An Ice-Planning Rule for Small Fishing Trips: Ice Needed to Chill the Catch and to Offset Heat Leak, and the Trip Length at Which a 1:2 Ice-to-Fish Ratio Runs Out

How much ice should a small fishing boat carry? Guidance is usually given as a single ratio of ice to fish, with no account taken of how warm the day is or how long the trip lasts. This paper separates the two jobs ice has to do — chilling the catch from its loading temperature to about 0 °C, and replacing the ice melted by heat leaking through the box walls during the trip — and combines them into a single planning rule for a reference insulated box (50 mm expanded polystyrene walls, 100 kg of fish). The rule is R = 0.01078 × T + 0.00706 × T × t, where R is kilograms of ice per kilogram of fish, T is ambient temperature in °C and t is trip length in days. Chilling alone consumes 0.216 kg of ice per kilogram of fish at 20 °C and 0.377 kg/kg at 35 °C. Heat leak melts a further 14.12 kg of ice per day per 100 kg of fish at 20 °C, rising to 24.72 kg per day at 35 °C. A commonly carried ratio of 1:2 ice to fish (0.50 kg/kg) is therefore exhausted after 48.3 hours at 20 °C, 20.0 hours at 30 °C and only 11.9 hours at 35 °C; indeed, at 35 °C a trip of just 12 hours already requires 0.501 kg/kg, slightly more than the whole 1:2 allowance. A two-day trip at 30 °C requires 0.747 kg/kg, and a five-day trip at 35 °C requires 1.613 kg/kg. A fixed ratio cannot be right at all temperatures and trip lengths; the rule and table given here replace it with arithmetic a skipper can do before loading. The study is simulated, not measured.