Microplastics contamination in Yellowfin tuna (Thunnus albacares) from the Indian Ocean

Yellowfin tuna (Thunnus albacares), a major export fin fish species in the Indian Ocean, is a vital indicator of ocean health due to its migratory behaviour and exposure to pollution. Detecting microplastics (MPs) in yellowfin tuna can aid in conserving marine ecosystems and safeguarding tuna-dependent communities. The study assessed the sources and concentrations of microplastics in Indian Ocean yellowfin tuna. Thirty-five randomly selected fish from commercial catches were examined. MPs in their gastrointestinal tracts (GITs) were extracted using a modified potassium hydroxide (KOH) digestion protocol. Visual identification under a microscope recorded the number, shape, size and colour of MPs in each sample. Fourier transform infrared (FTIR) spectroscopy was used to identify polymer types. The average weight of the fish was 36.87±8.20 kg, and the average fork length was 131.54±9.36 cm, indicating that they were mature.  MPs Ingestion rate was 100% with the mean microplastic particles per individual was 2.77 ± 1.81  items/individual. Fibres constituted 91%, and fragments comprised 6% of the MPs, with Polyethylene (PE) being the predominant type at 56%, followed by Nylon at 25%. Particle size ranged from 0.054 mm to 1.494 mm. This study  demonstrates significant MP contamination in the gastrointestinal tracts of yellowfin tuna,  and highlights the need for further investigations using additional samples that account for seasonal and geographical variations in catches.