Fish Passes,Riparian Vegetation and Stock Enhancement in River

PROTECTION AND RESTORATION OF FISH MOVEMENTS, MANAGEMENT OF RIPARIAN VEGETATION AND STOCK ENHANCEMENT

STRATEGIES IN RIVER

Presented by

Pranab Gogoi

FRM –MA2-09

CIFE, ICAR

Introduction

• Fish migration is a natural life cycle function found in most species. The migration is necessary for the fish to spawn, feed, grow and seek escape from predators. • Many streams and rivers have both natural and man-made barriers that prohibit natural migration. All barriers can lend to habitat fragmentation and limit natural migration pattern.

Classification of fish migration (Northcote, 1998)• Potamodromy• Diadromy: Anadromy, Catadromy, Amphidromy.

On the basis of distance (Waidbacher & Haidvogl, 1998)

- Long distance, Medium distance and Short distance migrants

Ecological background

Winter habitat

migration Feeding habitat

spawning habitat

Additional migration

Impairment by the structures of dams and weirs or any barrages is of two main types –

• Weirs and dams regardless of their height, constitute barriers to migration for most of the species which, during a certain phase of their life cycle depend on longitudinal movements.

Species are affected by morphological modification –- change in slope - river bed profile- structure of bottom surface - submersion of gravel zones- destruction of riparian vegetation - spawning grounds etc.

Fish species caught during survey at the river Nyamjang Chhu

• Most of the negative effects occur upstream of an obstruction, where lacustrine conditions are superimposed on the river.

• Downstream hydrological conditions severely altered through reduction of water discharge in the weir pool. The adverse conditions of the flow can extend over many kms downstream of the obstruction so that fish passage becomes difficult.

• When construction seems unavoidable, it includes an efficiently functioning fish way, ecological requirements of all riverine species, and particularly migrants, have to be taken in to consideration from the earliest stages in planning for the project.

“THE CONSTRUCTION OF BARRIERS ACROSS THE RIVERS HAS RESULTED IN DIMINISHED ABUNDANCE, DISAPPEARANCE AND EVEN EXTINCTION OF FISH SPECIES”.

“FISH PASSES MUST BE CONSIDERED WHEN THE RIVERS HOLDS, OR POTENTIALY COULD HOLD, STOCKS OF MIGRATORY SPECIES”.

Lower Subansiri H.E. Dam, AP, Civil works going on.

• The design of a fish pass, effectiveness closely linked to the water velocities and flow patterns, behaviour of the target species.

• A large water level difference between pools, excessive aeration or turbulence, large eddies or low flow velocities can act as a barrier for fish.

• In addition to hydraulic factors, fish are sensitive to other environmental parameters (level of dissolved oxygen, temperature, noise, light, odour, etc.), which can have a deterrent effect.

Four general requirements for fish passes-

• Sufficient capacity - dimension of the pass must be related to river size and the maximum volume of passage.

• Adapted to the swimming capacities of the fish: Pass should be designed to permit passage of slower swimming species and all life stages.

• Permanently functional - able to function over the different flow regimes.

• Positioning of entrance - entrance should be readily accessible to migrating fish.

• The best options for mitigation - maintained using natural watercourse and other technical devices.

• Several methods that are available –- Fish slopes (inclined planes; rocky ramp)- Natural by-pass channel

• Technical devices- Pool fish ways- Denil fish ways- Fish lifts- Fish locks

Description

Fish slopes: Fish ramps are constructions that are integrated into the weir but cover only a part of the river width; with as gentle a slope as possible to ensure that fish can ascend.

• Independently of their slope, all these structures are called ramps; in general the incorporation of perturbation boulders or boulder sills is required to reduce flow velocity.

• The main slope should not be steeper than 1 : 20. • The lateral connectivity (lateral slope) should not exceed 1:15.• Water depth over the slope should not less than 60 cm.

Slope is-• Inclined planes or rocky ramps or combination• Ideal : fan shaped which means the high lateral connectivity towards mid river.• Positioned in river bed : so easily accessible by fish• The slope should be studded with the boulders to stabilize the bottom and to create diversity of bottom substrate and flow patterns.• Rocky cascade – pass which is combination of rocky ramp and pool type fish pass.

Advantage:

One of the main advantage of fish slope is that the structure is positioned in the river bed which makes it easier for the fish to find.

By pass channel• The nature-like bypass channel, being very similar to a natural stream, is a waterway designed for fish passage around a particular obstruction.

• As noted by Parasiewitz et al. (1998), the function of a nature like bypass channel is, to some degree, restorative in that it replaces a portion of the flowing water habitat which has been lost due to impoundment. These channels are characterised by a very low gradient.

• It needs considerable space in the vicinity of the obstacle. 

One torrential sub-stream of river Nyamjang Chhu, AP

So, By pass channel –

• Must have similar character as of natural water body.• Migration is deflected from river axis.• Passage with V- shaped steps constructed with boulders: more suited to low gradient channel.

Disadvantage: • Need active search by migrants. • Need considerable space in vicinity.

By pass channel

A long by pass channel

Mitigation measures: Technical devicesPool fish ways-

Notched weir crest fish way

Vertical slot fish pass

Pool fish way• The basic principle of pool fish way is to divide the height to be passed into several small drops from 0.15 m to 0.45 m, depending on the species for which the pass is designed, to form a series of pools compartmented by cross walls. • The passage of water: either by surface overflow, orifices situated in the cross wall, vertical notches or slots.

• The main parameter of pool fish ways are the dimensions of the pool and the dimensions of the weir, slots and orifices of the cross walls which separate them.Disadvantage:• Space requirement• High cost

How a fish way works

Vertical slot fish way• First developed in Canada to enhance salmon migration.•In vertical slot fish way, the orifices extend from bottom to the surface of the channel. • Designs exist with single or paired vertical slots.• Advantage is that their efficiency is largely unaffected by variations in upstream water level provided that the level downstream varies in similar manner.

Other types of poll fish pass:• Rhomboid fish pass- inclined walls are inserted in a oblique angle.• Humped pass: Bottom and transverse walls are specially designed to provide flow for slow swimming performance.

Design of Pool fish way

pool and weir fish way

Vertical slot fish way

Denil fish ways

• Mr. Denil, a civil engineer, developed the first baffle fish passes in Belgium in 1910, mainly for Atlantic salmon.

• The principle is to place baffles on the floor and/or the walls of a rectangular flume with a relatively steep slope (10 to 25 percent) to reduce the mean velocities of the flow.

• These baffles, in shapes of varying complexity, cause secondary helical currents that ensure an extremely efficient dissipation of energy of the flow.

• The shape of the original baffles was later simplified with good results (Larinier 1983, 1992; Lonnebjerg 1980; Rajaratnam and Katopodis 1984).

Design of Denil fish way

baffles on 450 slope

The Denil fish way is a sloped flume with a series of baffles.

In a nutshell, we can say that-• Fish passes can be used to overcome large and small scale obstructions across the river……..• …… but large dams are generally too high for pool-type fish passes and more complex solutions like fish locks may need to be adopted.

Problems-• Downstream migration: diadromous species and for long distance riverine migrants. Mortality of downstream migrants may occur during passing throw hydroelectric turbines or spillways.• Despite years of research, techniques are less advance in downstream passage. No single system exist today which is biologically effective, operationally reliable and economically feasible.

Fish Lifts• The fish is attracted by a current and guided (or even forced by moving grids) to enter a holding pool containing water which is moved up.• The fish are released either directly or discharged in to a channel connecting to the upstream.

Fish locks• An Irish Engineer Borland (1949) developed fish locks.• Fish is attracted into down stream pool passes through the lock.• Migrants are encourage to leave the lock by creating descending current by opening a by-pass situated at the lower part of the facility.• As for other fish passes, the right positioning of the entrance is required.

Disadvantage• Discontinuity of the system: during the phase filling or release no fish can enter in the downstream pool.

Fish passes and migration facilities in India

• Sarada barrage and Farraka barrage on Ganga basin, Dakapathar and Hathnikhunda barrage on Yamuna .

• These facilities were provided to provide passage to the Anadroumous, Potadromous species and Amphidromous species Macrobrachium rosenbergii.

• A research carried out by CIFRI on Ganga observed that in spite of two fish locks between bay no. 24 and 26 with in the Farakka barrage, the commercially important hilsa has highly affected from the barrage since its construction (1975) blocking almost 1000 km of its migratory path.

• No detailed analysis as to the functioning of fish locks is available.

• CIFRI conducted extensive investigation in the upstream and downstream of the upcoming dams on river Bichum and Tenga in Arunachal Pradesh to design appropriate fish pass (pool type) for incorporation in the Bichum dam.

• Detailed study of other four projects also going on in AP under CIFRI riverine division.

1. Bhilwara H.E. Power project, on river Nyamjang Chhu Lumla, AP.

2. GMR Londa H. E. project, on river Kameng Seppa, AP .

3. Etalin H.E. project, on river Dri and Tangon, Etalin, AP.

4. Attunli H. E. project, on river Tangon Attunli, Dibang valley, AP.

Nyamjangchhu river: proposed dam site, Lumala, Tawang, AP.

Management of riparian vegetation

Definition• The word “riparian” is derived from Latin word riparius means land adjacent to the water body (Naiman and Decamps 1997). • Riparian vegetation had been recognized by wildlife biologists as a critically functionally dominant component of a terrestrial landscape (Tabacchi et al. 1998). Beinga transition zone between the aquatic and terrestrial habitats, it exhibits unique characteristics like hydric soil, floral and faunal composition, and community structural relationships and provides ideal habitat for wildlife. • Healthy riparian forests are essential to the maintenance of water quality and biological integrity in surface water systems, and their destruction often leads to subsequent degradation of adjoining aquatic ecosystems (Naiman and Decamps 1997).

Importance

• Aquatic vegetation plays many important roles in maintaining and improving the healthy waterways. Fishery is likely to require variations in water temperature, depths and velocities as well as huge variety of physical structures. Vegetation can often help provide all these, even in those which water course which have been heavily engineered in the past.

• Healthy fisheries may also depend upon, or be considerably enhanced by, the vegetation of the riparian zone and the land use of the abutting floodplain. In this context, the section of riparian zone is defined as that area of the bank stretching from the water edge to the top of the bank where there is potential for cultivation or building development.

Importance of aquatic plants to fish –• Water purification- by oxygenation and conversion of toxic ammonia to usable nitrates.• Nutrient re-cycling.• Physical link between water and air for many invertebrates.• Cover for huge range of invertebrates, many of which are food for fish.• Cover for fish – value and type varies with age/ species of fish as well as type of vegetation.• Spawning areas.• Food source – direct source for vegetarian fishes.• Affects flow patterns – accretes sediments and deflects flows so provides quieter waters and fasters shallows. • Creation of discrete habitat structure.

MANAGEMENT

WHY MANAGE IN-STREAM AND RIPARIAN VEGETATION ?

BECAUSE OF THE VITAL LINKS BETWEEN RIVER VEGETATION AND WATER QUALITY, PHYSICAL HABITATS AND ANIMALS, VEGETATION MANAGEMENT IS CRITICAL FOR A FISHERY.

SUBMERGED FLOATING AND EMERGENT VEGETATION OFTEN NEEDS TO BE CONTROLLED TO FACILITATE WATER FLOW.

Some key reasons for controlling in stream and riparian vegetation –In stream vegetation:

• Stop rise in water levels due to impedance of flow which would cause flooding and/or poor drainage on adjacent land.

• Removal of vegetation likely to snag on boats or get entangled in propellers.

• Open up areas of clear water to enable angling.

• Precaution in autumn to remove vegetation which might wash downstream and block culverts, sluices or pumps.

Riparian vegetation

• Mowing of banks and flood banks to encourage a tight root mat which aids bank stability and provides a means for visual inspection of banks susceptible to damage if colonized by burrowing animals.

• Mowing to create smooth banks to enable efficient passage of water downstream, ensuring all tall herbs and grasses are controlled and there is no succession to scrub.

• Mowing for amenity.

• Removal or, selective management of trees to avoid debris snagging and compromising conveyance of flows.

Important points to be consider when controlling riparian vegetation –

• Unless absolutely unavoidable, only cut one bank a year.

• Always leave a strip of vegetation at the base of the bank uncut to provide vital cover, food etc.

• Even a manage bank, narrow stripes of vegetation should be left uncut up the bank to provide congenial habitat for small mammals' and invertebrates until re growth occurs.

• Provide a site specific management regime for small patches of riparian vegetation with high conservation interest.

• Do not use herbicides unless essential but application may be desirable for control of invasive aliens spp.

Guidelines for sensitive tree and shrub management• No tree management during the bird breeding season.

• Always leave 50% of shrubs or mature trees unmanaged in one year.

•Check the large trees for protection of bats and other animal

• Cut material can be utilized for other purposes where many, mammal, bird, invertebrate and fungi species will benefit etc.

ESTABLISHING AQUATIC AND RIPARIAN VEGETATION TO BENEFIT FISHERIES

• Planting vegetation in or on the banks of water courses ca enhance a fishery as well as its conservation and aesthetic values.

• If there is plenty of native vegetation with in the river upstream, and fragments remain in protected areas, planting is usually not necessary; nature will take care of it….

• Where there is plenty of vegetation the natural process will usually result in recolonization.

In a nutshell, Function of riparian vegetation are-

• Riparian vegetation acts as a filter to trap sediment, nutrients and other contaminants, reducing their movement into streams.

• Riparian vegetation protects banks from surface erosion by rain, water flow or stock. The roots of riparian vegetation can help to dry and bank soils to prevent cracking and slumping.

• Native riparian vegetation provides shade which is crucial for maintaining natural levels of light intensity and water temperature for healthy in-stream ecosystems.

• Native riparian vegetation provides food inputs and aquatic habitat essential for aquatic ecosystems.

• Native riparian vegetation provides food inputs and terrestrial habitat essential for animals and plants that live in land adjacent to rivers and streams.

• Uncontrolled access by stock to riparian areas can result in over-grazing and trampling of vegetation, leaving areas of bare soil and stock tracks that can cause erosion. Animal wastes foul the water for downstream users and can transmit diseases that reduce stock growth and production.

• Special care is needed when clearing land within or adjacent to riparian areas to avoid damage to streams, water quality, and flora and fauna.

STOCK ENHANCEMENT STRATEGIES

• Stocking introductions and transfers of fish are valuable management tools which complement the physical rehabilitation of the environment.

• Manipulation of the fish stock either by releasing individuals of species that are already present in the target system or adding species that are new to the community are frequently essential if the environment is to be productive and is stocks are to be reconstituted or maintained.

•Proposals for stocking or for the stocking of new species should be based on strategic and tactical approaches with clearly defined objectives.

• The programme themselves should be based on pre operational assessment of the carrying capacity of the system, evaluation of natural or artificial factors that may be limiting and on scientific estimation of species, size and number of fish to be stocked.

PURPOSE OF STOCKING AND INTRODUCTION

• Compensation: Typically stocking with the native species to compensate for disturbance to the environment caused by human activities.

• Maintenance: Stocking to compensate for recruitment overfishing.

• Enhancement: Stocking to maintain the fisheries productivity of a water body at the highest possible level.

• Conservation

Two reasons for introducing new species include –• To establish new fisheries• To fill a vacant niche

Elements of stocking programme• Identify need for stock improvement• Establish stocking objectives• Assessment of stocking proposalThe stocking process• Source of fish• Preconditioning and acclimatization• Handling and transportation of stock• Size and age of stock• Timing of stocking

Mechanism for release

Three mechanisms for releasing fish can be used.

• Spot planting: introducing all the fish species into the receiving waters at the same site.

• Scatter planting: introducing fish into several sites in the same region.

• Trickle planting: introducing fish into the same region over a period of time.

Post stocking evaluation

• Evaluation is often neglected but it is an essential part of the programme.

• It should assess the efficiency and long term benefits of the various stocking practices and regimes and attempt to identify factors contributing to success or failure.

• Temporal, sequential evaluation data sets will provide feed back to improve formulation of realistic stocking management objectives, to improve stocking strategies and techniques and provide a database of experiences against which risk and feasibility of new proposals can be appraised.

POTENTIAL RISKS FROM STOCKING

• Genetic interactions: When embarking of any kind of stocking programme, consideration must be given to maintaining the genetic integrity of the indigenous stock.

• Carrying capacity of the target habitat.

• Species interactions

• Disease control

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