DFO ignores ocean fertility

By Debbie MacKenzie           (published by the Halifax Herald, Nov. 16,2003)

DFO RECENTLY presented findings of a 30-year ecological survey of the Eastern Scotian Shelf ecosystem. The messages that filtered through to the public emphasized themes of changing trends, plus a poor prognosis for any recovery in populations of groundfish such as the once dominant cod.

The 30-year change in marine life has been stunning. Where there once lived many large fish of various species, now there are virtually none. And the remnants of fish such as cod are small and in very poor condition; they are "not healthy." DFO reports that "groundfish appear to have lost their grip."

A plainer statement of this truth is that these fish are starving. DFO has admitted this in many reports and studies. However, no good reason has yet been found by science to explain just why the fish are starving.

Besides noting the loss of groundfish, the media reported three other themes: a spell of unusually cold water occurred in the area between 1985 and 1993; a massive increase in the numbers of "small pelagic" fish (herring, mackerel, capelin) has been seen as the groundfish have disappeared; and a large increase in numbers of grey seals in recent decades, including the population "doubling since 1997 to almost 225,000 last year" (as reported in the Herald on Nov. 6, neglecting the detail that seals have not been surveyed since 1997).

But none of these observations brings us close to discovering why cod are starving, because (1) the cold spell has been over for a decade; (2) small pelagics are normally eaten by bigger cod, and; (3) the more cod eaten by seals, the better fed the remaining individual cod should be.

The key question raised by the starving cod pertains to the fertility of the ocean. Despite DFO's recent collation of 64 data sets regarding the Scotian Shelf, ocean fertility estimation is not one of them. Dramatic plankton changes have coincided with the changes in fish populations, yet these have not been emphasized in media reports. These changes include a substantial decline in zooplankton, the tiny animals on which small fish feed, and this decline, along with a rise in uneaten phytoplankton, is consistent with a fall in ocean fertility.

Seaweeds are good direct indicators of ocean fertility, and visible changes in seaweeds along this coastline confirm this grave conclusion.

What seems to contradict the falling ocean fertility hypothesis is the massive increase in small pelagic fish. Fantastically, DFO reports a 400-500 fold increase in their numbers since the early 1980s. That's not a 400-500 per cent increase, but 400-500 fold. I remember fair numbers of these fish in the early 1980s, and if they have undergone such a phenomenal population explosion, the sea must be literally swarming with them now. But it doesn't appear to be, frankly, because it is not.

Small pelagic fish are hard to survey because they normally swim in schools throughout the water column, instead of collecting near the bottom. In other areas, these types of fish are sometimes assessed with "acoustics," which is basically sonar, or "fish-finders."

In Newfoundland, a recent unexpected acoustic finding has been a change in the habit of capelin on the now fish-bereft Grand Bank: scientists have recorded echoes which indicate capelin spread only in a thin layer over the bottom, rather than using the whole water column. If these capelin had been assessed only with a bottom net trawl, as DFO has done on the Scotian Shelf, a wildly incorrect impression might have been received of how many capelin were in the sea.

This may explain the small pelagic phenomenon in DFO's Scotian Shelf data. The maladies affecting the Grand Bank and the Scotian Shelf are undoubtedly one and the same: it appears that as fertility falls in an empty ocean, everything that is left just hugs the bottom more tightly.

Debbie MacKenzie lives in Prospect and does independent research on the fishery. On the Internet:




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