to be of great significance in relation to the survival capabilities of individuals and
the group as a whole.
Genetic diversity is thus also an indicator of population health for various
organisms. It is understood to be of great importance from the standpoint of
long-term development of the farming, forestry, and fishing industries, which
depend on organism production, and it also possesses great significance for industry
in terms of its being essential in providing a breeding stock for improvements in
marine aquaculture.
Why should we be interested in biodiversity? The decline in diversity that we are
bearing witness to today is both a direct and an indirect product of human activities.
Diversity has been diminishing by the day due to deliberate hunting and harvesting,
habitat destruction from development activities, and indirect causes such as global
environmental changes and oceanic pollution. Reduced diversity may lead to a
collapse in interdependent ecosystem relationships, resulting in the disappearance
of species of organism that may hold as yet unknown benefits for us. An excellent
example is the Pacific yew (Taxus brevifolia). Native to the west coast of the U.S.,
this tree previously received little attention due to its slow growth and small size.
Today, it has an important role in providing raw material for the powerful
anti-cancer medication Taxol. Declining species diversity, and the resulting
destruction to ecosystems, can also be a source of both spiritual and psychological
damage to human beings.
To address these issues, the United Nations Food and Agriculture Organization
(FAO) moved in June 1992 to establish the Biodiversity Convention, an agreement
with the aim of preserving diversity among species. The document affirmed the
need for genetic preservation of wild fish and shellfish preservations and assessment
of pure stocks from a breeding perspective, as well as the importance of developing
highly sensitive DNA markers as a means of studying them (Toledo and Burlingame 2006).
Population size is critical for species survival. Rare species living in special
habitat environments are often threatened with extinction due to declines in their
population numbers from loss of those habitats. Typically, genetic diversity is
reduced in populations of fewer than 100 organisms due to genetic drift, inbreeding,
and diminished genetic flow. Many research studies have shown that at least
100,000 organisms must exist within a population for it to be capable of long-term
preservation. The number of organisms that can produce the next generation of
gametes at an equal level of probability within a population is normally referred to
the effective population size (N e ), which is always smaller than the absolute population size N. N e may be calculated as 4(N m N f )/(N m + N f ), where N m is the number
of males and N f the number of females.
Effective population size is also affected by fluctuations in absolute population
size from one generation to the next.
For surviving organisms from an endangered species, a population may be
established through capture and breeding programs. Genetic diversity may be
reduced by bottlenecks (temporary reductions in population size) or the founder
principle (the emergence of new populations as a result of migration by small
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5 Genetic Diversity and DNA Markers in Fish
the group as a whole.
Genetic diversity is thus also an indicator of population health for various
organisms. It is understood to be of great importance from the standpoint of
long-term development of the farming, forestry, and fishing industries, which
depend on organism production, and it also possesses great significance for industry
in terms of its being essential in providing a breeding stock for improvements in
marine aquaculture.
Why should we be interested in biodiversity? The decline in diversity that we are
bearing witness to today is both a direct and an indirect product of human activities.
Diversity has been diminishing by the day due to deliberate hunting and harvesting,
habitat destruction from development activities, and indirect causes such as global
environmental changes and oceanic pollution. Reduced diversity may lead to a
collapse in interdependent ecosystem relationships, resulting in the disappearance
of species of organism that may hold as yet unknown benefits for us. An excellent
example is the Pacific yew (Taxus brevifolia). Native to the west coast of the U.S.,
this tree previously received little attention due to its slow growth and small size.
Today, it has an important role in providing raw material for the powerful
anti-cancer medication Taxol. Declining species diversity, and the resulting
destruction to ecosystems, can also be a source of both spiritual and psychological
damage to human beings.
To address these issues, the United Nations Food and Agriculture Organization
(FAO) moved in June 1992 to establish the Biodiversity Convention, an agreement
with the aim of preserving diversity among species. The document affirmed the
need for genetic preservation of wild fish and shellfish preservations and assessment
of pure stocks from a breeding perspective, as well as the importance of developing
highly sensitive DNA markers as a means of studying them (Toledo and Burlingame 2006).
Population size is critical for species survival. Rare species living in special
habitat environments are often threatened with extinction due to declines in their
population numbers from loss of those habitats. Typically, genetic diversity is
reduced in populations of fewer than 100 organisms due to genetic drift, inbreeding,
and diminished genetic flow. Many research studies have shown that at least
100,000 organisms must exist within a population for it to be capable of long-term
preservation. The number of organisms that can produce the next generation of
gametes at an equal level of probability within a population is normally referred to
the effective population size (N e ), which is always smaller than the absolute population size N. N e may be calculated as 4(N m N f )/(N m + N f ), where N m is the number
of males and N f the number of females.
Effective population size is also affected by fluctuations in absolute population
size from one generation to the next.
For surviving organisms from an endangered species, a population may be
established through capture and breeding programs. Genetic diversity may be
reduced by bottlenecks (temporary reductions in population size) or the founder
principle (the emergence of new populations as a result of migration by small
110
5 Genetic Diversity and DNA Markers in Fish