PHYSICOCHEMICAL VARIABLES AND FISH DIVERSITY IN HIZLAMEHENDIGANJ HILSA SANCTUARY IN BANGLADESH

Abstract

Out of six hilsa sanctuaries in Bangladesh, the newly established Hizla-
Mehendiganj sanctuary is significantly lacking in data in terms of fish diversity
and physicochemical properties. Therefore, the present study aims to assess
water quality variables and fish biodiversity of the Hizla-Mehendiganj hilsa
sanctuary. Water and fish samples were collected from different sites within and
outside the sanctuary. Physicochemical variables such as dissolved oxygen (DO),
temperature, pH, electrical conductivity (EC), total dissolved solids (TDS) and
transparency were measured and fish biodiversity was estimated using different
richness and evenness indices. The mean DO, temperature, pH and transparency
inside the sanctuary were 5.6 ± 0.1 mg/l, 29.1 ± 0.7°C, 8.3 ± 0.05 and 20.5 ± 2.3 cm,
respectively which were nearly similar to the estimated values of those variables
of the outside sanctuary. This study found a total of 374 individuals of 21 fish
species under 6 orders and 14 families. According to the IUCN report 2015, this
study found that 76.19, 9.52 and 4.76% of these species are listed in the Least
Concern, Endangered and Vulnerable category, respectively. Within the
sanctuary, 76 individuals of 13 fish species under 4 orders were recorded which
was lower than the recorded number of total individuals and number of species
outside the sanctuary sites. Within the sanctuary, estimated Shannon’s,
Simpson’s, Margalef’s and Buzas and Gibson’s indices were 1.881, 0.214, 1.881
and 1.156, respectively which indicated comparatively moderate diversity. The
highest biodiversity was found in the Ilisha river near Rukundi, outside the
sampling site of the sanctuary. The findings of this study can be used for future
biodiversity assessments, conservation and impact assessments of the Hizla-
Mehendiganj hilsa sanctuary.