Biology Reference
In-Depth Information
Two biological control agents initially deemed most likely to reduce
C. taxifolia
biomass in Mediterranean waters were the native sea slugs
Oxynoe olivacea
and
Lobiger serradifalci
. Both species perforated cell walls with uniserial radula and
sucked up the algal contents. Both species have been tested in aquariums and in
open ocean waters as potential biological control agents of
C. taxifolia
(Thibaut and
Meinesz 2000). In later laboratory studies,
L. serradifalci
created viable fragments
of
C. taxifolia
when feeding;
Oxynoe olivacea
did not produce fragments (Zuljevic
et al. 2001). The nonnative, tropical sea slug
Elysia subornata
was also tested
(Meinesz 2002). At 21°C,
E. subornata
fed on
C. taxifolia
at rates 2-11 times
higher than the native ascoglossan species (Thibaut et al. 2001). Meinesz et al.
(1995) projected that 1,000
E. subornata
/m
2
were required to have a significant
impact on the Mediterranean sea floor with 5,000 fronds/m
2
. Unfortunately, a cold-
resistant strain of this species could not be readily cultivated (Meinesz 2002) and,
in 1997, the International Council for the Exploration of the Sea (ICES) stated that
nonnative ascoglossans could not be introduced to Mediterranean Sea for biocon-
trol. The French Ministry of the Environment shared the same attitude based on
(1) possible dietary switching by the herbivore, (2) competition with other impor-
tant groups of herbivores in the event of eradication of the target food source,
(3) introduction of pathogens, and (4) spread of the introduced herbivore itself.
15.5.7
Outreach, Signage, and Closures
The most cost-effective management strategy is to prevent the introduction of
C. taxifolia
into coastal waters. To ultimately be effective, outreach concerns need
to be addressed at local, regional, national, and international levels (Hewitt 2003).
Many countries have provided public and private funds for creating a wealth of
outreach materials (animated videos, fact sheets, identification keys, lesson plans
for educators, etc.) designed to change behaviors for every age and interest group
that may contact
C. taxifolia
. The next goal is to get the information into the right
hands. As aquarium releases are an important, intangible source of marine inva-
sions, aquarium hobbyists and custom agents who inspect international aquarium
shipments are prime outreach targets. However, both audiences are fluid with new
customers entering the hobby every day and new individuals assigned to rapidly
assess live aquarium shipments for illegal importation. For example, Zaleski and
Walters (unpublished data) surveyed participants at MACNA 2006, the annual
meeting of the Marine Aquarium Societies of North America in Houston, TX and
found that 29% of the visitors had never heard of
C. taxifolia
, while an additional
25% had very limited understanding of the biology or global invasions of
C. taxifolia
.
In areas such as the Mediterranean and Australia that may never be able to eradi-
cate
C. taxifolia
, outreach can slow additional spread. In infested Australian waters,
signs are posted at all areas where boaters launch their craft and mandatory “wash-
down” stations are provided (Fig. 15.5). NSW visibly marks and bans anchoring at
