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SOURCES, FATES, AND EFFECTS OF SHIPBORNE GARBAGE 40 mations, which seem reasonable to the committee, suggest that fishing vessels produce the most garbage (by weight), followed by passenger cruise ships and then recreational boaters. Tile major differences between the committee's and Cantin's estimates illustrate how seemingly minor changes in assumptions can skew the data, thereby casting doubt on the utility of such exercises. It must be emphasized, once again, that the data provide only an initial perspective on where Annex V implementation problems may lie. In any case, the precise numbers become less important in light of the committee's determination that amount is only one of several factors related to garbage sources that are significant from the standpoint of implementing Annex V. Several other key factors are reflected in Table 2-3. Of special interest are the numbers of vessels in each sector, the duration of voyages, and the nature of the garbage generated. The number of vessels reflects the quantity of isolated points at which garbage is generated and must be handled properly. The huge number of recreational boats poses a unique challenge in this respect. Voyage duration is also a significant factor. Some Navy ships face extreme challenges in managing garbage because they remain at sea for weeks or even months, so shoreside disposal is a rare option. The problems are fewer on day boats, which easily can store garbage for the duration of their brief voyages. And the nature of the garbage is important because some materials can be disposed of more easily than can others. Vessels that produce multiple types of garbage (especially when many different materials are involved) may requite unusually involved Annex V compliance strategies. Thus, a complex of factors must be considered in identifying which fleets pose the greatest challenges in terms of garbage management. None of the key factorsâamounts of garbage, numbers of vessels, duration of voyages, or types of garbageâcan be defined with precision across all sectors, because reliable data are scarce and vessel characteristics, even within a single sector, vary widely. Each sector presents unique issues and must be examined individually. The following presentation is organized according to the number of vessels in each sector (the most objective factor), beginning with the largest fleet. Recreational Boats Recreational boats produce relatively small amounts of garbage per person and per vessel, due to the short duration of voyages. However, there are an estimated 7.3 million recreational boats in the United States, far more than in any other sector. This sector therefore poses unique challenges in Annex V implementation. Still, the total amount of garbage generated is probably lower than the Cantin estimate, which the committee believes was based on inflated assumptions for numbers of passengers per vessel and, as noted earlier, per- person garbage generation. Recreational boats produce mainly domestic garbage. Most of these boats
