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Cottiform Diversity
Ophidiiformes—Cusk-eels and Brotulas
Ophidiidae—Cusk-eels
Bythitidae—Viviparous Brotulas
Batrachoidiformes—Batrachoididae—Toadfishes
Lophiiformes—Anglerfishes
Antennariidae—Frogfishes
Ceratioidei—Deep-sea Anglerfishes
Lophiiform Diversity
Pleuronectiformes—Flatfishes
Paralichthyidae—Sand Flounders
Pleuronectidae—Righteye Flounders
Bothidae—Lefteye Flounders
Achiridae—American Soles
Cynoglossidae—Tonguefishes
Tetraodontiformes—Plectognaths
Balistidae—Triggerfishes
Monacanthidae—Filefishes
Ostraciidae—Boxfishes
Tetraodontidae—Puff ers
Diodontidae—Porcupinefishes
Molidae—Molas
Tetraodontiform Diversity
Glossary
References
Index
Phylogenetic hypothesis including all orders covered in this book
INTRODUCTION
In nearly every body of water around the world, the most abundant vertebrate is a fish. From the deepest parts of the ocean to high alpine streams, fishes live and reproduce, sometimes in places where no other vertebrates can survive. Whether peering out from a submarine while conducting deep-sea research, or stopping for a drink of water during a hike in the mountains, explorers, scientists, and naturalists find fishes.
With well over 30,000 species, fishes account for more than half of the total extant vertebrate diversity on Earth—in other words, there are more living species of fishes than of amphibians, turtles, lizards, birds, and mammals combined. Not only are fishes diverse in number of their species, but they are diverse in the habitats in which they live, the foods that they eat, the ways in which they reproduce, communicate, and interact with their environment, and the behaviors that they exhibit. Fishes can also be extremely abundant: the most abundant vertebrates on the planet are the small bristlemouth fishes (Gonostomatidae) that are common throughout the vast open ocean. In some cases abundant fishes such as cods, tunas, salmons, herrings, and anchovies support massive fisheries that feed hundreds of millions of people. By supporting coastal communities and societies, these fisheries (and the fishes they target) have helped shape human history, becoming the foundation for coastal economies and an engine for global exploration and expansion.
WHAT IS A FISH?
Humans use the term “fish” to refer to several groups of vertebrates that do not have a clear set of diagnostic characteristics unique to them. “Fishes” is not a monophyletic group (i.e., a group made up of an ancestor and all of its descendants) because the tetrapods, which share a common vertebrate ancestor with fishes, are excluded. Thus “fish” typically refers to any vertebrate that is not a tetrapod. Fishes (usually) live in water, (usually) obtain oxygen through gills, are (usually) ectothermic (i.e., cold blooded), and (usually) have limbs in the form of fins. Naturally, there are exceptions to each of these rules. Some fishes spend time out of the water, some breathe air, some are endothermic (i.e., warm blooded), and some have no limbs at all.
While there is no clear set of characteristics that distinguishes all fishes from all other vertebrates, there are four groups that collectively make up the fishes. The extant fishes include the jawless fishes (Agnatha), the cartilaginous fishes (Chondrichthyes), the rayfinned fishes (Actinopterygii), and a small portion of the lobe-finned fishes (Sarcopterygii). Of the extant fishes, the ray-finned fishes are by far the most speciose, accounting for more than 30,000 species, the cartilaginous fishes include about 1,200 species, and the jawless fishes include fewer than 100 species. Only eight species of lobe-finned fishes, two species of coelacanths, and six species of lungfishes are considered by most to be “fishes,” while the remaining 28,000 or more sarcopterygian species are tetrapods.
WHY THIS BOOK?
This book is intended to be a reference text for students and lovers of fishes to assist them in learning the morphology, diagnostic characters, and basic ecology of fishes. It started as a guide to the systematics of fishes, compiled by the senior author for use in ichthyology courses at Scripps Institution of Oceanography and the University of Arizona. It will serve that purpose, but will also provide an entry into the world of fishes for anyone interested in exploring their diversity. To our knowledge, no comparable volume exists. While numerous excellent regional guides to fishes are available (e.g., Eschmeyer and Herald, 1983; Hart, 1973; McEachran and Fechhelm, 1998, 2005; Page and Burr, 2011; Quéro et al., 1990; Robertson and Allen, 2008; Robins and Ray, 1986; Scott and Crossman, 1973; Scott and Scott, 1988; TeeVan et al., 1948–1989; Whitehead et al., 1986), these lack a global perspective. Fishes of the World (Nelson, 2006) covers the entire diversity of fishes, including all of the 515 families, but the scope of that impressive work prohibits the illustration of specimens and key characteristics of various groups. Our goal is to give an overview of the global diversity of fishes, together with more detailed accounts and illustrations of the common groups of fishes, as well as those important to humans and those widely discussed in the ichthyological literature.
The general anatomy of fishes is briefly covered, focusing on external features that help to distinguish major groups. These include external body regions, fin types and positions, body shapes, mouth positions, and selected skeletal features. We then provide accounts of approximately 180 groups of fishes, including all currently recognized orders of fishes and a variety of common and diverse families. We start with the jawless fishes (Agnatha) and progress through the cartilaginous fishes (Chondrichthyes), the lobe-finned fishes (Sarcopterygii), and the ray-finned fishes (Actinopterygii).
SYSTEMATICS OF FISHES
Ichthyologists have been interested in the evolutionary history of fishes for hundreds of years, and classification systems have attempted to capture that history in a hierarchical (Linnaean) system of names. It remains difficult to implement a truly monophyletic classification, one that recognizes only monophyletic groups, for any large group such as fishes, given both the complexity of the tree of life and our continuing uncertainty as to its form. Traditional classifications recognize several hierarchical levels, but students should keep in mind that a particular level in a classification, such as a family, has little meaning other than that it ideally includes all descendants of a common ancestor (i.e., it recognizes a monophyletic group) that are included in a higher level of the classification. For example, although ichthyologists have designated the two species of fangtooths and the 1,700 species
