Introduction

Step 2: Ecosystem Assessment

The second step of the integrated framework is to qualitatively assess the status of the marine ecosystem and the associated impacts of fishing. This step is important, because other impacts like pollution or loss of habitats due to coastal development can affect the success of fishery management, both in terms of sustaining fishery yields and maintaining ecosystem health. Ecosystem assessments can be done using local and/or expert knowledge of the area, or through simple-to-gather measurements such as fish biomass. Ecosystem assessments can be used to prioritize management measures to address the impacts that pose the highest levels of risk to ecosystems, and (if quantitative information is available), to set targets for fish biomass that are consistent with healthy ecosystems. In a multispecies fishery it may be necessary to identify differential impacts on different habitat components that are critical to the health of each of the species being caught, such as spawning grounds and feeding areas.

Ecosystem assessments can be done using local and/or expert knowledge of the area, or through simple-to-gather measurements such as fish biomass. Ecosystem assessments can be used to prioritize management measures to address the impacts that pose the highest levels of risk to ecosystems, and (if quantitative information is available), to set targets for fish biomass that are consistent with healthy ecosystems.

Users can apply any of the three methods outlined below to establish the status of their local ecosystem. The first method presented, the Ecological Risk Assessment for the Effects of Fishing, has been peer-reviewed and in use for a number of years. The Ecosystem Thresholds for Coral Reefs method and the Comprehensive Assessment of Risk to Ecosystems (CARE) Model are newer, but they have been applied and tested in a number of settings around the world. The Ecosystem Thresholds for Coral Reefs method is one of the few methods that we are aware of that is explicitly designed to assess ecosystem health in a multispecies fishery setting. However, the CARE and ERAEF methods can also be applied in multispecies fisheries.

 

Methods

Ecological Risk Assessment for the Effects of Fishing

In an Ecological Risk Assessment for the Effects of Fishing analysis (ERAEF), information from the literature, surveys and stakeholder interviews is used to generate a risk assessment that identifies the most vulnerable parts of the system (i.e., target species, bycatch species, threatened species, habitats, ecological communities). This analysis is used to detect high-risk activities that require immediate management attention and to screen out low-risk activities from further analysis. The three-step ERAEF analysis can be conducted in data-limited locations and can assimilate more data as they become available. The first two steps in the ERAEF (“scoping” and the Scale, Intensity, Consequence, Analysis (SICA)) comprise the qualitative ecosystem assessment. You'll be conducting the last step of the ERAEF, a Productivity and Susceptibility Analysis (PSA) for individual fish stocks, as Step 3 of the 11 Step Framework.

Comprehensive Assessment of Risk to Ecosystems (CARE) Model

The Comprehensive Assessment of Risk to Ecosystems (CARE) model can aid in the selection of sites for fishery reform interventions and guide threat reduction strategies in data-limited systems. This tool quantitatively considers the interaction of all system threats and assesses the risk to the entire ecosystem through inclusion of a comprehensive suite of attributes to characterize system productivity and functioning. These attributes quantify intrinsic system recovery potential (i.e. “regeneration time” and “connectivity”) and sensitivity to impact (i.e. “removability of system components” and “functional redundancy and diversity”). In addition, CARE quantifies risk to the differential production of ecosystem services in data-limited systems. CARE generates risk values for each Threat-Target pair, for ecosystem service production, and for the ecosystem as a whole. The assessments rely largely on local and expert knowledge, require minimal background research to complete, and can be implemented in the field in a matter of hours. These features make the CARE model singularly well-suited for use in Ecosystem Based Management in data-limited systems, for informing spatially explicit management decisions, and for prioritizing threats for efficient use of management resources. 

Ecosystem Threshold for Coral Reefs

For some ecosystems, including coral reefs, recent studies show the existence of quantitative thresholds associated with fish densities (measured in kg/ha). Below these thresholds, ecosystems change from desirable (e.g., high coral cover) to less desirable states (e.g., dominated by algae) that produce fewer ecosystem services. Fisheries in ecosystems with documented fishing thresholds can be managed to remain above these limits, reducing the risk of system collapse. At the moment, thresholds have been documented for coral reefs in the Indian Ocean and the Caribbean Sea. Densities of fished populations and unfished populations can be measured with fishing or visual surveys, and the resulting ratio can then be compared to the threshold limits.

Use the calculator below to determine the fish biomass ratio (kilograms/hectare) of your coral reef system and compare with the ratios for the Indian Ocean and Caribbean Sea in the tables shown under the calculator. Enter the fish biomass (biomass of fish surveyed by area surveyed) of a fished area in the left box, and the fish biomass of an unfished area in the right box.

Please note this method is relatively new and has only been piloted in a limited number of settings. Users are encouraged to consult with local reef experts to interpret the density ratio they have calculated for their system. 

Calculator
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Fish Density Ratio