Assessing impacts of habitat

fragmentation on fish

populations, and prioritisation

of restoration actions

Paul Kemp

International Centre for Ecohydraulics Research

Presentation plan

• Introduction to Fish Research at the University of Southampton

• History – river development in Europe

• Implications of EU Legislation - Water Framework Directive

• Assessing impacts of barriers to fish migration

• Developing inventories of barriers

• Prioritisation of restoration (or development) of rivers

Introduction – Fish Research at the

University of Southampton

University of Southampton

International Centre for

Ecohydraulics Research

• Research in Fish Ecology and Fisheries Engineering –

International

• Fish passage, screening, compensation flows

• Experimental and field based research

• Multiple species

• Behaviour and locomotory performance

• Fish response to hydrodynamics and acoustics

Facilities

• 1 Open channel external flume facility

- Trapezoidal concrete channel

- 60 m long and 2 m wide

Large channel swimming

performance tests

Trajectory of a migrating adult eel

using acoustic telemetry

Developing fish passage criteria for large

hydropower dams in China

………and United States

……. and Sweden (and other European

countries)

Fish Behaviour in response to turbulence

and other hydrodynamic factors

Developing screening

criteria for downstream

migrating adult eel

0.0 0.5 1.0 1.5 2.0 2.5

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120 = 10%

approaches

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80%

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idth

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Turbulence

intensity (K)

Infrasound

Infrasound induces an avoidance

response in migrating European eels

River Imsa, Norway Sand et al. 2000

Acoustic bubble screen River Frome, Dorset

A novel smolt counting system, developed by CEH, incorporating

acoustic bubble screens (Fish Guidance Systems Ltd) to divert fish

through counters (Welton et al., 2002).

Screening water intakes at power stations

Key message from research

• Need to consider fish behaviour when

developing fish passage and screening criteria

• Need to consider multiple species

• Need to develop realistic measures of swimming

performance

• Need to develop behavioural devices that deter

fish (e.g. using acoustics or hydraulics)

History – River Development in

Europe

“All kydells for the future shall

be removed altogether from

Thames and Medway, and

throughout all England, except

upon the sea shore”.

Kydells = fish weirs

The Magna Carta

England and Wales:

Area = 151,000 km2

(Minas Gerais = 586,528 km2)

Approx. 26,000 dams and weirs

that disrupt connectivity of ecological

processes

Majority = small

• UK and Europe = long historic legacy

of river development

• Negative impacts have been recognized

for a long time

• Structures are often relatively small

• High density of infrastructure

What’s the problem?

Disrupts connectivity

(longitudinal and

lateral) of ecological

processes and

fragments habitat

Year

An

nu

al c

atch

(sa

lmo

n a

nd

gri

lse)

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20000

40000

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95

2

19

55

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79

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82

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2000

Tay District Salmon Catch Statistics (1952-2001)

American eels – St Lawrence Freshwater fish extinctions: graph to show known

species extinctions by decade

Implications of EU legislation

Water Framework Directive

Conflict or Counterbalance?

Renewable Energy

Obligations

Water Framework

Directive

Requirements of EU Water

Framework Directive

• To maintain "good ecological status" in terms of the

quality of the biological community, the hydrological characteristics and the chemical characteristics.

• The controls are specified as allowing only a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact.

• Habitat fragmentation prevents rivers attaining good ecological status independent of water quality and availability of suitable physical habitat

Repair or removal of barriers is the

easiest and quickest way to maximize

benefits of restoration actions

The removal or mitigation of barriers that block fish dispersal have led to some

of the largest increases in fish production (Roni et al. 2002).

Scully et al. (1990) observed that 70% of increases in fish production in

rehabilitated Idaho streams were due to barrier removal versus in-stream

and other restoration techniques.

Europe - the challenge is to:

1. Develop methodologies to survey river infrastructure

2. Assess the impact of river infrastructure

on ecology (often fish) – what is the porosity to fish movements?

3. Construct inventories of river infrastructure and map networks of barriers

4. Efficiently prioritise restoration action

Assessing the impact of barriers to

fish migration

Locate the barrier

Record the location and

ownership information

Determine if the stream

is fish bearing No

Collect basic

barrier

measurements

Yes or unknown

Level A

Barrier Assessment Not a

barrier Stop

Conduct Level B

Barrier Assessment Not a barrier

or unknown Stop

Barrier

Prioritize the

Barrier for correction

Conduct Habitat

Assessment

unknown

Barrier

Barrier assessment protocol

Aerial surveys

Methodologies to quantify porosity of

barriers to fish migration

1. Direct observation and filming

2. Hydroacoustic sonar

3. Telemetry

4. Fish surveys

5. Presence/absence data

6. Genetic structure of populations

7. Rule-based simulation

8. Statistical models

9. Expert opinion

• Fine-scale

• Detailed information on behaviour and passage.

• Limited application

(e.g. low turbidity,

shallow depth)

1. Direct observation and filming

2. Hydroacoustic sonar

• Fine-scale.

• Detailed information on behaviour and passage.

• Expensive.

• Limited application.

• High data processing.

3. Telemetry

• e.g. Passive Integrated Transponder (PIT), Radio, Acoustic, combined.

• Fine-scale.

• Detailed information on timing, rates, and routes of migration, facilitating accurate estimates of fish passage, attraction, and guidance efficiency.

• Relatively expensive and resource intensive.

• Not viable at watershed, regional, or national scales.

PIT Telemetry

Radio

telemetry

From Brown et al. 2009

Downstream passage

(American eel) – Hydroacoustic Telemetry

4. Fish surveys

• Abundance and density estimation (e.g. electrofishing, redd counts netting, mark-recapture, catch depletion, trapping).

• Intermediate-scale.

• Provides spatial and temporal information on distribution, abundance, and density of populations and community composition in relation to river infrastructure and associated habitat fragmentation.

• Limited information on barrier passability associated with individual

structures.

5. Presence/absence data

• Coarse-scale.

• Low cost.

• Data collected rapidly through surveys or by canvassing local knowledge.

• Limited information on barrier passability associated with individual structures.

• Can be misleading if infrastructures are considered independently (e.g. absence of fish may be related to other factors or the presence of impassable barriers elsewhere in the watershed)

6. Genetic structure of

populations

• Coarse-scale

• Provides information on genetic isolation of populations that may indicate potential compromise of long-term population persistence which may be used to make conservation decisions.

• Highlights the impacts of lost

connectivity over the longer term.

• Potential high cost.

• Need for specialist expertise.

• Of limited value for diadromous

fish species.

7. Rule-based simulation

• e.g. FishXing.

• Multiple scale

• Low cost.

• Can be employed across scales.

• Requires detailed hydrological data.

• Information about multiple species of fish is often incomplete or lacking.

• Validation using fine-resolution fish data is rare.

FishXing –

helps design and evaluation of culverts for

fish passage based on estimates of swimming

capabilities of fish

8. Statistical models

• (e.g. multivariate regression)

• Multiple scale

• Low cost.

• Can be employed across scales.

• Identifies factors that influence passability.

• Transferability of predictions to barriers with similar physical and hydraulic conditions.

• Requires basic input data which must usually be obtained using fine-scaled approaches.

9. Expert opinion

• Multiple scales.

• Low cost.

• Can be employed across scales.

• Validation using fine-resolution fish data is

rare.

Developing Inventories of Barriers

Database

of barriers

- California Database of barriers

- England and Wales

The development of inventories

• Inventories of barriers tend to be GIS

based geospatial databases

• Problems - data quality

- obtained from multiple

sources

- ownership and

management

The development of inventories

Prioritisation of restoration actions

Prioritisation of restoration actions

Barrier removal or repair

• Scoring-and-ranking

• Network analysis

• Optimisation

Optimization modelling

Precedents in transport

system modelling

Network analysis can also be used to plan

river development in a way that minimises

environmental impacts

Conclusions • Europe – long historic legacy of river development

so high density of barriers to fish migration

• Extensive habitat fragmentation due to barriers

• Water Framework Directive – legislative framework for restoration

• Multiple methods for barrier porosity assessment

• Inventories of barriers based largely on GIS

• Prioritisation (of restoration or development) should use optimisation and network analysis and avoid scoring and ranking

Thank you