Geoscience Reference
In-Depth Information
Brunswick, whereas demersal (bottom-dwelling) fishes, like cods and flounders, prefer the western parts of the
coast. These distributions, it is believed, reflect the various mixing regimes within the gulf. In the west, the
phytoplankton is produced in the spring and promptly sinks to the bottom, where it becomes fodder for de-
mersal fish. But in the east at the mouth of the Bay of Fundy, where tidal mixing is stronger, the phytoplankton
remains in the water column throughout the year and thus attracts the pelagic fish.
The distribution of these major classes of fishes differs markedly also. Members of the cod family—cod,
haddock, pollack, cusk, and hake—each have a preferred haunt. For example, haddock are more abundant at
the eastern end of Georges Bank, whereas cod congregate in the nearshore waters of the western gulf. Simil-
arly other cod-related species have their special places, separate from the others. In addition, different cod spe-
cies spawn at different times of the year. This patchiness may be a mechanism that the ecosystem has evolved
to protect itself from the vagaries of nature. It seems important to the integrity and sustainability of the ecosys-
tem that there is a cod of some kind in abundance somewhere in the system at all times. This built-in resilience
and adaptability of the system appears to have been undermined, however, by overfishing. In the early 1990s,
groundfish stocks collapsed in the northwest Atlantic. In place of codlike fishes, dogfish and skates now hold
sway, and whether groundfish stocks will recover is not known. If they do, it is likely to be a slow process.
DIFFERENT SPECIES OF
whales also divvy up the banquet of marine resources in the gulf, according to their in-
dividual needs. Their travels and differing feeding strategies help to spatially integrate the ecosystem and give
it greater stability. Together, the five large whale species that occur in the gulf probably number 3,500, far few-
er than the 25,000 that likely existed before the colonial period of whaling. This difference translates as a
75,000-ton loss of whale biomass to the system. No doubt some of the energy that went into the growth of
whales now fuels other marine life, but the absence of so much higher animal life must have had a significant
impact on the ecosystem.
