Trial of an industry implemented, spatially discrete ... et al Urchin Cull.pdf · Baulch, Vanessa...
Transcript of Trial of an industry implemented, spatially discrete ... et al Urchin Cull.pdf · Baulch, Vanessa...
Sean Tracey, Craig Mundy, Klaas Hartmann, Travis Baulch, Vanessa Lucieer, Martin Marzloff
Trial of an industry implemented, spatially discrete culling program for Centrostephanusrodgersii in Tasmania
Background/Objectives
Determine the effectiveness of divers physically destroying urchins in situ to allow the re-establishment of native flora and fauna
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Methods/Results Cull 1 Yr 2 Yr
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Results
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– The average cull rate was 7.0 (SE = 0.4) urchins per diver per minute, highest was 14 urchins per div/min
– The average time to complete a plot (1,500 m-2) was 4.8 hours, or, 5.2 m-2 /min.
Cull rate
Depth Air EAN35 EAN40DCIEM Tables
Suunto Dive
Computer
Nitrox Tables SuuntoDive
Computer
Nitrox Tables
Suunto Dive Computer
5m 720 Unlimited 720 Unlimited 720 Unlimited10m 150 165 300 Unlimited 720 Unlimited15m 75 65 150 156 300 20520m 35 35 75 66 75 8825m 20 22 35 41 50 MOD 56 MOD30m 15 15 25 MOD 29 MOD > MOD > MOD
Limitations: Dive time at depth
Working at depth – Air vs Nitrox
Determine dive profile strategies to enable safe harvest of urchins at depths greater than 15m
Example: Maximum dive times for repetitive divesDive 1 - 25 metres
Surface Interval 1 Hour Dive 2 - 25 metres
• Maximum dive times on AirDive 1 20 mins + Dive 2 11 mins = TOTAL TIME 31mins
• Maximum dive times on Nitrox EAN40Dive 1 50 mins + Dive 2 29 mins = TOTAL TIME 79mins
Air = approx. 31 x 7 = 217 urchinsNitrox = approx. 79 x 7 = 553 urchins
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Limitations: Repetitive dives
– Tasmanian Combined Dive Clubs Weekend (CCW)
– Coordinated via John Keane via the Tas Uni Dive Club (TUDC)
– Attracts ~9 Tasmanian clubs, ca. 150 divers
Recreational Culling – Dive Clubs
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Conclusions
Targeted culling by divers;– Is effective at reducing urchin abundance
– Does facilitate recovery of kelp beds
– Probably limited to small discrete reef patches at intermediate depths
– Could be applied to protect high value reef patches (biodiversity, fishery, eco-tourism, etc)
– Repetition? (every 5 to 7 years?)
N.B. Must determine which diving standard applies: Research, Fishing, Recreational, or Occupational?