Biology Reference
In-Depth Information
200
150
Introduced
Cryptogenic
100
50
0
Major harbor area
Figure 13. Number of nonindigenous taxa in seven major ports of California.
Cryp-
togenic
refers to unknown origin. (Office of Spill Prevention and Response, Califor-
nia Department of Fish and Game)
cate aquarium purveyors and buyers about not releasing their pets into the
wild. Even the Clean Water Act classifies exotic organisms as biological
“pollutants.” But scientists say it is unclear whether these legislative mea-
sures, and subsequent vessel monitoring and public education, have made
any dent in the problem. No studies have been done to confirm any change
in the invasion rate. But more plans with good intentions have been com-
pleted in the form of California's first statewide aquatic invasive species
management plan.
Invasive species displace, disrupt, and in some cases even consume the
natives in their new habitats. Nationwide, about 400 of 958 species listed
as threatened or endangered are considered at risk due to the impacts of
non-native species. Non-natives contributed to 68 percent of fish extinc-
tions in the United States in the past 100 years.
“If we care anything about having some semblance of native biodiver-
sity or natural ecosystems, then this ongoing and almost wholesale re-
BALLAST EXCHANGE
Ships take on and discharge ballast water to balance their loads and control
how high they ride in the water. When released, ballast water often introduces
live organisms from one port into another. To prevent such alien imports to Cal-
ifornia waters, large vessels are now required to flush out and replace their
ballast in the open ocean, typically beyond 200 nautical miles from land. Far
fewer organisms live in the open ocean than in coastal waters, and those
taken up in ballast are unlikely to thrive in the very different environmental
conditions of the bay. Ships must document and report these “ballast ex-
changes,” but only limited resources are dedicated to follow-up and enforce-
ment. In the future, onboard or onshore treatment to kill alien organisms may
become the preferred option.
