Invasions of non-indigenous species are made possible by human actions all along the migration paths of such species, regardless of whether the transfer is a result of intentional or unintentional activity, whether the new species make their journey in ballast waters, as part of ship fouling, as contaminants of fish stocking material or in any other way. This means that the responsibility for invasions of non-indigenous species is shared by both the target country and the countries of origin and, in some cases, also by countries along the way. Consequently, with a few exceptions, no country, including Poland, bears sole responsibility for new invasions in its waters. This is well illustrated by the fact that the number of non-indigenous species in Polish Marine Waters is far lower than that in the Baltic Sea as a whole. It is only a question of time before these dozens of non-indigenous species that already inhabit the Baltic reach Polish Marine Waters and there is no way in which Poland can prevent this from happening. Therefore, prevention of further such entries of non-indigenous species into Polish waters requires action by other states aimed at preventing new species from reaching the Baltic in the first place. These countries include primarily, but are not limited to, countries along Europe's main navigation routes and countries sharing the Baltic Sea Basin.

With very few doubtful exceptions (commercially attractive fish, large crustaceans, large plants), non-indigenous marine species are practically impossible to eliminate from the environment and their population dynamics are controlled by processes largely beyond human control, i.e processes that may be referred to as natural. This does not mean that such species will necessarily proliferate. In a number of cases, non-indigenous species have retreated following initial colonization success. Nevertheless, once a species is introduced into the marine environment, both its expansion and retreat are almost exclusively due to natural causes, such as reproduction rate, predation or competition for suitable habitats.