There is a dependency of different species of fish on mangrove ecosystems as growing zones (Blaber et al. 1989, 1990; Robertson and Duke 1987,1990; Thayer et al. 1987). These studies reported mangroves have more juvenile fish than the adjacent coastal waters, and most fish in coastal areas spend some of their juvenile stage in mangroves.

Most of the shrimp of commercial importance caught on the continental shelf of tropical areas pass part of their juvenile stages in mangrove ecosystems. Some shrimp species, Litopenaeus stylirostris, L. occidentalis and L. vanamei, spend several months in the mangroves. At the end of their juvenile stage (6-7 months old), they migrate to the ocean.

In Brazil, the main shrimp fisheries depend on mangroves, whereas in Panama about 60% do (Lacerda et al. 1992). Some studies have tried to find a correlation between the size of the catch and the area covered by mangroves (Sasekumar and Ching 1987; Turner 1977). However, there has been no reliable information that correlated the reduction of the fisheries with the destruction of mangroves (Robertson and Blaber 1991).

Important roles of mangroves are providing protection and food supply for juveniles and breeding grounds for numerous marine animals.

Quantitative studies showing the role of mangroves in sustaining the diversity of the fish communities were done in tropical Australia. For example:

• In mangroves on Alligator Creek, north Australia, 128 different species of fish were captured, with a density of 31,000 individuals/1000 m² weighing a total of 30 kg (Bell et al. 1984; Robertson and Duke 1987; Stephenson and Dredge 1976; Stoner 1986).
• In Embly, north Australia, 197 fish species were caught. In one net which covered 9000 m², 650 kg of fish belonging to 39 different species were captured (Blaber et al. 1989, 1990; Blaber and Milton 1990).
• The maximum recorded catch in Queensland, Australia was 61.5 kg per 1000 m² (Morton 1990).
• In the largest mangrove ecosystem on the Mexican Pacific coast, 75 fish species with a biomass of 10 g wet wt m³ were captured. Several of the species were of highly commercial importance (Flores-Verdugo et al. 1990).
• In general, the average density of fish in mangroves varied between 300 and 161 000 individuals per 1000 m² with total weight of 7-30 kg, mostly juveniles.

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Version: 4 July 2000