WHAT is the most numerous vertebrate on Earth? Not the rat, nor the wildebeest, nor even the domestic chicken. The answer is the lanternfish, a deep-sea denizen rarely seen by human eye, and which number in the trillions.
Our surprise at this arresting fact flows from the widespread assumption that the most interesting life on Earth is terrestrial. And yet the world’s oceans, lakes and rivers are full of remarkable animals, whose behaviours and adaptations rival and surpass those we see on land.
Eye of the Shoal is a compelling invitation by marine biologist Helen Scales to share her passion for fishwatching. Along the way we learn that guppies are named after Lechmere Guppy, a 19th-century naturalist who worked in the Caribbean, that blueback herring can detect sounds at a frequency up to nine times higher than the human ear can, and that the bichir – a true fish – breathes through a pair of lungs and can drown in stagnant water.
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“The bichir – a true fish – breathes through a pair of lungs and can drown in stagnant water”
But this is not merely a curious compendium of fun fishy facts. Scales also seeks to draw us into the sensory world of fish, and to understand their place in human culture. Each chapter opens with a beautiful black-and-white illustration by Aaron John Gregory, and closes with a fish-centred folk tale. In between, Scales adroitly combines first-hand experience, interviews with leading fisher folk, and clear summaries of the latest piscine scientific research, from neuroscience to palaeontology.
As well as surprising examples of fish ecology and physiology, Scales addresses such complex questions as whether fish feel pain. It turns out that while fish do detect pain, whether they can feel it remains to be resolved.
Throughout the book, Scales paints vivid word pictures of her meetings with remarkable fish in warm waters around the world: Fiji, California, Senegal, the Great Barrier Reef, the list goes on.
But for most of us, such delights are unreachable, and the best we can hope for is a tank of fish at home or a DVD of Blue Planet II. The glimpse of a silvery roach in a murky Cambridgeshire fen, with which she atmospherically closes her account, is more likely to be typical of most readers’ fishwatching experience than some exquisite school (or shoal) of fish.
More space describing prosaic examples, such as the behaviour of blennies in rock pools, or the amazing array of morphology to be seen on a supermarket fish counter, would have helped link Scales’s amazing encounters with the apparently duller reality that most of us can access.
There is also a frustrating and important absence. Scales understandably focuses on the functions of the brilliant colours displayed by many fish living near the surface, and devotes a whole chapter to the incredible amount of noise produced by a range of species. But the chemical senses of fish – the way they smell and taste, and use pheromones – are relegated to a brief footnote.
And yet deep-sea fish – cusk eels, toadfish, fangtooths and many others – survive in an essentially black world, almost certainly using chemical signals to find prey and mates.
Furthermore, the smell of home enables many reef fish to return to base after a hard day’s foraging. Research shows that this ability will be altered as increased ocean acidification changes how sea smells are produced and detected. By the end of the century, Nemo might be lost forever.
So when it comes to the sensory world of these teeming trillions, Scales has missed an aspect that sheds light not only on their present, but also on their future. But this is a minor flaw in a delightful book that provides a welcome invitation to enter the amazing world of fish.
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Bloomsbury Publishing
This article appeared in print under the headline “A world of water”
