gender. Most of Hilsa fisherman face multiplevulnerabilities which affect different households. Alternativeincome generating opportunities of the Hilsa fisherman commu-nities are very limited. Their main source of income is on Hilsafishing and fisheries related activities. However, as resource basesbecome more fragile, there is a need to increase the access toincomes from alternative sources outside fisheries though suchemployment opportunities are very limited (Khan et al., 1989).As a predominant number of Hilsa fishermen are poor, theirdiversifying income is limited. Therefore, the micro-credit oppor-tunities could be provided in order to support the sustainablemanagement of fisheries resources of the BoB (Department ofFisheries (DoF), 2006)).

13. Stock discrimination for sustainable management of Hilsafish

Isolation and identification of Hilsa stock and analysis of Hilsasample, from the Irrawaddy river in Myanmar, Kuwait and north-ern Sumatra showed similar stock. The samples from the PersianGulf were found to be genetically distinct (Salini et al., 2004).Previous studies showed that the morphology of Hilsa varied

within Bangladesh and adjacent India. It is reported (Salini et al.,2004) that morphological variation was similar but not related topopulation structuring. The chemical composition of the otolith atthe spawning grounds in the Bay of Bengal showed that Hilsashould be treated and managed as a single population ( Milton andChenery, 2001).

14. Policy adaptation for marine fisheries development

The main management recommendations for marine Hilsa aresummarized below:

(a) Provide alternate employment for fishermen during off fishingseason.

(b) Regulate industrial and artisanal fishery to reduce over fishingfor sustainable production.

(c) Strengthen research on artificial breeding for marine Hilsa.(d) Prevent indiscriminate exploitation of marine Hilsa.(e) Control marine pollution through stop dumping of harmful

chemicals.(f) Reduce catch of immature fish.(g) Establish seasonally closed protected areas for spawners

and Jatka.(h) Improve registration of inland and marine fishing vessels

and gear.

15. Conclusion

Due to climate change, the marine environment is changing inparticular on the rise in sea water temperature, salinity and sealevel, pH of the sea water, and changes in the current, upwelling,water mass movement, El Niño and La Nina events. Climatechange affects the abundance of marine fish species. For many ofthe fish species, change of optimum temperatures affect the basicmetabolism, availability of food and breeding mechanisms. InBangladesh, as well as in other neighboring countries, no specificresearch has yet been conducted on this issue. Therefore, long-term research on impact of climate change on marine resourcesinvolving the common ecological conditions needs to be imple-mented in the Asia Pacific region.

Acknowledgements

This study was conducted with the financial support receivedfrom the Asia Pacific Networks (APN) through InternationalGeosphere and Biosphere Programme (IGBP) (Grant no. ARCP2011 16NMY- IGBP). The Research Team thankfully acknowledgestheir support. Sincere thanks also to Dr Opha Pauline Dube and toProfessor M Alimullah Miyan for their coordination and guidance.The Author sincerely acknowledge IUBAT—International Universityof Business Agriculture and Technology for giving the opportunityto do this study on impact of environmental changes on marinefishes of the BoB of Bangladesh.

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