Presence of microplastics in the digestive tract of skipjack tuna (Katsuwonus pelamis) in Chabahar Bay

Microplastic pollution due to its small size can be used by a wide range of marine organisms and accumulate mainly in their digestive system, as they have been found in the tissues of aquatic animals, including fish. Due to the nutritional importance of fish for humans, it is very important to check their contamination. The main purpose of this research is to investigate the presence of microplastics in skipjack tuna (Katsuwonus pelamis) in the Oman Sea.

17 pieces of skipjack tuna were used. After the biometry, dissection and isolation of the digestive system of the fish, the digestion and extraction of microplastics were done using KOH solution. Identification and counting were also done by a stereomicroscope equipped with a digital camera. FTIR spectrophotometric analyses were performed to investigate the polymers.

The total frequency and average frequency of microplastics are 331 particles and 19.4±7.3 particles per individual, respectively. String (64.35%) and pieces (28.7%) were the dominant forms in the samples. The highest color spectrum was assigned to red (28.7%) and the lowest to violet (1.51%). The largest number of identified microplastics had a size of 0.5-1 mm (53%). Analysis of particles by ATR-FTIR method showed that nylon polymer and polycarbonate were the dominant polymer particles.

Microplastics are present in all samples. The abundance of microplastics in water, sediments and contaminated bait makes them easily available and swallowed by fish, which is most likely the main reason for the presence of microplastics in fish.