Flatfishes

Biology and Exploitation

Robin N. Gibson, Richard D.M. Nash, Audrey J. Geffen, Henk W. Van der Veer

• Publisher: Wiley-Blackwell
• Year: 2014
• ISBN:
  9781118501177
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Fisheries & Aquaculture
• Index: Technology & Engineering

Fascinating and instantly recognizable, flatfishes are unique in their asymmetric postlarval body form. With over 800 extant species recognized and a distribution stretching around the globe, these fishes are of considerable research interest and provide a major contribution to commercial and recreational fisheries worldwide. This second edition of Flatfishes: Biology and Exploitation has been completely revised, updated and enlarged to respond to the ever-growing body of research. It provides: • Overviews of systematics, distribution, life history strategies, reproduction, recruitment, ecology and behaviour
• Descriptions of the major fisheries and their management
• An assessment of the synergies between ecological and aquaculture research of flatfishes. Carefully compiled and edited by four internationally-known scientists and with chapters written by many world leaders in the field, this excellent new edition of a very popular and successful book is essential reading for fish biologists, fisheries scientists, marine biologists, aquaculture personnel, ecologists, environmental scientists, and government workers in fisheries and fish and wildlife departments. Flatfishes: Biology and Exploitation, Second Edition, should be found in all libraries of research establishments and universities where life sciences, fish biology, fisheries, aquaculture, marine sciences, oceanography, ecology and environmental sciences are studied and taught.

Reviews of the First Edition • A solid, up-to-date book that advanced students and research scientists with interests in fish biology will find interesting and useful. Aquaculture International
• A data-rich book that outlines much of what you might ever want to know about flatfishes. Fish & Fisheries
• Well presented with clear illustrations and a valuable source of information for those with a general interest in fish ecology or for the more specialist reader. You should make sure that your library has a copy. J Fish Biology
• An excellent and very practical overview of the whole, global flatfish scene. Anyone interested in flatfish at whichever stage of the economic food chain should invest in a copy immediately. Ausmarine
• Because of the high quality of each chapter, written by international experts, it is a valuable reference. Reviews in Fish Biology and Fisheries

Chapter 1
Introduction

Robin N. Gibson

Mark Corner, Twynholm, Dumfries and Galloway, Scotland, UK

Abstract

The unique asymmetric structure and appearance of flatfishes, their abilities to change colour to match the background and to burrow in the sediment all make them a fascinating subject of study. Following a brief history of flatfish research and its contribution to fish biology and fisheries science, the scope and contents of Flatfishes: Biology and Exploitation are outlined. The contents can be roughly divided into three parts with numerous links between them. The first part deals with systematics, distribution and life history stategies; the second with biology and covers development, recruitment, ecology, growth and behaviour. The final five chapters describe and discuss aspects of exploitation including the major fisheries, management and assessment and the contributions of aquacultural studies to flatfish biology. A final section on nomenclature discusses the difficulties inherent in using common and scientific names and describes the method used to ensure that there is no ambiguity in the text.

Keywords: Flatfishes; systematics; distribution; life history; ecology; growth; behaviour; fisheries; management; aquaculture

1.1 The fascination of flatfishes

Most people's first encounter with flatfishes is on a fishmonger's slab where their unusual shape makes them instantly recognizable. Flatfishes have certainly featured in the human diet for millennia. They appear in prehistoric rock carvings (Muus & Nielsen 1999), their remains are found in ancient middens (Nicholson 1998; Barrett et al. 1999) and they continue to make up a significant proportion of the world groundfish catch today. Gastronomy apart, the interested layman's curiosity is aroused not only by the presence of both eyes on the same side of the head and their flattened shape, but also by the remarkable ability of flatfishes to match the colour and pattern of their background and to bury in the sediment. The last three characters are present in some other bottom-living fishes (e.g. skates and rays, anglerfishes) but together with eye migration in the larva and the less obvious features of protrusible eyes and a dorsal fin that continues onto the head, they make the flatfishes unique.

An intriguing question is why some flatfishes have their eyes on their right side whereas in others the eyes are on the left side. Examination of the occurrence of left and right ‘sidedness’ within the Order Pleuronectiformes shows that although some families are predominantly left or right sided (see Chapter 2 this volume), the trait for a particular direction of asymmetry does not reflect relationships within the order. This conclusion holds true whether morphological or molecular evidence is used to deduce interrelationships (Berendzen & Dimmick 2002). Furthermore, in some species, for example the fossil Amphistium (Friedman 2008), the primitive Psettodes and the European flounder (Platichthys flesus) and starry flounder (P. stellatus), ‘reversed’ individuals are common. Also, in these two Platichthys species at least, sidedness varies geographically (Policansky 1982a, 1982b; Fornbacke et al. 2002). Breeding experiments with starry flounder have demonstrated that the direction of asymmetry is predominantly under genetic control but there may also be some environmental influence (Policansky 1982a; Boklage 1984). The exact mechanism involved is unclear and remains a subject of debate (McManus 1984; Morgan 1991), although the optic chiasma may be involved (see Chapter 7, this volume). To return to the original question, inheritance of eye position suggests that there should be some selective advantage of having eyes on one or other side of the head. It seems intuitively reasonable to assume that it would be advantageous for all members of the population to have the same eye position (Policansky 1982a), particularly during mating, and in most species this is indeed the case. However, Fornbacke et al. (2002) have suggested that left-sided individuals of young European flounder may be favoured by less competition with the right-sided European plaice (Pleuronectes platessa). In addition, the two morphs of starry flounder are not simple behavioural images of one another. Differences in behaviour together with slight anatomical differences between them suggest that the morphs are not ecologically identical and that the polymorphism may be driven by competitive interactions between left- and right-sided forms (Bergstrom 2007; Bergstrom & Palmer 2007).

The ability of flatfishes to camouflage themselves against the seabed on which they lie is also a source of fascination for many. Background matching is the result of rapid nervous and slower hormonal responses to visual stimuli received by the eyes and is achieved by differential responses of the chromatophores in the skin. In this way flatfishes can match not only the general colour of their background but also its pattern, even to the extent that the sizes of the spots on a spotted background can be mimicked (Ramachandran et al. 1996; Healey 1999; Burton 2010).

The variety of flatfishes and their adaptations to a benthic existence also make them intriguing subjects for study by fish biologists. Flatfishes vary in adult size from a few centimetres up to 2 m or more. They are widely distributed in cold, temperate and tropical seas in depths from the intertidal zone to the continental slope, including hydrothermal vents, but seem to be absent from the deepest parts of the sea (see Chapter 3 this volume). This variation in size and habitat means that they display a considerable range of patterns in ecology and life history and in physiological and behavioural adaptations to life on and in the bottom. Their value as food has also resulted in numerous investigations of these patterns and adaptations in relation to growth, feeding, reproduction and population structure, and the application of the results to management. Yet the intraspecific and interspecific roles of flatfishes in benthic ecosystems as predators, competitors and prey are still largely unresolved, even though flatfishes may account for around a quarter of groundfish species richness and biomass in some areas such as the North Sea (Daan et al. 1990). In some coastal nurseries, juvenile flatfishes may numerically dominate the benthic fish fauna (e.g. Gibson et al. 1993).

1.2 A brief history of flatfish research and its contribution to fish biology and fisheries science

Although flatfishes feature in many early descriptive zoological treatises and several common species were given their scientific names by Linnaeus in 1758, the first detailed articles describing research on flatfishes appear in the scientific literature at the end of the nineteenth century. Much of this early research was stimulated by the need for information on the biology of the common foodfishes and was fuelled by a concern for the state of their fisheries and why catches fluctuated (e.g. Petersen 1894; Holt 1895). At that time, fluctuation in catches was considered to be due principally to changes in migration patterns but also to the possibility that stocks were being overfished, challenging the earlier assertion by T.H. Huxley that the sea was an inexhaustible resource. It was realized that basic information was lacking and this lack led to the development of numerous research programmes to collect data on age, growth and size at maturity and examine whether fishing did, in fact, have any effect on populations. It rapidly became evident that fishing could have significant effects and Holt (1895), for example, recommended the imposition of a size limit for European plaice and common sole (Solea solea) in the North Sea. He also considered the possibility of protected areas, close seasons, mesh restrictions and artificial propagation. He dismissed stock enhancement using reared young stages as impractical and uneconomic even though the development of rearing techniques for fishes on a large scale both in North America and Europe had been in progress for some time (Ewart 1885; Dannevig 1897; Blaxter 1975; Smith 1994). Subsequent trials indicated that Holt's opinion was correct and the emphasis in the North Sea moved to the transplantation of wild fish with some success (see Blaxter 2000 for review). Flatfishes played a significant part in the development of these conclusions following experiments in Scotland and the ‘Great Fishing Experiments’ resulting from cessation of fishing in the North Sea during the two World Wars (summarized by Smith 1994). In these ‘experiments’ it was clearly demonstrated that the population structure of North Sea plaice could be greatly altered by fishing but was also capable of recovery when fishing pressure was released.

The early studies in Europe and the United States represented the beginnings of fisheries research and contributed to the formation of bodies such as the International Council for the Exploration of the Sea (ICES) (Rozwadowski 2002) and the International Pacific Halibut Commission (Smith 1994). Much of this work is summarized in subsequent chapters in this book and it has made significant contributions to fish biology and fisheries science. Particular mention can be made of the classic early works on tagging (Petersen 1894) and colour change (e.g. Mast 1914). Beverton & Holt's (1957) seminal treatise on the dynamics of exploited populations incorporated the results of many flatfish studies and intensive investigations of flatfish movements in the North Sea (summarized by Harden Jones 1968) added greatly to our understanding of migration, a topic that continues to produce novel insights into fish behaviour (e.g. Metcalfe & Arnold 1997; Metcalfe et al. 2006). The development of ageing techniques for fishes owes much to studies of flatfish species (see Chapter 9 this volume) and the renewed interest in mass rearing to the juvenile stage pioneered in Europe (Rollefsen 1934; Shelbourne 1964) provided material for studies of larval behaviour and physiology that would not have been possible using wild-caught individuals (see, for example, Blaxter 1986). Studies of sex determination and the endocrine control of metamorphosis in flatfishes have also contributed significantly to our wider understanding of these topics (Borski et al. 2010). Mass rearing techniques, which for several species are now routine (Daniels & Watanabe 2010), also paved the way for further evaluation of the feasibility of flatfish stock enhancement, particularly in Japan, using juveniles rather than eggs and larvae. The International Flatfish Ecology Symposia (see Preface) provide a platform for the presentation and discussion of the most recent studies.

In a wider context, anatomical studies of flatfishes have contributed to discussions of evolutionary mechanisms. The origins of flatfishes were a contentious issue in early debates because intermediate stages between symmetric and asymmetric forms (i.e. those with incomplete eye migration) had not been found. Furthermore it was considered that such intermediate forms could not be adaptive. Consequently, arguments for saltatory change were invoked and even natural selection itself was attacked. However, the subsequent discovery and description of the fossils Amphistium and Heteronectes, the most primitive flatfishes currently known, showed that the attainment of asymmetry of the eyes and of cranial anatomy could indeed have been gradual (Friedman 2008).

1.3 Scope and contents of the book

The book is an overview of the biology and exploitation of flatfishes. Although necessary constraints on length mean that the coverage of each topic is not fully comprehensive, ...

Table of contents

• Cover
• Title Page
• Copyright
• List of contributors
• Series editor's foreword
• Preface to the second edition
• Preface to the first edition
• Acknowledgements
• Chapter 1: Introduction
• Chapter 2: Systematic diversity of the Pleuronectiformes
• Chapter 3: Distributions and biogeography
• Chapter 4: Life-history traits in flatfishes
• Chapter 5: Ecology of reproduction
• Chapter 6: The planktonic stages of flatfishes: physical and biological interactions in transport processes
• Chapter 7: Development and regulation of external asymmetry during flatfish metamorphosis
• Chapter 8: Recruitment level and variability
• Chapter 9: Age and growth
• Chapter 10: Distribution and dynamics of habitat use by juvenile and adult flatfishes
• Chapter 11: The trophic ecology of flatfishes
• Chapter 12: The behaviour of flatfishes
• Chapter 13: Atlantic flatfish fisheries
• Chapter 14: Pacific flatfish fisheries
• Chapter 15: Tropical flatfish fisheries
• Chapter 16: Assessment and management of flatfish stocks
• Chapter 17: Synergies between aquaculture and fisheries
• Appendix A: List of scientific and common names of living flatfishes used in the book
• Appendix B: Common synonyms of Pleuronectidae used in the text
• Index of scientific and common names
• Subject index
• End User License Agreement