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Detailed Ecological Assessment Report 2008 – Keenjhar Lake
During the winter survey the primary productivity of the Keenjhar Lake was high
and the greenish colours owing to the abundance of algae and other phytoplankton
persisted. The fisheries practice was less than the summer days and the mesh size
of the nets deployed was usually two inches, which is considered reasonably
acceptable as most of the small fish and other fry can easily escape this net and
therefore survive till they achieve maturation.
The fisheries practices are reduced tremendously during winter as the most of the
fishery is done through licensing which helps to reduce the exploitation of
resources. There was however some large nets deployed at certain places that
also were huge spawning place for fish. There is a visible decline in the prawn
population due to the seasonal variation. In Keenjhar the prawn population reaches
its maximum during June/ July periods and turn to their minimum during the
Nov/Dec.
During the winter survey the sampling for invertebrates was done at every
significant site of the lake. The most suitable time for zooplankton collection is
during the sunset periods and against the direction of the wind, still the zooplankton
population was found to be much less than the summer survey
In the adjoining areas of the Keenjhar Lake there is a healthy population of
arachnids including spiders as well as the solifugids, which are supported by the
lake water for their survival. The population of spiders is mostly isolated in pockets
in the suburbs of the lake still their sufficient abundance states that the ecological
linkages in the area are unbroken and are less affected by pollution or any other
environmental factors. These populations also indicate the stable ecological
balance of the area. During the winter the population of arachnid including the
Araneae and Solifugids also declined tremendously.
3.7.8 Threats and recommendations
No threats or recommendations were submitted with the study report. However the
author did note that there is an urgent need to make a detailed list of species
before conservation measures are undertaken. Known species of invertebrates
represent only a small proportion of the actual number likely to occur, particularly
from freshwater, saline lakes, deserts and hot springs. Little data is available to
demonstrate the decline in species populations. Systematic plankton investigations
have not been made in most freshwaters of the country. The information on the
distribution of planktonic organisms must be regarded as tentative. The distribution
of most of the organisms described here must be expected to be wider than
reported. Many of the invertebrates have life cycle phases or temperature
restrictions (thermoclines), which limit their presence or abundance during times of
the year.
The author also pointed out that while studying the invertebrate fauna of an area,
different sampling gear and different approaches of sampling have different
biases. Absolute accuracy of the diversity and abundance is difficult to determine
because the only baseline for comparison is often our own samples. The
researcher should therefore be familiar with the bias inherent in the individual
sampling gear and analyses. Sampling at each station with a wide variety of sizes
of nets and meshes, for example, significantly increases precision in the study of
invertebrates.
WWF Pakistan – Indus for All Programme Page 84 of 165