A No-Ice Working Clock for Landed Fish: Hours to the Quality Limit across Temperatures, and the Extension from Wet Sacking in Shade

Where ice is unavailable, unaffordable, or exhausted, a seller's practical question is simply: how long have I got? This paper builds a working clock for that question. Taking a reference shelf life on ice of 12 days (288 hours) at 0 °C to the limit of acceptable quality, and a Q10 of 2.5 for the temperature dependence of spoilage, the remaining saleable time is 182.1 hours at 5 °C, 115.2 hours at 10 °C, 72.9 hours at 15 °C, 46.1 hours at 20 °C, 29.1 hours at 25 °C, 18.4 hours at 30 °C and 11.7 hours at 35 °C. The clock therefore runs about 15.62 times faster than on ice at 30 °C and 24.71 times faster at 35 °C: a catch landed in the morning in hot weather reaches the quality limit the same evening. The paper then evaluates the oldest no-ice remedy, covering the boxes with wet sacking in shade so that evaporation holds the fish near the wet-bulb temperature. The benefit depends entirely on humidity. In arid air at 35 °C with a wet-bulb depression of 9 °C, the window lengthens from 11.7 to 26.6 hours, an extension of 14.9 hours. In temperate summer air at 24 °C with a depression of 4 °C, it lengthens from 31.9 to 46.1 hours, an extension of 14.1 hours. In humid tropical air at 32 °C with a depression of only 2 °C, it lengthens from 15.3 to 18.4 hours — an extension of just 3.1 hours, helpful for reaching a market but not for holding a catch overnight. Wet sacking is worth doing in dry air and is a weak defence exactly where heat and humidity combine. The study is simulated, not measured.