resurvey of the longspined sea urchin & barren grounds in ... · * crown-o (-dhorns o µtbrea l...

Scott Ling, John Keane1444ththth Dec 2018

Resurvey of the Longspined Sea Urchin & barren grounds in Tasmania

Late 1960’s

1978

Mid 1980s2005

EAC

18 yrs

11 yrs5 yrs

13 yrs

16 yrs

20 yrs

Climate driven range-extension

August 1945-2016

Kelp bed Urchin barren

Centrostephanus barrens

Centrostephanus behaviour

Dynamics of urchin overgrazing

resil

ienc

e

Kelp collapse 2 2 rchins -2 550 g -2)

Kelp

bed

cove

r (%

)

0 1 0 2 0 0 4 0 5 0

Sea rchin densit (no -2)

An o nce o prevention is orth a ton o c re

18 onths

ecover 0 4 rchins -2 (70 g -2)

Resurvey of Longspined Sea Urchins & barren grounds2001/02 vs 2016/17

• A total o 156 Dive 156 ideo ransects

• Sites spaced ever 20 along open coast, at each site s b-sites ere s rve ed

ith 4 transects s rve ed at each s b-site

• es rve o e isting sites ‘Apples vs Apples’ co parison thr ti e

Dive survey (4(4-4-18 m depth)

VVideoo survey (4(4-4-40 m depth)

0 1 2 412

456789

1011121


Eastcoast change: 1 75 increase

Centrostephanus ab ndance ( ean no rchins 5 -2 ± SE)

1,200 rchins per ha 2,600 rchins per ha*20 illion individ als

* Crown-o - horns o tbrea triggered at 15 star ish per ha

12

456789

0 10 20 0 40 500 10 20 0 40 50

Planar percent cover is sum of:Type I barrens = continuousType II barrens => 40% coverType III barrens = 20-40% coverType IV barrens = <20% cover

Eastcoast onl

Eastcoast change: 4% -> 15 2% 4 5 increase


440 ha

178 ha

86 ha

otal 1,726 ha barrens

250 ha

205 ha

188 ha

04 ha

47 ha

25 ha

lanar percent cover rchin barrens( ean % ree ± SE)


12

456789

0 10 20 0 40 50 60 70 80 901000 10 20 0 40 50 60 70 80 90 100

ercentage o ree with barrens o an t pe ( ean % ± SE)

Barren types:Type I barrens = continuousType II barrens => 40% coverType III barrens = 20-40% coverType IV barrens = <20% cover

Eastcoast change: 9% -> 47%

5 2 increase

Eastcoast onl


Eastcoast onl

Depth categor ( )

Distribution by depth

lana

r per

cent

cove

r rc

hin

barr

ens

(ea

n %

ree

±SE

)

Resurvey of the Longspined Sea Urchin & barren grounds2001/02 vs 2016/17

Distribution by reef type & depth


Eastcoast onl


Re-survey summary:• Signi icant increase over 15 ears:

Urchins al ost do bled ( 1 75 increase)arrens ore than adr pled ( 4 5 increase)

• M ch o Eastcoast showing signs o gra ing i pact, so e ree s approaching overgra ing tipping-point in co ing ears

• “Ounce of prevention worth ton of cure> st act be ore it is too late, so where how sho ld we act


Eastcoast onl

C ll while catch

Predators of Longspined Sea Urchins: Large lobsters >140 mm carapace

oct rnal predators, can pre on large rchins when the e erge at night

Predators of Longspined Sea Urchins: Large wrasse >30cm

Da ti e predators, can pre on s all rchins when e posed

Blue Throat Wrasse

Eastern Blue Grouper (NSW footage)

Da ti e predators, can pre on large rchins in crevices present in as

Predators of Longspined Sea Urchins: Large wrasse >30cm

Double header wrasse (Middleton Reef footage) Predators of Longspined Sea Urchins: Large wrasse >30cm

Double header wrasse (Middleton Reef/ Lord Howe footage) Predators of Longspined Sea Urchins: Large wrasse

Fishing predators

Kelp

bed

re

silie

nce

Kelp Barrens

Fishing large predators= loss of kelp bed resilience

Low

kel

p be

d Re

silie

nce

Hig

h ke

lp b

ed

Resi

lienc

e

A.

B.

Barr

ens

resi

lienc

e

Reversing fishing ?

Rebuilding predatorsincluding human harvest& culling approaches=> integrated approach

State-dependent Integrated Pest Management (sIPM)Prevention

C re

Kelp bed Urchin barrenReef state:

Effectiveness of control over a 5 yr period

Control optionPrevention

(kelp bed resilience)Cure

(recovery of barrens) Depth range Est. cost per ha Cost per 500 ha

1 iological control - predation b enhancing large lobsters Yes No 0 - 40 ranslocation social costs

ranslocation social costs

2 iological control - predation b enhancing l e ro per Yes 0 - 40 ranslocation costs ranslocation costs

Abalone rec divers c lling rchins while ishing Yes No 0 - 18 Cost ne tral Cost ne tral

4 arvesting o rchins ranching to i prove ar etabilit Yes No 0 - 18 Mar et develop ent costs

Mar et develop ent costs

5 Dedicated rchin c lling b co ercial divers rec divers Yes 0 - 18 $18 K $9 M

6 A tono o s robotic c lling

7 ic -li ing (diver or deeper water)

8 io-tech control (triggering disease o tbrea on barrens )

*

* ranslocation or lobster reb ilding wo ld not a ect trends in the re-s rve beca se o ti ing

resurvey of the longspined sea urchin & barren grounds in ... · * crown-o (-dhorns o µtbrea l...

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