|
Dear Marine Scientist,
Taking a fish out of the sea does NOT leave a type of "vacuum" that nature
is somehow compelled to fill in with another fish!
...PLEASE TAKE A FEW MINUTES TO CONSIDER THIS IDEA.
I ask you to consider a new explanation for the collapsing fisheries and
other recent changes in the marine ecosystem. My theory is that the TOTAL
MARINE BIOMASS IS NOW SEVERELY DEPLETED (it is obviously a direct result of
fishing, and is in fact a CUMULATIVE effect, instead of something that
happened because of recent "mismanagement.") If you look at this theory
closely, all of the trends that we are seeing in marine populations begin
to make logical sense. Before I discuss the evidence for "starvation,"
please consider how and why this overall biomass depletion has occurred.
WHAT IS THE NATURAL "PRODUCTIVITY" OF THE OCEAN? (The answer to this is
fairly well understood.)
Carbon fixation and nitrogen fixation naturally occur in the ocean and are
the mechanisms by which new "life" is constantly produced. Nitrogen
fixation is more important in determining the absolute quantity that can
be "made" each year since very few organisms (only some blue-green algae)
are able to accomplish it. Fixed nitrogen is the limiting nutrient for
phytoplankton (at least in the Northern hemisphere) and the rate of
nitrogen-fixation therefore determines how much new protein will ultimately
be added to the marine ecosystem each year.
WHICH FACTORS AFFECT THE "RATE" OF THIS NATURAL "PRODUCTION" IN THE OCEAN?
(The answer to this question is NOT well understood.)
The productivity of the blue-green algae probably varies with climate
change, but in the last millenium has likely changed very little, other
than a possible recent decrease. Since the total area of the sea and the
number of hours of sunlight in a day have been the same, and temperature
has really varied very little, it is reasonable to assume that the rate of
nitrogen fixation by blue-green algae is basically the same now as it has
been for many thousands of years. It is the means by which life slowly
accumulated in the sea over many millions of years. "SLOWLY" is the key
word, and "slowly" is how it STILL is being produced. It was able to
accumulate (over a VERY long time) and become very rich in life since the
fixed nitrogen was constantly recycled through the marine ecosystem, only a
small amount of "new" stuff was added each year, just a tiny annual gain in
the total biomass - removals by land animals were insignificant until
humans became adept at fishing. The amount of fixed nitrogen (protein) that
we have removed from the sea has increased dramatically in the last
century - there is no reason to believe that the blue-green algae have
responded to this by stepping up their "production."
THE RATE OF PRODUCTION IN THE SEA IS NOT RELATED TO THE RATE AT WHICH WE
CATCH FISH! ...And it never has been....Annual worldwide fish harvests are
around 100 million tons - if no-one went fishing next year would the blue-
green algae respond to this change by putting the brakes on and NOT fixing
the nitrogen required for 100 million tons of fish? No, the blue-green
algae are relatively unaffected by fishing and will only do what they have
always done, that is: produce a SMALL annual gain in protein. "IF" they
were capable of producing LARGE amounts of protein on an annual basis they
would have done so a long time ago, and the result, over the millions of
years of the ocean's existence, would have been a sea overloaded with life
that would have sickened and died as a consequence long ago.
Life has been slowly accumulating in the sea this way for MILLIONS of
years. Over the last 500+ years humans have removed what probably amounts
to half of the original biomass that was there before the fishing industry
began. We have run up a huge debt with the sea because our relationship has
essentially been "all take and no give."
HOW DID FISH STOCKS WITHSTAND FISHING PRESSURE IN THE PAST? ...HOW DID THEY
REPLENISH THEMSELVES?
Stocks like the northern cod on the Grand Banks of Newfoundland supported
major fisheries for many years, apparently up to 30% of that cod stock was
removed repeatedly on an annual basis and for a long time it seemed to have
a great ability to "rebound" and "rebuild" itself. It took many years of
heavy exploitation before the northern cod appeared to suffer significant
losses. The cod rebuilt itself all those years at the expense of it's
neighbours, it drew on the other compartments of the ecosystem, including
it's many prey species and affected all lower levels, even the plankton. So
the catching of the cod depleted not only the actual cod stock but drained
the system as a whole. All fishing and whaling ultimately has this effect.
People were, and still are, largely unaware of this fact. An old myth is
still widely believed: "there are lots of other fish in the sea."
STARVATION - the end result of the depleted biomass - why?...and what
evidence supports this?
The reduction of the total marine biomass has resulted in marine life now
being relatively diluted or "watered down" compared to conditions years
ago. Individual animals today are therefore faced with diluted prey, which
leads to difficulty in getting enough to eat, which ultimately leads to
starvation. For many species this now appears to be a critical problem.
Plankton is also similarly depleted.
THE EVIDENCE?
The most convincing piece of evidence of starvation that I see is a
widespread decline in "weight-at-age" in fish over the last two decades.
Nothing except food shortage would cause this in whole populations. It's
not a case of too many of one species competing for the normal amount of
food, since the abundance of these fish is rapidly declining along with
their individual size. Other evidence...
- decline in abundance of virtually all fish stocks, except for a few of
the smaller ones and some crustaceans which are at a temporary advantage
because their predators have disappeared first.
- decline in the average size of fish that are caught, virtually all
fisheries are no longer catching any "big" ones.
- fish are maturing at smaller sizes than they did in the past
- widespread failure of Atlantic and Pacific salmon stocks to return from
their time at sea
- gray whales dying of starvation in the Pacific Ocean
- malnourished right whales in the Atlantic Ocean
- orcas and belugas in decline, not reproducing normally
- Sea lions, seals and seabirds dying in the Bering Sea due to starvation
- Sea otters (California and Alaska) in decline
- zooplankton in decline; this has been recorded in many places
- coccolithophores "blooming" in the Bering Sea: a new development, a type
of plankton that thrives in "nutrient poor" water in a normally nutrient
rich part of the sea..
THE CAUSE OF THESE CHANGES? ...WHY NOT "EL NINO" AND OTHER RECENT
TEMPERATURE/CLIMATE ABNORMALITIES?
Temperature changes doubtlessly affect marine organisms, putting some
species at a relative advantage and others at a disadvantage, so the
species mix in the system as well as the ranges of species could well
change with the temperature. But the SUM TOTAL OF LIFE in the ecosystem
should not be decreasing from the small-scale temperature changes that we
have seen recently from global warming. It's not logical. The overall
decline in sea life is simply the end result of centuries of fishing.
FURTHERMORE...since fishing has been dragging down the whole system for
centuries, plankton levels have also been in decline for that length of
time. This includes phytoplankton...and the result of the gradual drop in
phytoplankton has been a gradual increase in atmospheric carbon
dioxide...so it looks most likely that declining fish stocks may be the
CAUSE and not the RESULT of global warming...
(This view is very much against the grain of current thinking but makes
logical sense, especially considering the time frame of the CO2 rise...it
was up significantly before the industrial revolution...and lots of fishing
and whaling had already been done by that time...)
WHAT CAN BE DONE ABOUT THE PROBLEM? ONE THING ONLY: "FEED THE FISH"
Regardless of what you think about my final conclusion, I am really
interested in your opinion on the "starving ocean" theory, and would love
to hear your comments. If you see a flaw in the logic, please tell me; I am
trying to stimulate a serious debate on this topic. I have done a lot of
research into this theory and have recently made a website on the theme if
you are interested in taking a look at it - my main "starvation" argument
is at http://www.fisherycrisis.com/starving.html
Sincerely,
Debbie MacKenzie
[log in to unmask]
http://www.fisherycrisis.com
><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
To leave the Fish-Sci list, Send blank message to:
mailto:[log in to unmask]
For information send INFO FISH-SCI to [log in to unmask]
><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
|
