Disclaimer note - WWF - Pakistan

Detailed Ecological Assessment Report 2008 – Keenjhar Lake
Planktonic nutrient regeneration is a fundamental process that maintains most of
the primary productivity in freshwater environments, and the phosphorus supply for
stream plankton comes primarily from within the plankton community, rather than
from external loading or from larger organisms such as fish.
Even though the zooplankton may seem a minor link in the pathway of energy from
algae to higher trophic, they are extremely important as food for young fish and for
certain forage fish. The zooplankton graze on phytoplankton and are themselves
the primary food source for many larval fish, some larger fish and most
invertebrates found in the freshwaters (Darnell 1961). Planktivorous (plankton
eating) fish regulate the abundance and size structure of zooplankton populations.
Prey is targeted usually on an individual basis, although the gill rakers of certain
fish collect some zooplankton as water passes through the mouth and across the
gills. Planktivorous fish prefer larger zooplankton and can eliminate many important
crustacean groups from the water body. Planktonic animals, especially rotifers,
cladocerans, and copepods of the order Cyclopoida are the most important food
items in freshwater aquaculture, and copepod nauplii are especially valuable for
feeding fry.
The most important aquatic invertebrates in the Keti Bunder area are the shrimps,
crabs and oysters. Shrimps form the backbone of marine fisheries industry of
Pakistan and earn a large amount of foreign exchange. The management of
responsible and sustainable fisheries in the coastal areas and Indus delta has
direct impact on the economy of the country. Fishing activities should be
streamlined so that the coastal populations inhabiting the area receive maximum
benefits and their socio-economic conditions can be improved. These biological
resources need protection against inappropriate uses and overexploitation. A large
amount of data is available on shrimps. It has been estimated that annual average
catch of shrimps associated with mangrove forest at Sindh coast surpasses
thousands of tons. When expressed on the basis of per km coastline length, this
production is estimated at around hundred tons per kilometer in Sindh as
compared to one ton per kilometer in Balochistan. The underlying cause of this
productivity in Sindh water is the wealth of extensive mangroves. To sustain the
marine fishery the man-agreement and rehabilitation of the mangroves is
imperative.
Finally it is imperative to note that the value assignments for direct and indirect
uses of ecosystem goods and services can be very useful in order to establish
the physical/ecological linkages that make such uses possible and also partially
measure the derived economic benefits from these uses. Knowing these values,
and by incorporating the benefits and costs of environmental effects into an
analysis of development alternatives, we are better positioned to decide which
alternative would provide the largest net benefit to society. Similar analyses are
becoming widespread and many examples relevant for wetland services are
available (Hamilton et al., 1989; Ruitenbeek, 1992; Barbier and Strand, 2000;
Cesar et al., 1997; to name a few relevant to coastal areas).
Although there are few directly marketed products from mangroves of Keti
Bunder, local coastal communities continue to depend on mangroves for a range
of goods such as fuel, wood, shellfish and on ecosystem services such as
maintenance of the productivity of important estuarine dependent fisheries, water
quality regulation, flood reduction and shoreline stability just as in the other
mangroves of the world. Communities further inland similarly depend on many of
these same products, transported to markets as finished or primary products.
These areas provide vital nurseries for fisheries that support global communities
WWF Pakistan – Indus for All Programme Page 109 of 188