University of Western Australia - Gregory

Restoration Project

University of Western Australia - Gregory

Restoration Objective:

This study tested the efficacy of bubble curtains as an exclusion device for herbivorous fishes. Specifically, it asked whether changes in transplanted seaweed biomass and fish feeding rates differ among unprotected transplants, caged transplants or transplants protected by bubble curtains. In addition, they compared bubble curtains with a benthic exclusion area of 0.785 and 3.14m2 to examine the effect of curtain size on herbivore exclusion.

Site Selection Criteria:

This study was conducted in Port Gregory in Western Australia. This site was selected because it has some of the highest browsing herbivore biomasses and feeding rates reported from either temperate or tropical reef systems.

Cause Of Decline:

In marine systems, herbivores are estimated to consume 68% of benthic primary production on average globally. Moreover, abrupt changes in herbivore abundances and over-grazing have contributed to catastrophic regime shifts from vegetated to denuded states in temperate systems. In addition to the direct effects of herbivores, many vegetated marine ecosystems such as seagrass meadows and kelp forests are in decline as a result of anthropogenic disturbances from eutrophication, climatic warming and extreme events, sediment-loading, salinity changes and invasive species.

Key Reasons For Decline:

Overgrazing

Scientific Paper

Bubble Curtains: Herbivore Exclusion Devices for Ecology and Restoration of Marine Ecosystems?

S. Bennett, T. Wernberg, T. Bettignies
Frontiers in Marine Science, Vol. 4.
https://doi.org/10.3389/fmars.2017.00302

Organisation:

University of Western Australia

Site Observations:

Observation Date

1st Oct 2014 – 2nd Oct 2014

Action Summary:

Ecklonia radiata individuals were collected, measured and transplanted onto reefs with high herbivore pressure in steel exclusion cages covered in steel mesh. Kelps were weighed down using weights and cable ties. Following the 2 hour feeding trial, translocated kelps were recollected and transported to the laboratory where fresh weight and length were re-measured to assess herbivore impact.

Lessons Learned:

This study provides preliminary evidence that bubble cages can exclude herbivorous fishes as effectively as traditional steel cages.

Project Outcomes:

Kelp biomass loss was significantly lower inside the bubble curtains compared to unprotected kelps, and did not differ from kelp loss rates in traditional exclusion cages. Consistent with this finding, no herbivorous fishes were observed entering into the bubble curtain at any point during the experiment. In contrast, fish bite rates on unprotected kelps were 1,621 ± 702 bites h−1 (mean ± SE).

Key Reasons For Decline:

Overgrazing

Area of Restoration (Ha)

0

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

67.4290
%
100.0000
%
Transplant Info:
Adherence Method:Cable Tie
Life Stage:Adult

Observation Date

1st Oct 2014 – 2nd Oct 2014

Action Summary:

Ecklonia radiata individuals were collected, measured and transplanted onto reefs with high herbivore pressure in steel exclusion cages covered in steel mesh. Kelps were weighed down using weights and cable ties. Following the 2 hour feeding trial, translocated kelps were recollected and transported to the laboratory where fresh weight and length were re-measured to assess herbivore impact.

Lessons Learned:

This study provides preliminary evidence that bubble cages can exclude herbivorous fishes as effectively as traditional steel cages.

Project Outcomes:

Kelp biomass loss was significantly lower inside the bubble curtains compared to unprotected kelps, and did not differ from kelp loss rates in traditional exclusion cages. Consistent with this finding, no herbivorous fishes were observed entering into the bubble curtain at any point during the experiment. In contrast, fish bite rates on unprotected kelps were 1,621 ± 702 bites h−1 (mean ± SE).

Key Reasons For Decline:

Overgrazing

Area of Restoration (Ha)

0

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

95.2000
%
100.0000
%
Transplant Info:
Adherence Method:Cable Tie
Life Stage:Adult

Observation Date

1st Oct 2014 – 2nd Oct 2014

Action Summary:

Ecklonia radiata individuals were collected, measured and transplanted onto reefs with high herbivore pressure in steel exclusion cages covered in steel mesh. Kelps were weighed down using weights and cable ties. Following the 2 hour feeding trial, translocated kelps were recollected and transported to the laboratory where fresh weight and length were re-measured to assess herbivore impact.

Lessons Learned:

This study provides preliminary evidence that bubble cages can exclude herbivorous fishes as effectively as traditional steel cages.

Project Outcomes:

Kelp biomass loss was significantly lower inside the bubble curtains compared to unprotected kelps, and did not differ from kelp loss rates in traditional exclusion cages. Consistent with this finding, no herbivorous fishes were observed entering into the bubble curtain at any point during the experiment. In contrast, fish bite rates on unprotected kelps were 1,621 ± 702 bites h−1 (mean ± SE).

Key Reasons For Decline:

Overgrazing

Area of Restoration (Ha)

0

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

94.8600
%
100.0000
%
Transplant Info:
Adherence Method:Cable Tie
Life Stage:Adult
Source:Wild
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