Book Review: The Unnatural History of the Sea by Callum Roberts


Posted: July 24, 2016

By Katelynn Conedera

In 2007, writer and marine biologist Callum Roberts published a book called The Unnatural History of the Sea. In this book, Roberts outlines the history of human interactions with the ocean. The book is separated into three parts outlining the past, present, and future of the ocean’s fisheries. For those not familiar with salt water fisheries, much of this book comes as a surprise. From mammoth sized sea cows to meter-long cod, The Unnatural History of the Sea has it all. Unfortunately, most of the gigantic creatures from the past have gone extinct or shrunk exponentially. Some of the animals, like the massive Seller’s Sea Cow, had been in decline for centuries before they had any contact with humans. Others, however, can blame their mass shrinkage on overfishing and human interaction. Much of this is in the past, but there is still a lot that humans can do to avoid further destruction. We cannot bring Seller’s Sea Cows back from extinction, nor can we single-handedly reverse the destruction that has accrued over millennia. What we must do now is stop the cycle before it is too late. There are many vital organisms and habitats in danger, and Callum Roberts convincingly advocates for their survival in The Unnatural History of the Sea.

Writing this book was only the first step towards becoming what New York Times writer Claudia Dreifus (2002) called “the Rachel Carson of the fish world” (para. 3). He first started writing with his wife, conservation biologist Julie Hawkins; Together they wrote a free guide called ''Fully-Protected Marine Reserves: A Guide'' (Dreifus, 2002). He has now independently written two books: The Unnatural History of the Sea and The Sea of Life, published in 2012. His interest in marine life, however, can be traced all the way back to his first trip to Saudi Arabia (“Biography,” n.d.). He was there to study freshwater fish, but he fell in love with the coral reefs that he encountered during the trip (“Biography,” n.d.). Years later, in the 1990s, he changed his focus to the conservation of his beloved coral reefs, as they were in great danger (“Biography,” n.d.) The plight of the coral reefs was what created the marine conservation biologist today. This newfound passion led to a Pew Fellowship in Marine Conservation “to tackle obstacles to implementing marine reserves” in 2000 and Harvard’s Hardy Fellowship in Conservation Biology in 2001 (“Biography,” n.d.). He is currently a researcher and professor in conservation biology at the University of York in England (“Biography,” n.d.).

It may be his widely respected place in academia, but The Unnatural History of the Sea has been cited by over 300 works just in the Google Scholar database. Of these, most are research papers on marine fisheries, sustainability, and marine conservation biology. There are also several books on oceanography, conservation, and sustainability. Since the book is such an in-depth look at marine fisheries over time, books and articles focusing on more narrow topics such as shark and jellyfish preservation should and do use the book for their general information. The book covers so many topics that it is a great general information source. The Unnatural History of the Sea also provides a comprehensive description of many ecological issues. Roberts calls for better marine management and an end to overfishing and destructive fishing practices. It makes sense, then, for many of the articles and books citing Roberts to have a strong focus on sustainability. Roberts makes a very strong case for sustainable fishing practices with more than enough proof.

Sometimes, it seemed, there was too much proof. Chapter after chapter described how a once bountiful fishery was depleted by boundless overfishing. The book became largely repetitive relatively quickly, but it also showed how time and time again, humans depleted their limited food supplies. The first section of the book described the history of marine fisheries, and much of it dealt with the depletion of fish populations. Take, for example, the reason people switched to marine fisheries from freshwater fisheries. According to Roberts, a combination of population growth and an increase in agriculture led to the decrease in freshwater stock (Roberts, 2007, p. 23). Because of this decrease, more people began to fish from the ocean (Roberts, 2007, p. 25). There was no immediate issue with the move from freshwater to saltwater fish. Unfortunately, the impacts of fishing the ocean did not show at first.

Cod, for example, grow throughout their lifetime. When the largest ones are fished, the population as a whole becomes statistically smaller (Roberts, 2007, p. 38). The shrinking of the geographic range is also usually a result of overfishing (Roberts, 2007, p. 40). In the case of cod, the historically huge fish began to shrink and disappear from the outer edges of its range. When the same overfishing issues began to affect America’s relatively new fisheries, the government attempted to regulate fishing practices (Roberts, 2007, p. 52). Unfortunately, these regulations largely failed because most people wanted to continue making money off of the remaining fisheries and rejected any sort of government intervention (Roberts, 2007, p. 53). At this time, the fisheries of the New World were still somewhat productive and getting people to limit their catch was very difficult.

The Caribbean faced an even worse crisis due to the nature of the overfishing in the region. Many people traveling to the Caribbean did so in order to write about their adventures. Many people in Europe enjoyed reading about the exotic area, so there was a large market for books written about the Caribbean (Roberts, 2007, p. 58). This brought a lot of people into the region leading to mass over fishing and hunting (Roberts, 2007, p. 60-61). The turtles and crocodiles of the Cayman Islands were two organisms that were particularly affected. Pirates visiting the islands often needed fresh food and eventually “decimated” the turtle population in order to fill this need (Roberts, 2007, p. 66). Despite laws set in place by the local government in order to protect the once plentiful turtle population, the creatures became extremely rare on the islands (Roberts, 2007, p. 66). Crocodiles faced a much worse fate, and were hunted to extinction for sport before the government could intervene and protect them (Roberts, 2007, p. 65). This, unfortunately, was not an isolated incidence. The hunting of animals to extinction was a common theme of The Unnatural History of the Sea.

The otters of the New World were hunted nearly to extinction due to greedy fur traders exploiting their large population numbers. People in the East had valued otter fur for some time, and once explorers discovered this, they began hunting the vast amounts of sea otters on the West Coast of America (Roberts, 2007, p. 76-77). In a very short time, the California sea otter went from extremely plentiful to nearly extinct due to their mass hunting (Roberts, 2007, p. 79-80). While the near loss of the sea otter was tragic enough, there were many more environmental implications that the fur traders did not take into account. The sea otters of the West Coast fed mostly on sea urchins and abalone. This kept the invertebrates’ populations at a reasonable level, thus lowering the “grazing pressure” on the kelp forests. This allowed the forests to flourish and provide habitat for a vast array of species. Once the otter population began to drastically decline, the invertebrates began to live uninhibited in the kelp forests. All along the West Coast, the kelp forests began to disappear. This meant an almost guaranteed extinction for the Seller’s sea cow, whose main diet was kelp (Roberts, 2007, p. 80-81). Clearly, overfishing has implications that affect an entire ecosystem and can be drastic for more than one species.

This is not the only issue with historical overfishing outlined in the book. One of the most famous examples of marine fisheries gone wrong was the global whaling industry. Roberts refers to whaling as the “first global industry” that took hold in the early 1800s (Roberts, 2007, p. 83; 92). Not only did the industry led to the once abundant whale becoming nearly extinct, but it also severely cut down the habitat of the creatures. Whalers used to fish for whales right along their migration routes (Roberts, 2007, p. 93). Unfortunately, when animals are killed on their way to mate, this severely cuts down the amount of animals actually replenishing the population. It was no surprise, then, that the populations of whales along fished migration routes began to plummet (Roberts, 2007, p. 93). Instead of giving up, whalers began to look for whales elsewhere. This made it seem as though there was no change in whale population because whenever an area dried up, the whalers would just move elsewhere and have equal yields (Roberts, 2007. P. 95). Since there were so many whalers doing this, the fishery collapsed and whales are still largely endangered today.

Another industry that faced collapse was the subsequent seal industry. Just like the whaling industry, seal hunters would move from one densely populated area to the other, depleting the population as they went along (Roberts, 2007, p. 107). Due to this constant depletion, fur seals were unable to ‘bounce back’ the way other fisheries could once a hunter moved on (Roberts, 2007, p. 109). Luckily, in 1911, seals became a protected species and their populations began to rise again (Roberts, 2007, p. 172). However, the gains in population were quickly lost, and nobody understood why. Then, researchers realized that killer whales were hunting fur seals more and more, and the huge creatures were depleting the population rapidly (Roberts, 2007, p. 173; 182). Why were these whales targeting creatures that they had never eaten before? The answer is simple: the predators used to prey on the other whales in the region. Once the whalers depleted a large amount of the local whale population, the killer whales had no choice but to target smaller prey in large amounts (Roberts, 2007, p. 174). Finally, people were starting to realize the full extent of the damage caused by overfishing.

Unfortunately, much damage had already been done. Many larger predatory fish were overfished and the fisheries had collapsed. Fisherman had to find more and more invasive ways to catch enough fish to make a living. The answer to this problem was a fishing technique called trawling, or the “dragging of nets across the seabed” (Roberts, 2007, p. 131). Trawling was, and still is, incredibly destructive. Dragging nets along the seafloor destroyed countless invertebrates and habitats that were hundreds of years old (Roberts, 2007, p.152). Many organisms were completely destroyed, and seabeds were irrevocably damaged. Even more destructive was the bycatch, or the unintentionally caught organisms (Roberts, 2007, p. 153). Trawls picked up whatever was near the net at the time, so many organisms were wasted by fishermen who simply did not need the extra organisms. Trawling is still practiced today, and little has been done to decrease the damage caused by it.

This leads to the second section of the book on modern day fisheries. The health of today’s fisheries are still very poor. In fact, in 1977 only 10% of the fisheries were overfished. However, by 2000, 50% of fisheries were considered overfished and only 18% were considered healthy (Roberts, 2007, p. 194). This shows that there have been few significant changes in the way humans manage fisheries. Of course, all countries are different. The Caribbean is a great example of this. In one of Roberts’s studies outlined in his book, he discovered that, “from Bonaire, the least fished island we studied, to Jamaica, the most heavily exploited, there was a 90% fall in the weight of predatory fish present” (Roberts, 2007, p. 235). This shows that marine fishery management could be the key to ending overfishing. However, Roberts paints a bleak picture for the rest of the Caribbean, as coral reefs are dying en masse and diseases are killing vital invertebrates (Roberts, 2007, p. 238-240). One country’s management tactics can only go so far. For real change, the whole world must work together.

For many, this book can seem pessimistic and apocalyptic. Sometimes, it is. Roberts continually states that if nothing is done, life as we know it will end, and there is some grain of truth in this statement. One chapter is entirely devoted to the fact that advanced fishing technology has led to more extensive overfishing than ever before. Roberts claims that because of this technology, there is no safe haven for species to hide and prosper. No part of the ocean is safe, and all creatures are at risk of overfishing (Roberts, 2007, p. 312; 316). Because of this, Roberts claims that humans may end up having to eat jellyfish because all other viable options are extinct, a process called “fishing down the food web” (Roberts, 2007, p. 318-319). This basically means that as humans continue to collapse fisheries, larger predator fish will begin to disappear and humans will continually settle for smaller fish.

But what can we, as humans, do to avoid this catastrophic crash? While there are already several policies in place to protect species from overfishing, Roberts claims that many do not completely do their job. For example, the maximum sustainable yield, the process of fishing a population down to half its size and allowing it to rebound, makes some incorrect assumptions (Roberts, 2007. P. 323). What happens if the species does not rebound the way it should? Cod and seals did not rebound, so one cannot assume that every organism would respond the same and rebound effortlessly (Roberts, 2007, p. 323). After all, it has already been proven that overfishing a population has other unpredictable consequences. Sometimes, to avoid dealing with this issue, a developed country uses a developing country’s ocean territory to fish (Roberts, 2007, p. 328). This does not do anything to avoid overfishing and creates more problems for the developing country. Therefore, this method is simply a way to avoid the problem of overfishing for a longer period of time

If none of the current responses to overfishing work, then what can we do? Roberts spends a brief two chapters discussing this question. He lists seven tactics to address the issue of overfishing:

1) Reduce present fishing capacity
2) Eliminate risk-prone decision making
3) Eliminate catch quotas and instead implement controls on the amount of fishing
4) Require people to watch what they catch
5) Require fishers to use gear modified to reduce bycatch
6) Ban or restrict the most damaging catching methods
7) Implement extensive networks of marine reserves that are off-limits to fishing
(Roberts, 2007, p. 342)

Some of these tactics may be idealistic, but if the current solutions are not working, experts must develop newer methods before it is too late. Roberts claims that by 2048, all of today’s fisheries will have collapsed (Roberts, 2007, p. 330). The collapse of so many fisheries would be catastrophic. Now is the time to begin discussing how to preserve our oceans for the next generation. Roberts supplies his readers with more than enough proof that our current fishing practices need to be reformed.

This is not even all of the information supplied by Roberts. There was a lot of information in The Unnatural History of the Sea that felt repetitive or unnecessary. Many chapters, especially in the first section on the history of fisheries, focused on how a fishery started out as abundant but became degraded over time. While it is important to show that this had happened many times, whole chapters were often unnecessary and redundant. This was coupled with the sheer volume of information included. It was simply not possible to summarize every single chapter and topic covered in the book. There was so much information, and Roberts always had something to say about his sources. Anybody familiar with scientific writing would know that most books used scientific articles as citations. The Unnatural History of the Sea was very different in this sense. While much of Roberts’s argument was backed by scientific research, most of his information about the history of fishing came from logs, journals, and personal anecdotes. While some may argue that these are unreliable sources, they are the only ones present. They also all agree with each other and support the claims made by the author. The book is unique in its field because of its successful use of anecdotes to create the first real comprehensive history of overfishing.

After reading this book, a person can feel one of two things: distress or determination. There are a lot of bleak scenes within the book that can really feel impossible to fix. For example, if trawlers take out huge amounts of reefs and bottom-dwelling organisms that have survived for centuries, how does a person fix that? The organisms cannot simply be brought back and the floor has been changed forever. The book does not provide solutions for such problems, but one cannot expect solutions for every single problem listed in the book. More likely, one would be inspired to develop their own solutions. One person cannot provide answers for all issues pertaining to overfishing, and multiple perspectives are important. This book provides the necessary information to develop opinions and pique interests. Since The Unnatural History of the Sea is a fairly general book covering topics pertaining to nearly every part of the ocean, there are a lot of avenues available for an individual to pursue. Hopefully this book will inspire people to draw their own conclusions and develop their own solutions rather than wallow in despair over the state of our home. These two possibilities make this book particularly unique because it allows the reader to draw his/her own conclusions.

The Unnatural History of the Sea is a very unique book. Not only does it include nearly everything a person should know about overfishing, but it created a comprehensive history based off of journals and personal stories collected from various sources. Still, despite its unusual citations and sources, it is still widely respected in the academic world. It is widely cited amongst specific research papers and books on a variety of scientific subjects. The book is, however, slightly disheartening. There are many issues with the management of today’s fisheries that have been around since people first started to fish from the ocean. How can these issues be easily brushed aside? This is one area where the book is lacking. While Roberts does list off seven recommendations, he only briefly describes each. After an entire book about the failings of the world’s fisheries, one expects at least a portion to be dedicated to how to fix them. However, while the book does lack comprehensive solutions, it opens up a wider conversation about how overfishing could only be seen between the pages of a history book.


Biography. (n.d.). Retrieved from

Dreifus, C. (2002, March 4). A Conversation With: Callum Roberts; A Biologist Decries the 'Strip Mining' of the Deep Sea.

Roberts, C. (2007). The Unnatural History of the Sea. Washington, DC: Shearwater Books.