To Eat Glass or Fish, That Is the Question: A Trans-Atlantic
Examination of Haddock (Melanogrammus aeglefinus) Food Habits
Jason S. Link1, Bjarte Bogstad2, Alida Bundy3, Adam Cook3, Gjert E. Dingsør2, Daniel Howell2, Sean Lucey1, Alexander
Kempf4, John K. Pinnegar5, Anna Rindorf6, Sabine Schückel7,8, Anne F. Sell4, Nancy Shackell3, Brian Smith1
1National
Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543, USA; 2 Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway; 3Bedford Institute of
Oceanography, PO Box 1006, Dartmouth, NS B2Y 4A2, Canada; 4Thünen Institute of Sea Fisheries, Palmaille 9, 22767 Hamburg, Germany; 5Centre for Environment, Fisheries & Aquaculture
Science, Lowestoft, NR33 0HT, UK; 6Technical University of Denmark, National Institute of Aquatic Resources, Jægersborg Allé 1, 2920 Charlottenlund, Denmark; 7Senckenberg am Meer,
Department of Marine Science, Südstrand 40, 26382, Wilhelmshaven, Germany; 8BioConsult Schuchardt & Scholle GbR, Reeder-Bischoff Str. 54, 28757 Bremen, Germany
Abstract- Haddock (Melanogrammus aeglefinus) are a commercially and ecologically important
gadoid across the North Atlantic; their importance in the food web and economies of these many
regional ecosystems has been well documented. The feeding habits of haddock have similarly
been well described. What remains intriguing is that in some locales or at some times haddock
are primarily piscivores whereas in other situations they are primarily echinoderm feeders.
Additionally, haddock have exhibited comparable shifts in primary dietary focus over time for any
given ecosystem. Haddock do not regularly exhibit the increase in piscivory with ontogeny that
other gadids often show. Here we explore and contrast the food habits of haddock across
multiple northeastern and northwestern Atlantic ecosystems, using databases that span multiple
decades. The results show that the major determinants of the diet are indeed difficult to unravel,
but common patterns do emerge regarding when haddock primarily eat fishes versus
echinoderms. We view this apparent binary choice as actually part of a gradient of prey options,
contingent upon a suite of factors external to haddock dynamics. We discuss the energetic
consequences of this prey choice, noting that in some instances it may not be a “choice” at all.
Temporal changes in haddock diet- fish and echinoderm prey
• Echinoderms have remained a consistent component of haddock diet
over time
• It does not appear that echinoderms are replacing fish in the diet
• Although they may be inversely proportional at some times in some
ecosystems
60
Barents Sea
50
% Echinoderm
% Fish
Gulf of Maine
% Fish
50
40
40
30
30
20
20
10
10
0
1980
1985
1990
1995
2000
40
2005
2010
2015
Georges Bank
% Echinoderm
% Fish
0
1975
1995
1985
2005
2015
Scotian Shelf
70
% Echinoderm
60
30
Barents Sea
% Echinoderm
% Fish
50
40
20
30
20
10
10
North Sea
0
1975
Irish Sea
Celtic
Sea
Gulf of
Maine
1985
1995
2005
2015
0
1975
1985
1995
2005
2015
Figures denoting the change in percent composition of echinoderms and fish over time (% by weight), for
times series presented in 5 yr blocks except Barents Sea which had annual sampling in various years
Eastern Scotian Shelf
Western Scotian Shelf
Georges Bank
% Echinoderm
Eastern Scotian Shelf
% Fish
40
% Echinoderm
% Fish
North Sea
15
30
Map denoting the ecosystems with haddock examined in this study
10
20
5
Haddock diet (with respect to echinoderms and fish)
Haddock feed on a wide variety of invertebrate and fish species
Echinoderms can comprise up to 30% of the diet of haddock; So can fish
It may or may not be that fish and echinoderms are inversely
proportional in the diet of haddock
Most of the echinoderms consumed are ophiuroids (brittle stars) or
echinoids (urchins, sand dollars)
•
•
•
•
35
% Echinoderm
% Fish
Celtic Sea
40
North Sea
Spitzbergen
10
0
1958-1970
% Echinoderm
25
5
0
1950s
Gulf of
Maine
Ophiuroids
Barents Sea North Sea
Figure denoting overall diet of haddock with respect to
echinoderms and fish for various ecosystems (% by weight)
2000s
1958-1970
1995-2009
Figures denoting the change in percent composition of echinoderms and
fish over time (% by weight), except Dogger Bank is % by number)
0
Georges
Bank
Western Scotian Shelf
10
0
5
Western
Eastern
Scotian Shelf Scotian Shelf
% Fish
10
Irish Sea
10
0
% Echinoderm
1991
20
20
10
Dogger Bank
% Fish
15
30
15
1981
20
1900s
20
1995-2009
30
30
25
0
Crinoids
Holothuroids Echinoids Asteroids
other
(Urchin,
Echinoderms
Sand dollar)
Figure depicting specific composition of echinoderm
prey of haddock for various ecosystems (% by number)
Selectivity of haddock for echinoderms
• Haddock are generally selective for benthic prey (not shown)
• Haddock tend to select smaller echinoids over larger echinoids or ophiuroids
• Selectivity can vary seasonally and geographically
1.0
0.8
Ophiopecten affinis (<1 cm)
Echinocyamus pusillus (02.-1.4 cm)
Echinocardium spp. (5-10 cm)
Amphiura spp. (10-20 cm)
0.6
Ivlev Index
0.4
Haddock diet across size
• There is no clear ontogenetic shift towards piscivory across
ecosystems, although some systems suggest it
• Haddock eat echinoderms across their life history
• Unlike other gadids (not shown), haddock remain highly
benthivorous throughout their life
Georges Bank
60
Gulf of Maine
Scotian Shelf
Barents Sea
North Sea
Barents Sea
North Sea
Scotian Shelf
Georges Bank
0.0
-0.2
Box M
Box L
Box D
-0.4
-0.6
-0.8
-1.0
Figure denoting the Ivlev selectivity index for haddock
on echinoderms at various locales in the North Sea
Map of various locales sampled for haddock
and the benthic community in the North Sea
Gulf of Maine
30
50
% Echinoderm
40
% Fish
0.2
30
20
Echinoderm energetics
• Echinoderms contain more energy than suspected
• More like potato chips or cheese puffs than glass
20
10
• Ophiuroids and echinoids average energy density = 4-5 kcal g-1
10
0
0
10-29
30-49
50+
Figure denoting percent composition of fish
in haddock diet by size class (% by weight)
10-29
30-49
50+
Figure denoting percent composition of echinoderms in
haddock diet by size class (% by weight)
• Notable seasonal and taxonomic differences, range from 1-6
kcal g-1
• From comparison, fish typically range from 1-5 kcal g-1
Thanks D. Packer for information
Summary
• Echinoderms are a core, and often
preferred, feature of haddock diet, unlike
most other gadoids
• No one feature determines the amount
of echinoderms in haddock diet
• No other major prey, including fish, are
replaced by or replacing echinoderms