Specials Environment

Updated April 1999

Special: Remote Sensing for Decision-makers

Aquaculture study and lagoon management

Pilot study in Morocco


Introduction | Aquaculture | Forest management | Rangeland assessment | Groundwater exploration | Forest fire management | Forest decline assessment | Crop information systems | Inventory and monitoring of shrimp farms


Aquaculture in a lagoon environment needs to address the technical, economic and social implications of the growing demand for marine products, new consumer requirements and the strong pressure for fishery and environmental conservation. An understanding of the physical, chemical and biological characteristics of the lagoon site is vital if aquacultural yield is to be maintained and raised. Full geographic coverage of the area under study, environmental projections and anticipated development works are all factors that can be readily captured by synoptic and multitemporal satellite imagery.


High-resolution satellite imagery

The operational availability of high-resolution satellite data, such as Landsat Thematic Mapper, SPOT, Soyouz and ERS-SAR, opens up new possibilities for studying marine coastal strips. These means of observation have a number of advantages over conventional tools.


Case study in Morocco: aquacultural potential of Nador Lagoon

Nador Lagoon, covering an area of 11 500 ha, lies along Morocco's Mediterranean coast. It has been the focus of several national and international programmes mainly because of its aquacultural potential. Localized yields encouraged the study of the lagoon as a whole. SPOT and Landsat satellite imagery and a concurrent ground survey produced a database able to deal with varying operating scenarios (floating cage aquaculture). Appropriate indices extracted from satellite imagery were employed to generate turbidity and bathymetric maps for the total lagoon area. Ground surveys were conducted to calibrate the satellite images and gather the necessary chemical and biological data.


SPOT image XS of Nador Lagoon
  
Left: Depth profile.
Right: Concentration of suspended matter in surface water


Concentrations of nitrates (left) and phosphates (right)
 
Salinity (left) and concentrations of dissolved oxygen


Cartographic documents for decision-makers

The satellite images and ground data were combined to form a lagoon data bank encompassing the criteria for any expansion of floating cage aquaculture.

Physical description of the site: satellite imagery was used to describe the physical characteristics of the lagoon, producing detailed environmental mapping by overlaying the area under study and turbidity and bathymetric maps.

Chemical and biological description of the site: the ground surveys enhanced understanding of the general chemical and biological conditions in the lagoon (phosphates, nitrates, dissolved oxygen, salinity ...).

Construction of a digital database for the site: a geographic information system (GIS)2 was elaborated for the site to assist decision-making regarding future expansion and development works.


Evaluation and recommendations

Costs and delivery times

 Costs (US$/km2)Time (months)
Acquisition of satellite data2.01.0
Digital processing and modelling2.42.5
Thematic interpretation1.21.0
Ground survey1.51.0
GIS and databases2.41.5
Map preparation1.250.5
Total10.757.5

The evaluation of costs and delivery times is based on the overall implementation of the study through a combination of national expertise and minimal international assistance. Delivery times may vary slightly according to the complexity of other study sites.

A cost-effective technique

The use of satellite imagery helped enhance the understanding of the lagoon site within a reasonable time frame. The digitized satellite data made it possible to evaluate and model natural phenomena, thereby helping decision-making for enhanced aquacultural management and development. The building of a database that can be continuously updated will be a useful tool for developers as they plan future actions.

Recommendations

The methodology developed in this study can be easily extrapolated to other large lagoon areas. It can also serve as the basis for identification of other off-shore sites along the coast, employing different types of satellite imagery to improve the understanding of circulation fronts, surface temperatures, geomorphological mapping and other aspects.

This study was conducted by the Royal Centre of Spatial Remote Sensing, the Ministry of Ocean Fisheries and the Merchant Navy of Morocco.


  • Adapted from FAO Remote Sensing for Decision-makers Series, No. 14, "Satellite imagery for aquaculture study and lagoon management - Pilot study in Morocco". For a full list of issues available in the Series, see FAO Publications on Remote Sensing

    The designations employed and the presentation of material in this brochure do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authority, or concerning the delimitation of its frontiers or boundaries.


    Remote sensing Introduction | Aquaculture | Forest management | Rangeland assessment | Groundwater exploration | Forest fire management | Forest decline assessment | Crop information systems | Inventory and monitoring of shrimp farms



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