FLOOD CONTROL IMPACTS ON FISHERIES: GUIDELINES FOR MITIGATION · FLOOD CONTROL IMPACTS ON...

FLOOD CONTROL IMPACTS ON FLOOD CONTROL IMPACTS ON FISHERIES:FISHERIES:

GUIDELINES FOR MITIGATIONGUIDELINES FOR MITIGATION

UK Department for International Development (DFID)UK Department for International Development (DFID)Fisheries Management Science Programme (FMSP)Fisheries Management Science Programme (FMSP)

June 2005 June 2005

A. S. Halls, A. S. Halls, AquaeAquae SulisSulis Ltd (ASL), UKLtd (ASL), UK

BackgroundBackgroundThis presentation is one of a series of five presenting key outpThis presentation is one of a series of five presenting key outputs uts frfromom FMSP floodplain projects, carried out in the Asian region FMSP floodplain projects, carried out in the Asian region between 1992 and 2005. The five papers focus on:between 1992 and 2005. The five papers focus on:

–– General management guidelines for floodplain river fisheries (asGeneral management guidelines for floodplain river fisheries (aspublished in FAO Fisheries Technical Paper 384/1)published in FAO Fisheries Technical Paper 384/1)

–– Selection and management of harvest reserves (key messages)Selection and management of harvest reserves (key messages)–– Materials for a training course on harvest reservesMaterials for a training course on harvest reserves–– Flood Control Impacts on Fisheries: Guidelines for MitigationFlood Control Impacts on Fisheries: Guidelines for Mitigation–– ModellingModelling floodplain river fisheriesfloodplain river fisheries

This presentation was prepared by FMSP Project R8486 This presentation was prepared by FMSP Project R8486 ––‘‘Promotion of FMSP guidelines for floodplain fisheries managementPromotion of FMSP guidelines for floodplain fisheries managementand sluice gate controland sluice gate control’’

IntroductionIntroduction

•• Flood Control Drainage and Flood Control Drainage and Irrigation (FCDI) structures Irrigation (FCDI) structures exist widely in Bangladesh exist widely in Bangladesh and other parts of Asia.and other parts of Asia.

•• Built to control water levels Built to control water levels to improve agricultural to improve agricultural production based upon HYV production based upon HYV of rice (cannot tolerate of rice (cannot tolerate rapid inundation or require rapid inundation or require irrigation).irrigation).

•• Provide protection from Provide protection from extreme flood events.extreme flood events.

IntroductionIntroduction•• Benefits to agricultural sector Benefits to agricultural sector

significant (80% more production significant (80% more production inside) butinside) but……

•• Fish production typically lowered.Fish production typically lowered.

•• Halls et al (1998;1999) found that Halls et al (1998;1999) found that in Bangladesh fish yields were in Bangladesh fish yields were 50% lower yields inside 50% lower yields inside FCDIsFCDIscompared to outside compared to outside with up to 25 with up to 25 species of fish absent or less species of fish absent or less abundant. abundant.

•• Lower rates of recruitment of Lower rates of recruitment of migratory migratory whitefishwhitefish species found species found largely responsible (Hoggarth et al largely responsible (Hoggarth et al 1999).1999).

•• Migrations obstructed by Migrations obstructed by embankments.embankments.


•• Predicted effects of Predicted effects of climate change in South climate change in South Asia include: Asia include: –– more extreme floodingmore extreme flooding

–– hotter and more arid dry hotter and more arid dry season conditionsseason conditions

•• May necessitate the May necessitate the construction of construction of moremoreFCDI schemes! (to FCDI schemes! (to control floods and provide control floods and provide dry season irrigation)?dry season irrigation)?


•• Q: How can we mitigate the impacts of FCDI Q: How can we mitigate the impacts of FCDI Schemes?Schemes?

•• A:A: Improve the management of sluice gates to:Improve the management of sluice gates to:

–– (1.) Improve the recruitment (access) of (1.) Improve the recruitment (access) of migratory fish to migratory fish to FCDIsFCDIs..

–– (2.) Improve production of resident (non(2.) Improve production of resident (non--migratory) fish populations.migratory) fish populations.

Whilst Whilst minimising impacts to agricultureminimising impacts to agriculture sector sector

(Integrated floodplain management (Integrated floodplain management -- IFM)IFM)

1. Improving fish access to 1. Improving fish access to FCDIsFCDIs

•• Based on fisheries Based on fisheries monitoring and markmonitoring and mark--recapture studies recapture studies undertaken at 3 sluice undertaken at 3 sluice gates (Halls 2005a; Halls gates (Halls 2005a; Halls et al 1998; Halls et al et al 1998; Halls et al 1999; Hoggarth et al 1999; Hoggarth et al 1999), the following 1999), the following guidelines have been guidelines have been developed to developed to improve the improve the accessaccess of migratory fish of migratory fish to to FCDIsFCDIs……


•• 1.1 Sluice gate 1.1 Sluice gate managers should managers should aim to aim to maximisemaximise the the flowflow of water (and of water (and therefore fish) therefore fish) intointoFCDI during the FCDI during the rising floodrising flood period.period.

•• Aids the passive inward Aids the passive inward migrations of fish.migrations of fish.

-200 -100 0 100 200Inside flow rate (m 3s-1)

0

20

40

60

80

100

120

Pas

sage

suc

cess

(%)

1 2 3 4 5 6 7 8Inside flow rate (m 3s-1)

0

20

40

60

80

100

120

Pas

sage

suc

c ess

(%)


•• 1.2 Sluice gate managers 1.2 Sluice gate managers should aim to open sluice should aim to open sluice gates as gates as frequentlyfrequently as as possible and attempt to possible and attempt to minimiseminimise the the turbulenceturbulence of of water water outsideoutside sluice gates sluice gates during the during the risingrising flood period.flood period.

•• Anecdotal evidence (Halls et al Anecdotal evidence (Halls et al 1998;1999; Hoggarth et al 1999) 1998;1999; Hoggarth et al 1999) suggests that biodiversity & fish suggests that biodiversity & fish production benefit from more production benefit from more frequent gate openings, frequent gate openings, particularly during particularly during risingrising flood flood period.period.

•• Turbulence in front of gate may Turbulence in front of gate may act as an obstacle to induction act as an obstacle to induction and smooth passage of fish.and smooth passage of fish.

500000 1000000 1500000 2000000Outside turbulence (Reynolds No.)

30

40

50

60

70

80

90

100

Pas

sage

suc

cess

(%)

1. Improving fish access to 1. Improving fish access to FCDIsFCDIs•• 1.3 Sluice gate managers 1.3 Sluice gate managers

could control could control ebbebb flows flows from sluice gates to from sluice gates to attractattract more fish more fish towards sluice gates but towards sluice gates but that do that do not exceednot exceed the the maximum swimming maximum swimming speeds of fish.speeds of fish.

•• The figure opposite shows The figure opposite shows how the abundance of fish how the abundance of fish caught trying to migrate caught trying to migrate towards the towards the TalimnagarTalimnagarsluice gate in NW sluice gate in NW Bangladesh varies in Bangladesh varies in response to outresponse to out--flowing flowing current velocity. current velocity.

•• It suggests that best It suggests that best attraction velocity is about attraction velocity is about 0.1ms0.1ms--11. .

Optimal Attraction velocity

Average MaxSwimming Speed

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0 0.1 0.2 0.3

Current Velocity (ms-1)

CPU

E (k

gm-2

h-1) x

1000

Calculating maximum current speedsCalculating maximum current speeds

•• Maximum swimming speeds of fish, thus maximum permissible ebb Maximum swimming speeds of fish, thus maximum permissible ebb current speeds flowing out from sluice gates (Max Outflow Velocicurrent speeds flowing out from sluice gates (Max Outflow Velocity), ty), can be easily estimated using the current empirical formulae can be easily estimated using the current empirical formulae (R(R22=0.80):=0.80):

•• Where UWhere Umsms=maximum sustainable swimming speed, L = mean =maximum sustainable swimming speed, L = mean length of migrating fish, W=mean weight of migrating fish, length of migrating fish, W=mean weight of migrating fish, n=constant=3.n=constant=3.

•• LiftnetLiftnet sampling of fish during ebb flow will give estimates of L and sampling of fish during ebb flow will give estimates of L and W. W. LiftnetsLiftnets could also be sampled for CPUE data to estimate could also be sampled for CPUE data to estimate optimal attraction velocities.optimal attraction velocities.

100))(1.1(( 14.0−

=<WnLUVelocityOutflowMax ms

1. Improving fish 1. Improving fish access to access to FCDIsFCDIs

•• 1.4 Managers should 1.4 Managers should control fishing control fishing activities along activities along channels channels connecting connecting the sluice gates to the the sluice gates to the main rivers. main rivers.

•• In In BadiaBadia River biomass River biomass of immigrating fish was of immigrating fish was reduced by 40reduced by 40--50 % 50 % along 5km stretch from along 5km stretch from mouth to gate (Halls mouth to gate (Halls 2005).2005).

July 2004

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 1 2 3 4 5 6

Distance from mouth of river (km)

Mea

n CP

UE

x 10

0 (k

g da

y -1

m2)


•• Controlling fishing in these channels Controlling fishing in these channels may be as important as fine tuning may be as important as fine tuning sluice gate operations.sluice gate operations.

•• First step in right direction First step in right direction -- avoids avoids any potential impacts to farmers any potential impacts to farmers arising from sluice gate operations.arising from sluice gate operations.

•• Should benefit the wider fishery Should benefit the wider fishery (fishing during this period exploits (fishing during this period exploits sexually immature fish that are still sexually immature fish that are still growing rapidly).growing rapidly).

•• Reducing effort during this period Reducing effort during this period could increase size of spawning stocks could increase size of spawning stocks and thus overall yield, as well as yieldand thus overall yield, as well as yield--perper--recruit. recruit.

2. Improving Production of Resident Fish2. Improving Production of Resident Fish

•• 2.12.1 Sluice gate managers Sluice gate managers should consider should consider closingclosing sluice sluice gates gates towards end of ebb floodtowards end of ebb floodto to retainretain more more waterwater within within FCDI schemes during the FCDI schemes during the dry dry seasonseason..

•• Fish overFish over--winter in permanent winter in permanent channels and residual channels and residual waterbodieswaterbodieson floodplain. Area of water on floodplain. Area of water remaining on the floodplain may be remaining on the floodplain may be less than 5% of that during the flood less than 5% of that during the flood season!season!

•• Model predictions indicate that fish Model predictions indicate that fish production is more sensitive to the production is more sensitive to the amount of water remaining during amount of water remaining during dry season than flood season dry season than flood season conditions conditions (see accompanying (see accompanying floodplain modeling presentation).floodplain modeling presentation).

•• Studies (Halls et al 2001; Studies (Halls et al 2001; ShankerShanker et al 2004; 2005) at et al 2004; 2005) at the PIRDP have predicted that raising dry season water the PIRDP have predicted that raising dry season water levels by as little as 0.25m, could increase fish levels by as little as 0.25m, could increase fish production by about 9% at a loss of only 8 ha of rice production by about 9% at a loss of only 8 ha of rice production, mainly from marginal, lowproduction, mainly from marginal, low--lying land. lying land.

•• Increased availability of dry season water would help Increased availability of dry season water would help reduce pressure placed upon critical dry season fish reduce pressure placed upon critical dry season fish habitat resulting from dry season crop irrigation habitat resulting from dry season crop irrigation strategies. strategies.

•• Such irrigation strategies are likely to become Such irrigation strategies are likely to become increasingly necessary in the face of climate change increasingly necessary in the face of climate change (Halls 2005b).(Halls 2005b).



•• 2.2 Managers should seek to 2.2 Managers should seek to encourage encourage alternative cropping alternative cropping strategiesstrategies and the and the retirement of retirement of marginal lowmarginal low--lyinglying agricultural agricultural land land that is that is prone to early floodprone to early floodrisk.risk.

•• Dry season (Dry season (boroboro) rice production based ) rice production based upon high yielding varieties (HYV) often upon high yielding varieties (HYV) often relies upon smallrelies upon small--scale irrigation scale irrigation systems e.g. low lift (taxi) pumps (systems e.g. low lift (taxi) pumps (LLPsLLPs) ) to abstract water from dry season to abstract water from dry season waterbodieswaterbodies. .

•• But these residual water bodies provide But these residual water bodies provide criticalcritical dry season habitat for floodplaindry season habitat for floodplain--resident fish. resident fish.


•• Studies (Studies (ShankerShanker et al 2004; et al 2004; 2005) have predicted that 2005) have predicted that beyond some threshold, beyond some threshold, floodplain fish production is floodplain fish production is highly sensitive to removals highly sensitive to removals of water from these bodies of water from these bodies impacting upon fish impacting upon fish catchabilitycatchability, natural mortality , natural mortality rates and recruitment.rates and recruitment.

•• Switching to alternative dry Switching to alternative dry season crops such as wheat season crops such as wheat or onions that require less or onions that require less irrigation (less frequent and irrigation (less frequent and smaller applications of water) smaller applications of water) could alleviate this problem could alleviate this problem to some extent.to some extent.

0 500 1000 1500Area Irrigated (ha)

0

50

100

150

CP

UA

(kg

h a -1

)


0

50

100

150

CP

UA

(kg

h a -1

)


0

50

100

150

CP

UA

(kg

h a -1

)

0 1000 2000 3000 4000 5000Area Irrigated (ha)

0

50

100

150

CPU

A (k

g ha

-1)

0 1000 2000 3000 4000 5000Area Irrigated (ha)

0

50

100

150

CPU

A (k

g ha

-1)

WheatOnions

Low

Boro rice Irrigation Schedules

MediumHigh


•• Switching to other dry season Switching to other dry season crops such as spices and crops such as spices and vegetables that are harvested vegetables that are harvested several weeks before several weeks before boroboro rice, rice, and greater emphasis on more and greater emphasis on more floodflood--tolerant tolerant AmanAman rice rice would would also allow for earlier, more also allow for earlier, more frequent opening of sluice gates frequent opening of sluice gates for longer periods during the for longer periods during the rising flood (rising flood (ShankerShanker et al et al 2004;2005)2004;2005). .

•• Such adaptive strategies are Such adaptive strategies are likely to become increasingly likely to become increasingly necessary in South Asia where necessary in South Asia where precipitation is predicted to precipitation is predicted to increase during the flood season, increase during the flood season, but decrease during the dry but decrease during the dry season in response to climate season in response to climate change (Halls 2005b). change (Halls 2005b).

ReferencesReferencesHalls, A. S. (2005a). The Use of Sluice Gates for Stock EnhanceHalls, A. S. (2005a). The Use of Sluice Gates for Stock Enhancement and Diversification ment and Diversification

of Livelihoods (R8210). Fisheries Assessment Report. London, MRof Livelihoods (R8210). Fisheries Assessment Report. London, MRAG, 75pp. AG, 75pp. http://www.fmsp.org.uk/FTRs/r8210/.htmhttp://www.fmsp.org.uk/FTRs/r8210/.htm

Halls, A.S. (2005b). Promoting New Knowledge of Climate Change Halls, A.S. (2005b). Promoting New Knowledge of Climate Change Impacts on Fisheries Impacts on Fisheries (R8457): A Review of Impacts and Interactions in the Context of(R8457): A Review of Impacts and Interactions in the Context of Other Renewable Other Renewable Natural Resource Sectors. Natural Resource Sectors. ASLASL, April, 2005, 46pp., April, 2005, 46pp.

Halls, A.S., Kirkwood, G.P. and Payne, A.I. (2001). A dynamic pHalls, A.S., Kirkwood, G.P. and Payne, A.I. (2001). A dynamic pool model for floodplainool model for floodplain--river fisheries. river fisheries. EcohydrologyEcohydrology and Hydrobiologyand Hydrobiology, , 1 1 (3): 323(3): 323--339. 339. http://http://www.ecohydro.pl/index.phpwww.ecohydro.pl/index.php

Halls, A.S., Hoggarth, D.D. & Debnath, D. (1999). Impacts of hyHalls, A.S., Hoggarth, D.D. & Debnath, D. (1999). Impacts of hydraulic engineering on draulic engineering on the dynamics and production potential of floodplain fish populatthe dynamics and production potential of floodplain fish populations in Bangladesh. ions in Bangladesh. Fisheries Management and Ecology Fisheries Management and Ecology 66: 261: 261--285285. . http://www.blackwellhttp://www.blackwell--synergy.com/loi/fme?opensynergy.com/loi/fme?open=1999=1999

Halls, A.S., Hoggarth, D.D. & Debnath, D. (1998) Impact of flooHalls, A.S., Hoggarth, D.D. & Debnath, D. (1998) Impact of flood control schemes on d control schemes on river fish migrations and species assemblages in Bangladesh. river fish migrations and species assemblages in Bangladesh. Journal of Fish BiologyJournal of Fish Biology5353 ((SupplSuppl. A), 358. A), 358--380. 380. http://www.blackwellhttp://www.blackwell--synergy.com/toc/jfb/53/sasynergy.com/toc/jfb/53/sa

Hoggarth, D.D., Halls, A.S., Dam, R. K. & Debnath, K. (1999) RecHoggarth, D.D., Halls, A.S., Dam, R. K. & Debnath, K. (1999) Recruitment Sources for fish ruitment Sources for fish stocks inside a floodplain river impoundment in Bangladesh. stocks inside a floodplain river impoundment in Bangladesh. Fisheries Management and Fisheries Management and EcologyEcology 6: 2876: 287--310. 310. http://www.blackwellhttp://www.blackwell--synergy.com/loi/fme?opensynergy.com/loi/fme?open=1999=1999

Shankar, B., Halls, A.S., & Barr, J. (2005). The effects of surShankar, B., Halls, A.S., & Barr, J. (2005). The effects of surface water abstraction for face water abstraction for rice irrigation on floodplain fish production in Bangladesh.rice irrigation on floodplain fish production in Bangladesh. Int. J. Water, Vol. Int. J. Water, Vol. 33, No. 1, , No. 1, 2005.2005.

Shankar, B., Halls, A.S., & Barr, J. (2004). Rice versus fish Shankar, B., Halls, A.S., & Barr, J. (2004). Rice versus fish revisited: on the integrated revisited: on the integrated management of floodplain resources in Bangladesh.management of floodplain resources in Bangladesh. Natural Resources ForumNatural Resources Forum, , 2828: 91: 91--101. 101. http://www.blackwellhttp://www.blackwell--synergy.com/toc/narf/28/2synergy.com/toc/narf/28/2..

Project details and creditsProject details and credits

FMSP Project R8210 FMSP Project R8210 –– The Use of Sluice Gates for Stock The Use of Sluice Gates for Stock Enhancement and Diversification of LivelihoodsEnhancement and Diversification of Livelihoods

•• Start Date: Start Date: 03/2003 03/2003 •• End Date: End Date: 02/200502/2005

•• Project Collaborators: Project Collaborators: –– MRAG (Ashley Halls, Ian Payne) MRAG (Ashley Halls, Ian Payne) –– IIED (Hannah Reid, Saleemul Huq); IIED (Hannah Reid, Saleemul Huq); –– BCAS (Atiq Rahman, BCAS (Atiq Rahman, Liaquat Ali, Sarder Shafiqul Alam, Shyamal

Kanti Barman, and Monirul Islam).

•• Key References: Halls (2005).Key References: Halls (2005).•• Project web page: Project web page: http://http://www.fmsp.org.ukwww.fmsp.org.uk/FTRs/r8210//FTRs/r8210/.htm.htm

FMSP Project R5953 FMSP Project R5953 –– Fisheries dynamics of modified Fisheries dynamics of modified floodplains in southern Asiafloodplains in southern Asia

•• Start Date: Start Date: 03/1994 03/1994 •• End Date: End Date: 03/199703/1997

•• Project Collaborators: Project Collaborators: –– MRAG (Dan Hoggarth, Ashley Halls); MRAG (Dan Hoggarth, Ashley Halls); –– CRIFI, Indonesia (CRIFI, Indonesia (FuadFuad CholikCholik, , AgusAgus UtomoUtomo, , OndaraOndara); ); –– BAU BAU MymensinghMymensingh (M.A. (M.A. WahabWahab, Kanailal Debnath, , Kanailal Debnath, RanjanRanjan Kumar Kumar

Dam)Dam)

•• Key References: MRAG (1997); Halls et al (1998); Hoggarth et al Key References: MRAG (1997); Halls et al (1998); Hoggarth et al (1999); Hoggarth et al (1999b). (1999); Hoggarth et al (1999b).

•• Project web page: Project web page: http://http://www.fmsp.org.ukwww.fmsp.org.uk/FTRs/r5953//FTRs/r5953/.htm.htm

This presentation is an output from a project funded by the UK DThis presentation is an output from a project funded by the UK Department for epartment for International Development (DFID) for the benefit of developing cInternational Development (DFID) for the benefit of developing countries. The views ountries. The views

expressed are not necessarily those of the DFID.expressed are not necessarily those of the DFID.

This project was funded through DFID's Fisheries Management ScieThis project was funded through DFID's Fisheries Management Science Programme nce Programme (FMSP). For more information on the FMSP and other projects fund(FMSP). For more information on the FMSP and other projects funded through the ed through the

Programme visit Programme visit http://http://www.fmsp.org.ukwww.fmsp.org.uk

FLOOD CONTROL IMPACTS ON FISHERIES: GUIDELINES FOR MITIGATION · FLOOD CONTROL IMPACTS ON...

Documents

Transcript of FLOOD CONTROL IMPACTS ON FISHERIES: GUIDELINES FOR MITIGATION · FLOOD CONTROL IMPACTS ON...