How to Rebuild the Atlantic Canadian Groundfish stocks?
beginning with the ZOOPLANKTON.
by Debbie MacKenzie, April 14, 2003
Standing Senate Committee on Fisheries and Oceans
Dear Committee members,
In your press release of March 27, 2003, you have stated that
“We must rebuild cod and Atlantic groundfish stocks...The Senate Committee finds it incredible that the reasons why Atlantic groundfish are not recovering remain unknown at this time.”
I could not agree with you more! I presume that you find this ongoing mystery to be “incredible” because of the amount of resources that Canadians have invested to date in the scientific study of the question. After all, reams of data and documents have been generated. So, why are there still no clear answers emerging?
I suspect that this has a lot to do with political and economic concerns to which the Department of Fisheries and Oceans has long been closely linked, and also perhaps due to an inertia in academic circles that have long believed that they understood how something worked. It was no small deal to admit that the earth is not flat.
Science has in fact revealed the answer to the groundfish mystery, and the truth is that the fish stocks are not recovering because their food base is shrinking. Growth in all fish species is now increasingly being slowed as it is limited by simple starvation. But, since I am merely an independent researcher voicing a different view, the Committee cannot be expected to take my word for this. Instead, take a look at the evidence in DFO Science publications which supports my conclusions.
Although no press releases have been issued on the subject, a significant decline in the abundance of zooplankton in our coastal waters has been measured by DFO. Zooplankton are the tiny animal forms that ultimately provide food for all larger carnivorous species, and one’s intuitive sense that the disappearance of these small creatures will spell the end for cod and associates…well, that is one hunch that can surely be trusted.
The graphs in the illustration at right summarize data from four decades of intermittent plankton sampling done by DFO on the Scotian Shelf. And the information from Newfoundland mirrors this. A most unexpected and worrisome trend has been revealed, in which phytoplankton (microscopic plant forms that capture energy from the sun and transform it into organic material) appear to be increasing, while zooplankton (the tiny animals that are the ‘first order consumers’ of phytoplankton) are declining. Zooplankton have long been believed to be a vital link in the transfer of energy from phytoplankton to fish, and undoubtedly this is true. But an important question raised by the plankton data is this: “Why are the zooplankton declining in the presence of an increasing abundance of their basic food, the phytoplankton?” These diverging trends, with plant growth apparently rising while animal growth declines, contradict currently accepted models of marine production. And this presents a real conundrum for marine science. Incredibly, this unexpected inconsistency in their findings and the possible reasons for it, have not been addressed in DFO’s “ State of Plankton ” report.
Standard views of the workings of marine systems would be more likely to predict a rising abundance of zooplankton as their major predators, the fish, decline in numbers. And this would be expected even more so if zooplankton ‘food’ were increasing. But this is the exact opposite of what appears to have occurred. Zooplankton is mysteriously falling. The abundance of fish and fish-food have unexpectedly declined together. And it is critical that the reasons for this be investigated.
Rather than the standard view, which considers phytoplankton to be the “base” of the marine food web, it may be more useful to imagine zooplankton as being the “base” of the marine animal assemblage, and a “base” which can only exploit phytoplankton to optimum advantage when it is backed up by a robust, complex web of larger creatures.
Fishermen, scientists and the FRCC have all recently voiced concern that a shortage of capelin is adversely affecting the current growth potential of northern cod. This is true, and the next logical step must then be to look down the line and assess the adequacy of the food available to capelin. But capelin feed on zooplankton…and therein apparently lies the root of the problem.
Do physical observations of the fish support the conclusion that they are food limited? Beyond any doubt, the current condition of Atlantic Canadian fish strongly suggests that feeding is a major problem. For a prime example, look at the cod on the Eastern Scotian Shelf.
Perceiving the fisheries crisis as a reflection of, or as a problem which includes a zooplankton crisis, suggests that “zooplankton conservation and protection” become a useful concept and a new focus of fishery science. If the ailing ocean ‘needs more zooplankton,’ then the sources of zooplankton and the factors (beyond phytoplankton) which enhance zooplankton growth need to be carefully considered. Interestingly (although not generally described as such in marine science literature) it can be seen that all marine organisms which disperse their spawn into the plankton, contribute to nourishing and strengthening the zooplankton assemblage. Zooplankton do not only eat phytoplankton, but also happily consume the tiny floating offspring of everything from cod to crabs, worms and scallops, during the time they spend in the surface water. Indeed, this is the fate of the vast majority of these young, and must therefore be their real ecological ‘purpose.’
This unappreciated supportive link between fish and zooplankton may explain why food production in the ocean appears now to have become “unhinged” at the point of energy transfer between phytoplankton and zooplankton. It is because zooplankton health is also coupled to the existence of the many larger, spawn-producing forms of marine life. This is how the massive removal of the once phenomenal “standing stocks” of adult fish in the ocean may have unexpectedly weakened the zooplankton and ultimately slowed marine production overall. Such a realization is likely to be a significant jolt to fishery scientists who were taught that large, mature fish in a population are “surplus.”
A quick wake-up and reassessment of these points needs to be done now by marine science. It must be admitted that not only are zooplankton critically important for fish production, but that fish are also important to the maintenance of zooplankton production. Should marine science adopt this view, the ramifications for fisheries will obviously be major ones. But a fear of economic adversity does not justify continuing to keep our heads in the sand.
The declining abundance of zooplankton can be directly related to the recent cod die-off in Smith Sound, Newfoundland, although not via the acute starvation route in this instance. Falling zooplankton numbers result in a smaller fraction of the spring algae bloom being eaten. More algae then sinks and rots, which depletes the oxygen in the bottom water. This causes suffocation of fish, some of whom will die at the bottom while others try to escape by swimming towards the surface. This particular hypothesis offers answers to “why now?” and “why in Smith Sound?”, two questions which are not well addressed by the simple “cold water” explanation that has been offered by DFO. (Please read also my web articles on the Smith Sound cod kill.) The declining abundance of zooplankton not only increases the vulnerability of fishes to death by starvation and death by suffocation, but it also increases the likelihood of other nasty surprises occurring in the ocean, such as toxic algae blooms. Should the current plankton trends continue, sudden, ‘unexpected’ mass mortalities may be expected to affect any of the larger marine animals. Populations already clearly under stress, such as the endangered northern right whale, can be expected to be particularly vulnerable. It is therefore imperative that marine science immediately address the problem of the zooplankton decline.
The Committee should know also that one form of marine life that contributes directly to the health of zooplankton is the seals. In their warm bellies, seals incubate large numbers of worms and they excrete copious quantities of floating worm spawn into the plankton. In a sea with shrinking zooplankton stocks this represents a valuable contribution, exactly where it is needed, and this fact should strengthen the scientific arguments against a seal cull.
The planned killing of seals to “aid the groundfish recovery” is a useless, and purely political, diversionary tactic. The fishermen want to kill the seals because of their own frustration, desperation and lack of understanding of what has gone wrong. That much is understandable. But, even barring the appreciation of marine mammals as agents which enhance zooplankton health, marine scientists are overwhelmingly convinced that killing seals will never ultimately work to the benefit of the cod stocks. Removing more seals will, in all likelihood, result only in a further weakening of the ecosystem. Beyond a reconsideration of the wisdom of the annual Canadian seal hunt, the recent decision to allow fishermen to kill “nuisance seals” must be reversed…and be reversed in the name of protecting the fish, and much else.
What should the worried fishermen in Atlantic Canada do?
If possible, we need to find a positive strategy that will enhance zooplankton growth. Besides leaving spawn-producers (including fish and seals both) in the sea, it may be useful to provide them with a solid food subsidy. I have suggested before that dispersal of our solid organic waste (food) in the ocean may help the recovery of the fish stocks. And I remain convinced that this would be a worthwhile experiment. If done carefully, and widely scattered to avoid undue concentration of bacterial breakdown (which will cause oxygen depletion), any food not eaten by fish in the water column will most likely be consumed by bottom-dwelling invertebrates. Starfish, molluscs, worms or crustaceans…all of these scavengers produce vast quantities of excess spawn which float to the surface and help to sustain the zooplankton, which then helps to sustain the fish. These organisms are valuable, essential components of a healthy ocean, and repeatedly battering them with bottom trawls represents just one more ignorant and ill-considered assault, which likely has the potential to have a negative impact on the whole ecosystem…My suggested feeding experiment, by encouraging the growth of all of those ‘horrible little creatures’ at the sea bottom, may just help to turn around today’s declining trends in marine life, while offering unemployed fishermen an active, positive role in restoring the health of the ocean.
I find it incredible that DFO Science has ignored the warning signs in the plankton for years now, in favor of pursuing such questions as “what is in a seal’s stomach?” And yet they have failed to appreciate the significance of everything that IS in a seal’s stomach. Missed is the seal’s role as incubator of marine worms, as a virtual, mobile ‘zooplankton factory.’
The Committee’s recommendation for a “multi-faceted plan to rebuild the northern and Gulf cod stocks” initially sounds good. But such a plan must be based on an honest, holistic assessment of the many “facets” of the problem. Can we now please stop wasting tax dollars on feeding the public a constant stream of pro-seal-killing propaganda, and start to deal sensibly with the true scope of what is a very grave problem?
For more information see:
Seals and Cod
DFO, 2002. Chemical and Biological Oceanographic Conditions 2000 - Newfoundland Region. DFO Science Stock Status Report G2-02(2002). http://www.dfo-mpo.gc.ca/csas/csas/status/2002/SSR2002_G2-02e.pdf