Rehabilitation projects to

conserve threatened Cape

fynbos fishes: getting invasive

alien fishes out of selected

priority inland waters

Dean Impson¹, Riaan van der Walt²,

Martine Jordaan¹, Jeanne Gouws¹, Sean

Marr³ & Olaf Weyl³

¹ CapeNature

² Advanced Environmental Corporation

³ South African Institute for Aquatic Biodiversity and

Centre of Excellence for Invasion Biology

Unique and Imperiled freshwater fishes of the Cape

fynbos region

• Distinct aquatic eco-region of Africa (Cape Fold Ecoregion)

• 4 fish families present, all river dwelliers

• 18 of 21 species endemic, no piscivorous species

• Most species small and v. susceptible to alien fish impacts

• High number of threatened species and taxa

• New species being discovered e.g. giant and Verlorenvlei

redfins

• Priority area for fish conservation

Cyprinidae – 17 spp

dominated by small redfins

Anabantidae – 1

species??

Galaxidae – a species

complex of likely more

than 10 species being

described

Austroglanididae – 2 species

Major threats, focusing on invasive

fish species

• No 1 threat – invasive alien fishes.

• Habitat degradation also a major problem

• From mid 1850s > 20 species introduced for

angling, fish farming and biological control purposes

• All major river systems invaded - 21 species

• Predatory black basses had most severe impact

• Invasive fishes are however backbone of substantial

recreational angling and fish farming (trout) industry

Extent of alien fish invasion in river systems

no non-native species

1-3 non-native species

4-6 non-native species

7-9 non-native species

10-12 non-native species

Figure:

Sean Marr

Addressing the threat of invasive alien fishes

in five priority rivers in the Cederberg region

Pilot project – Rondegat River

• Rondegat is a small shallow perennial river about 20km long

with clear acidic water. It flows into Clanwilliam Dam.

• Lower 4 km of river invaded by alien bass - severe effects on

indigenous fishes. Alien fish in river are small with no angling

value.

• Primary goal of CapeNature – eradicate alien fish between weir

and waterfall (4km of river) using the piscicide rotenone.

• Secondary goal – remove invasive trees from riparian zone

• One land-owner in treatment area – very supportive of project

Location of project

Rondegat

River

Olifants River

Olifants

River

Waterfall

Cape

Town

Cedarberg

Wilderness

Area

Generally single channel shallow river

Alien fish

Indigenous

fish

Project was controversial as it involved alien fish control and rotenone use

Alien fish eradication:

• Trout, bass are highly valued by recreational fishing sector

• Both sectors well organised in South Africa

• Concern expressed by effect of rotenone projects if these

were planned for popular bass and trout waters

Rotenone:

• Project critics used info on internet to challenge scientists

• Effect of rotenone on non-target fauna (aquatic insects) used

frequently as a weapon to attack project

• Project critics used media and internet to try and stop

project

The controversy

Experts slam plan to poison fish

May 10 2008 at 04:26pm

By Helen Bamford

Conservationists, anglers and

scientists are up in arms over plans by

CapeNature to poison four rivers to get

rid of invasive alien fish like trout and

bass.

They fear poisoning the rivers will

not only kill off the alien fish but

could result in a mass extermination

of all endemic insect and aquatic

species in the rivers and devastate

the fragile eco-systems.

From: Cape Times May 10, 2008

Rotenone application

according to best practice

• Major funding from 2010 by DEA’s Working for Water programme –

allowed integrated control of invasive fishes and trees on Rondegat

• Project components plans developed in 2011 (e.g. Comms, Fish

Rescue, Safety and Security, Rotenone Treatment and Rotenone

Neutralisation)

• Legal approvals obtained from Dept. of Agriculture and Dept. of

Water Affairs for import and experimental use of CFT Legumine

• Independent biological monitoring started in 2011 to quantify

recovery of river (funded by Water Research Commission)

The Rondegat treatments of 2012 and

2013

• On 13 March 2013, 4 treatment stations

used with backpack sprayers apply

0.75 ppm CFT Legumine for 6 hours

• De-toxification station below weir

achieved neutralisation at Potassium

permangenate concentration of 2.5%

• key stakeholders observe treatment –

e.g. regulators, universities, funders,

water users, angling bodies

• Treatment Application Plan used with international supervision

• On 29 Feb 2012, 7 treatment stations on river and backpack sprayers

apply 1 ppm CFT Legumine for 6 hours. Water temp ~ 26 C, flow 70 l/s

2012 treatment: CapeNature team

trained by experts

Impson, Finlayson, Steinkjer on

day of historic first treatment

Finlayson and Steinkjer

training CapeNature staff

Drip can station and backpack sprayer

Improved second treatment in 2013

Cleared river channel

Saving and releasing rotenone affected fish –

80% success!

Strong recovery of threatened endemic fishes!

Labeobarbus capensis

Pseudobarbus phlegethon

Barbus calidusSite

1 11 21 31

Density (

fish/m

2)

0.0

0.5

1.0

1.5

2.0

2.5

Cla

nw

illia

m D

am

Density (

fish/m

2)

0

1

2

3

4

Invaded zone

Rooidrai

waterfallWaterfall

Cla

nw

illia

m D

am

Barbus calidus (N)

Pseudobarbus phlegethon(N)

Labeobarbus capensis (N)

Micropterus dolomieu (A)

Other alien fishes

Weir

Invaded

zoneRooidrai

waterfallWaterfall

Weir

Pre-treatment (February 2012)

1 year post-treatment (February 2013)

Impact on non-target taxa

Control

Year

May 10 Mar 11 Jan 12 Nov 12 Oct 13 Aug 14 Jun 15

Den

sity

(E

PT

taxa

/cm

2)

0.0

0.1

0.2

0.3

0.4

Treatment

Treatment 1

Treatment 2

Pilot Project on river a success, finally!

• Project 10 years from inception to completion

• Biological monitoring confirms all bass killed in treatment area and

excellent recovery of threatened indigenous fishes

• CapeNature involvement at all levels, also now have trained team

• Very positive media coverage of treatment and outcomes

(newspapers, magazines, television)

• Scientific credibility of project through peer reviewed publications

• Range of stakeholders see value in piscicide projects

Cleared riparian zone of alien vegetation

Positive publicity finally..

Scientific credibility

Two dams successfully treated with

rotenone in 2017

• Pilot project of two small farm dams in support of

registration of CFT Legumine for controlled use

• GA’s obtained from DWS

• Offstream dam on Krom River invaded with Bluegill

sunfish. Dam successfully treated with rotenone by

CapeNature on 25 January 2017.

• Off-stream dam on Oorlogskloof River, N. Cape invaded

by carp. Dam successfully treated with rotenone by

CapeNature on 29 March 2017

• Monitoring led by SAIAB, assisted by Freshwater

Research Centre, and post graduate students of

University of Venda, Fort Hare, Rhodes, Stellenbosch,

Zululand and Western Cape

• Funding from WRC

Krom River

Dam

Aquatic Invertebrates

Phyto- and

Zooplankton

Nieuwoudtville Dam

Treatment

Control

• Analysis of aquatic invertebrates, phyto-and zooplankton, rotenone breakdown and water parameters ongoing by researchers

SASAQS 2017

• A comparison of the biology of bluegill sunfish Lepomis macrochirus from lentic and lotic environments in the Krom River catchment, Western Cape.– Kanie Chauke, Stefan Foord, Hermien Roux, Lubabalo Mofu,

Sean Marr

SASAQS 2017

• An evaluation of rotenone treatment by comparing the detection probability of three fish survey methods (fyke nets, gill nets and cameras) in the rivers and dams of Cederberg Krom River.– Lorraine Ramotjiki, Stefan Foord, Hermien Roux, Bianca

Hannweg, Sean Marr

Current plans to control of alien fishes

• Successful projects will be used to motivate for

registration of CFT Legumine for controlled use

• Krom River – plan to clear largemouth bass and bluegill in

2017/18

• Biedouw River – plan to clear smallmouth bass and

bluegill in 2018/19

• Breekrans River – plan to clear spotted bass in 2019/20

18 rivers in total have been earmarked for alien fish control

in the Cape fynbos region to more effectively conserve

threatened fynbos fishes. These have been communicated

to organized angling. None are priorities for angling.

ACKNOWLEDGEMENTS

Early funders

Best practice guiders

Main funder

Biological monitoring

Photos / Images: C. Garrow,

R. Bills, S. Marr, P. Skelton,

O. Weyl, K. Montgomery