Something is Rotten in the Gulf of St. Lawrence:
Eco-logical reasons to abolish the Canadian harp seal hunt
By Debbie MacKenzie
February 11, 2005
stocks cannot “rebuild” where life at the sea bottom is increasingly
stifled by rot, as in Canada’s Gulf of St. Lawrence, early in the 21st
century. Modern “ocean ecosystem managers” must realize that dead seals
increase the ominous environmental problem of “rot,” while live seals act
to curtail it.
A silent killer: the
oxygen content of the bottom water has been steadily falling for decades
in vast regions of the Gulf of St. Lawrence (1). While the reason for this
is officially unknown, the ill effects of oxygen loss on the health of cod
(and other fish) are well understood by scientists. It can kill them (2).
This mounting problem signals, in essence, the advance of rot in the very
ecosystem. A dying ocean, a thing starting to decompose.
(click to enlarge)
"In the northern
Gulf, cod avoided areas with less than 30% oxygen saturation, which
is close to the incipient lethal threshold (28%) determined in the
laboratory. However, a large proportion of the stock was found in
waters with 30-70% saturation in 1991 and 1995..." (Dutil
et al, 2003
(ref 2)) DFO's authors went on to explain that cod feed, grow
and swim more efficiently in the presence of more oxygen - up to 70%
oxygen saturation, above which there is no further positive effect.
Between 70% and 30%, cod health declines as oxygen declines. Below
30% oxygen saturation, cod begin to suffocate and die.
affected by lethal hypoxia is expanding in the Gulf of St. Lawrence,
threatening "nothing less than an environmental disaster" in the
(“hypoxia”) has recently reached levels that can sicken or kill cod in
large areas ("more than 1000 km2") of the Gulf of St. Lawrence, and no
live cod have been found in these areas in recent surveys done by The
Canadian Department of Fisheries and Oceans (DFO) (2).
(see map at right - click on map to enlarge)
Why a shortage of
oxygen? Bacterial decomposition (rot) of dead organic matter (animals or plants)
exerts a severe oxygen-draining effect on seawater, and this process is
widely recognized as a primary cause of “hypoxic” seawater. This is how
ocean “dead zones” are being formed in various other parts of the world
ocean (e.g. the Gulf of Mexico, Chesapeake Bay, Baltic Sea and others)
Any dead organic
matter in the ocean will undergo bacterial decomposition, unless it is
instead eaten fairly promptly by an animal. The metabolism of animals,
while using oxygen, does not severely drain this crucial substance from
the water, as does bacterial metabolism. Uneaten dead plants or animals on
the seafloor can aggravate any existing problem of hypoxia,
because the tiny nibbles taken by crabs and starfish, for instance, will
seldom consume the bulk of a larger corpse before oxygen-draining rot
(bacterial decomposition) becomes established.
predators are therefore crucial to ocean ecosystem health in part for this
reason: they have a unique ability to quickly devour substantial chunks of
dead flesh, before it can begin to rot. Animals like large sharks, called
“apex predators,” perform a crucial “ecosystem hygiene” service by
efficiently consuming large marine animals that are dead or dying, and
thereby denying bacteria an opportunity to become sufficiently established
to consume all the oxygen in the area. (Note that this anti-bacterial
service in the ocean is not performed by sharks alone: all other
animals contribute too, each from its own “niche,” eating what it can.
Many people will easily accept the logic of this, but marine scientists
might argue the point.)
“biting” ability of sharks allows them to consume very large prey, even
including whales. In contrast, the majority of other ocean fish, living at
“lower positions in the food web,” have no real ability to “bite” their
prey, and these fish are therefore limited to eating items that they can
engulf and swallow whole. The well-known pattern is that “bigger fish eat
littler fish,” but it is important to note that this rule is broken by the big sharks, positioned at
the “apex” of the food web. Too few sharks patrolling the ocean might
realistically result in an increase in the presence of their de facto natural
“competition” in the sea, which is actually microscopic bacteria, or
A drastic decline in
numbers of large sharks in North Atlantic waters, including the Gulf of
St. Lawrence, has occurred in recent decades (4), as seawater oxygen
levels have fallen, and bacterial counts have risen. One predictable
consequence of the great loss of sharks is that efficient animal consumption of
dying post-spawning fish may no longer occur, and that these mature fish,
who have essentially lived out their lives and run out of energy, might
instead rot after death, and thereby contribute to sickening the
environment for both their offspring and for food potentially eaten by
their offspring. (For example, hypoxia will kill worms too, and various
other small bottom creatures that might have served to feed young cod…and
a cascade of negative consequences can occur.) For reasons like these, it
is far preferable for an exhausted mature fish to be eaten by a shark, or
a seal, than for it to simply die and rot.
conditions in the Gulf of St. Lawrence, including episodes of low
temperature, hypoxia and starvation, are thought to have caused
undetected mass mortalities of cod in recent years, while the
"productivity" of these stocks has been uncharacteristically low
(2). If uneaten by seals, or other "predators," those dead cod will
An unacknowledged flaw
in DFO's extensive efforts to "quantify" the "effects of seal
predation on cod stocks" has been the implied assumption that all
cod flesh digested by seals is the result of seals having killed
otherwise-viable cod. The insinuation is always that the "tonnage"
of cod eaten by seals represents a "loss" to commercial fishermen,
and that these beleaguered souls could otherwise have ultimately
taken those fish to market - hence the perpetuation of the "seals
are destroying the cod fishery" myth (9). Fishermen may honestly not
know any better than this, but DFO Science should. Unfortunately,
DFO has publicly played along with the naive arguments offered by
the fishing industry, giving them "scientific credibility" in the
eye of the public, and great numbers of Canadian tax dollars have
been spent by DFO, raising the false alarm of the "threat" of seals.
Seals in Atlantic
Canada have recently been observed to be eating larger cod than they did
previously (5), suggesting that individual cod fish that are exhausted,
dying, or perhaps already dead, are now being cleaned up by seals rather
than by larger fish, such as sharks. This is a good thing, although seals
are sometimes only able to eat the bellies from larger fish (6). In this
way, seals are somewhat less efficient than sharks. The average seal is
not as “fearsome” or as “toothy” a predator as a large shark.
Large sharks are
vanishing from the ocean en masse today, and they are reappearing only
on endangered species lists. This human-induced change in the ocean,
unprecedented for millions of years, may soon cause profound negative
effects on the entire ocean food web - especially if other predators,
like seals, are hampered in their efforts to step into and maintain
the large animal "apex predator" role. Removing more of these animals
does not tip the "natural balance" of power to small fish, as the
fishing industry naively hopes, but it deals the upper hand to
bacteria and "rot" instead...the most "fearsome" predator of all, from
the perspective of all animals, including humans.
Believe it or not, this
animal can go, and can function efficiently, where sharks "fear to
tread" - i.e. where seawater oxygen has been dangerously depleted.
Note that seals possess nostrils, which is better than having the
biggest teeth in some situations...
(DFO often describes
seals as "important" predators of fish. Well, that much is right.)
This cod was caught
(alive) on a baited hook, but its emaciated condition is reason to
think it may have been on the verge of succumbing to "natural
mortality" instead. DFO has found cod in the Gulf of St. Lawrence,
which scientists classify as "deceased-like," and with "extremely low
chances to recover and survive." (2) Only a few cod
fit this classification, but this seems certain to reflect the short
survival time of a fish in this condition, rather than implying rarity
or insignificance of the problem. A dramatic unexplained increase in
adult natural mortality now affects all Canadian cod stocks. If
"deceased-like" cod are being eaten by seals, this is a good thing,
but DFO wrongly construes all such "consumption" (9)
as "damage to cod stocks" perpetrated by seals. Ridiculous. The
current "management" strategy threatens to replace cod and seals both
with a rotting dead zone.
While seal numbers
in Atlantic Canada have increased in recent years, they have not expanded
nearly enough to fully compensate for the adverse ecosystem effects of the
massive disappearance of large fish (7). For this reason alone, to
ensure the continued provision of natural predator/scavenger services in
an oxygen-stressed marine environment, seal hunting should be immediately
banned in the Gulf of St. Lawrence.
It is worthy of
note, and of particular value in this situation, that, unlike sharks and
other fish, seals draw no oxygen from the seawater, since they are
air-breathers. Along with whales and seabirds, the value of living seals
today increases because they conserve ocean oxygen. This characteristic also renders seals immune to being
overwhelmed and asphyxiated themselves when swimming through hypoxic
waters, a risk faced by all predatory fish, whose subsequent deaths can
then cause a snowballing of the “dead zone” effect, as they, too, rot.
Sometimes, massive fish-kills are triggered by this dynamic. From this
perspective, it can be appreciated that seals are somewhat more efficient
than sharks, because they are less dependent on the oxygen content of the
immediate water column. Ideally, of course, as was evident in the robust,
fish-filled ocean ecosystem of several centuries ago, both sharks and
seals should exist in substantial numbers.
"Why don't the sharks get 'em? I just figure with all the predators
out there, a nice big piece of meat wouldn't last long."
operator hired to bury beached gray whales in California
Hemingway wouldn't have been able to catch marlin without them being
covered by shark bites."
- Ransom Myers
The Canadian harp
seal hunt is doubly injurious to the health of the ecosystem in the Gulf
of St. Lawrence because, not only are large numbers of important
predator/scavengers prevented from performing their natural
ecosystem-cleansing role, but massive numbers of seal corpses are dumped
in the Gulf yearly and allowed to rot on bottom. There is nothing living
in this region today that is capable of consuming thousands of tons of
dead seal flesh…that is, there is nothing there that can do this job
except oxygen-greedy bacteria. This presents a second compelling
eco-logical reason* for imposing an immediate ban on seal hunting in the
Gulf of St. Lawrence.
(*But one immediate objection to this particular suggestion can be
anticipated: it may be claimed by some that the dead seals - even
thousands of tons of dead rotting seals - would be but a trivial bit of
pollution in comparison to the vastness of the Gulf of St. Lawrence, and
that dumping dead seals (the current practice) would therefore be
inconsequential from an environmental water quality/oxygen perspective.
Scientists should not be quick to dismiss this warning, however, and they
should carefully consider events in another dying cold water ocean inlet,
in Hood Canal, in the state of Washington, U.S.A. In that case, a 60-mile
long ocean inlet, a fjord, has lately become severely hypoxic, and massive
fish-kills have occurred where marine life once thrived. Investigators
have determined that a significant amount of the hypoxia (15%) can be
accounted for by the practice by chum salmon fishermen in the area of
stripping the eggs for market and discarding the fish carcasses in the
fjord. About 24 tons of dead salmon have been discarded in Hood Canal
yearly, and efforts to ameliorate the hypoxia problem now include the
banning of this practice. (8) The parallel to the
ecological stupidity of skinning seals and dumping their corpses (not to
mention those of untold thousands of "struck and lost" seals) in the
hypoxic Gulf of St. Lawrence should be obvious.)
wholesale removal/destruction of fish predators from an environment like
the Gulf of St. Lawrence, where fish stocks are crumbling, and are known
to be suffering accelerated attrition due to hypoxia, starvation, and
temperature stress (2)…this practice, of killing seals by the hundreds of
thousands and transforming them into "pollutants," as the Canadian harp seal
hunt blindly forges ahead into the 21st century; this is beyond
eco-logically unjustifiable. Refusing to blow the whistle and to end this
bloody seal hunt, as DFO and the Government of Canada continue to do (10), is
pathetically gutless and outrageously
Copyright 2005, Debbie MacKenzie
Marine scientists may argue with my
premise that sharks, seals, and other animals tend to decrease the
strength and dominance of bacteria in the sea. This is because
scientists have long been operating on the assumption, essentially,
that everything ultimately rots anyhow.
If a dead cod is eaten by a seal,
it is now generally assumed that seal feces, or perhaps the dead
seal, will rot eventually, before the original broken-down organic
matter from the cod ever becomes available to fertilize new plant
growth in the surface water. Bacteria, the "decomposers," have been
classically imagined by marine scientists as a bottleneck through
which all dead organisms must pass before they can be recycled into
However, the integrated web of
ocean animal life can be shown to be working in direct competition
with bacteria, and to be carrying out its own oxygen-sparing
Dead cod flesh eaten by a seal may
fall to the sea floor as feces. Seal feces (food passed through one
digestive system) are typically eaten by invertebrates, such as
starfish. Starfish, like a great many other related bottom species,
divert a large fraction of the food they eat into the production of
billions of tiny eggs. Their innards become filled with roe.
Starfish eggs, among countless others, float to the surface, where
they release chemicals into the water that work directly to
fertilize the growth of plants and other new sea life. This
describes one nutrient cycling "loop" in which a series of animals
effectively works to bypass bacterial decomposition of dead animals
in the ocean. Many other similar "loops" can be described, and it
soon becomes clear that the more established and diverse the animal
web in the sea, the stronger will be its inherent, self-sustaining
This concept I have not found
described in the mainstream scientific literature - but that does
not serve to disprove it. Am I right? ...well, do
fish eggs float?...do sharks bite?
...does uneaten food rot on the seabed?
Is not the finding of increasing
hypoxia in the Gulf of St. Lawrence alarming enough to prompt Canada
to take any possible corrective action? If so, the harp seal hunt
must be stopped.
on this website, I have often described the natural anti-hypoxia
and "biological forcing" role of ocean animals, but it has been very
difficult to engage scientists in serious discussion of the issue.
But I've tried...last September I explained to
an audience of DFO scientists that I
hoped they would soon reach the point where a seal cull
proposal would be rejected because they realized that the oxygen
content of the seawater was falling, and because they understood how
to "connect" these two "dots"...
Anonymous. "Hypoxia in the Gulf of St. Lawrence"
www.eps.mcgill.ca/~sundby/MarineGeochemistry/hypoxia.html ). Also:
"There is no doubt that the oxygen levels in the bottom waters of the
lower St. Lawrence Estuary are low, and that they have been decreasing
over the last 70 years or so. The reasons for the decrease are not
certain..." (Dr. Bjorn Sundby, pers. comm.) And from DFO: "The deep waters
of the Gulf of St. Lawrence have low dissolved oxygen concentration. The
prevailing saturation levels in the Laurentian Trough are so low that they
can affect various aspects of the biology and ecology of populations and
communities. In certain areas, they can even lead to the death of
organisms. This information has rarely been integrated in research on
distribution, migration, growth and production." (From "Experimentation
and Innovation - Experimental Biology" online at:
www.osl.gc.ca/exp_innov/en/bio_exp/intro.html ) ......My conclusion:
this type of "information" should be immediately "integrated" into an
"innovative experiment": into a switch to a DFO-led practice of protecting
seals in the Gulf of St. Lawrence.
J.-D., J. Gauthier, Y. Lambert, A. Frechet, and D. Chabot. 2003. Cod
stocks rebuilding and fish bioenergetics: low productivity hypothesis.
Canadian Science advisory Secretariat Research Document 2003/060
Clayton, 2004. 'Dead zones' threaten fisheries.
http://www.csmonitor.com/2004/0527/p13s01-sten.html Widely reported in
the scientific literature and, lately, in the public media, is the
mounting problem of hypoxia in marine waters. This article is typical of
many, and the blame is laid primarily on human-caused "pollution."
However, "natural" dead-zone-type incidents are on the rise in the ocean
observation of a shift by harp seals toward eating bigger, older cod is
included in this report of the "Independent Seal Panel" to the "Council of
Canadian Professional Fish Harvesters"
"The Northern Cod Stock Status Report also found that not only are harp
seals travelling further south to feed on cod, they are also eating older
fish ... From 1986 to 1996, cod up to one year old were the predominant
age found in harp seal stomachs. In 1997 and 1998, older fish (aged 3-5
years) were the dominant age group and fish as old as age 7 were found in
seal stomachs more frequently than in previous years." References are
readily found in the scientific literature to support the claim of the
2003. Northern (2J3KL) cod Stock Status Update. DFO Can. Sci. Advis. Sec.
Status Report 2003/018.
Bundy, A. 2004. Mass balance models of the eastern Scotian Shelf before
and after the cod collapse and other ecosystem changes. Can. Tech. Rep.
Fish. Aquat. Sci. 2520: xii + 193 p.
Christopher Dunagan. 2004. "Hood Canal: Salmon plan may help fix oxygen
Excerpt: "What's the problem? Salmon carcasses dumped into Hood Canal
consume oxygen as they break down and decompose. One study suggests that
salmon carcasses might be responsible for up to 15 percent of the
low-oxygen problem in the waterway. Other sources of nitrogen, including
septic tank effluent and fertilizers, trigger the growth of plankton,
which consume oxygen when they die and decay."
Stenson, G. B. 2004. Quantifying uncertainty in estimates of Atlantic cod
(Gadus morhua) consumption by harp seals (Phoca groenlandica).
Canadian Science Advisory Secretariat Research Document 2004/089
Consider this sampling of relevant Canadian government publications:
DFO, 2003. Understanding
Seals & Sealing in Canada - the Atlantic Seal Hunt Management Plan.
The introduction to this piece states that "Seal management is founded on
sound conservation principles..." and that "The report of the Eminent
Panel on Seal Management, along with consultations with more than 100
stakeholders at the 2002 Seal Forum in St. John's, greatly assisted in the
development of this plan." Unfortunately, publicly available records from
both the "eminent panel" and the "stakeholder consultations" indicate that
no consideration was given by either group to the mounting problem of
bottom water oxygen depletion in the Gulf of St. Lawrence. Have the
experts not considered this....might they be "sleeping their heads into
train oil?" (Report of the Eminent Panel on Seal Management:
Many groups are raising protests in an effort to stop the Canadian harp
seal hunt in 2005. For more information see: