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Bias in lobster tethering experiments conducted for selecting low-predation release sites


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Mills, DJ, Johnson, CR and Gardner, C 2008 , 'Bias in lobster tethering experiments conducted for selecting low-predation release sites' , Marine Ecology Progress Series, vol. 364 , pp. 1-13 , doi: 10.3354/meps07527.

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Juvenile spiny lobsters Jasus edwardsii,
grown in tanks for 1 yr following capture as pueruli,
may be released to coastal reefs in Tasmania, Australia,
to offset possible stock depletion resulting from
the harvest of pueruli for commercial culture. We
assessed the utility of tethering experiments for selecting
sites with low predation pressure appropriate for
lobster releases, and address a concern that experimental
artefacts are likely to vary across sites, providing
biased estimates of relative mortality. A multicamera
surveillance system used to observe tethered
juvenile lobsters at 4 isolated reefs revealed lowdiversity
of predators, which included wrasse (45%
of observed predation events), octopus (21%), crabs
(17%) and large lobsters (16%). Wrasse and octopus
were the dominant predators at 3 of the 4 sites, while
crabs and large lobsters dominated the fourth. Survival
rates in 48 h tethering trials varied substantially (24.4
to 62.2%) among sites. Tethers substantially increased
the success rates of all predators in a reef mesocosm.
The magnitude of the tethering effect was similar for
wrasse and octopus, while large lobsters caught relatively
few untethered juvenile lobsters, and crabs
appeared incapable of catching untethered lobsters.
Survival rates for each site were adjusted by applying
a site-specific correction factor calculated using knowledge
of predator suites at each site and magnitude of
tethering bias for each predator. Corrected survival
rates did not vary among sites, and the rank order of
sites in terms of predation rates did not change following
correction; overall, there was a significant correlation
between adjusted and unadjusted values. Our
results suggest that tethering trials are appropriate as a
tool for selecting release sites only if complementary
data on predator assemblages and tethering artefacts
are collected with sufficient rigour to enable calculating
site-specific correction factors.

Item Type: Article
Authors/Creators:Mills, DJ and Johnson, CR and Gardner, C
Keywords: Spiny lobster · Jasus edwardsii · Fishery enhancement · Tethering experiments · Predation · Experimental artefacts
Journal or Publication Title: Marine Ecology Progress Series
ISSN: 0171-8630
DOI / ID Number: 10.3354/meps07527
Additional Information:

Copyright © 2008 Inter-Research

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