Fishermen often perceive marine
mammals as posing a threat to their business. Seals, sea lions,
dolphins and whales can be viewed as pests that cause damage to
nets and deplete fish stocks that are necessary for commercial
fisheries to survive. Moreover, seals can also act as hosts for
various parasites whose larval stage occurs in commercial fish. An
example of this is the cod worm, which lives as an adult in the
stomach of grey seals but as larval form in cod and cod-like fish.
If too many commercial fish are effected by parasites in an area,
the fish become harmful to human consumption and the fisheries may
even need to relocate to an alternative stock. To avoid such
problems, at times in the past seal populations have been culled to
reduce their impact on the fish populations.
From the marine mammal side, the
relationship is no less negative. For one thing, marine mammals
frequently get caught in commercial fish nets and these animals,
being air-breathing mammals, drown when trapped under the water by
nets. This includes both nets currently used for fishing as well as
discarded nets and debris left by fishermen in the water.
Most significantly, even when
marine mammals and fishery operations do not directly interact, the
enormous scale of the growing human population is having a
significant negative impact on marine mammals. Over fishing of the
oceans by commercial fleets has significantly reduced fish
populations that are main sources of food for marine mammals. It is
plain to see that if the amount of fish in the ocean continues to be
reduced due to human consumption, it will lead to severe
consequences for marine mammals.
It is important to remember that
there are only so many fish in the ocean. If humans take too many,
the marine mammals and other creatures of the sea will have nothing
left for them.