In a Perfect Ocean: The State of Fisheries and Ecosystems in the North Atlantic Ocean (The State of the World's Oceans Series) - Softcover

Pauly, Daniel; Maclean, Jay L.; MacLean, J. L.

Softcover

ISBN 10: 1559633247 ISBN 13: 9781559633246

Verlag: Island Press, 2003

Inhaltsangabe

Recent decades have been marked by the decline or collapse of one fishery after another around the world, from swordfish in the North Atlantic to orange roughy in the South Pacific. While the effects of a collapse on local economies and fishing-dependent communities have generated much discussion, little attention has been paid to its impacts on the overall health of the ocean's ecosystems.

In a Perfect Ocean: The State of Fisheries and Ecosystems in the North Atlantic Ocean presents the first empirical assessment of the status of ecosystems in the North Atlantic ocean. Drawing on a wide range of studies including original research conducted for this volume, the authors analyze 14 large marine ecosystems to provide an indisputable picture of an ocean whose ecology has been dramatically altered, resulting in a phenomenon described by the authors as "fishing down the food web." The book:

• provides a snapshot of the past health of the North Atlantic and compares it to its present status
• presents a rigorous scientific assessment based on the key criteria of fisheries catches, biomass, and trophic level
• considers the factors that have led to the current situation
• describes the policy options available for halting the decline
• offers recommendations for restoring the North Atlantic

An original and powerful series of maps and charts illustrate where the effects of overfishing are the most pronounced and highlight the interactions among various factors contributing to the overall decline of the North Atlantic's ecosystems.

This is the first in a series of assessments by the world's leading marine scientists, entitled "The State of the World's Oceans." In a Perfect Ocean: The State of Fisheries and Ecosystems in the North Atlantic Ocean

is a landmark study, the first of its kind to make a comprehensive, ecosystem-based assessment of the North Atlantic Ocean, and will be essential reading for policymakers at the state, national, and international level concerned with fisheries management, as well for scientists, researchers, and activists concerned with marine issues or fishing and the fisheries industry.

Über diesen Titel

Über die Autorin bzw. den Autor

Daniel Pauly is the principal investigator for the Sea Around Us Project, sponsored by the Pew Charitable Trusts and based at the Fisheries Centre of the University of British Columbia in Vancouver. Jay Maclean is an independent writer and marine biologist based in the Philippines.

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In A Perfect Ocean

The State of the World's Ocean Series

By Daniel Pauly

ISLAND PRESS

Copyright © 2002 Island Press
All rights reserved.

ISBN: 978-1-55963-324-6

Contents

The Sea Around Us Project, 
About Island Press, 
The State of the World's Ocean Series, 
Title Page, 
Copyright Page, 
Dedication, 
Table of Figures, 
Preface, 
Acknowledgments, 
Introduction, 
CHAPTER 1 - A Brief History of the North Atlantic and its Resources, 
CHAPTER 2 - The Decline of North Atlantic Fisheries, 
CHAPTER 3 - How Did We Get Here?, 
CHAPTER 4 - What to Do?, 
Notes, 
References, 

CHAPTER 1

A Brief History of the North Atlantic and its Resources

Unmarked and trackless though it may seem to us, the surface of the ocean is divided into definite zones, and the pattern of the surface water controls the distribution of its life. Rachel Carson, The Sea Around Us, 1961.

... the number of the cod seems to equal that of the grains of sand ... These are true mines, which are more valuable, and require much less expense than those of Peru and Mexico. Charlevoix, 1720s.

The Atlantic Ocean as we know it is only about 20 million years old, geologically quite young, and its breadth is still increasing by a few centimeters each year. The Ocean developed from the splitting up of Pangaea, the only land mass, or continent, in pre-Jurassic times. At that time a single giant ocean, Panthalassa, surrounded the land. Pangaea began to break into northern and southern segments about 200 million years ago, and a fissure that is now the mid-ocean ridge began to divide the American continent from what became Europe and Africa, creating the Atlantic Ocean between the two landmasses (Figure 1).

Along with a slow but continuing expansion, there are environmental processes operating in the North Atlantic Ocean at different time scales. Long-term processes such as climate change include the ice ages, the last of which occurred roughly 15,000 years ago, and caused northern North America and northern Europe to be covered under one kilometer (one-half mile!) of ice. This greatly reduced sea levels, to the extent that shelf areas such as the Georges Bank off New England and the North Sea were exposed, covered by extensive forests. Medium-term processes last for periods from a few weeks to a decade, and include the North Atlantic Oscillation, which affects the weather in North America and Europe, and can be presumed to affect, as well, the marine "weather" to which fish are exposed, and which, jointly with parental population size, determines their reproductive success.

Finally, short-term processes occur on daily, seasonal, or annual cycles, including tides, which mix nutrient-depleted surface waters with subsurface water, and seasonal upwelling, where wind-driven current parallel to coastlines forces deep water toward the surface. These processes are important, as it is only through mixing of the nutrient-depleted surface waters with nutrient-rich subsurface or deeper water that the nutrients (nitrogen, phosphorus, etc.), which are required for the growth of the algae at the base of marine food webs, are renewed.

The major currents which, from a satellite's-eye view, describe huge arcs, swirls and eddies across thousands of kilometers, define the oceanic ecosystems of the North Atlantic, while its bottom features define the ecosystems on shelves down to depths of 200 m (600 ft). The major surface current systems in the North Atlantic travel broadly clockwise; those in the southern hemisphere move counter clockwise. This results in very different climates on the east and west sides of the Ocean—the relatively warm water of the Gulf Stream flows the whole year north past the British Isles, while the sea off Labrador at the same latitude is frozen for half the year.

The world's oceans are divided into 4 biomes: the Polar biome, containing polar and subpolar oceans, which make up only about 6% of the total; the Westerlies biome, containing the temperate and subtropical areas of the oceans, about 54%; the Tradewinds biome, corresponding roughly to tropical sea areas, 33%; and the Coastal Boundary biome, comprising all the shelf waters adjacent to land masses, which constitute the remaining 7% of the total ocean area. Globally, these biomes are further subdivided into 57 dynamic biogeochemical provinces—"dynamic" because their borders vary seasonally, and "biogeochemical" because the living organisms ("bio-") therein respond to local ("geo-") processes that determine delivery of nutrients ("chemicals") to the sunlit surface waters, and hence determine the intensity and duration of primary production. The North Atlantic contains 18 of these 57 provinces.

Most of the North Atlantic's provinces are in the open ocean, where the surface waters are infrequently enriched with nutrients from deeper waters. This leads to a low production by planktonic algae, and a generally impoverished environment, similar to terrestrial deserts, inhabited only by large fish such as tuna, which are capable of quickly crossing their large unproductive expenses to find scattered patches of high production "oases."

In contrast, the provinces of the coastal biome, an area of strong water mixing, support high levels of primary production, and it is from the ecosystems embedded in these provinces, e.g. Georges Bank or the North Sea, that most North Atlantic fisheries catches are, or were, taken. These coastal areas, which extend out to the seaward boundary of continental shelves and the outer margins of ocean current systems, can be divided up into "large marine ecosystems" (LMEs), regions of ocean space with distinct bathymetry (the oceanographic equivalent of topography) and productivity patterns. Fourteen LMEs cover the coastline boundaries of the North Atlantic. Fortunately, there is great congruence between the LMEs and coastal biogeochemical provinces, enabling data from both sources to be jointly mapped in a rigorous manner using geographical information systems (Figure 2).

Within each of these larger ecological units, or ecosystems, the numbers and types of fish, the fish "communities," are unique or at least distinctly different from those in other ecosystems. (Note that the term "fish" is used in this book to mean organisms fished: all the animals caught by humans, including fish per se, i.e., "fin fish", shellfish such as crabs and shrimp, mollusks such as oysters, clams, conches and squid, and other invertebrates like sea urchins. Seaweeds and other algae, although sometimes included among "fish," are not covered here.)

The communities of each ecosystem are interrelated through unique and complex food webs. The animals prey on each other; some marine mammals and sharks prey on large fish such as cod and mackerels; the large fish prey on smaller fish such as herrings and anchovies; and these small fish prey generally on animals among the plankton—composed of tiny less-mobile animals and plants (algae). Other small fish and the animal plankton (zooplankton) eat the plant plankton (phytoplankton), which constitute the bottom of the web. These microscopic phytoplankton use the energy in sunlight in a process called primary production to produce new matter in the form of themselves, as plants do on land. As on land, the sun provides the energy that drives the system. Humans earlier impacted marine food webs at the level of marine mammals and sharks, i.e., as top predators, but the versatility that made our species so...

Details zur Ausgabe

• Verlag: Island Press
• Erscheinungsdatum: 2003
• Sprache: Englisch
• ISBN 10: 1559633247
• ISBN 13: 9781559633246
• Einband: Taschenbuch
• Anzahl der Seiten: 175
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: preigu; mail@preigu.de; ; Lengericher Landstr. 19; Osnabrück; 49078; Deutschland