While a significant effort has been made to reduce marine diesel exhaust emissions, there is a need to examine the world fleets and assess the current levels of engine emissions. This paper introduces an emission assessment scheme that the authors have applied to analyse the US fishing fleet with length L . 22.9 m. The present results give an estimate that the 1051 vessels in the US fishing fleet produce 306 tonnes/day of nitrous oxides (NO x ). The largest power values are found in the decades of 1960 to 1980. The actual power (kW) is compared with a reference power (kW o ) using the powering index ratio (PIR 5 kW/kW o ). It was found that 50-80 per cent of the power in seiners, trawlers, and crabber/trapper/clam vessels have a PIR . 2.5. Based on this assessment, it is clear that a large number of trawlers and seiners are overpowered -resulting in high diesel engine NO x emissions.

This paper presents the results of SNAME Small Craft Panel SC-3 Fishing Systems investigation of trends in US fishing vessel (Fig. 1) (L> 22.9 m) powering and NOx emissions (1900–2000). The study estimates the 1, 299 vessels in the US fishing fleet produce 306 tons/day of NOx. The largest powers are found in the decades of 1960–1980. The actual power kW is compared to a reference power kWo using the Powering Index Ratio PIR = kW/kWo. It was found that 50 to 80% of the power in seiners, trawlers, and crabber/ trapper/clam vessels have PIR > 2.5. The reduction of fishing vessel diesel engine NOx can be best achieved by adopting acceptable levels of vessel power/length for the basis of revenue and tax rather than using the vessel age as emissions reduction criteria.