The Zone Spilleth Over: Evaluating Fish Conservation Zones

March 31, 2014

To answer this question FISHBIO worked with WWF, the Lao Department of Livestock and Fisheries, and local officials to develop a mark-recapture fish tagging study. The goal of the study was to evaluate the spillover contribution from the FCZs to fisher catches in nearby villages. 'Spillover' is the concept of fish increasing in abundance within a protected area then moving ('spilling') outside of the protected boundaries, where they can be caught by fishers. Protecting fish in an FCZ is like creating a fish savings account, and spillover is like the interest that can be withdrawn. This is a commonly cited benefit of fish protected areas; however, this concept has rarely been tested scientifically in Lao PDR. Our study found evidence to support the idea of spillover in Nam Kading, and a final report of the results is now available in English and Lao.

Hypsibarbus.  

After one year of participatory village research, local fishers recaptured and reported about 10% of the total tagged fish, representing eight fish species. Most fish were recaptured within 2 km of the FCZ where they were released, but the maximum distance for a recapture was 10.7 km. The two most abundant fishes in the tagging effort, "pa pak" and "pa mang," also dominated the recaptures, and had recapture rates of 14% and 10%, respectively. While "pa vienfai" made up a large proportion of the fish tagged inside the FCZ, only 3% of these fish were recaptured outside the FCZ. This low recapture rate may be due to the behavior of the fish (e.g., it has a small range and is unlikely to move outside of the FCZs), or may be because the species is unusually sensitive to handling and did not survive after tagging.

The results of this study show that at least eight species of fishes do move outside of FCZs, and this spillover can contribute to nearby fisheries (within at least 10 km). Because the fish tagging focused on a transitional period at the beginning of the rainy season, when many fish species are thought to migrate, it is possible that the fish captured for tagging were just briefly migrating through the FCZ and were not typical inhabitants of the habitat. The FCZ would still protect these migratory fish from fishers during their passage, but this would not constitute the typical definition of a "spillover effect," which is caused by the density of a fish population inside a reserve reaching capacity, and the adult fish 'spilling' out of the reserve. To clarify whether different fish species are remaining in the FCZ habitat or just passing through it, a more extensive study could be conducted to tag fishes over a longer period of time, with periodic surveys of the FCZs to estimate the number of tagged fish remaining inside. FISHBIO and WWF hope to continue investigating the dual role FCZs can play in protecting fish and sustaining fisheries and livelihoods.