Spillover effects of a community-managed marine reserve

• Published in: PloS one 2015-04, Vol.10 (4), p.e0111774-e0111774
• Main Authors: da Silva, Isabel Marques, Hill, Nick, Shimadzu, Hideyasu, Soares, Amadeu M V M, Dornelas, Maria
• Format: Article
• Language: English
• Subjects: Abundance; Analysis; Animals; Communities; Fish; Fisheries; Fisheries management; Fishery management; Fishes; Fishing; Herbivorous fish; Herbivorous fishes; Human populations; Humans; International economic relations; Management tools; Marine fish; Models, Biological; Mozambique; Nature reserves; Petroleum Pollution; Poverty; Protein sources; Protein transport; Reef fish; Regression analysis; Reserves; Statistical models; Time Factors; Underwater; Water Pollution, Chemical
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0111774

The value of no-take marine reserves as fisheries-management tools is controversial, particularly in high-poverty areas where human populations depend heavily on fish as a source of protein. Spillover, the net export of adult fish, is one mechanism by which no-take marine reserves may have a positive influence on adjacent fisheries. Spillover can contribute to poverty alleviation, although its effect is modulated by the number of fishermen and fishing intensity. In this study, we quantify the effects of a community-managed marine reserve in a high poverty area of Northern Mozambique. For this purpose, underwater visual censuses of reef fish were undertaken at three different times: 3 years before (2003), at the time of establishment (2006) and 6 years after the marine reserve establishment (2012). The survey locations were chosen inside, outside and on the border of the marine reserve. Benthic cover composition was quantified at the same sites in 2006 and 2012. After the reserve establishment, fish sizes were also estimated. Regression tree models show that the distance from the border and the time after reserve establishment were the variables with the strongest effect on fish abundance. The extent and direction of the spillover depends on trophic group and fish size. Poisson Generalized Linear Models show that, prior to the reserve establishment, the survey sites did not differ but, after 6 years, the abundance of all fish inside the reserve has increased and caused spillover of herbivorous fish. Spillover was detected 1 km beyond the limit of the reserve for small herbivorous fishes. Six years after the establishment of a community-managed reserve, the fish assemblages have changed dramatically inside the reserve, and spillover is benefitting fish assemblages outside the reserve.