Spillover effects of a community-managed marine reserve
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 1km 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.
MS is grateful to FCT(Fundação para Ciencia e Tecnologia), for supporting this work through a Doctoral scholarship (SFRH/BD/51413/2011). We thank WWF Mozambique, the Zoological Society of London, Martin Andersson, Vamizi lodge and Ideia Wild for supporting this work. MD and HS thank the ERC project BIOTIME for support. MD is grateful for support from the Scottish Funding Council (MASTS -grant reference HR09011). IMS and AS thank Fundação Calouste Gulbenkian and Oceanário de Lisboa for support given through the 2010 Galardão Gulbenkian/Oceanário de Lisboa to the project “Conhecer para Preservar a Biodiversidade Marinha de Pemba (Cabo Delgado, Moçambique)—Ordenação Sócio-Ambiental para a Sustentabilidade”
- Mathematical Sciences