Consumers purchasing tinned fish may not be getting what they expect, according to recent investigations revealing widespread mislabelling in the seafood industry. Products marketed as mackerel often contain Chilean jack mackerel, a species unrelated to the traditional northeastern Atlantic mackerel typically consumed in Europe and North America. While both fish share a common name, Chilean jack mackerel belongs to the Carangidae family rather than the Scombridae family to which Atlantic mackerel belongs.

This distinction has implications beyond taxonomy. Chilean jack mackerel, sourced primarily from the South Pacific, generally offers lower nutritional value, containing about half the Omega-3 fatty acids and fewer calories than true mackerel. Its texture and taste have also drawn criticism from consumers accustomed to northeastern Atlantic varieties. However, this substitution benefits suppliers by avoiding the tighter fishing restrictions imposed on Atlantic mackerel stocks, which experts believe require a 70 percent catch reduction to prevent further depletion.

Mislabeling and fish fraud extend beyond mackerel, with numerous documented instances affecting other popular seafood items. A 2019 study in the United Kingdom found that nearly 90 percent of fish and chip shops sold shark meat disguised as common species like haddock or cod. Almost half of shark species are severely endangered, and stricter regulations now mandate fishermen to land entire sharks rather than finning and discarding the remainder, resulting in surplus shark meat entering the market under false identities.

Other common misrepresentations include selling escolar labeled as white tuna, farmed salmon designated as wild-caught, and tilapia marketed as red snapper. Seafood fraud remains the second most prevalent type of food fraud globally, following olive oil, facilitated by the complex and opaque nature of global seafood supply chains. As consumers increasingly prefer processed forms such as fillets or canned products, accurate species identification becomes more challenging.

Efforts to improve traceability and combat fraud face significant obstacles. Only about 2 percent of the global fishing fleet carry fisheries observers who monitor catch authenticity, partly due to the high-risk conditions observers face aboard vessels operating far from shore. Emerging technologies, such as remote video monitoring systems, show promise but are not yet widely implemented.

Given these challenges, experts advise consumers to diversify their seafood choices and seek sources with strong traceability. Alternatives like herring, sardine, sea bass, coley, hake, and plaice can relieve pressure on overfished species including cod and haddock. Switching from farmed salmon, which can produce harmful environmental waste, to farmed freshwater trout is another suggested measure. Selecting smaller tuna species such as skipjack or albacore, especially those caught by pole and line methods, can also help promote sustainable fishing practices.

Some fisheries producing prawns experience bycatch rates as high as 90 percent, intensifying environmental concerns. Responsible sourcing from certified prawn farms in regions like South America or Indonesia is recommended.

Bivalves such as mussels offer a sustainable alternative: farmed on ropes in ocean waters, mussels require no feed, help filter and clean water, and provide a nutritious, low-fat protein source.

With the seafood industry characterized by extensive complexities and frequent mislabelling, consumers face challenges in making informed choices. Direct purchasing from trusted fishermen using sustainable methods, such as Cornish handline-caught mackerel, remains ideal but is increasingly difficult due to depleted fish stocks. Ultimately, diversifying seafood consumption and supporting transparent supply chains may be the most practical steps toward reducing environmental impact and food fraud in the sector.