Conclusion

A typical fishery in tropical waters may harvest a hundred different species, each species often consisting of several local groups with a distinct genetic make-up. A detailed study of each group is difficult. There will be uncertainties with all scientific endeavors to monitor abundance and productivity of stocks and the underlying causes. Further, there is an uncertainty with regard to climate, aquatic ecosystem productivity, predation and fishing pressure. Managing for ichthyo diversity provides a useful clue against these uncertainties. Managing for fish diversity represents the epitome of water stewardship, quite distinct from simply maintaining reliable stocks of individual species. Fishers and ichthyologists have a critical role to play in understanding and protecting diverse fish resources. The long-term ability of this aquatic regime to sustain the generation of fish and fish products and values that we expect of them may depend on this ichthyo species diversity.

Concomitant to the above, the ongoing process of ecosystem change, as is evident in lake Sone today, directly or indirectly affects the abundance and composition of the fish species; and, is, to a large and increasing degree, due to human activities which are sometimes unconnected to fisheries. Such increasing impacts of other human activities on the lake Sone ecosystem highlights the need for a regional aquatic ecosystem approach to fisheries management including water-use patterns. The state of the fish community may be seen as a valid integrative indicator of aquatic ecosystem quality and health and - somewhat more distantly - of the regional quality of life for the humans.

We find that lake Sone is a vast aquaregime with rich ichthyo diversity of 70 species, the diversity followed same pattern during both the sessions. The conservation of fish diversity assumes topmost priority under changing circumstances of gradual habitat degradation. Whether or not the Sone aquatic ecosystem would be able to maintain its ichthyo diversity would be largely determined by the water-use patterns since fish diversity is an interdependent part of a cluster of diversities in the human society and in the aquatic ecosystem. In order to assure ecological and economic sustainability of the lake Sone fisheries, matching human activities with the natural pulses of the ecosystem should be particularly stressed in management practices rather than basing such practice on an unrealistic expectation that fish populations provide a steady exploitation source.

The average fish yield from Sone has been estimated to be 96.8 kg per hectare. Species such as Puntius chola contributed to bulk of the lake fish landing registering an annual relative yield of 24.60%. This study reveals that in Lake Sone, a) maximum fish yield occurs in pH range of 6.9 - 7.1. b) fish yield declines with increase in WC, SOC and AMB. The stepwise regression analyses indicate that the variartions in fish yield are mostly caused by DO, WpH, t, TA and ST. while variation in fish production due to variables such as FCO2, WC, SpH, SOC, SP, SK and AMB are less. These analyses clearly indicate that factors such as DO, WpH, t, TA, ST and to some extent WT determines the fish production in lake Sone eco system.