For thousands of years, humans and
many other species have thrived off of marine life for nourishment and
functional materials. However, as our population grows and modern fishing
methods make capturing large quantities of sea life more accessible, we pose a
threat to their genetic, species, ecosystem, and functional diversity. In the
face of environmental change, the loss of genetic diversity hinders a
population’s ability to adapt; the loss of species diversity hinders a
community’s ability to adapt; the loss of functional diversity hinders an
ecosystem’s ability to adapt; and the loss of ecological diversity hinders the
whole biosphere’s ability to adapt.
Genes are the driving force behind
an organism’s defining characteristics and functions. Overfishing can act as a
form of environmental change that selects for and alters certain physical and
developmental traits, essentially causing evolution. One example of this selection
pressure is the preferential exploitation of larger fish in a population.
Obviously, a larger fish provides more nourishment for more people, and it also
offers more in terms of marketable profit. However, if these larger fish are
removed much more frequently, over time the survival of smaller fish is favored
and they gain an evolutionary advantage. Individuals that mature earlier than
others in their reproductive lives begin to flourish and do most of the
reproducing. These fish are the ones that have a chance to consistently pass
their genes on before being caught, and the genetic variability of the
population begins to change in favor of the fish that begin reproducing at a younger
age and/or smaller size.
One example of this effect has been
observed in Pacific pink salmon. Over-fishing placed an uncustomary pressure on
their species by catching nearly 80 percent of spawning fish; researchers
examined the catch data and identified a steady decrease in the average weight
per fish. Even after accounting for outside factors such as environmental woes,
they concluded that our human inflicted fishing pressure was the sole cause of
this miniaturization of Pacific pink salmon.
No comments:
Post a Comment