It is not just the increased proximity of alien marine
species to a nation’s ports that should be of concern as
they spread through to neighbouring regions and
trading partners; as alien marine species establish in
new areas,they adapt to a variety of environments. For
example,there may currently be some protection against
temperate species with a strongly seasonal life history
establishing in the opposite hemisphere from which they
are native. There were originally very few ports in
Australia where the North Pacific seastar could establish
as it needed a port where the summer temperatures were
not greater than the upper limits of its winter tolerance
(this seastar spawns in the northern hemisphere winter).
Now that it is established in southern Australia and has
reversed its seasonal cycle to match austral seasons,
ports from Sydney to Perth in Australia,as well as ports
in New Zealand,South Africa and South America have
become potential invasion sites.