Good fences make good neighbours:

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Good fences make good neighbours: experimental rehabilitation of the spawning habitat of. Galaxias maculatus. Mike Hickford and David Schiel ...
Good fences make good neighbours: experimental rehabilitation of the spawning habitat of Galaxias maculatus Mike Hickford and David Schiel

Galaxias maculatus Indo-Pacific (+Atlantic!) distribution

Image: Ryan photographic

Galaxias maculatus Indo-Pacific (+Atlantic!) distribution

Image: Ryan photographic

Diadromous fish: crossing major ecosystems ‘Terrestrial’ Egg phase ~ 28 days Riparian

Freshwater Adult phase ~180 days

Marine Larval phase ~180 days

Restricted spawning habitat

Restricted spawning habitat

Restricted spawning habitat

Source/sink populations Oceanic

Riverine

•Larvae

Source

• Juveniles and adults

Intact spawning habitat • lots of eggs produced

Spawning site selection

Sink

Up to 100% egg mortality

Degraded spawning habitat • very few eggs produced •Typical of many rivers in NZ

Hickford MJH & DR Schiel (2011). Population sinks resulting from degraded habitats of an obligate life-history pathway. Oecologia 166(1): 131-140

Whitebait fishery

• Culturally and commercially important • Catching juveniles

Whitebait fishery

• Culturally and commercially important • Catching juveniles

Riparian spawning habitat

Multiple stressors

Livestock grazing

Livestock grazing

Goughs Bay

Goughs Bay

Goughs Bay

Goughs Bay

Spawning site

Ungrazed exclosures

Design • 8 exclosures installed in Jan 2007 • grazed and ungrazed areas surveyed for vegetation and eggs during spawning seasons in 2007, 2008, 2009 and 2011

Ongoing livestock grazing

Root wad depth (mm)

Tiller density (No. cm-2)

Vegetation height (mm)

Vegetation characteristics 400

p < 0.001 F2,294 = 12.52, Grazed

Ungrazed

200 4 3 F2,294 = 6.71, p < 0.05 2 1 40 30 20 F2,294 = 46.43, p < 0.001 10 0 Feb 07

Feb 08

Feb 09 Feb 11

Physical environment Temperature 40

100

2007

50

20 0

Frequency (%)

40

0 100

2008

50

20 0 40

0 100

2009

50

20

0 100

0 40

Relative humidity

2011

Too dry

Too hot 50

20 0

0 0 5 10 15 20 25 30 35

Maximum daily ground-level temperature (oC)

Grazed

40 50 60 70 80 90100 Minimum daily ground-level relative humidity (%)

Ungrazed

14d survival (%)

Egg density (No. cm-2)

Egg production 15

Grazed

Ungrazed

10 5

F2,263 = 17.17, p < 0.05

0 80 60 40 F1,94 = 27.64, p < 0.05 20 0 Feb07

Feb08

Feb09 Feb11

Total egg production Total egg production (x1000)

Area x density x survival 300

Grazed

Ungrazed

200

100

0 Feb 07

Feb 08

Feb 09

Feb 10

Feb 11

Summary Removal of major stressor (livestock grazing) produces: – – – – –

Tall, dense vegetation Thick, aerial root wad Buffered ground-level physical conditions More Galaxias maculatus eggs Better egg survival

Even a wide-ranging species with many robust adult populations can be compromised if a relatively small, stage-dependent habitat is required to complete its life history

Acknowledgements

Funding: Ministry of Science and Innovation (CO1X1002) National Institute of Water and Atmospheric Research Fieldwork: Kerry O’Connell, Malene Møhl, Kimberley Seaward, David Taylor, Russell Taylor, Renny Bishop & MERG End-user partners: