Balanced Harvest and the
Ecosystem Approach to
Fisheries
Jeppe Kolding, University of Bergen
Sjømatkonferansen 2017
Unutilized?
Courtesy of Geir Huse
Sustainability: Fishery objective
UNCLOS (1982), WSSD (2002) Declaration § 31 (a):
«Stocks should be kept at biomass levels
that can produce maximum sustainable
yields (MSY).»
Sustainability: Conservation objective
CBD (1998) The Malawi principles for Ecosystem Approach:
«A key feature of the ecosystem approach
includes conservation of ecosystem
structure and functioning»
FAO adopted EAF in 2001
The overall key question
 How
do we maximize the food outtake
from the oceans while we minimize the
ecological footprint?
 How
do we harvest MSY without
changing the structure and function of
the ecosystem?
Can we harvest the
oceans as land?
Global
planteproduksjon
Global
plant production
Billion tonn
ton carbon
Milliarder
karbon(Giga
(Gigat)t)
60
50
40
30
20
10
Land
Oceans
0
 4-5% ofLand
the primary production
Hav on
land is directly consumed by humans
Courtesy of Yngvar Olsen
The food chain in fisheries and agriculture




4-5% of the primary
production (TL 1) on land is
directly consumed by
humans
All domesticated animals for
food are herbivores (TL 2)
Humans (TL 2.21) feed 2
trophic levels higher in the
oceans than on land
Very inefficient utilization of
the marine resources
Food chain agriculture
Food chain fisheries
Eaters of
wolf-eaters . 5th
Wolf-eaters
Wolverine
Wolf
Tuna
4th
2%
Salmon
Herring
3rd
2nd
niveau
sheep
Clams
zooplankton
cow
98%
Anchovy
1st trophic level
Corn/rice
Algae
Vegetables
Fruit
(80% of human diet)
Phytoplankton
Kelp
After Duarte et al 2009
Land based aquaculture?
Fish do not eat grain, they eat fish
Master, I marvel how the fishes live in
the sea. Why, as men do a-land; the
great ones eat up the little ones.
Shakespeare, Pericles, prince of Tyre
Cartoon by Frits Ahlefelt
 The
ecosystem approach to
fisheries requires a multi-species
approach to management
ECOPATH a multi-species model
Walters et al. (1997)
Flow diagram of the central South China Sea pelagic ecosystem in the 1980s. Arrows
indicate flow (t km-2y-1) and boxes (≈ log10 of B) the size of biomass (t km-2).
150 Ecopath models ≈ 40% of oceans
Christensen et al. 2014
Global mean exploitation rate vs trophic level
Our highly selective fishing pattern is very unbalanced and very
inefficient in terms of healthy food
Global ocean production
Human TL
1 kg
1000 kg
Kolding et al. 2015
The aquatic food web is size structured…
Top predators
Log Biomass
Tertiary consumers
Secondary consumers
Primary consumers
Primary producers
Size
..abundance is inversely correlated with size
Community size spectrum
Log Biomass
The distribution of biomass by body size
follows regular patterns
phytoplankton
zooplankton
Small fish
Large fish
Size
Under conventional selective fishing slope and
intercept will change
Log Biomass
Changes in the North Sea
Unfished
1983–1987
1998–2002
Size
Garcia et al. 2012
Log Biomass
Balanced harvesting… (Garcia et al 2012)
It will reconcile objectives
by maintaining community
structure while returning
highest yields
Size
.. is fishing as many sizes and species as possible in
proportion to natural productivity
How to measure the balance?
Annual catch = fraction of annual production.
Distance from 1:1 line gives fishing pressure
Slope gives fishing pattern (ideal slope = 1)
Under Balanced harvest the fraction should be
constant across all components in the ecosystem
Kolding et al. 2015
Global fishing pattern (151 ecosystems)
Low trophic
level forage fish
High trophic
level carnivores
Kolding et al. 2015
Temperate fisheries (ICES, North Pacific)
Slope not
significantly
different from 0!
Kolding et al. 2015
Tropical upwelling
Kolding et al. 2015
Is the Norwegian Fishery in balance?

Balanced harvest = catches proportional to
natural production
Norwegian Sea and the Barents Sea:
ECOPATH model (1997-2001)
3 million km2
B arents sea
N orw e gian sea
Skaret og Pitcher, in press
The whole ecosystem in 58 functional
groups from whales to plankton
FG
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Common name Latin name
Minke whale Balaenoptera acutorostrata
Sperm whale Physeter macrocephalus
Killer whale Orcinus orca
Other toothed whales
Northern bottlenose whale Hyperoodon ampullatus
White beaked dolphin Lagenorhynchus albirostri
Harbour porpoise Phocoena phocoena
Other baleen whales
Fin whale Balaenoptera physalus
Humpback whale Megaptera novaengliae
Blue whale Balaenoptera musculus
Harp seal (0) Phoca groenlandica
Harp seal (1+) Phoca groenlandica
Other seals (0)
Other seals (1+)
HarbourSeals Phoca vitulina
GreySeals Halichoerus grypus
HoodedSeals Cystophora cristata
Atlantic puffin Fratercula arctica
Other seabirdsa
Brünnich's guillemot Uria lomvia
Northern fulmar Fulmarus glacialis
Black-legged kittiwake Rissa tridactyla
NE Arctic cod (0-2) Gadus morhua
NE Arctic cod (3+) Gadus morhua
Coastal cod (0-2) Gadus morhua
Coastal cod (3+) Gadus morhua
Haddock (0-2) Melanogrammus aeglefinus
Haddock (3+) Melanogrammus aeglefinus
Saithe (3+) Pollachius virens
Saithe (0-2) Pollachius virens
Flatfishes and rays
European plaice Pleuronectes platessa
Long rough dab Hippoglossoides platessoides
Thornback ray Raja clavata
European flounder Platichthys flesus
Common dab Limanda limanda
Brill Scophthalmus rhombus
FG
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
Common name Latin name
Other benthic fish
Cusk Brosme brosme
Ling Molva molva
Pollack Pollachius pollachius
Monkfish Lophius piscatorius
Whiting Merlangius merlangus
Eel Anguilla anguilla
European hake Merluccius merluccius
Atlantic halibut Hippoglossus hippoglossus
Blue ling Molva dypterygia
Greenland halibut (0-4) Reinhardtius hippoglossoides
Greenland halibut (5+) Reinhardtius hippoglossoides
Deep-sea redfish (0-4) Sebastes mentella
Deep-sea redfish (5+) Sebastes mentella
Golden redfish (0-4) Sebastes marinus
Golden redfish (5+) Sebastes marinus
Blue whiting (0-1) Micromesistius poutassou
Blue whiting (2+) Micromesistius poutassou
Mackerel Scomber scombrus
Herring (0) Clupea harengus
Herring (1-2) Clupea harengus
Herring (3+) Clupea harengus
Polar cod Boreogadus saida
Capelin (0) Mallotus villosus
Capelin (1) Mallotus villosus
Capelin (2+) Mallotus villosus
Basking shark Cetorhinus maximus
Other sharks
Spiny dogfish Squalus acanthias
Porbeagle Lamna nasus
Atlantic salmon Salmo salar
Lumpsucker Cyclopterus lumpus
Small pelagic fish
Greater silver smelt Argentina silus
Horse mackerel Trachurus trachurus
Norway pout Trisopterus esmarkii
Sprat Sprattus sprattus
FG
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
Common name Latin name
Mesopelagic fish
Pearlside Maurolicus muelleri
Glacier lanternfish Benthosema glaciale
Arctozenus risso
Squid Gonatus fabricii
Edible crabs and lobster
Edible crab Cancer pagurus
European lobster Homarus gamarus
Red king crab Paralithodes camtschaticus
Corals Lophelia pertusa
Other macrobenthos
Prawns Pandalus borealis
Krill
Meganyctiphanes norvegica
Thysanoessa inermis
Thysanoessa longicaudata
Pelagic amphipods
Themisto libellula
Themisto abyssorum
Themisto compressa
Calanus
Calanus finmarchicus
Calanus hyperboreus
Zooplankton 2mm+
Zooplankton 0-2mm
Jellyfish Periphylla periphylla
Seaweeds
Wolffishes
Common Anarhicus lupus
Spotted Anarhicus minor
Northern Anarhicus denticulatus
Phytoplankton
Detritus
Skaret og Pitcher, in press
Average catches 1997-2001
Is the Norwegian fishery in balance?
Annual production (kg/km2)
in 58 functional groups
How about the North Sea (1991)
Mackinson & Daskalov (2007)
Balanced harvest = catches proportional to production
Norwegian and Barents Sea
North Sea
Thank you for your attention!
Jeppe Kolding
[email protected]