itself, and does not concern fish farming or other activities that are conducted outside the watercourse, ZQW (3) Article 24 requires watercourse States to “take all measures necessary” to orevent the introduction of alien or new species. This expression, which is also utilined in article 196 of the 1962 United Nations Convention on the Law of the Sea, indfcatss that watercourse States are to undertake studies, in so far as they are able, and take the precautions that are required to prevent ’ alien or new species from being introduced into a watercourse by public authorities or prLvate persons. The obligation is one of due diligence, and will not be regarded as having been breached if a watercourse State has done all thai can reasonably be expected to prevent the intl.oduction of such species. ZQV See paragraph (2) of the commentary to article 22. z!u/ 1982 United Nations Convention on the Law of the Sea, art. 196, pare. 1. 2Qw Thus the term would include parasites and disease vectors. m/Appropriate precautionary measures may be required, however, to prevent any alien or new species involved in such activities from making their way into the watercourse. - 168 -(4) The t@introduction@’ that watercourse States are to taks all measure8 necessary to prevent is one that "may have effects detrimental to the ecosystem of the international watercourse [system] resulting In appreciable harm to other watercourse States@‘, While any iiltroduction of an alien or new species into an international watercourse [system] should be treated with great caution, the Commission was of the view that the relevant legal obligation under the present draft articles should be kept in harmony with the general rule contained An article 8.Since detrimental effect8 of alien or new species will, almost invariably, manifest themselves first upon the
**Analysis**
The text appears to be discussing the obligations of states to prevent the introduction of alien or new species into international watercourses, with a focus on the potential harm this could cause to the ecosystem and other states. This suggests that the text is related to environmental and natural resource issues.

**Category**
Natural resources and environment, International trade