Using very high resolution remote sensing for the management of coral reef fisheries: Review and perspectives

Abstract

Coral reef fisheries are critical for food security and as a source of income in developing and developed countries, but they are collapsing in many areas. Following the emergence and routine availability of commercial very high spatial resolution (0.6–10 m) multispectral satellite images, we reviewed the use of these new high-quality remote sensing data and products for coral reef fisheries management. The availability of habitats maps improves management by guiding sampling strategies, mapping resources, involving local communities, identifying conservation areas, and facilitating Ecosystem Based Fishery Management (EBFM) approaches. However, despite their potential, very little use of products designed specifically for fishery management can be reported, likely due to high costs, inherent technology limitations and lack of awareness on the possibilities. Given the theoretical benefits brought by relevant habitat maps in EBFM frameworks, we advocate the use of adequate remote sensing products that integrate fishery technical services demands and local requirements.

Introduction

Fisheries are an important source of food and livelihood worldwide (FAO, 2009) but they increasingly appear under threat of collapse (Worm et al., 2006). Overexploitation of many stocks, both for commercial and subsistence purposes, have largely depleted the populations of species of interest (Grainger and Garcia, 1996, Mullon et al., 2005). Fisheries have been widely studied for many decades but failure or non-application of management plans, resource crash, fishing down marine food webs and overexploitation did occur (Botsford et al., 1997, Pauly et al., 2002). In a global context of increasing population and protein-demand, there is an urgent need to promote sustainable management solutions that could mitigate fishery collapse more successfully. This includes Ecosystem Based Fishery Management (EBFM) and Ecosystem Approach to Fisheries (EAF) (Garcia et al., 2003, Hall and Mainprize, 2004, Pikitch et al., 2004). After a slow start in the years 1970s, the creation of networks of no-take marine reserves and protected areas (MPAs) became common practice as part of such frameworks (Roberts, 1995). MPA networks are increasingly designed to ensure that all habitats and functional processes are included to represent and protect ecosystems services and functions, including fishery stocks integrity (Bohnsack, 1998). EBM frameworks emphasize the links between fishery stock sustainability and habitat quality (Pikitch et al., 2004). As such; management actions must assess and conserve habitats with their physical and biological connections, and, in a fishery context, their valuable resource stocks.

Habitat is a key level of biological descriptions, and can be a convenient criterion for management decisions. Indeed, among the different levels of biological descriptions (from genes to ecosystems) on which reef management decisions focus, the habitat-level is the only one that can be synoptically observed and mapped with current remote sensing technology (Andréfouët et al., 2004). Remote sensing (RS) technology is an emerging tool which should contribute to help coral reef fisheries management, especially when management use habitat-level guidelines and recommendations (UNEP/CBD/COP/8/31, 2006). In favorable shallow depth and water clarity conditions, remote sensing may provide information on the reef itself (direct reef sensing, sensu Andrefouet and Riegl, 2004, Dalleau et al., 2010, Wabnitz et al., 2010), such as benthic cover, habitat locations, habitat diversity and patchiness, geomorphologic structures, bathymetry, and water circulation. Satellites also sense the reef environment (indirect reef sensing), including the ocean (temperature, wave height, sea level, turbidity, chlorophyll and colored dissolved organic matter concentrations), the atmosphere (wind, aerosols, rain, solar insolation, cloud cover) and the nearby lands (vegetation cover, watershed structure, urban growth) (Andréfouët, in press).

The objective of this paper is to draw an updated picture of the current and potential applications of direct remote sensing for coral reef fishery science and management, particularly in the light of the capacities and limits of the very high spatial resolution multispectral data available since the early years 2000. These sensors provide commercial panchromatic and multispectral images anywhere on the planet. As a consequence of there enhanced spatial resolution, they also provide in many cases a better thematic resolution, i.e. the capacity to map accurately a greater number of habitats. In a fishery context, this means that they should be useful in mapping more precisely the specific shallow habitats of selected fishery resource of interest, and thus should open new perspectives for fishery science and management.