higher values of condition factor of all the species collected from the Hooghly
estuary (compared to those collected from the Matla estuary) confirm the adverse
effect of hyper salinity on the growth and condition factor of the species.
Keywords Salinity Á Condition index Á Fin fish Á Climate change
1 Introduction
The lower Gangetic delta at apex of Bay of Bengal sustains a wide spectrum of fin
fishes. The litter and detritus contributed by mangroves provide nutrition to the fish
community by triggering the growth of plankton. The fish fauna of the present
study area may be classified into residents and transients (migrants). The species
whose individuals of different sizes are present during all the months of the year in
any zone of the estuary are referred to as resident species. The important resident
finfish species are Mugil parsia, M. tade, Polynemus paradiseus, Polydactylus
indicus, Otolithoides biauritus, Lates calcarifer, Hilsa toli, Arius jella, Harpodon
nehereus, Setipinna taty, Ilisha elongata, Setipinna phasa, Coilia ramcarati, Pama
pama and Sillaginopsis panijus. The transient or migratory fishes enter and stay in
the Bay of Bengal associated estuaries for a short period. Depending on their
migratory pattern and direction, the migrants are divided into three categories
(Jhingran 1982; Mitra 2013): (1) Marine forms that migrate upstream and spawn in
freshwater areas of the estuary such as Tenualosa ilisha, P. paradiseus, S. panijus
and P. pama, (2) Freshwater species, which spawn in saline area of the estuary such
as Pangasius pangasius, and (3) Marine species, that spawn in less saline water of
the estuary such as A. jella, Osteogeneious militaris and Polydactylus indicus.
Two important estuaries in the lower Gangetic delta are the Hooghly and the
Matla estuaries. These two estuaries exhibit pronounced variation with respect to
salinity. The Hooghly estuary in the western sector is relatively low saline compared to the Matla estuary in the central sector. This contrasting salinity may be
attributed to discharge of fresh water through Farakka barrage in the Hooghly
estuary and complete closure of fresh water discharge in the Matla estuary due to
siltation of the Bidyadhari River since the late fifteenth century. The difference in
salinity has profound influence on the condition factor of the fin fishes, which has
been attempted to study in the present programme.
Our main aim is to determine the impact of salinity variation on the condition
factor of the selected fin fish species as the price of the fish mostly depends on their
growth (in terms of length and weight).
348
A. Mitra et al.
estuary (compared to those collected from the Matla estuary) confirm the adverse
effect of hyper salinity on the growth and condition factor of the species.
Keywords Salinity Á Condition index Á Fin fish Á Climate change
1 Introduction
The lower Gangetic delta at apex of Bay of Bengal sustains a wide spectrum of fin
fishes. The litter and detritus contributed by mangroves provide nutrition to the fish
community by triggering the growth of plankton. The fish fauna of the present
study area may be classified into residents and transients (migrants). The species
whose individuals of different sizes are present during all the months of the year in
any zone of the estuary are referred to as resident species. The important resident
finfish species are Mugil parsia, M. tade, Polynemus paradiseus, Polydactylus
indicus, Otolithoides biauritus, Lates calcarifer, Hilsa toli, Arius jella, Harpodon
nehereus, Setipinna taty, Ilisha elongata, Setipinna phasa, Coilia ramcarati, Pama
pama and Sillaginopsis panijus. The transient or migratory fishes enter and stay in
the Bay of Bengal associated estuaries for a short period. Depending on their
migratory pattern and direction, the migrants are divided into three categories
(Jhingran 1982; Mitra 2013): (1) Marine forms that migrate upstream and spawn in
freshwater areas of the estuary such as Tenualosa ilisha, P. paradiseus, S. panijus
and P. pama, (2) Freshwater species, which spawn in saline area of the estuary such
as Pangasius pangasius, and (3) Marine species, that spawn in less saline water of
the estuary such as A. jella, Osteogeneious militaris and Polydactylus indicus.
Two important estuaries in the lower Gangetic delta are the Hooghly and the
Matla estuaries. These two estuaries exhibit pronounced variation with respect to
salinity. The Hooghly estuary in the western sector is relatively low saline compared to the Matla estuary in the central sector. This contrasting salinity may be
attributed to discharge of fresh water through Farakka barrage in the Hooghly
estuary and complete closure of fresh water discharge in the Matla estuary due to
siltation of the Bidyadhari River since the late fifteenth century. The difference in
salinity has profound influence on the condition factor of the fin fishes, which has
been attempted to study in the present programme.
Our main aim is to determine the impact of salinity variation on the condition
factor of the selected fin fish species as the price of the fish mostly depends on their
growth (in terms of length and weight).
348
A. Mitra et al.