Decline in Diversity and Production of Exploited Fishery Resources in Vembanad Wetland System: Strategies for Better Management and Conservation

Abstract

This paper describes the fishery catch structure of Vembanad wetland system during August 2012 to July 2013. The estimates of fishery production indicated an annual landing of 4387.31 t, in which 480.98 t and 3906.33 t contributed by southern and northern zone of Vembanad respectively. Eighty species of finfishes, five species of penaeid shrimps, three species of palaemonid prawns and two species of crabs were identified from the study period. The catch per unit effort (CPUE) value was maximum for gill net (3.04 kg•h −1) followed by stake net (2.43 kg•h −1), Chinese dip net (2.01 kg•h −1), seines (1.2 kg•h −1), cast net (0.72 kg•h −1) and hook and line (0.34 kg•h −1). Biological integrity and fishery production of estuaries in the country are declining mainly due to various man induced activities. Thaneermukkom barrage, the salinity barrier, constructed across the Vembanad wetland system in 1976, transforming the water body into two distinct ecosystems, a fresh water zone on the south and a brackish water zone on the north, resulting in gross changes in physical, chemical and biological entity of the aquatic ecosystem. In the southern zone of Vembanad the marine fish species were less available with the closure of the barrage period. There are signs of decline of the Vembanad fishery resources, evident in the lesser number of species and decline of fishery production. This will lead to biodiversity loss, fish stock reduction and will ultimately affect the livelihood support of the traditional fishers to a large extent, besides affecting other ecological services. A better conservation measure must be implemented for maintaining the sustainable fishery resources in Vembanad.

Ecosystem analysis of the degrading Vembanad wetland ecosystem, the largest Ramsar site on the South West Coast of India — Measures for its sustainable management

“…Among the environmental parameters, variation in fish assemblage, composition and abundance in Vembanad estuarine system the depth, temperature, pH and salinity seemed to be the key factors [114]. Salinity acts as a prime factor influencing the distribution and abundance of organisms in estuaries and many dominant fish species in the pre barrage phase have become a rarity [27] and their distribution pattern was determined by salinity gradient prevailing in the estuary [26]. Anthropogenic activities along with increase in fishing pressure on estuarine systems affects the species threatening its very existence [115,116].…”

“…Analysing the fishery of both sectors of the estuary, the southern stations noted a radical decline in annual landings from 500 t in 1988-1989 [24] to 486 t from 1995 -1999 [112], to a slight increase upto 507t during 2000-2001 [26] and further decline to 480.98t during 2012-2013 [27]. In the southern zone of Vembanad estuary, 67 species of finfishes and 14 species of shell fishes were recorded during 2008-2010 [113].…”

“…The closure of TMB (DecemberMay) results in complete absence of flushing in the upper reaches causing serious ecological degradation in the southern zone of Vembanad estuary [26]. The 'unscientific operation' of TMB, still remains as an everlasting conflict between fisher folk and farmers over the opening and closing of the barrage [27]. Bijoy Nandan and Unnithan [28] also reported the need for maintaining the continuity of the estuary on both sides of the TMB for reducing the stress on the environment by natural tidal flushing of the system.…”

Threats to Seagrass Ecology and Indicators of the Importance of Seagrass Ecological Services in the Coastal Waters of East Lombok, Indonesia

“…Furthermore, Stolephorus indicus and Sardinella gibbosa are both in the pelagic fish group on seagrass in the study area. Another study states that, Sardinella gibbosa is a pelagic fish that can be found in coastal waters dominated by mangrove and in turn contributes to regional offshore fisheries (Khatoon et al, 2014;Kumar et al, 2016;Swapna et al, 2016) and Stolephorus indicus is belonging pelagic-neritik and become the target of a small fishing catch (Asha et al, 2014). Consequently, the abundance of fish species diversity in seagrass beds highlights the importance of seagrass for these fish to survive and is an important factor to considered in conservation strategies for seagrass in the study area.…”

Study on Techno Economic Status of the Local and Migratory Fishermen in Cochin Back Waters

“…According to Asha et al, (2014) in Vembanad lake gill net showed highest CPUE of 3.04 kg•h −1 followed by stake net having 2.43 kg•h −1 , Chinese dip net 2.01 kg•h −1 , seine net with 1.2 kg•h −1 , cast net with 0.72 kg•h −1 , hook and line with 0.34 kg•h −1 and traps with 0.26 kg•h −1 . The difference in the catch observed in the present study may be due to restricted study to few landing centers of the Vembanad Lake despite the former study covered a wider area.…”