Study finds microplastics in mackerels, mullets

Abdul Wahab Khan

Panaji

A three-year study conducted in Goa has pointed to the concerning levels of microplastic pollution in two commercially significant fish species, the Indian mackerel (Rastrelliger kanagurta) and the mullet (Mugil cephalus).

Both fish varieties are consumed in Goa, making them critical indicators of microplastic pollution in marine ecosystems.

The study findings have indicated that the guts of these fish contained an average of six microplastic particles, raising alarms about the potential health risks to fish eaters.

It has found that both fish varieties contained microplastics in their gastrointestinal tracts, with an average of six particles per fish. This finding is particularly alarming given the omnivorous feeding habits of mullets and the carnivorous behaviour of mackerels, which may influence their exposure to microplastics.

The ingestion of these particles raises concerns about the potential transfer of microplastics through the marine food chain. The research was conducted along the 160 km coastline of Goa, covering eight sampling sites that included both estuaries and beaches.

These sites are Querim, Baga, Colva, Galgibag beaches and several rivers such as Chapora, Mandovi, Zuari, and Sal, which are crucial for local communities and agriculture.

The study was published in the journal Regional Studies in Marine Science in February 2025.

The selection of the Indian mackerel and mullet for the study was based on their ecological and economic significance.

The mackerel, known for its carnivorous diet, and the mullet, which exhibits omnivorous feeding habits, provide a diverse perspective on how microplastics can enter the food web.

The study has highlighted the potential for microplastics to transfer through the marine food chain, underscoring the urgent need for pollution mitigation efforts.

As noted in the research, “The ingestion of microplastics by local fish species (mackerel and mullet) highlights its potential entry into the food
chain”.

The study revealed a concerning size distribution of microplastics in the water and sediments of Goa’s estuaries and beaches.

 “A significant proportion of microplastics was found in the size range of 100 μm to 1 mm, accounting for 72% of the total microplastics collected, while only 28% belonged to the 1-5 mm size range were found to be isolated from coastal and estuary waters and sediments over different seasons,” the research has noted.

This distribution indicates that smaller microplastics are more prevalent in coastal and estuarine environments, posing a greater risk to marine organisms that may inadvertently ingest them.

The study was conducted by five researchers – Veda Manerikar and Sanjeev Ghadi from School of Biological Sciences and Biotechnology,  Goa University (GU);   Vinod Mandrekar, Vishnu Nadkarni from School of Chemical Sciences, GU and Manojkumar Kulkarni, from the department of community medicine, Goa Medical College.

Sample collection commenced during the Covid-19 lockdown in 2021, allowing researchers to evaluate pollution levels during a period of reduced human activity.

The study spanned three seasons: pre-monsoon, monsoon, and post-monsoon, providing a view of microplastic distribution across varying environmental conditions.

The findings of the study are alarming, as they represent the first comprehensive seasonal assessment of microplastic pollution in Goa’s coastal and estuarine ecosystems. The researchers employed quantitative indices such as the Coefficient of Microplastic Impact, Pollution Hazard Index, and Pollution Load Index  to evaluate the ecological risks associated with microplastic pollution.