+44 (0)207 697 8598

The effects of short-term spatio-temporal closures of mangrove areas on fish populations

Supervisors: Garth Cripps, Olivia KempKate England or Charlotte Gough
Location: desk
Duration: 6 months

Since 2011, Blue Ventures has been working with communities in and around the rural village of Belo-sur-Mer, western Madagascar, to implement short-term closures (3-5 months) of discrete areas of mangrove forest and associated fishing grounds (mangrove creeks).

These closures have focused primarily on improving catches of the commercially important mud crab (Scylla serrata), but anecdotal evidence, and impressive production on reserve opening days, has suggested that there may be knock-on effects in abundance in local fish populations. While these temporary closures benefit from strong community support, and have begun to spread to surrounding villages, significant gaps in our understanding of the population dynamics of mangrove-associated fish species impede our ability to inform local management associations as to the optimal size and timing of these reserves.

A key phenomenon to generating community support for temporary mangrove closures has been a perceived increase in abundance of local fish populations upon reserve openings. Anecdotal evidence from fishers who are familiar with these fishing grounds has suggested that in some cases the 3-5 month closures have dramatically increased fish populations.

Mangroves are widely understood to be crucial fish breeding grounds, and to play an important role in the life histories of many coral reef associated fish species. The observation by local fishers is that short-term closures are dramatically increasing abundance of certain fish species. However, a lack of understanding regarding mangrove fish population dynamics and the impacts of reserves on mangrove-associated fish has limited our ability to provide guidance to local management associations regarding mangrove fisheries management.

This research will aim to elucidate the impacts of short term mangrove fisheries closures on local fish population. Additionally, this research will aim to understand how the abundance of fish in mangroves is influenced by tidal cycles, and what the implications of this relationship are on the timing of reserve openings. Other problems will be investigated as part of this research, including the potential impact of “fisher flooding” during reserve openings, when fishers saturate small areas. This problem will be investigated by gaining an understanding of the timing of life history traits for target species.

This project will require an analysis of existing data and literature review in order to understand why fishers are seeing more fish upon reserve openings, and how this impacts local fish populations.

Independent research projects (2013-2014) - Madagascar

Independent research projects (2013-2014) - Belize