Refocusing the role of <scp>DNA</scp> technology towards a sustainable seafood supply

Our special fondness for fishes—and here I particularly refer to their flesh—began early in our pre-history, as soon as we developed ways to catch them. Starting at least 90,000 years ago we began to carve bone tools to spear catfish in shallow freshwaters (Yellen et al., 1995), while only a few tens of millennia later we were already capable of faring into the open ocean to catch large pelagic prey (O'Connor et al., 2011). Subsequent progress, culminating in the industrial era, then led to full exploitation of the vast majority of profitably catchable species, often in unsustainable fashion, with plentiful literature emphasising various angles around the issue (Hilborn & Hilborn, 2019; Pauly, 2019). With the growing importance of seafood, coastal and fish-eating communities grew in their appreciation and knowledge of the diversity of fish species, as widely documented, for instance, in ancient Roman art and literature (Marzano, 2018). However, in modern times, a cultural reversal in seafood literacy is being observed. The industrialisation of fish processing and logistics (Anderson et al., 2018), market demand from wealthy countries and unfair, unethical value chain distribution along the supply (Pitcher & Lam, 2014) are fuelling the most diverse and globally traded food commodity on the planet (Watson et al., 2015), half of which is still underpinned by entirely wild populations (FAO, 2022). Such complexity and diversity have two major implications: first, the journey of a fish from its natural habitat to our plate is difficult to track (Cawthorn & Mariani, 2017); second, most consumers around the world have little knowledge or understanding of the distribution, biology, population status or even appearance of the fish species they eat, especially in urban communities (Cusa et al., 2021). With such astounding complexity remaining largely intractable for decades, it was hardly surprising that the advent of DNA technology would produce the proverbial shockwaves across the discipline. From the earliest realisation that genetic variation could be directly employed to resolve ambiguities in fishery landings (Bartlett & Davidson, 1991), through the very first application of DNA sequencing to unveil species substitution on the markets (Marko et al., 2004) and the subsequent establishment of the DNA barcode of life as the gold standard for fish species identification (Yancy et al., 2008), the 21st century bore witness to the rapid expansion of a plethora of molecular tools devised to determine the identity and the origin of seafood products. Massively parallel and long-read sequencing technologies subsequently slashed costs and allowed for entire genomes to be routinely screened. The availability of genome-wide markers used to characterise populations (Han et al., 2020) and understand their susceptibility to environmental changes (Layton et al., 2024) also offers the opportunity to develop assays for provenance testing of market products (Cusa et al., 2025). Major advances in biochemical synthesis have turned once unwieldy laboratory procedures into rapid and portable assays (Naaum et al., 2021; Prasetyo et al., 2023). The direct sequencing of billions of nucleotides from DNA extracted from fresh and frozen market products is also possible via small portable devices to identify species in real time and infer their geographic origin (Shum et al., 2024). Similar approaches are mature for in situ amplicon screening of catch composition from fishing vessels (Maggini et al., 2024), with its next natural application being the characterisation of mixed seafood products (Lorusso et al., 2024). Although several of the latest genomic advances continue to present technical barriers that often still hinder or slow down their intake, the overall trajectory over the last three decades demonstrates how genomic tools have drastically transformed the way we can now investigate and monitor the diversity, legality and sustainability of global seafood supply. Despite the undeniable success of molecular genetic techniques, there remains a generally weak link between the increased sophistication and availability of DNA screening tools and the extent to which such discoveries are embedded in routine, real-world seafood supply chain operations. There is broad scientific consensus that the currently available—and ever improving—genomic tools can tackle the vast majority of issues of authenticity and traceability of seafood from a technical standpoint (Andersson et al., 2024); however, each seafood supply challenge has its own complex geographical, societal, and economic constraints and sector involvement. Some scenarios involve highly prized species with complex and dynamic population structures at oceanic scale (e.g. Díaz-Arce et al., 2024) and significant corporate and policy pressures from multiple entities, which hinder the swift implementation of monitoring protocols. In other instances, the patterns are considerably easier to unravel, but the trade mechanisms underlying them are very difficult to examine and influence positively, or may depend on unique conditions occurring at specific times and places (Mariani et al., 2014). In some cases, the local socio-economic model is marred by structural inequalities (e.g. Calosso et al., 2020), in others, routine DNA tests should be carried out at various points along the supply chain, which would encounter resistance at some nodes (Lorusso et al., 2024; Miller et al., 2012). It clearly emerges that even the most powerful and sophisticated DNA-based approach can only escalate positive change in the sector if judiciously embedded in a truly transdisciplinary, cross-sector framework. While it is in our nature of biologists to be inherently drawn to develop new methods, generate new data and produce new evidence, we should place emphasis on some essential conditions when designing, or engaging with, seafood identification and traceability investigations (Figure 1). The case of restaurants that advertise ‘local grouper’ in the Caribbean Island nation of Turks & Caicos, but instead primarily serve imported iridescent catfish (Pangasianodon hypophthalmus) farmed in South-East Asia (Calosso et al., 2020), exemplifies the fundamental considerations that ‘seafood geneticists’ should see as beacons that illuminate the path towards more effective implementation of DNA technology. First, tools and evidence should be directly relevant to the socio-ecological system underpinning the fisheries: in Calosso et al. (2020) it would be unfair and overly simplistic to solely put emphasis on testing the local fishers' compliance to the harvest closure for Nassau grouper (Epinephelus striatus), but rather examine in depth the socio-economic impacts of the seafood supply uncovered on the local communities. Secondly, the policy/legal framework of the context should be at the core of the investigation: What regulations are being contravened? Who is responsible for a clearly unjust price inflation? Can deliberate fraud be demonstrated? Is there scope for fair punishments that could serve as deterrent and, subsequently, escalate changes towards a more sustainable seafood service provision within the island? Lastly, and perhaps of greater difficulty, efforts should be made to incentivise entities and stakeholders outside academia to embrace and apply the tools developed over an extended period of time. Examples exist of government (Graham, 2020) and NGO (Barendse et al., 2019) adoption of DNA-based control programmes, and perhaps in the near future there may be room for market-based incentives (e.g. Rasal et al., 2023) that could bring more regular investment on the industry's part. While the first two actions essentially represent cultural shifts in the way we do research, the last point requires greater continued efforts towards the standardisation, streamlining and translation of a constantly changing biotechnological landscape. The molecular revolution enabled the unravelling of patterns and processes along the seafood supply that had remained intractable for decades. Its relentless increase in power, accuracy, throughput and affordability massively benefited researchers, government agencies, industry and consumers. DNA never broke its promises; it simply found itself in an arena where even its finest contribution can be only one of the ingredients required to tackle the big issues. No billion-base pair data set can alone fix the problem of a mis-managed mixed fishery in a megadiverse region of the world, exploited by unscrupulous exporters/importers supplying vaguely labelled products to ill-informed consumers in the global north. Our responsibility lies in the commitment to engage in transdisciplinary synergies at the onset of every project, and in our determination to democratise technology and resources, while educating and training the next generation of ocean stewards. I am grateful to the FSBI and the organisers of the 2024 Symposium for inviting me to contribute with this topic, and to the reviewers that helped me tweak the message. I also thank Giulia Maiello for inspiring me to produce Figure 1. Lastly, and most importantly, very special thanks go to the wonderful younger researchers, including, chronologically, Dana Miller, Andrew Griffiths, Amanda Brechon, Sara Vandamme, Cristina Di Muri, Peter Shum, Donna Cawthorn, Marta Calosso, Marine Cusa and Lucilia Lorusso, who collectively walked this seafood path with me for nearly two decades.