The Intrinsic Vulnerability To Fishing Of Coral Reef Fishes And Their Differential Recovery In Fishery Closures

Coral reef fisheries play a role in livelihoods and local economies around the world, but the impacts of fishing on targeted species of reef fish is poorly understood. The authors of this study examined the vulnerability of different species of coral reef fish to fisheries and evaluated the effectiveness of no-take reserves and periodically-harvested closures. Using life history traits to characterize the vulnerability of fish species to fishing, they found that larger-bodied carnivorous fish have a higher vulnerability compared to smaller-bodied herbivores and detritivores. In no-take areas, moderately to highly vulnerable species take a significantly longer time (decades) to recover than less vulnerable species. Based on these findings, they make the following recommendations for managers:

    • Expand studies of reef fish to improve estimates of vulnerability; Maintain long-term (20-40 year) no-take areas for full population recovery
    • Enforce compliance of no-take areas
    • Control timing and intensity of periodic closures for long-term fishery benefits
    • Use periodic and closures and no-take areas together as fishery management tools

    Author: Abesamis, R.A., A.L. Green, G.R. Russ, and C.R.L. Jadloc
    Year: 2014
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    Reviews in Fish Biology and Fisheries. doi: 10.1007/s11160-014-9362-x

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Herbivory And The Resilience Of Caribbean Coral Reefs: Knowledge Gaps And Implications For Management

This paper explores herbivory and how it affects the resilience of coral reefs in the Caribbean. The authors identify important knowledge gaps that limit our ability to predict when herbivores are most likely to support resilience. The authors explore:

  • What processes operate to prevent or facilitate coral persistence and recovery, and how are these influenced by herbivory?
  • What are the independent and combined effects of different species of herbivores in limiting algae and facilitating reef-building corals?
  • What factors limit herbivore populations and the process of herbivory on coral reefs?

The impacts of herbivores on coral reef resilience are likely to be highly context- dependent, thus it is necessary to understand the roles that particular types of herbivores play in limiting harmful algae and facilitating corals under a range of environmental conditions to improve sustainable management of coral reef ecosystems.

The paper provides specific information to guide how to manage herbivore populations to facilitate healthy, resilient coral reefs. The authors present the following management recommendations/guidance:

  • Local management efforts should focus on minimizing direct sources of coral mortality, such as sedimentation and pollution, as well as restoring ecological processes, such as herbivory, that are important for coral persistence and recovery
  • Maintaining healthy herbivore populations is likely to mitigate the negative impacts of ocean warming since abundant herbivores can control algae that inhibit coral recovery following coral decline
  • Better spatial management of fishing could minimize trade-offs between the need to maintain high levels of grazing while supporting sustainable fisheries
  • Implementation of marine protected areas or other spatial restrictions on herbivore fishing will only be effective if we can sustainably manage herbivore populations outside of protected areas. Different species of parrotfishes have different life-history traits and different impacts on benthic communities, thus should not be managed as a single species complex
  • Managers will need to ensure that reefs have the right mix of herbivores to carry out the full set of functions normally performed by the herbivore guild
  • It is critical to protect seagrasses and mangroves, which are important nursery habitats for several species of Caribbean herbivores
  • In cases where degradation has been severe and feedbacks are operating that could slow or prevent coral recovery, management actions targeted specifically at breaking feedbacks that maintain reefs in a degraded state are necessary

Author: Adam, T.C., D.E. Burkepile B.I. Ruttenberg, and M.J. Paddack
Year: 2015
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Marine Ecology Progress Series 520:1-20

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Recovery Potential Of The World’s Coral Reef Fishes

Fishing is the primary source of reduced reef function globally. Marine reserves are a critical tool to help fish populations recover, however, there are no benchmarks to determine if the protection is effective, or whether a reserve has recovered enough to be fished again. By studying remote and marine protected areas, they estimate how many fish would be on a coral reef without fishing, and how long it should take newly protected areas to recover. This helps to assess the impact of reef fisheries, and make informed management decisions that include timeframes for recovery.

Specifically, this paper presents the first empirical estimate of coral reef fisheries recovery potential, compiling data from 832 coral reefs across 64 localities (countries and territories. The authors estimate the expected density of reef fish on unfished reefs; quantify the rate of reef fish biomass recovery in well-enforced marine reserves; characterize the state of reef fish communities within fished and managed areas; predict the time required to recover biomass and ecosystem functions; and explore the potential returns in biomass and function using off-reserve management throughout the broader reefscape. The research team studied the fish biomass on coral reefs around the world and discovered that near-pristine reefs contain 1,000 kg of fish per hectare. Using this figure as a benchmark, they found that 83% of fished reefs have lost more than half of their fish biomass (volume of fish).

The authors discuss how reef fish populations were better off when fishing activities were restricted (e.g., including limitations on the species that could be caught, the gears that could be used, and controlled access rights). The authors determined that once protected, fished reefs take about 35 years to recover, while heavily depleted reefs take almost 60 years. Although the influence of marine reserves can be detected within several years, this global analysis demonstrated that full recovery of reef fish biomass takes decades to achieve. Importantly, this suggests that most marine reserves implemented in the past 10–20 years, will require many more years to achieve their recovery potential. This has important implications for managing expectations of MPAs and also reinforces the need for continued, effective protection and consideration of other viable management options. The authors also found that in reef areas where MPAs cannot be implemented, a range of fisheries can have substantial effects on fish functional groups that support important reef processes.

Author: MacNeil, M.A., N.A.J. Graham, J.E. Cinner, S.K. Wilson, I.D. Williams, J. Maina, S. Newman, A.M. Friedlander, S. Jupiter, N.V.C. Polunin, and T.R. McClanahan
Year: 2015
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Nature 520: 341-344. doi:10.1038/nature14358

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Biogeography And Change Among Regional Coral Communities Across The Western Indian Ocean

Following the major 1998 coral bleaching event between 2004 and 2011, 291 coral sites from 11 Western Indian Ocean (WIO) countries were surveyed to evaluate regional biogeographic patterns of coral communities along latitudinal gradients and in relation to biogeography and fisheries management. Coral reef abundance, biodiversity, and susceptibility to bleaching were assessed during that period to develop an extensive database on coral reef communities and researchers aimed to evaluate possible impacts such as fishing and fishing closures on reef patterns and status. Patterns show that coral communities are influenced by large-scale interactions between biogeographic factors and temperature abnormalities but not so much by fisheries management. All coral reefs in the WIO are experiencing climate change and coral bleaching since the early 1980s, but at variable rates, timing and scale depending on the geography. The region was characterized by a complexity of a large number of significant interactions among variables tested. The northern Mozambique Channel demonstrated the strongest signs of resilience to climate disturbances.

Author: McClanahan, T.R., M. Atewberhan, E.S. Darling, N.A.J. Graham, and N.A. Muthiga
Year: 2014
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PLoS ONE 9(4): e93385. doi: 10.1371/journal.pone.0093385

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Larval Dispersal And Movement Patterns Of Coral Reef Fishes, And Implications For Marine Reserve Network Design

Marine reserves are an effective tool for conservation and fisheries management in tropical marine ecosystems. They provide benefits to surrounding areas through the export of eggs, larvae, juveniles and adults to other reserves and fished areas. To increase conservation and fisheries benefits, connectivity (i.e. demographic linking of local populations through the dispersal of individuals as larvae, juveniles or adults) is a key ecological factor to consider when designing marine reserves. Consideration of the spatial scale of movement of coral reef fish species at each stage in their life cycle is also critically important in designing the size, spacing and location of networks of marine reserves.

This study evaluates movement patterns of 34 families (210 species) of coral reef fishes. Results showed that movement patterns (home ranges, ontogenetic shifts and spawning migrations) vary among and within species, and are influenced by a variety of factors such as size, sex, behavior, density, habitat characteristics, season, tide and time of day. The following recommendations on the size, spacing and location of marine reserves are made:

  1. Marine reserves should be more than twice the size of the home range of focal species (in all directions). Marine reserves of various sizes will be required depending on which species need protection, how far they move, and if other effective protection is in place outside reserves.
  2. Reserve spacing should be <15 km, with smaller reserves spaced more closely.
  3. Marine reserves should include habitats that are critical to the life history of focal species (e.g. home ranges, nursery grounds, migration corridors and spawning aggregations), and be located to accommodate movement patterns among these.

In addition to connectivity, other ecological considerations are required to ensure that the design of marine reserves maximize their benefits for conservation and fisheries management: (a) representing 20–40% of each habitat in marine reserves to ensure that a large proportion of the meta-population is protected overall; (b) protecting at least three widely separated examples of each habitat in marine reserves to minimize the risk that they might all be adversely impacted by a single disturbance; (c) ensuring marine reserves are in place for the long term; (d) protecting special and unique areas in marine reserves (e.g. resilient sites, turtle nesting areas, FSAs); (e) minimizing and avoiding threats in marine reserves; and (f) creating large multiple-use MPAs that include, but are not limited to, marine reserves.

Recommendations in this paper can be used by practitioners to design marine reserve networks to maximize benefits for focal species. In addition, recommendations for marine reserve network design regarding connectivity of reef fish populations must be considered alongside other ecological design criteria, and applied within different, context-dependent, socioeconomic and governance constraints.

Author: Green, A. L., A.P. Maypa, G.R. Almany, K.L. Rhodes, R. Weeks, R.A. Abesamis, M.G. Gleason, P.J. Mumby, and A.T. White
Year: 2014
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Biological Reviews 90: 1215–1247. doi: 10.1111/brv.12155

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New and improved Network Forum

The Reef Resilience Network has launched a new and improved online discussion forum!

Now part of the Reef Resilience website, this interactive online community is a place where coral reef managers and practitioners from around the world can connect and share with others to better manage marine resources.

If you work to protect, manage, or promote coral reefs please join the conversation:

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Hawaii – Fisheries Management

Monitoring Coral Reef Communities in Hawai‘i’s First Herbivore Protection Area

North Kāʻanapali, West Maui, Hawai‘i

The Challenge
In the summer of 2009, the state of Hawai‘i established Hawai‘i’s first MPA designed entirely to promote resilience, the Kahekili Herbivore Fishery Management Area (KHFMA), in which take of all herbivores (parrotfish, surgeonfish, chub and urchins) and fish feeding is prohibited, but other forms of fishing are permitted. The establishment of the KHFMA provides a test case for the prohibition of fishing of herbivores on Hawai‘i’s reefs. Compelling evidence of its effectiveness could lead to wider adoption of this form of management and/or additional fishing regulations. As an example, in 2014, the state of Hawai‘i introduced a bag limit of two parrotfish per fisher per day and no take for terminal phase of the two largest parrotfish species for reefs in Maui, in part, due to evidence that came from the KHFMA monitoring project. In Hawai‘i, as in other parts of the world, fishery regulations and marine protected areas are contentious. Therefore, both supporters and potential critics of these management approaches are carefully observing the outcomes of the herbivore management.

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
Early in the process of establishing the KHFMA, Hawai‘i Division of Aquatic Resources (DAR) and partners at the University of Hawai‘i established a long-term monitoring program within the proposed MPA boundaries to gather data to provide a pre-closure baseline for the KHFMA. The first surveys occurred in January 2008, 18 months prior to the establishment of the reserve. The monitoring program consists of intensive biannual surveys conducted by DAR and NOAA’s Coral Reef Ecosystem Division.

The survey design involved subdividing the habitat within the reserve into 6 habitat categories based on physical structure and depth (shallow aggregate reef, deep aggregate reef, shallow spur-and-groove, deep spur-and-groove, pavement, and mixed mid-depth), that also corresponded with location along the shoreline and with proximity to shore. Within each habitat class, pairs of divers surveyed 25m-long transects haphazardly located, with one diver surveying fishes and the other conducing a photo-transect survey and also recording numbers of sea urchins on their return swim. Typically, dive teams completed ~90-100 surveys in each 4-day monitoring round, images are subsequently analyzed, and all fish, urchin, and benthic data is synthesized within habitat classes and at the scale of the KHFMA, with each habitat weighted by its relative size.

How Successful Has it Been?
In September 2014, 5 years after establishment of the KHFMA, results to date indicate strong evidence of herbivore recovery. There has been more than doubling of parrotfish biomass, particularly increases in numbers of large individuals, and there has been an increase in parrotfish diversity, particularly in shallow habitats that likely were most heavily fished prior to closure. Surgeonfish biomass has also increased significantly, but to a lesser degree. Over the same time period, cover of crustose coralline algae (CCA), considered indicative of high grazing pressure and which is suitable substrate for coral settlement and growth, has increased from 2% cover pre-closure to >10% cover after 5 years of protection. Coral cover has also begun to increase within the KHFMA over approximately the last 18 months, but the increase thus far is relatively small. See the related Case Study on the Kahekili Herbivore Fisheries Management Area for details on actions taken and lessons learned from managing the area for reef resilience.

Therefore, preliminary evidence suggests that herbivore protection is working; grazing pressure has increased and as a result, the competitive balance has shifted from algal to coral dominance following a long period of decline on local reefs.

The ability to produce high quality data showing recovery has been very important in maintaining public and broader support for the KHFMA. Additionally, the ability to separate out patterns of recovery in different areas of the reserve has been very helpful in understanding factors such as the likely degree of compliance. For example, in the first two years of protection, although there was clear recovery in deeper habitats, there was initially little change in the shallow fringing reef areas close to parking facilities, and therefore, most vulnerable to poaching. Certainly some poaching occurred in the first years after closure. However, compliance appears to be improving, based on data indicating strong recovery in those areas and reports from a motivated and engaged community.

Lessons Learned and Recommendations
Lessons learned and key recommendations include:

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 strong partnership involving an active local management agency (DAR) with strong links in the community has been fundamental to ensuring that the positive monitoring results have been widely disseminated.

As is common in Hawai‘i, the reefs in the KHFMA are highly variable, encompassing a wide range of habitat types and habitat quality. Therefore, we designed a survey strategy to maximize the number and spatial spread of transects within the KHFMA to increase confidence that the results are representative of the entirety of reef habitats within the reserve. There are trade offs in all design decisions, but key choices were made to:

  • haphazardly locate transects rather than utilize permanent transects. Data from permanent transects would have lower variability between survey rounds, but with significant overhead to install and maintain them, and even to locate them in the course of survey dives; and
  • develop a habitat map of the KHFMA reef, with all reef areas stratified into the habitat classes described above

The habitat map simplifies the program operationally because it allows divers to conduct as many transects as possible within each dive, then use the transect locations to classify each transect into one of the pre-defined habitat categories. We could then generate summary data per survey round separately for each habitat class and for the KHFMA as a whole. That allowed us to discern the different trajectories of recovery in the different habitat zones due to different species compositions, history of fishing, and degree of local compliance.

Another key lesson is that sampling multiple times a year is important because of strong seasonal differences in macroalgal cover. We sampled in spring and late summer each year. More regular sampling would be desirable, but would be operationally challenging because each of our sampling events involves bringing together teams from different islands (Oahu and Maui) and agencies which have other priorities and programs.

It is important to measure change over time within the reserve, but it is also necessary to compare those trends with patterns occurring on comparable reefs outside the reserve. The state of Hawai‘i has long-term monitoring programs at 8 reef areas in Maui. Although the survey design for that long-term monitoring was not exactly the same, the methods used are compatible. We used data from the KHFMA to measure change over time within the reserve and used the existing long-term monitoring data for ‘outside-MPA’ comparisons. While there are some drawbacks to that (e.g., inside and outside reserve data are gathered using different methods and survey designs), the benefit is that we did not have to establish specific KHFMA controls for this project, and therefore were able to focus all our survey effort on the KHFMA rather than dividing it between two (KHFMA and one control) or three or more areas (KHFMA and two or more controls).

As with nearly any new monitoring program, there are enormous potential benefits from being able to compare and share data with other local programs. Therefore, we strongly advise anyone establishing a new program to adopt methods and ideally designs that are widely utilized in the region. More generally, increased data sharing across programs is critical given the difficulty and cost of gathering coral reef survey data. In Kahekili, the availability of abundant high-quality local data has contributed to the scientific focus on the KHFMA – researchers wishing to study the region make use of the rich dataset available to them.

Finally, although preliminary evidence demonstrates the effectiveness of the KHFMA, there is still a long way to go before the full extent of reef recovery may occur. Herbivore biomass is increasing 5 years post closure, yet studies elsewhere have shown that reef fishes can take 10 or 20 years post closure to reach new maxima (surgeonfish being particularly slow to fully recover, perhaps because of their long life spans). Further, although increased herbivory does appear to have generated conditions more suitable for coral recruitment and growth, the relatively slow growth of corals means that it will be a long time (e.g., 10-15 years or more) before ultimate impacts of herbivore protection on coral assemblages are fully evident. Survey programs aiming to measure the effectiveness of herbivore management should therefore (i) expect that full recovery will be a process of decades not years; and (ii) ideally incorporate process studies (e.g., coral recruitment growth and mortality) to have the greatest scope for early detection of positive impacts. Although we have attempted to initiate such studies at KHFMA, we have not yet been successful in raising funds for that work.

Funding Summary
Hawai‘i Coral Reef Initiative Research Program
NOAA Coral Reef Conservation Program

Lead Organization
Hawai‘i Division of Aquatic Resources, Department of Land and Natural Resources
NOAA Coral Reef Ecosystems Division, Honolulu

University of Hawai‘i at Manoa, Department of Botany

Responses of Herbivorous Fishes and Benthos to 6 Years of Protection at the Kahekili Herbivore Fisheries Management Area, Maui (pdf)

Information on establishment of the Kahekili Herbivore Fishery Management Area

Kahekili Herbivore Fisheries Management Area Rules

Kahekili Herbivore Fishery Management Area Facebook

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Perceived Benefits of Fisheries Management Restrictions in Madagascar

Support for fisheries restrictions in coastal villages along coral reefs in Madagascar was studied to help guide the development of effective management practices. In Madagascar, as in other places with low enforcement capacity, effective management depends on understanding how to facilitate self-compliance. The researchers interviewed 465 people in 24 fishing villages using a questionnaire which included questions on fishing restriction and management preferences, in addition to socioeconomic questions. Support for management restrictions was high and unexpected given the poverty and dearth of past fisheries management. Incorporating this type of information on individual and village management preferences into management plans can increase the rate of compliance. To that end, the authors conclude that based on respondents’ perceptions, gear restrictions have broad appeal and could be implemented at the national level; while closed seasons and minimum size fish restrictions are more likely to be adopted on the village level. With low support for species restrictions, this type of management is expected to lead to conflict and undermine management. The authors point out the discrepancies between local and international donor and conservation group preferences, the latter groups often prefer closures and species restrictions, which can lead to slow progress of implementation. Thus, they advocate for working towards finding common ground and implementing the most supported restrictions first to support effective management.

Author: McClanahan, T. R., J. E. Cinner, C. Abunge, A. Rabearisoa, P. Mahatante, F. Ramahatratra, and N. Andrianarivelo
Year: 2014
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Ecology and Society 19(1): 5. doi: 10.5751/ES-06080-190105

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