Atlantic Cod E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 978

Veröffentlichungsjahr: 2018

Beschreibung

A comprehensive handbook, covering all aspects of the Atlantic cod including the biology, ecology, life histories, behaviour, commercial exploitation and conservation Not only is Atlantic cod one of the most valuable food fish in the world's oceans, it is an important component of North Atlantic ecosystems and has been subject to much research into its biology, ecology and exploitation. After hundreds of years of exploitation, overfishing in the last half of the 20th Century caused many stocks to collapse, most famously the Northern cod stock off Newfoundland and Labrador, Canada. Since then, most cod stocks have been better researched and managed, but remain in a variety of states, from fully recovered to continued decline. This book, written by world experts, describes that research and management, and the importance of cod and its fisheries on North Atlantic cultures and economies, with impacts well beyond the range of the species. Atlantic Cod: Bio-Ecology of the Fish offers insightful chapter coverage of cod nomenclature, taxonomy, phylogeny and morphology; physiology and ecophysiology; reproduction and spawning behavior; early life history and pre-recruitment processes; migrations, movements and stock identity; feeding, growth and energetics; the place of cod in the ecosystem; the exploitation of cod through history and present day commercial fisheries and precautionary management for sustainable fisheries; impacts of climate change on cod biology and ecology; and the future of the species and its fisheries. * Discusses the major commercial importance of Atlantic cod through history * Provides a comprehensive treatment of the bio-ecology of the most researched and highly exploited fully marine species * Examines how the decline (and recovery) of cod stocks is of great political and scientific interest * An essential purchase for marine fisheries scientists Atlantic Cod: Bio-Ecology of the Fish is a vital book for all fisheries scientists, managers and fish biologists.

Leseprobe

Atlantic Cod

A Bio‐Ecology

Edited by

George A. Rose

Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, Canada

Copyright

This edition first published 2019

© 2019 John Wiley & Sons Ltd

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Library of Congress Cataloging‐in‐Publication Data

Names: Rose, George A. (George Arthur), 1948‐ editor.

Title: Atlantic cod : a bio‐ecology / Dr. George A. Rose

Institute for the Oceans and Fisheries, University of British Columbia,Vancouver, BC, Canada.

Description: First edition. | Hoboken, NJ, USA : John Wiley & Sons, Inc.,

[2018] | Includes bibliographical references and index. |

Identifiers: LCCN 2018029738 (print) | LCCN 2018032425 (ebook) | ISBN 9781119460633 (Adobe PDF) | ISBN 9781119460671 (ePub) | ISBN 9781405119108 (hardcover)

Subjects: LCSH: Atlantic cod–Ecology. | Atlantic cod fisheries. | Fishery management.

Classification: LCC QL638.G2 (ebook) | LCC QL638.G2 R66 2018 (print) | DDC 597/.633–dc23

LC record available at https://lccn.loc.gov/2018029738

Cover Design: Wiley

Cover Image: Courtesy of Richard Larocque

Preface

I met George Rose more than 20 years ago. At the time I was researching my book on cod. The Northern stock off Newfoundland and Labrador, the greatest commercial fish stock in human history, had just collapsed. I was turning to scientists for insights. I got quite a few from my meeting with George. But I also came away with this very important insight – not nearly enough was known about cod. Certainly not enough to save it.

But that was about to change. Now everyone wanted to know about cod and funding and support to research it were becoming available. This book is a by‐product of this growth of research.

I think that the theme song for marine biology should be the Joni Mitchell song ‘Big Yellow Taxi’:

Don't it always seem to go

That you don't know what you've got till it's gone

At the time we were all focused on a cultural tragedy. The culture of Newfoundland was crushed. How sad today to watch the Canadian government try to replace the culture of commercial fishing with the culture of tourism. Today there are cod souvenirs of all kinds for purchase everywhere in Newfoundland – cod hats, cod tee‐shirts, cod stuffed animals, I even got a ceramic cod stand for my business cards. In the old days Newfoundland was a fishing community. It did not sell tchotchke.

But it was not only Newfoundland and Labrador or even just much of Atlantic Canada that was at risk. What would become of my native New England? What was the future of Gloucester, New Bedford and Point Judith? What was the future of Newlyn on the Cornish coast and Grimsby on the North Sea and all the other cod ports in Iceland, the Faroe Islands, Norway and Denmark?

Is there anything more important than saving all the cultures of the northern world? But there is the problem of Darwin. Darwin had it right. And in On the origins of species he explains two natural laws that marine biologists cannot ignore. The first is that a species needs a large population in order to survive. How large that is hard to say but certainly the Northern cod stock and several others were driven well past the tipping point. The other is that all species are dependent on many other species to assure the survival of the natural order. If a species is lost, especially one as important as cod, others will be affected. We are already beginning to see this in the disappearance, despite tightly regulated fisheries, of other fish stocks and the disappearance of sea birds.

Yes, the earth could completely unravel. People want their cultures back, fishermen want to get to work. Governments want to say that their programmes have been a success, but natural laws, as Gandhi once said about the law of love and the law of gravity, will work, whether we believe in them or not.

Is there an answer to all this? While cod and other fish are faced with many challenges such as pollution and climate change, for the moment fishery management seems the problem with the best chance of being resolved. In fact, with the help of better science, it is steadily improving and showing results. Cod fisheries that have abandoned the wasteful practices of the past and become based on well‐thought‐out science and an accounting of the full ecosystem are doing well. Others not so. Highlighting that science is essential. And that is the purpose of this book.

Mark Kurlansky

List of Contributors

Keith Brander

Institute for Aquatic ResourcesDanish Technical UniversityKgs. LyngbyDenmark

Denis Chabot

Institut Maurice‐LamontagneFisheries and Oceans CanadaMont‐Joli, QuebecCanada

Guy Claireaux

Université de Bretagne OccidentaleLaboratoire des sciences de l'environnement marin (UMR‐6539)Centre Ifremer de BretagneUnité PFOM‐ARN, PlouzanéFrance

Olav‐Rune Godø

Institute for Marine ResearchBergen, Norway; Christian Michelsen Research ASNorway

Timothy B. Grabowski

U.S. Geological Survey Hawaii Cooperative Fishery Research Unit University of Hawaii at Hilo Hilo USA

Jonathan H. Grabowski

Department of Marine and Environmental SciencesNortheastern UniversityBoston, MassachusettsUSA

Jason S. Link

National Oceanic and Atmospheric AdministrationNational Marine Fisheries ServiceWoods Hole, MassachusettsUSA

Guðrún Marteinsdóttir

Institute of Life and Environmental SciencesUniversity of IcelandReykjavikIceland

Julian Metcalfe (retired)

Centre for Environment, Fisheries and Aquaculture Science (CEFAS)Lowestoft, SuffolkUK

David Righton

Centre for Environment, Fisheries and Aquaculture Science (CEFAS)Lowestoft, SuffolkUK

George A. Rose

Institute for the Oceans and FisheriesUniversity of British ColumbiaVancouver, British ColumbiaCanada

Sherrylynn Rowe

Centre for Fisheries Ecosystems ResearchMemorial University of NewfoundlandSt. John's, Newfoundland and LabradorCanada

Graham D. Sherwood

Gulf of Maine Research InstitutePortland, MaineUSA

Peter J. Wright

Marine Scotland ScienceMarine LaboratoryAberdeen, ScotlandUK

Atlantic Cod: A Bio‐Ecology

Introduction

Atlantic cod (Gadus morhua) has been called fish for centuries in the many languages of fishing cultures across the North Atlantic. There was no need to say more, it was just fish. Cod was fish, and fish was cod. In Norway, Scotland, the Faroes, Iceland and Newfoundland, if fish was for dinner there was no doubt that it was cod. It could be nothing else. As with deities, it was considered inappropriate to refer directly to something held in such esteem. And rightly so, because for coastal communities around the North Atlantic, life or death depended on the cod. If fish failed to appear during their annual migrations, starvation, or severe economic depression was a likely outcome. All other species were referred to with common names, without reverence. In New England, despite the rapid advancement of industry and commerce that soon subsumed the cod fishery in the nineteenth century, the ‘sacred cod’ still hangs in the Massachusetts State House, bearing tribute since 1798 to a fish that gave life, and some say freedom, to a fledgling nation (Figure I.1).

Figure I.1 The ‘Sacred cod’, in the State House of the Commonwealth of Massachusetts. On 17th March 1784, Mr John Rowe of Boston arose from his seat in the Hall of Representatives at the Old State House, and offered the following motion: ‘That leave might be given to hang up the representation of a cod fish in the room where the House sit[s], as a memorial of the importance of the Cod‐Fishery to the welfare of the Commonwealth…’. A symbolic cod was placed in the hall, and was later moved to the new State House building in 1798. A wooden ‘Sacred cod’ has remained there ever since – the current carving is the third since 1784. From Celebrate Boston and Ecology and Evolutionary Ethology of Fishes websites.

The association of cod with the North Atlantic is more than a human construction. Gadoids, the classification group that includes the Atlantic cod, are one of the few families of fishes endemic to the North Atlantic, many others having made their way to these waters from the Pacific or southern waters (Chapter 1). Gadoids began, as have other key groups, as rather small and inconspicuous species, but once gaining a foothold in the expanding waters of the North Atlantic, over the past five million years have evolved to become dominant components of these ecosystems. The gadoid family came to occupy most all of the continental shelf regions of the North Atlantic, and even expanded to the North Pacific (see Chapter 1). The Atlantic cod became the most dominant of all. The main stocks – this is a human construction – are given in Table I.1, along with their commonly used names, with their geographic range shown in Figure I.2.

Table I.1 Atlantic cod stocks, their management, statistical areas, geographic areas, and commonly used names (most stocks are referred to by their geographic location).

Management

Statistical area(s)

Name of area

Common names

ICES

NAFO 1 inshore

West Greenland inshore

ICES

NAFO 1 A‐E offshore

West Greenland offshore

ICES

ICES 14b and NAFO 1F

East and South Greenland

ICES

ICES 1 and 2

Barents Sea‐Norway

Northeast Arctic cod, Arcto‐Norwegian cod, Barents Sea cod

ICES

ICES 1, 2, 4a

Norwegian coastal

Norwegian Coastal cod

ICES

ICES 3a

Kattegat

ICES

ICES 3b, c

Western Baltic

ICES

ICES 3d

Eastern Baltic

ICES

ICES 4, 7d, 3a

North Sea, Eastern English Channel, Skagerrak

ICES

ICES 5a

Iceland

Icelandic cod

ICES

ICES 5b

Faroe Plateau

Faroe Island cod

ICES

ICES 6a

West Scotland

ICES

ICES 6b

Rockall

ICES

ICES 7a

Irish Sea

ICES

ICES 7e‐k

Eastern English Channel and Southern Celtic Sea

NAFO

NAFO 3M

Flemish Cap

NAFO

NAFO 3NO

Southern Grand Bank

Grand Bank cod

Canada

NAFO 2JH

Labrador

Canada

NAFO 2J3KL

Northeast Newfoundland‐Labrador

Northern cod

Canada

NAFO 3Ps

Southern Newfoundland

3Ps cod

Canada

NAFO 4RS (3Pn‐4RS)

Northern Gulf of St. Lawrence

Canada

NAFO 4T (4TvN)

Southern Gulf of St. Lawrence

Canada

NAFO 4Vs

Northern Scotian Shelf

Canada

NAFO 4W

Southern Scotian Shelf

Canada

NAFO 4X

Bay of Fundy

USA

NAFO 5Y

Gulf of Maine

USA‐Canada

NAFO 5Z

New England offshore‐Georges Bank

Georges Bank cod

Figure I.2 The statistical regions assigned to the Atlantic cod stocks (red are the NAFO zones and blue those of ICES). The 500 m bathymetric contour which encompasses most but not all of the cod range appears as grey line.

A highly adaptable physiology has enabled cod to inhabit a wide variety of habitats from coastal bays to large offshore banks across its range (Chapter 2). Cod exist over a wide range of sea temperatures, salinities, and feeding opportunities, with large and small populations adapting to local conditions. There is literally a cod for every continental shelf habitat.

Cod are highly fecund, as are most gadoids. Large females can produce tens of millions of very small eggs, and being a broadcast spawner, offer no parental care (Chapter 3). Cod rely on numbers and egg release in the right place at the right time. Thousands of years of behavioural conditioning and selection have resulted in spawning locations that result in sustainable if imperfect and variable survival. Only a tiny fraction of released eggs will ever grow to adulthood, most dying, or being consumed by predators. The act of spawning is far from a mundane occupation. The cod is above all a social species, with complex behaviours occurring both before and during courtship and spawning, involving soundings, spatially‐specific and pelagic behaviours whose functions are only partially understood.

Cod begin life as a drifting egg, completely at the mercy of the prevailing near‐surface currents (Chapter 4). If their release timing and location leads to drift to waters with favourable environmental and feeding conditions after their on‐board food supply (the yolk sac) is depleted, there is a small chance they may survive through the larval stage and settle to near bottom in a liveable location. If not, they cannot survive. It is perilous journey – many factors must work in their favour for survival. Predicting survival of young cod to adulthood or to a fishery, one of the holy grails of cod science, has proven to be an elusive goal.

The biggest cod stocks, those in the Barents Sea (Northeast Arctic cod), Icelandic waters and off the Northeast coast of Newfoundland and Labrador (Northern cod), are all highly migratory. Other stocks are less so and many are sedentary (Chapter 5). Nonetheless, most stocks move to some extent over the North Atlantic seasons, even if within small coastal regions. Many groups exhibit what can be very exact homing behaviour between spawning and feeding areas, repeating patterns that largely determine stock structures. Fisheries have been dependent on this regularity for hundreds of years (Chapter 7).

Cod can and will consume most anything (Chapter 6). No doubt, their success as a species partly depends on being a ‘generalist’ predator – feeding on a wide range of prey across their range – and often focussing on prey that are both abundant and available. Nonetheless, they appear to have developed a preference for and dependence on certain types of prey with high energy content. The strongest association of cod with a singular prey occurs in the most northerly groups, the Northeast Arctic, Icelandic and Northern cod off Newfoundland and Labrador, that depend heavily on capelin (Mallotus villosus) and appear to have developed a preference for this prey. Cod appear to know what is good for them, and will pursue choice prey when available, for some stocks basing their entire annual cycle on intercepting this prey. Growth rates vary greatly among cod groups, dependent mostly on sea temperatures and the availability of high value prey. Cod are a key if not dominant component of the energy transfer up the food web in many North Atlantic ecosystems.

A thousand years ago, cod fisheries off present day Norway began as seasonal food gathering activities of peoples who farmed and fished for subsistence (Chapter 7). The advent of drying and salting of cod enabled not only the preservation of a high protein food for consumption year‐around at home but enabled the Viking voyages of discovery and commerce. As the large stocks off Iceland and then Newfoundland and the New World became accessible to European interests, cod became one of the dominant trade items of the eighteenth and ninetieth centuries. Whole economies became dependent on fish. In the twentieth century, major increases in technology and unrestrained harvests led to decimation of many stocks. Science‐based management in the twenty‐first century has led to increases in some stocks, and rebuilding in others, but some groups have yet to recover from the major declines that occurred in the last half of the twentieth century.

Although cod occur over a relatively wide range of sea temperatures, they are fundamentally a species of the cool waters of the North Atlantic. But climates change, and at present the North Atlantic is experiencing relatively rapid changes in sea temperatures that will influence cod distribution and abundance (Chapter 8). Northern areas have in the past benefitted from warming periods, and are likely to see increased cod abundance in coming years, but others near the southern limits of distribution are likely to see contraction.

So what of the future for this iconic species? Will cod's long history as a key component of the continental shelf ecosystems of the North Atlantic and as a human food source continue? The answer must be a qualified yes (Chapter 9). Despite the massive overfishing that depleted most stocks in the twentieth century, some stocks have regained their abundance (they have literally retaken their place in the ecosystem) or are increasing. For all stocks, the key to continuance or resurgence remains uncompromising scientific management. Failures of the past all stem from one mistake: harvesting more than a stock can produce. Much of the knowledge needed to prevent this from reoccurring is contained in the extensive information given in the following chapters. Some commonly used acronyms and short forms used are given in Table I.2.

Table I.2 Important Abbreviations

Acronym or short form

Definition

NAFO

Northwest Atlantic Fisheries Organization

ICES

International Council for the Exploration of the Sea

ICNAF

International Commission for the Northwest Atlantic Fisheries

PNAS

Proceedings of the National Academy of Science, USA

F

Instantaneous rate of fishing mortality

M

Instantaneous rate of natural mortality

Z

Instantaneous rate of total mortality (

F + M

)

This book has been a work dictated not only by science but by a love for the fish