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What Doesn’t Kill You Makes You Wary? Effect of Repeated Culling on the Behaviour of an Invasive Predator

Researchers in the Bahamas found that lionfish on culled reefs altered their behavior. They were less active and hid deeper during the day, when culling took place. This led them to hunt more often during dawn and dusk, which is also when their prey are more active. Researchers are not sure whether this shift in behavior is learned (lionfish have learned to perceive the threat of divers hunting for them) or evolutionary (the bold lionfish are being culled, leaving the shy and more hidden ones). This has management implications because if they are learning to hide it is important to cull them at longer intervals, so that they ‘forget’ their fear of divers. If their behavior is evolutionary, and the more bold lionfish are being hunted and killed, this could have positive benefits for conservation efforts. The remaining population would have a lower fitness because shyer predators capture fewer prey.

Author: Cote, I.S., E.S. Darling, L. Malpica-Cruz, N.S. Smith, S.J. Green, J. Curtis-Quick, and C. Layman
Year: 2014
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PLoS ONE 9(4): e94248. doi:10.1371/journal.pone.0094248

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Hawaii – Invasive Species


Building Reef Resilience Through Invasive Algae Removal and Urchin Biocontrol in Kāne‘ohe Bay

Location
Kāne‘ohe Bay, O‘ahu, Hawai‘i

The Challenge
Kāne‘ohe Bay lies below the dramatic Ko‘olau mountain range on the windward side of O‘ahu. It is the largest sheltered body of water in the main Hawai‘ian Islands, and is surrounded by numerous freshwater streams and wetlands. It is the only bay in Hawai‘i that includes fringing reefs, patch reefs, and barrier reefs. It has significant cultural and ecological value, and has long been a rich resource for commercial, recreational and subsistence uses. The bay has more than 40,000 people living near its shores or in the mountains above it, as well as a U.S. Marine Corps Base, the University of Hawai‘i Institute of Marine Biology on Moku o Lo‘e (Coconut Island), and a public pier that provides daily access to hundreds of tourists and fishermen.

Invasive alien algae are a significant threat to Hawai‘i’s nearshore coral reef ecosystems. In ocean ecosystems that are already threatened by land-based pollution and overfishing, they can easily take over and smother reefs to death. Unfortunately, the reefs in Kāne‘ohe Bay are suffering from an overgrowth of invasive algae that forms thick, tangled mats. Gracilaria salicornia (gorilla ogo) and Kappaphycus/Eucheuma spp. (smothering seaweed) were introduced to the bay for aquaculture purposes in the early 1970s. These fast growing algae have now spread throughout the entire bay where they outcompete native seaweeds, smothering and killing coral reefs, covering up native fish habitat, preventing new corals from attaching to the reef, and reducing the overall health and biodiversity of the entire bay. Fortunately, native sea urchins (Tripneustes gratilla) like to eat it, but their populations are depleted in the bay.

If nothing is done to stop the spread of invasive algae, it will continue to move northward, spreading from the bay to reefs along the rest of O‘ahu’s shoreline.

Actions Taken
To restore Kāne‘ohe Bay coral reefs and prevent the further spread of invasive algae, the State of Hawai‘i’s Division of Aquatic Resources (DAR), in partnership with The Nature Conservancy (TNC) and the University of Hawai‘i (UH), embarked on a dual-phased restoration project to control the invasive algae by:

  • Removing invasive algae to allow coral reefs and native fish habitat to thrive
  • Restocking the reefs with native sea urchins that eat the invasive algae and keep it from growing back
Divers using the Super Sucker to remove invasive seaweed © Hawai‘i DLNR

Divers using the Super Sucker to remove invasive seaweed. © Hawai‘i DLNR

Invasive Algae Removal
DAR, TNC, and UH developed the first Super Sucker barge in 2005 to “suck up” invasive algae. The Super Sucker is a suction pump on a barge with hoses that are used by divers to vacuum the invasive algae off the reefs. The invasive algae are then delivered to local farmers who use it for compost.

The Super Sucker is capable of removing anywhere from 600-1,000 pounds (270-450 kg) of algae per hour depending on location and conditions. Last year, TNC built a second Super Sucker and a mini Sucker to be used in shallower water, to help speed up the operation.

Native Sea Urchin Biocontrol
Although the Super Sucker is effective at removing the bulk of the invasive algae, the algae can return within six months if nothing is done to stop it. In order to prevent the algae from growing back, DAR operates a sea urchin hatchery at their Anuenue Fisheries Research Center. These native “collector urchins” were once plentiful in Kāne‘ohe Bay, but their populations have declined over the last few decades.

Juvenile collector urchin being outplanted to the reef. © Hawai‘i DLNR

The state has successfully reared T. gratilla from the larval stage all the way through to adulthood. The hatchery has been producing approximately 5,000 urchins each month, and they are working to dramatically increase that number to keep pace with the rate of invasive algae removal. The urchins are transplanted directly onto the reefs to graze after the Super Sucker has removed the majority of invasive algae. Because the urchins will not cross the sandy areas between reefs, they are likely to stay put; they can also be re-collected and moved to other patch reefs if necessary.

Keeping the reefs clear of invasive algae opens up new space for coral recruits and native seaweeds, and helps restore natural habitat for fish and other sea creatures, making Kāne‘ohe Bay more resilient to future threats.

How Successful Has it Been?
Since October 2012, the coordinated TNC/DAR crews have removed 250,000 pounds (114,000 kg) of invasive algae from 20 acres (8 ha) of reef. The algae are given to local farmers for compost.

As of August 2013, the team marked a huge milestone: a total of 100,000 urchins from the Anuenue hatchery have been transplanted onto the reefs. Research is being done to determine the optimal density of urchins needed per acre to keep the algae in check. And field monitoring continues on urchin density, coral cover, coral recruitment, and algal density and diversity.

Lessons Learned and Recommendations
Lessons learned and key recommendations include:

  • Recommend cleaning all boating, fishing and dive gear to prevent the spread of invasive species to new areas.
  • Encourage local fishermen to take only what they need. Leave herbivorous fish and native sea urchins to eat the invasive algae, and other sea life to reproduce and replenish the bay.
  • Work with the local community to keep the watershed clean – educate residents about proper land clearing and maintenance and other ways to reduce runoff of sediment and nutrients into the bay.
  • Encourage the public to volunteer with local community organizations who are working to restore the streams, wetlands, fishponds, and native agricultural lands in this watershed.

Funding Summary
State of Hawai‘i
For the past three years, the Super Sucker barge and urchin hatchery have been funded through the state’s Hawai‘i Invasive Species Council, in addition to federal grants from the National Oceanic and Atmospheric Administration. Mitigation funds are also a source of current and future support.

The Nature Conservancy
The Nature Conservancy has committed to raise $2.5 million (US) to pay for the construction of the new Super Sucker and three years of operation.

Lead State Organization
Hawai‘i Department of Land and Natural Resources, Division of Aquatic Resources

Partners
Hawai‘i Department of Agriculture
Harold K.L. Castle Foundation
Hawai‘i Invasive Species Council
Kākoʻo ‘Ōiwi
Kama‘aina Kids
Kāne‘ohe Canoe Club
National Oceanic and Atmospheric Administration
The Nature Conservancy
University of Hawai‘i Institute of Marine Biology

Resources
Reef Resilience Webinar — Restoring a Reef Flat: Benefits of Invasive Algae Removal in Hawai‘i
Hawai‘i Invasive Species Council
Protecting Hawai‘i’s Reefs from Invasive Seaweed, Hawai‘i Department of Land and Natural Resources
Hawaii Coral Reef Strategy, State of Hawaii (pdf)
The culture of native collector sea urchins as a biocontrol option for alien algae control
Hawai‘i Aquatic Invasive Species Management Plan, Hawai‘i Division of Aquatic Resources (pdf)
Invasive Algae of Hawai‘i poster, Hawai‘i Division of Aquatic Resources (pdf)
Reef Revival, The Nature Conservancy
Reef Revival: A Campaign to Restore Kāne‘ohe Bay, The Nature Conservancy

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Hawaii – Fisheries Management


Managing Fisheries for Reef Resilience: Kahekili Herbivore Fisheries Management Area

Location
North Kāʻanapali, West Maui, Hawai‘i

The Challenge
Long term monitoring of coral reefs along the leeward coast of the Island of Maui began in 1999 by the State of Hawai‘i’s Division of Aquatic Resources (DAR) and the University of Hawai‘i’s (UH) Institute of Marine Biology’s Coral Reef Monitoring Assessment Program. Many of these coral reef survey locations were established at previous study sites, providing managers with a longer term picture of the changes on these reef systems. Assessments have shown that of the nine reefs monitored, many sites experienced a significant decrease in live coral cover as reefs became overrun by invasive algae. At Kahekili in north Kāʻanapali, reef monitoring sites indicated a decrease in coral cover from 55% to 33% between 1994 and 2006.

The significant increases of invasive algae were seen as a major threat to West Maui’s coral reefs. At Kāʻanapali, specifically, red algal blooms of Acanthophora spicifera had become much more abundant, which was suggested by UH research to be a result of elevated nutrients from wastewater and fertilizers. Despite the sources of land-based pollution, the increasing abundance of algae was exacerbated by the fact that there was a decrease in abundance of reef grazing herbivores, which fish surveys at the same sites confirmed.

Boundaries of the KHFMA along the Kāʻanapali Coast, West Maui. © Hawai‘i DLNR

Boundaries of the KHFMA along the
Kāʻanapali Coast, West Maui. © Hawai‘i DLNR

Actions Taken
A cooperative “Fish Habitat Utilization Study” by DAR and the National Oceanic and Atmospheric Administration (NOAA) revealed clear evidence of the relationship between grazing fish and the abundance of invasive algae; the more herbivorous fishes present, the less algae on the reefs.

Therefore, in July of 2009, the State of Hawai‘i designated the Kahekili Herbivore Fisheries Management Area (KHFMA) in order to control the overabundance of marine algae on coral reefs and restore the marine ecosystem back to a healthy balance. The killing, injuring, or harming of sea urchins and certain herbivorous fishes, including sea chubs, parrotfish, and surgeonfish is prohibited in order to increase the local abundance of these beneficial fishes and sea urchins in the area. Feeding of these fishes is also prohibited in order to promote grazing. The onshore boundaries extend from Honokōwai Beach Park (and offshore for a distance of 1,292 yards) south approximately 2 miles to Hanaka’ō’ō Beach (and offshore for a distance of 335 yards) (Hawai‘i Revised Statues, Chapter 13-60.7).

How Successful Has it Been?
Although some fishermen and cultural practitioners opposed fishing rules, the majority of the community was in strong support of the KHFMA. Many of the local fishermen understood the poor conditions of the reef, and realized the benefits of fisheries management. The overwhelming support for the KHFMA has led to more education within the area as well as compliance with the rules.

Since the establishment of the KHFMA in 2009, DAR, in partnership with UH and NOAA’s Pacific Islands Fisheries Science Center (PIFSC), has continued monitoring the reefs at Kahekili. According to the PIFSC Interim Monitoring Report from February 2013, results thus far indicate the following:

  • Consistent upward trend in biomass of parrotfishes, which more than doubled between 2009 and 2012
  • Increases in parrotfish biomass have not been distributed evenly across the KHFMA, and, in particular, there has been little or no recovery of parrotfish biomass in the shallow, nearshore reef areas adjacent to Kahekili Beach Park;
  • Strong positive relationship between total parrotfish biomass and total crustose coralline algae (CCA) cover. CCA is a benign algae that is important for coral settlement, and studies show that increases in parrotfish biomass leads to increased CCA cover
  • No clear overall trend in biomass of surgeonfishes
Beneficial herbivorous fishes now fully protected within the KHFMA © Hawai‘i DLNR

Beneficial herbivorous fishes now fully protected within the KHFMA. © Hawai‘i DLNR

A possible reason for the lack of change in biomass of surgeonfish could be linked to their lifespan; they can live up to 40+ years, so with three years of data, it is not surprising that biomass has not changed.

The steady increase in biomass of parrotfishes since the establishment of the FMA has potentially significant indications for reef resilience. The larger the fish, the deeper the excavating bites, which is important because this removes algae from the substrate, exposes bare rock and opens up new sites for coral recruitment.

Lessons Learned and Recommendations
Lessons learned and key recommendations include:

  • In addition to increasing stocks of herbivorous fishes on the reefs to control invasive algae, management must also include reducing sources of land-based pollution that is resulting in high levels of nutrients (nitrogen and phosphorus) found in nearshore waters, which is likely driving the algal blooms.
  • Poor habitat quality resulting from invasive algae and subsequent degradation of reefs will also have lower economic (commercial and recreational) and cultural value.
  • Studies have shown that reef deterioration in the monitored sites occurred rapidly; therefore, resource managers must take steps to not only restore reefs back to their healthy conditions, but also prevent any further threats from degrading Maui’s reefs.
  • Public awareness about coral reef health and the negative impacts of land-based pollution on reef ecosystems has increased since the designation of the KFHMA. With the community’s support, West Maui reefs have since been designated as a priority site under the Hawai‘i Coral Reef Strategy, have been chosen for a Ridge to Reef cooperative watershed management project by the state and the U.S. Army Corps of Engineers, and have been designated as a priority site in the Pacific by the U.S. Coral Reef Task Force.
  • Reef recovery takes time – although three years of data indicates an increase in biomass of parrotfishes, slow-growing corals will need long-term protection to fully recover.
  • Making a genuine effort to provide data and have a dialogue with the local community at the beginning of the planning process is essential to the success of the project. Community members will gain more trust, offer input, and be part of the problem solving process.
  • Data that is specific, real time, and applicable is vital to having a supportive, knowledgeable community.
  • Identifying and engaging key stakeholders and fishers from the area can provide a wealth of local knowledge, as well as buy-in and compliance later on.

Funding Summary
The process to establish the KHFMA was funded and staffed by the State of Hawai‘i’s Department of Land and Natural Resources (DLNR) as part of the agency’s mission and core responsibilities. Monitoring efforts have been funded primarily through a Sports Fish Restoration Program grant administered by the U.S. Fish and Wildlife Service. The islands of Maui and O‘ahu receive roughly $300,000/year (US) from the program, of which Maui spends about $200,000 (US) for monitoring staff and other associated costs. Other funding partners include:

NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center
NOAA Coral Reef Conservation Program
University of Hawai‘i
Graduate students with funding

Lead Organization
Hawai‘i Division of Aquatic Resources, Department of Land and Natural Resources

Partners
Hawai‘i Coral Reef Initiative Research Program
NOAA Coral Reef Conservation Program
NOAA Pacific Islands Fisheries Science Center, Coral Reef Ecosystem Division
The Nature Conservancy
Hawai‘i Institute of Marine Biology
University of Hawai‘i at Manoa, Department of Botany

Resources

Hawaii Coral Reef Strategy, State of Hawaii (pdf)
Responses of Herbivorous Fishes and Benthos to 6 Years of Protection at the Kahekili Herbivore Fisheries Management Area, Maui (pdf)
Kahekili Herbivore Fishery Management – Interim Monitoring Results (pdf)
Kahekili Herbivore Fisheries Management Area Rules
Status and Trends of Maui’s Coral Reefs, Hawai‘i Division of Aquatic Resources (pdf)
The Kahekili Herbivore Fisheries Management Area, Herbivore Management in an Effort to Improve Coral Reef Resilience (pdf)

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