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Samples of flesh were excised from the middorsal region of 67 siscowets (Salvelinus namaycush siscower) and 46 lake trout (Salvelinus n. namaycush) collected from Lake Superior. Chemical analysis of the samples revealed a range in fat content (dry weight) of 32.5 to 88.8 per cent in siscowets and 6.6 to 52.3 per cent in lake trout. Percentage fat increased progressively with increase in length of fish in both forms, but the average rate of increase was far greater for siscowers than for lake trout at lengths between 12 and 20 inches. Despite substantial individual variation, the percentage fat in the two forms was widely different and without overlap at all comparable lengths. The range in iodine number of the fat was 100 to 160 for siscowers and 103 to 161 for lake trout; average values were generally lower for siscowets than for lake trout among fish of comparable length. Percentage fat and relative weight were not correlated significantly in either subspecies. The fat content of flesh samples from a distinctive subpopulation of Lake Superior lake trout known as "humpers" was more closely similar to that of typical lean lake trout than to siscowers, but the rate of increase in fat with increasing length was greater than for lean lake trout. Flesh samples from hatchery-reared stocks of lake trout, hybrid lake trout X siscowers, and siscowers tended to support the view that the wide difference in fat content between siscowets and lake trout is genetically determined. INTRODUCTIONThe identity of a number of subpopulations of lake trout, Salvelinus namaycush, in Lake Superior is revealed by differences in spawning localities and/or dates, and size at first maturity (Eschmeyer, 1957). Although fish of the different subpopulations are not easily recognizable by sight, commercial fishermen differentiate between, and market separately, two forms which usually are given subspecific rank the "lean" lake trout, Salvelinus n. namaycush, and the siscowet or "fat" lake trout, Salvelinus n. siscowet. The lean lake trout of Lake Superior is similar to fish of many other populations of the species in waters throughout its range, but the siscowet has somewhat different appearance and characteristics, and is believed to be confined to the Upper Great Lakes--principally to Lake Superior.Most siscowets are caught at depths of 50 to more than 100 fathoms, in contrast to lake trout, which usually are caught in shallower water. The bathymetric distribution of the two forms overlaps broadly, however; occasional siscowets are taken in shallow water, and lake trout and siscowets are sometimes taken in about equal numbers in gill nets at depths greater than 50 fathoms. Typical sis-62

Hybrid fuel cell propulsion systems for marine applications are attracting widespread interest due to the need to reduce ship emissions. In order to increase the potential of these systems, the design of an efficient energy management strategy (EMS) is essential to distribute the required power properly between different components of the hybrid system. For a hybrid fuel cell/battery passenger ship, a multi-scheme energy managements strategy is proposed. This strategy is developed using four schemes which are: state-based EMS, equivalent fuel consumption minimization strategy (ECMS), charge-depleting charge-sustaining (CDCS) EMS, the classical proportional-integral (PI) controller based EMS, in addition to a code that chooses the suitable scheme according to the simulation inputs. The main objective of the proposed multi-scheme EMS is to minimize the total consumed energy of the hybrid system in order to increase the energy efficiency of the ship.The world's first fuel cell passenger ship FCS Alsterwasser is considered and its hybrid propulsion system is modelled in MATLAB/Simulink environment. The performance of the developed multi-scheme EMS is compared to the four studied strategies in terms of total consumed energy, hydrogen consumption, total cost and the stresses seen by the hybrid fuel cell/battery system components considering a daily ship operation of 8 hours. Results indicate that a maximum energy and hydrogen consumption savings of 8% and 16.7% respectively can be achieved using the proposed multi-scheme strategy.