NAca Section 2.pmd - Maryland Department of Natural Resources

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production, their contribution had grown from an insignificant level in 1989 to around 2000 mt in 1997
(FAO FishStat).
FAO’s Database on Introductions of Aquatic Species (DIAS)
Much of the data on introductions of aquatic species presented in this paper was obtained from FAO’s
Database on Introductions of Aquatic Species (DIAS) (http://www.fao.org/fi/statist/fisoft/dias/index.htm). 1
Information from DIAS’ databases has also been incorporated into FishBase, a WorldFish Centre/Food
and Agriculture Organization of the United Nations/European Union (ICLARM/FAO/EU) Project (http:/
/www.fishbase.org). FishBase is a relational database available on CD-ROM that contains many types of
information on fish and fisheries (e.g., species distributions, photographs, taxonomy, ecology, genetics,
aquaculture, etc.).
Benefits and Risks of Species Introductions
Aquatic species have been moved around the world for various purposes. According to DIAS data on the
reasons given for introducing marine and brackishwater species, introductions of new species for aquaculture
development (701 of 1738 cases, 40.3%) is most frequently cited, followed by capture fisheries
development (346 cases, 19.9%). Other reasons cited include accidental releases (6.3%), diffusion (5.2%),
biocontrol (5.1%), ornamentals (3.0%), research (2.9%), other reasons (2.7%) and unknown (14.4%)
(see Fig. 4).
There are many examples of the positive socio-economic benefits arising from the introduction of aquatic
species. These include improved livelihoods, increased production and trade, etc. However, there have
also been cases where serious negative impacts have resulted. Data from DIAS (Fig. 5) shows that the
vast majority of introductions (88.4%) are perceived as having had positive socio-economic benefits. On
the other hand, the ecological impacts of introducing new species are far less certain, only a slight majority
of cases (23 vs. 19 cases) are considered beneficial as opposed to harmful. Figure 6 shows that the
socio-economic impacts of intentional introductions of aquatic species are generally perceived as being
beneficial, particularly so for introductions for aquaculture (95 cases considered beneficial), with intentional
introductions for angling (23 beneficial cases), fisheries (17), ornamental (6) and biocontrol (2)
purposes also considered to have good socio-economic impacts. On the other hand, there have also been a
significant number of cases where intentional introductions for aquaculture, angling, fisheries, etc. have
been considered to have negative ecological impacts. The serious negative consequences that often result
from unplanned introductions are also shown, 26 cases occurring where accidental introductions were
perceived as having detrimental ecological impacts, while only four cases were regarded as having positive
socio-economic impact.
An important and often strongly debated question is whether or not the introduction of an exotic species
for aquaculture development will lead to the establishment, through escapes, of wild populations of the
introduced species. In the case of mariculture (Fig. 7), DIAS information shows that there is about an
equal chance that a new species introduction will or will not establish itself in the wild (286 cases indicating
yes or probably yes, and 243 cases indicating no or probably no).
When all exotic species introductions in all aquatic environments are considered (see Fig. 8), a slightly
different picture emerges. In this case, in both marine/brackish and freshwater environments, the likelihood
of establishment is much greater (814 cases of establishment in marine/brackish waters vs. 415
cases where establishment did not occur, and 787 cases of establishment in fresh water vs. 417 cases of
non-establishment). This difference is likely due to the inclusion of data from intentional releases in this
data set.
1 For the purpose of DIAS, an introduced species is defined as a species that has been moved across a national border to a country outside
of its natural range.