Limnological study of Thrissur Ponnani kole wetlands with special reference to the ichthyofauna

Abstract

Wetlands are encompass a diverse range of environments including rivers, lakes, marshes, rice fields and coastal areas, stand as vital ecosystems crucial for maintaining ecological equilibrium and fostering biodiversity. Their significance extends far beyond ecological boundaries and contributes to human well-being and poverty alleviation. The study presents a comprehensive analysis of the ecological dynamics, physicochemical parameters, fish abundance and production in the Thrissur-Ponnani kole wetlands over a period spanning 2018 to 2022. The research reveals significant variations in fish species composition, abundance, and distribution across different sites within the wetlands andeffectsof abiotic factors. The kole lands in Thrissur and Malappuram districts of Kerala are often described as the rice hub of these regions. Ponnani kole, situated in southwestern region of Malappuram district, is the northern most extension of the Vembanad kole Ramsar site. The study was conducted in seven randomly selected site; Marancherry, Mavinchuvad, Tholur, Mullassery, Enamav, Nedupuzha and Muriad kole wetlands which lie between Muriyad and Ponnani kole. The studies of fish production in kole wetlands were done by direct visit and questionnaire. A detailed questionnaire was prepared and data collected from fishermen based on that. The objectives of the present study are- to study the diversity of fishes in Thrissur-Ponnani kole wetland ecosystem; to study the interrelationship between physio-chemical parameters of water and Thrissur-Ponnani kole wetland fish diversity; to estimate the annual fish production by the kole wetlands of the Thrissur- Ponnani kole wetland ecosystem; traditional fish harvesting methods employed by stakeholders of the Thrissur-Ponnani kole wetlands ecosystem; economic evaluation of the fishery resources of Thrissur-Ponnani kole wetlands ecosystems and evaluation of the interventions by the local self governments in the Thrissur-Ponnani kole wetlands fishery. Taxonomic identification done and was 46 fish species from 23 families and 13 orders, with notable variations in abundance and composition observed across months and study sites. The dominance of certain orders, such as Cyriniformes, Siluriformes, and Anabantiformes indicates the ecological importance of these taxa in the wetland ecosystem. However, declines in abundance, especially in economically andecologically important species like Anguilla bengalensis and Macrognanthus guentheri, highlight potential environmental challenges. There was significant variations in fish abundance among different sites, with some sites consistently exhibiting higher abundance than others. Diversity indices indicated moderate levels of diversity, with fluctuations attributed to variations in species composition and abundance over time and space. The analysis conducted on the correlation between fish diversity and water quality parameters revealed several significant findings. Some fish species, such as Xenentodon cancila and Parambassis thomassi, exhibited strong positive correlations with multiple parameters like water temperature, air temperature, and dissolved oxygen. Conversely, species like Aplocheilus lineatus showed negative correlations with certain parameters, indicating their sensitivity or avoidance of those conditions. The study highlighted the interconnected nature of water quality parameters and the complexity of water chemistry in aquatic ecosystems. Understanding these relationships is essential for assessing water quality, identifying sources of contamination, and implementing effective management strategies to protect water resources and ecosystems. Physicochemical parameters analysis indicated temporal variations between 2018 and 2019. High fish production sites were Society Padavu and Akattan, and low- production sites were Nedupotta. Economic evaluation revealed the significant contribution of fish production to the local economy, emphasizing the importance of sustainable management practices. The present study provides valuable insights into the ecological dynamics and socio- economic significance of the Thrissur-Ponnani kole wetlands. Sustainable management strategies informed by scientific research are essential to preserve biodiversity, support livelihoods, and ensure the long-term sustainability of this vital ecosystem.