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The Second Advisory Roundtable on the Assessment of Inland Fisheries was convened in partnership with United States Geological Service (USGS), from 25 to 27 November 2019. It reviewed progress of work that had been initiated as a response to the recommendations of the “Advisory Roundtable on the Assessment of Inland Fisheries” that was convened in partnership with United States Geological Service (USGS) and Michigan State University (MSU) in FAO Rome, from 8 to 10 May 2018. The Second Roundtable covered two aspects of the assessment of inland fisheries.

As its first task, the Roundtable reviewed a threat mapping framework developed by USGS and University of Florida, which seeks to provide a robust assessment method for inland fisheries and the associated ecosystems/basins upon which they depend. This is intended to support the management of aquatic systems and the continued delivery of ecosystem services. The status map that the analysis provides is a visual (and quantifiable) relative indication of the levels of anthropogenic and natural environmental pressures to inland fisheries at the basin or sub-basin level. Five major threats to inland fisheries (and their 21 sub-threat categories) were scored according to global studies and modelling.

Connectivity and land use were the highest weighted variables, with close agreement between literature and expert opinion. Literature and expert opinion disagreed on the relative importance of water abstraction and pollution. The Roundtable noted that the assessment appeared to work better with flowing water/river basins rather than large water bodies. It was also noted that specific and more localized pressures from cities or irrigation and other land uses within basins may have local effects rather than basin-scale impacts. The Roundtable concluded that local expert knowledge will still be required to validate model findings and ground-truth results in the local context. The Roundtable also concluded that the value of mapping pressures is that it enables an objective, downscaled evaluation of potential threats to inland fishery food production and biodiversity at the basin and sub-basin level. It also enables the prioritization of needs for ecosystem restoration and improved conservation.

The second task of the Roundtable was to review the potential of using length-based (LB) assessment methods as a tool to support management advice in data-poor inland fisheries. Simple indicators such as abundance and size distribution of the fish caught in combination with local knowledge enable better understanding of underlying causes of historical trends in a fishery and an indication of the current status of a fish stock. This can be further used to inform planning using the Ecosystem Approach to Fisheries management (EAFm). Where information about the life cycles of the fish (i.e. size at maturity) is available, the Length-Based Spawning Potential (LB-SPR) model can be applied, otherwise, simpler empirical LB models must be used. The two approaches have been applied to data from five inland fisheries: the TonléSap dai fishery in Cambodia; the tilapia fishery in Lago Bayano, Panama; the sábalo fishery in Paraná Argentina; the goliath catfish fishery in the Amazon Basin and four recreational fisheries in South Africa. The case studies showed that the LB-SPR model can provide consistent interannual evaluations of stock state that concur well with local scientific expert judgement, and the model can therefore be used in certain inland fisheries. However, LB assessment methods require a number of assumptions to be fulfilled, and may, in some situations, provide misleading information. They may also be no easier than a standard assessment approach that incorporates fishing effort. The Roundtable suggested some criteria where the LB-SPR approach can be used effectively and agreed that these should be more comprehensively elaborated. With the most data-poor fisheries, the intuitive combination of empirical indicators and expert narrative will be the only effective/practical approach.