Impact of sedimentalogical processes on mangrove ecosystem of the Indus Delta

A detailed sedimentalogical study concerning the depletion of mangrove in the Indus Delta due to the marked decrease in the supply of silt was undertaken. Thirty one stations were established for sampling in a selected area of 12000 hectares between Korangi creek and Wad do Khuddi creek. Seventy one samples of soil were collected from 6cm and 1m depth, out of which fifty one samples were selected for sedimentalogical studies. It was inferred from this study that the marine depositional processes are distinctly dominating over the fluvial processes, which is major cause in decreasing the growth of mangrove. It was also inferred that among the sampled stations the sites having clayey silt (with silt 60%-70% and clay 25%-30%) are most favourable for mangrove plantation.

Impact of mangrove conversion

The article presents the impact of mangrove conversion on fisheries and on coastal areas. The mangrove areas which serve as nursery grounds for important species of fish and crustaceans are also rich feeding ground for many species from various trophic levels. Thus, the destruction of mangroves could affect the availability of fry and broodstock and, consequently, aquaculture production and fisheries. While in coastal areas, the destruction of mangroves increased the risk of coastal erosion from storm surges and winds, accelerates the erosion of riverbanks, exposes acid sulfate soils, leading to poor production and mass mortality of stocks, and affects the freshwater supply through salt intrusion upstream among others.

Management of mangrove areas

The article discusses the management of mangrove areas in the Philippines to prevent further negative effects of mangrove depletion on the income of coastal fishers. The article suggests that the conversion of mangrove areas should be regulated by means of land lease.

Mangrove community structure survey

Highlights are given of a mangove community structure survey conducted in the coastal barangays of Carles, Panay Island, Philippines, in April 2003. The survey aimed to qualitatively describe the species composition, community structure and plant biomass of mangrove forests. The 13 sample sites showed a total of 18 mangrove species, dominated by Avicennia marina. The findings, which indicate a modest yet declining diversity of mangroves in Carles, reinforce the need for their protection and management. This is due not only to their importance as habitats for fish and shellfish juveniles that replenish stocks for capture fisheries and aquaculture, but also due to the fact that Carles is one of the few remaining areas in Panay where rare mangrove species can still be found.

Establishing a mangrove nursery

Mangroves play an important role in creating habitats for a diverse community of organisms ranging from bacteria and fungi to fishes and mammals. They grow in intertidal flats, estuaries and offshore islands. In the Philippines, mangrove forests have dramatically decreased in area since the start of the century, and therefore there is a need to reforest. However, first mangrove nurseries must be established since they serve as sources of planting materials for different mangrove species. Furthermore, nurseries would mean a sustainable source of livelihood for coastal communities because of continuous demand for propagules. A brief account is given of procedures as to the establishment of a mangrove nursery, describing the construction of a nursery, preparation of potting materials, seed collection, seed sowing, and maintenance and protection. Details are provided of the most common true mangrove species in the Philippines. The mangrove nursery is a place for raising and tending seedlings until they are ready for permanent planting. The establishment of mangrove nurseries is in line with government s efforts to rehabilitate the coastal and mangrove ecosystems.

Aquaculture of the mangrove red snapper

Mangrove red snapper (Lutjanus argentimaculatus) is an important marketable species throughout the Indo-Pacific region. It is a euryhaline species; it can tolerate freshwater, brackishwater and marine water. Modular culture is the common system in snapper production in the Philippines. Stocking density is 4,000 fry per cropping; there could be 2 croppings per year. Brief details are given of investment costs and returns for culture in brackishwater pens.