OCCURRENCE OF MICROPLASTICS IN GUT CONTENTS OF Sahyadria chalakkudiensis INHABITING A TROPICAL RIVER SYSTEM IN S. INDIA

Occurrence of microplastics in fishes has emerged as an alarming issue world over. This paper describes the detection of microplastics (Fig.1) among gut contents of Sahyadria chalakkudiensis (red line torpedo barb) inhabiting Periyar river, S.India. S. chalakkudiensis  is an endemic endangered fish used as food fish as well as ornamental fish. Endangered indigenous fishes encounter many detrimental activities, yet microplastic has never been described in any previous studies on these fishes.

478 fish samples were collected from  Pooyamkutty ranges of Periyar river during April, 2015 to March, 2017 and were fixed in 10% buffered formalin solution. After recording morphometric data, guts were dissected out and food items were identified to nearest taxonomic units. The unidentified matter was transferred to 10% KOH and later subjected to hot needle test.The undigested content was recorded with Motic Image Plus2.0.  Micro plastic fibres were identified in 71 guts (14.85%). Guts containing microplastics were encountered in all months except May and September. Highest number of guts with microplastics was recorded in October (23.94%) followed by December(19.72%)  and July(16.90%). It could be observed that among plastic ingested fishes, 74% of guts contained high amount of food and their temporal occurrence revealed signficant correlation with total number of guts examined(r=0.60, p<0.05). Monthly percentage occurrences of guts containing high amount of food  and guts containing food in traces revealed significant difference (Kruskal Wallis test, Hc= 4.11p<0.05). This indicated  that the fishes consumed plastic fibres inadevertently along with their preferred food items.  

Upper  reaches of Periyar river have many tourism destinations and also support rigorous fishing activities during post monsoon period. These microplastics generally enter freshwater environment as discards from fishing net material, household waste and tourism. Unbridled use of synthetic netting materials has resulted in large scale plastic pollution in aquatic environment. Further, abandoned netting materials succumb to weathering and biodegradation. The present results indicate serious concern on severe plastic pollution in this Western Ghat river system and consequent challenges to its biota which necessitates their conservation.