Illegal Fishing and Its Impacts on Conservation and Fisheries

The increasing incidence of illegal fishing activities around the globe is reducing conservation as well as fisheries success, yet the exact causes and consequences of illegal fishing remain difficult to unravel.

Illegal Fishing

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The extent of illegal, unreported, and unregulated fishing

Despite overfishing remaining a major problem in many fishing countries, threatening food security, livelihoods, and conservation, empirical data on factors exacerbating overfishing remains scarce.

It is estimated that nearly 20% (11–26 million metric tons) of global fish catch is caught illegally every year. For fisheries, this leads to a loss of 10–23.5 billion USD. Such patterns also vary across regional scales, as illegal fishing in the western and central Pacific Ocean and eastern central Atlantic accounts for over 30% of the total catch.

Illegal fishing can be defined as illegitimate, unreported, and unregulated fishing in illegal areas, such as protected zones or foreign water, or targeting protected species. Although many small-scale fishers target such areas for recreational fishing, the large-scale, long-distance, fishing operations are the ones most damaging.

Over recent decades, the rapid expansion of distant-water fishing due to better technology, engineering capacities, and increased fishing efforts, has been associated with high incidences of illegal, unreported, and unregulated fishing activity. This is of particular concern for the sustainability of global fisheries, the preservation of key marine areas, and the protection of endangered species.

In response, scientific research examining the opportunities of illegal fishing has grown exponentially, as studies have gradually unveiled the extent of wildlife crime in the last decade. Increased awareness and concern have in turn grown the field of environmental criminology in particular.

From a policy standpoint, countries have differed in their response to address illegal fishing, yet mounting evidence suggests that addressing such activities in national waters boosts protection and conservation success, and also generates a profit for local fisheries.

This was evident in a case study of Indonesian fishers published by Reniel Cabral and colleagues in 2018 in the Journal Nature Ecology & Conservation. Researchers were able to assess the impacts of illegal fishing activity from foreign-flagged vessels as well as the outcome of response measures to curtail illegal activities.

Findings demonstrated that reducing illegal fishing generated a 14% increase in catch and a 12% increase in profit. This was primarily a result of the aggressive strategies used by Indonesia, which avoided the fishing losses generally encountered in other countries.

Addressing the increase of illegal fishing activity

However, to address long-term illegal fishing activity, it is necessary to better understand the causes of the activity, which requires a far more complex picture.

In a study by Damian Weekers and colleagues from New York University and the University of Paris, the authors were able to explore the opportunity structure of illegal recreational fishing (poaching) in no-take zones in Australia’s Great Barrier Reef Marine Park. The study published in 2021 employed a situational approach to illegal fishing using MPAs as primary tools to accumulate data.

After running a series of Boosted Regression Trees to predict the spatio-temporal distribution of poaching risk within no-take Marine National Park zones, researchers showed that certain factors account for most of the poaching effort.

Results of the models demonstrated that five risk factors account for nearly three quarters (73.6%) of the relative importance for poaching in no-take zones and that temporally varying conditions influence risk across space.

Specifically, the models suggested that the variation in illegal fishing in no-take MNPs could be explained by fishing capacity and accessibility (two measures of ‘fishing’), distance to facilities (one of the two ‘management’ measures) as well as wind speed and swell height.

The authors then discussed how to address such activity and factors. Aligning with the mounting empirical evidence suggesting that to reduce illegal fishing one should focus on addressing specific contextual factors that facilitate it, the authors concluded that the crime was largely a product of opportunity.

Addressing contextual factors through management of fishers, monitoring at specific sites and during particular conditions, could then lead to immediate and lasting outcomes. Indeed, the six strongest interactions of models all included weather-related predictors (wind speed and swell height). As such, prevention measures could be improved at specific times and dates related to environmental factors.

Tracking Illegal Fishing—From Space | National Geographic

Emerging issues over illegal fishing in current and future world

The increasing rates of depletion in fish stocks have affected conservation efforts and the long-term success of protected areas around the globe. This is further exacerbated by illegal fishing, which is predicted to increase further into the future due to a range of issues.

Notable causes of increased illegal fishing include political and international tensions such as the increasing aggressiveness of Chinese fishing fleets into foreign waters as well as disputes due to Brexit. Such conflicts lead conservation and preventative efforts astray and require longer-term insights to ensure sustainable fishing practices. However, these are not the only issues to address to prevent further illegal fishing.

In a collaborative study lead by first author Clare Collins, researchers were able to further explore the social-ecological drivers of the Sri Lankan fishing fleet. The case study provided highly valuable insight into the dynamics of nearly 100 fishers, revealing that an increasing number admitted to illegal fishing practices.

Through a series of Generalized Linear Models (GLMs) aimed to determine the reasoning of fishing practices, models showed social factors including interpersonal and community social networks and perceptions of higher catch value were the most important determinant factors.

These findings demonstrate the value of adopting a social-ecological lens to investigate drivers for human behavior and non-compliance with rules across fishers. Importantly, the authors advocated for a nuanced approach to monitoring and managing fleets. This can be done by investigating localized social drivers for illegal fishing and enhancing regional transparency in fleet monitoring as well as considering the importance of community networks on a regional scale.

In a future world characterized by increasingly depleted fishing stocks as well as an increasing number of protected areas and species, fishers and their associated communities will be forced to adapt to rapidly changing seascapes. Policies should therefore aim to improve education, livelihood, and fishing practices, as well as consider how spatiotemporal factors can affect practices.


  • Agnew, D. J., Pearce, J., Pramod, G., Peatman, T., Watson, R., Beddington, J. R., & Pitcher, T. J. (2009). Estimating the Worldwide Extent of Illegal Fishing. PLoS ONE, 4(2), e4570. doi: 10.1371/journal.pone.0004570
  • Cabral, R. B., Mayorga, J., Clemence, M., Lynham, J., Koeshendrajana, S., Muawanah, U., Nugroho, D., Anna, Z., Mira, Ghofar, A., Zulbainarni, N., Gaines, S. D., & Costello, C. (2018). Rapid and lasting gains from solving illegal fishing. Nature Ecology & Evolution, 2(4), 650–658. doi: 10.1038/s41559-018-0499-1
  • Collins, C., Nuno, A., Benaragama, A., Broderick, A., Wijesundara, I., Wijetunge, D., & Letessier, T. B. (2021). Ocean‐scale footprint of a highly mobile fishing fleet: Social‐ecological drivers of fleet behaviour and evidence of illegal fishing. People and Nature, 3(3), 740–755. doi: 10.1002/pan3.10213
  • Weekers, D., Petrossian, G., & Thiault, L. (2021). Illegal fishing and compliance management in marine protected areas: a situational approach. Crime Science, 10(1). doi: 10.1186/s40163-021-00145-w

Further Reading

Last Updated: Oct 7, 2021

James Ducker

Written by

James Ducker

James completed his bachelor in Science studying Zoology at the University of Manchester, with his undergraduate work culminating in the study of the physiological impacts of ocean warming and hypoxia on catsharks. He then pursued a Masters in Research (MRes) in Marine Biology at the University of Plymouth focusing on the urbanization of coastlines and its consequences for biodiversity.  


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