does overfishing promote algal blooms? - European Parliament

74 Pages·2011·5.07 MB·English

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Directorate-General For internal Policies
POLICY DEPARTMENT B
STRUCTURAL AND COHESION POLICIES
Directorate-General For internal Policies
POLICY DEPARTMENT B
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STRUCTURAL AND COHESION POLICIES
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DIRECTORATE GENERAL FOR INTERNAL POLICIES
POLICY DEPARTMENT B: STRUCTURAL AND COHESION POLICIES

FISHERIES

DOES OVERFISHING PROMOTE
ALGAL BLOOMS?

NOTE
This document was requested by the European Parliament's Committee on Fisheries.

AUTHOR

Britas Klemens ERIKSSON
Department of Marine Benthic Ecology and Evolution, Centre for Ecological and Evolutionary
Studies, University of Groningen
The Netherlands

RESPONSIBLE ADMINISTRATOR

Irina POPESCU
Policy Department Structural and Cohesion Policies
European Parliament
E-mail: [email protected]

EDITORIAL ASSISTANCE

Virginija KELMELYTE

LINGUISTIC VERSIONS

Original: EN
Translations: DE, ES, FR, IT, PT

ABOUT THE EDITOR

To contact the Policy Department or to subscribe to its monthly newsletter please write to:
[email protected]

Manuscript completed in November 2011.
Brussels, © European Parliament, 2011.

This document is available on the Internet at:
http://www.europarl.europa.eu/studies

DISCLAIMER

The opinions expressed in this document are the sole responsibility of the author and do
not necessarily represent the official position of the European Parliament.

Reproduction and translation for non-commercial purposes are authorized, provided the
source is acknowledged and the publisher is given prior notice and sent a copy.
DIRECTORATE GENERAL FOR INTERNAL POLICIES
POLICY DEPARTMENT B: STRUCTURAL AND COHESION POLICIES

FISHERIES

DOES OVERFISHING PROMOTE
ALGAL BLOOMS?

NOTE

Abstract
This note provides scientific evidence for a connection between
overfishing and the development of algal blooms, and presents several
European case-studies supporting this hypothesis. Overfishing has
contributed to the increasing problem of algal blooms in Europe. Over-
exploitation of offshore stocks has changed the structure of many marine
ecosystems, which has promoted the accumulation of algal biomass.
Today, detrimental effects of overfishing on offshore food webs are
spreading to coastal ecosystems, causing problems with near shore
water quality and habitat loss.

IP/B/PECH/IC/2011-105 November 2011

PE 474.461 EN

Does overfishing promote algal blooms?

CONTENTS

LIST OF ABBREVIATIONS 5
LIST OF FIGURES 7
LIST OF TABLES 9
EXECUTIVE SUMMARY 11
1. INTRODUCTION 15
2. TYPES AND EFFECTS OF ALGAL BLOOMS 19
2.1. What are algal blooms? 19
2.2. Ecological effects of algal blooms 19
2.3. Harmful algal groups 20
2.4. General societal problems and costs 22
2.5. Specific effects on fisheries in Europe 23
3. THE ECOLOGY OF ALGAL BLOOMS 27
3.1. A natural process that increases in frequency with eutrophication 27
3.2. Nutrients and grazing together control algal bloom development 30
3.3. Decreases in top predatory fish coincide with increases in algae 32
3.4. Trophic cascades depend on resources and predator diversity 33
4. DOES OVERFISHING CONTRIBUTE TO ALGAL BLOOMS IN EUROPE? 37
4.1. Modelling effects of overfishing and eutrophication 37
4.2. The North Sea case study 40
4.3. The Black Sea case study 42
4.4. The Kattegat case study 46
4.5. The Baltic Sea – offshore case study 49
4.6. The Baltic Sea – coastal case study 53
5. CONCLUSIONS AND RECOMMENDATION 57
REFERENCES 61

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Policy Department B: Structural and Cohesion Policies

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Does overfishing promote algal blooms?

LIST OF ABBREVIATIONS

ASP Amnesic Shellfish Poisoning
CFP Ciguatera Fish Poisoning
CPUE Catch Per Unit Effort
DSP Diarrhetic Shellfish Poisoning
EBM Ecosystem-Based Management
FK Fish Killing algal blooms
GLM General Linear Model
HAB Harmful Algal Bloom
HBT High Biomass Toxic algal blooms
HBNT High Biomass Non-Toxic algal blooms
NAO North Atlantic Oscillation
PSP Paralytic Shellfish Poisoning
NSP Neurotoxic Shellfish Poisoning
ST Seafood Toxic algal blooms
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Policy Department B: Structural and Cohesion Policies

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