Assessment of the impacts of a new artificial lake mouth on the hydrobiology and fisheries of Chilika Lake, India

Abstract

The degraded state of the fragile ecosystem of Chilika Lake, located on the east coast of India, was undergoing restoration through an effective hydrological intervention during the year 2000. Studies on the lake's hydrobiology and fisheries for the period of 7 years before and 7 years after the hydrological intervention indicated a rapid recovery of the lake fishery immediately after opening of the new lake mouth, with a sixfold increase in the average annual fish landings. During the average fisheries output (11 051.3 t), catch per unit effort (6.2 kg boat )1 day )1 ), the economic valuation of the average annual catch (637 million rupees) and productivity (11.97 t km )2 ) exhibited dramatic increases of 498%, 464%, 1177% and 498.5%, respectively, compared with the 7-year pre-intervention data. Multivariate statistical analysis inferred that most of the lake's environmental variables are strongly associated with salinity factor, which seems to have governed the lake ecology. The salinity dynamics of the lake are governed by both freshwater inflows and seawater ingress through the new artificial lake mouth. Correlation analysis indicated that salinity was positively correlated with prawn catch (R 2 = 0.542; d.f. = 25; P < 0.01), crab catch (R 2 = 0.628; d.f. = 25; P < 0.001) and fish catch (R 2 = 0.476; d.f. = 25, P < 0.05). The average increase in the salinity regime (43.8%) for the lake during the post-hydrological intervention period, compared with the pre-hydrological intervention period, appears to have positively impacted the fish, prawn and mud crab catches. A gradual decrease in total fisheries output since 2005-2006, however, was attributed mainly to a continuing increase in destructive fishing practices in the absence of any conservation and regulatory measures for fishing, and large-scale collection of shrimp juveniles from the outer channel for shrimp aquaculture. Thus, carefully planned conservation and regulation measures must be ensured, with active participation of local communities during this early phase of lake restoration. In the absence of such measures, the present scenario of fisheries enhancement might not be sustained over the long term.

Effect of dietary protein level on fattening and mineral profiles of mud crab,Scylla serrata, in individual cages under mangrove ecosystem

“…In the process of moulting, a series of physiological and biochemical changes take place where some of the essential nutrients and minerals are absorbed into the muscle tissues or body fluids from the carapace or from the surrounding water, so that these nutrients will be utilized during the new carapace formation (Mohanty, Mohapatra, & Mohanty, ; Paez‐Osuna, Perez‐Gonzalez, Izaguirre‐Fierro, Zazueta‐Padilla, & Flores‐Campana, ). The present study, therefore, evaluated the effect of formulated feeds on the growth and survival of mud crab, S. serrata, reared in the mangrove ecosystem with feeds containing two different protein levels (32% and 36%).…”

Ichthyofaunal diversity of Chilika Lake, Odisha, India: an inventory, assessment of biodiversity status and comprehensive systematic checklist (1916-2014)

“…It is one of the region's finest repositories of aquatic biodiversity and a fisheries resource supporting the livelihoods and nutritional security of more than 200,000 local fishers. The unique and fragile ecosystem of Chilika Lake gradually began to lose its ecological integrity due to coastal processes, significant decrease in salinity regime, and degraded drainage basin with associated anthropogenic impacts (Mohanty et al 2009). Between 1950 and 2000, the lake fishery was in a continuing state of decline when the fisheries output reached its lowest point by the end of the 1990s.…”

“…Between 1950 and 2000, the lake fishery was in a continuing state of decline when the fisheries output reached its lowest point by the end of the 1990s. The lake fishery suffered serious setbacks since the later part of the 1980s with the salinity level sharply decreasing to 9.6 PSU, compared to a level of more than 22.0 PSU in the 1960s (Banerjee and Roychoudhury 1966;Siddiqi and RamaRao 1995;Mohanty et al 2009). The recruitment corridors (outer channel and Palur canal) also gradually silted up, adversely affecting the recruitment of fish and shellfish seed from the sea into the lake, while silted up river mouths (Mahanadi tributaries draining into the lake) in the northern sector of the lake also affected freshwater seed recruitment from riverine sources.…”

Growth, mortality and stock status of mullets (Mugilidae) in Chilika Lake, India

“…The 14‐km‐long Palur Canal also connects the southern end of the lake to the sea through the Rushikulya River mouth in the south‐east. The first hydrological intervention of opening a new lake mouth at a strategic location during September 2000 was implemented by the Chilika Development Authority (CDA) for eco‐restoration of the lake (Mohanty, Mohapatra, & Mohanty, ; Mohapatra et al., ), allowing ingress of seawater into the lake to maintain its salinity profile. The period after opening of new artificial connection into the sea (September 2000) is herewith referred as post‐restoration period.…”