Plastics are a major contaminant in the world’s oceans because it takes a very long time for them to degrade naturally (Mendenhall 2018; Law et al. 2010). It has been estimated that, since 1950, 196 million tons of plastics have entered the ocean and the global production of plastic resins in recent years is about 380 million tons annually (Gibb, 2019; Anthony, 2017; Kolemans et al. 2017). Large plastics continuously degrade to small-sized plastics and are the precursor of microplastics (< 5 mm; Kuhn & van Franeker 2020; Mendenhall, 2018). The longevity and buoyancy of microplastic means that pollutants can travel long distances before they settle into sediments (Markic & Nicol, 2014). Therefore, microplastics are widely distributed in every sub-zone/layer (pelagic and benthic) of coastal and marine systems (Jiang & Li, 2020; Thushari & Senevirathna, 2020) and are essentially found in all investigated species regardless of their habitat preference or trophic level (Savoca et al. 2021; Hale et al. 2020). The incidence of plastic ingestion in marine fish has been annually growing by > 2% since 2010. Therefore, microplastics have become an increasingly concerning problem as they may pose a potential health risk for marine organisms and humankind (Barboza et al. 2018b; Zhang et al. 2021).
Microplastic ingestion by marine fishes has been of particular interest, as many species are the target of commercial fisheries and, thus, have a strong connection with human health (Walkinshaw et al. 2020). Fish may intentionally ingest microplastics by mistaking particles for a natural prey (e.g., plankton) or unintentionally, if the microplastics were already present inside or adhered to the prey (Jovanovic 2017). This ingestion in some species can generate the physical blockage of their digestive organs and interference with feeding (Savoca et al. 2021; Jovanovic 2017; Wang et al. 2020). Plastics are not composed entirely of plastic polymers but contains numerous additives (e.g., fillers, coupling agents, plasticizers, colourants, stabilizers) which may leach out once ingested, possibly having indirect physical impacts on fish, as the decreased feeding or predatory performance, disturbed energy metabolism and inflammation in different organs, decreased mobility, growth, reduced body condition, and overall performance (Markic et al. 2020; Jovanovic 2017; Kogel et al. 2020).
In addition, plastic garbage absorbs anthropogenic compounds present in the water, such as pesticides, fertilizers and industrial chemicals, thus becoming potential carriers of these dangerous substances (Markic et al. 2020; Wang et al. 2020). These chemicals (including some with endocrine-disrupting properties) attached to the plastics can be liberated inside the fish and result in physiological damage to the organism (Gallo et al. 2018; Markic et al. 2020). For example, there are reports in which fish that had ingested microplastics had oxidative lipid damage in the brain, muscles, and gills (Barboza et al. 2020). The net consequence of microplastic consumption combined with high concentrations of exposure to associated chemical additives and contaminants, and habitat degradation are likely to alter behavior and survival rates of juvenile fishes since there are documented negative impacts in predatory performance, activity, olfactory threat cues and risk exposure behavior (Loonstedl & Eklov et al. 2016; Guven et al. 2018; McCormick et al. 2020).
Microplastic ingestion is also related to the trophic level or feeding strategy. For example, due to distribution differences in the abundance and the characteristics of microplastics, the living habitats of fish are important factors related to the probability of ingestion (Wang et al., 2021). Sathish et al (2020) reported that species in shallow habitats had higher ingestion rates than species in the deeper oceanic habitats. In terms of feeding habits, benthivores ingest the highest abundance of microplastics with the greatest variety of polymer types (Wang et al., 2021). Feeding strategy also influences the intake of microplastics in fish. Planktivores have high probability of consuming microplastics directly from the environment, while piscivores consumption is expected via trophic transfer through prey or accidental ingestion (Walkinshaw et al. 2020). Fish that mainly rely on visual foraging cues ingest microplastic particles significantly more often and in higher numbers than species that mainly perform chemosensory foraging (Roch et al. 2020). Despite the increasing literature on marine plastic contamination, there are few studies that address the role of biotic factors on the ingestion of microplastics (e. g. Wang et al. 2021, Sathish et al. 2020, Savoca et al. 2021, Roch et al. 2020, Markic et al. 2020; Kibria et al. 2022). Therefore, increasing our knowledge on how ecological traits relate to the likelihood of consuming microplastic particles is key to understanding the human exposures that can occur through the consumption of species that are targeted by fisheries.
Plastic debris entails direct and indirect impacts on human activities and poses a clear cost to the economy and human wellbeing relating to the provision of sustainable and safe fisheries and aquaculture products (Mendenhall 2018; Beaumont et al. 2019). Concerns have been raised that the presence of microplastics, and chemical compounds present in or adhered to microplastics, represent a risk for fisheries resources’ production, with adverse effects on food security and implications for seafood safety (Du et al. 2020; Lusher et al. 2017). The negative consequences of microplastic pollution for fisheries production are based on the risks that microplastic contamination poses to commercial fish species (Walkinshaw et al. 2020).
Direct adverse effects on human health associated to human consumption of microplastic through the food chain are still controversial and not well understood (Barboza et al. 2018). However, it is possible that microplastic consumption has toxic effects as several chemical substances can be bioaccumulated by microplastic and could potentially pass from fish to humans (Du et al. 2020). Even low concentration, the chronic exposure and intake, increase the threshold of hazardous chemicals that represents a potential threat to humans (Kogel et al. 2020; de la Torre 2020; Sathish et al. 2020). For instance, it is known that the plastic serves as a vector for the bioaccumulation of Persistent Bio-accumulative and Toxic Substances (PBTs) (Rochman et al. 2013). In contrast to microplastic particles, PBTs build up in the tissues of organisms and accumulate up the food chain, leading to increased body burdens in higher trophic levels (Lusher et al., 2017). Furthermore, the most common additives used in the fabrication processes and reported in macro-and microplastic debris collected in environmental surveys are phthalates, bisphenol A and flame retardants (Hermabessierere et al. 2017). Some of these molecules can act as endocrine disruptors (Lusher et al., 2017; Gallo et al., 2018). Research has shown that other chemical compounds present in plastics or adhered to microplastics, like residual low molecular weight styrenes, polyvinyl chloride monomer, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), oral contraceptive pills (OCPs), and pharmaceuticals, including their metabolites, could become carcinogenic, mutagenic, and endocrine disruptors after being uptaken (de la Torre, E. 2020).
Consumption of microplastics thru seafood is likely to be particularly significant among those social groups that highly depend on fish as a source of protein and/or as a primary source of income. In developing countries, such as Mexico, a large proportion of coastal communities rely on small-scale fisheries as a means of income, subsistence, and protein intake (Cinner & Pollnac 2004; de Oliveira et al. 2019), and generally, live with economic uncertainty and heterogeneous profits across the year (Coronado et al. 2020). Microplastics in fish species might therefore compromise fishers’ income and health since fish is the main diet and a significant component in the regular food intake of thousands of families in coastal communities (Benitez & Flores-Nava. 2019). In Mexico, approximately 70% of the fisher’s population have a high or very high marginality level that also faces food insecurity and low living standards derived from low income and low average wages (DOF, 2020; Fernandez et al. 2011). In this context, it is essential to consider the implications of the emergent pollution problems of microplastics on target species and the people who rely on them. Here we first aim to characterize the presence of microplastics in species targeted by small-scale fishers; and explore if the fish consumption of microplastic particles is associated with biological factors (as home range), to understand possible consequences that lead to the uptake of microplastic by fish. Second, we applied semi-structured interviews to small-scale fishers to approach, from a socio-environmental perspective, the potential social and environmental impacts of contamination by microplastics on the local communities. Since the possible presence of microplastic items inside of the main commercial fishes in the area, and the associated risks that may imply in the people that relies on the benefits of the fishing activity, an assessment of the social and environmental negative implications is relevant to conform an integral analysis of this global issue from a local perspective.