In past articles we have discussed the advantages of using ice to cool fish, as well as the different factors that affect seafood cooling rates. In today’s article we will turn our attention to how to calculate the amount of ice needed to properly chill fish to 0°C (32°F). In addition to the basic formula and rule of thumb for calculating ice amounts, we will also take a look at a couple of additional factors which may influence how much ice is needed for the trip.

The Importance of Correct Estimation

Accurately estimating the amount of ice needed for a fishing trip is crucial and walking the line between having too much and having too little may be difficult. Space is at a premium on most fishing vessels. If the fishermen bring too much ice they may not have enough space for fish and other cargo and they will incur needless extra expenses. On the other hand if they do not bring enough ice it may all melt before they can return to shore or it may be insufficient to cool the caught fish to a safe temperature. This can result in spoiling and a completely wasted, expensive trip. These problems can be avoided by considering the following.

Basic Formula and Rule of Thumb

The following chart shows the amount of ice needed to lower 10kg (22.04lbs) of fish to 0°C (32°F) for various starting temperatures of the fish.

• 3.4kg (7.5lbs) of ice for 30°C (86°F) fish
• 2.8kg (6.2lbs) of ice for 25°C (77°F) fish
• 2.3kg (5.1lbs) of ice for 20°C (68°F) fish
• 1.7kg (3.8lbs) of ice for 15°C (59°F) fish
• 1.2kg (2.7lbs) of ice for 10°C (50°F) fish
• 0.6kg (1.3lbs) of ice for 5°C (41°F) fish

Thus for 10kg of fish at 30°C it will require 3.4kg of ice to lower the temperature to 0°C. These same formulas can be adjusted for different amounts of fish. For example if the weight of fish caught is 100kg and the fish are at a temperature of 30°C then it will call for 34kg of ice. This works out to roughly a 3:1 ratio of fish to ice.

However, it is crucial to note that the amounts of ice given by the calculations above are only to lower the fish to initial temperatures of 0°C. They do not take into consideration the amount of ice needed to maintain that 0°C for the duration of the trip. Nor do the calculations account for ice that will be lost to melting. These circumstances will vary based on the circumstances in play for a given trip and boat. Instead a loose rule of thumb for calculating how much ice will be needed is to assume about a 1:3 ratio of fish to ice (the opposite of the previous 3:1 fish to ice ratio) if the fishing expedition is taking place in a tropical climate.

Consider the Size of the Fish

Another important consideration to determine the amount of ice that will be needed for a fishing trip is the size of the fish that will be caught. Naturally as shown above the more fish caught the more ice will be needed to safely cool them. However, besides the pure weight of fish itself, the size of the individual fish is also a factor. That is because it requires more ice to cool larger, thicker fish because the fish themselves do not cool as quickly and efficiently as smaller, thinner fish.

Consider the Length of the Trip

A fishing trip that lasts a day or two is quite a bit different than one that lasts more than a week. Naturally the longer the vessel is out to sea the more ice is needed on hand to compensate for melting. Likewise longer duration trips may yield more fish which would require more overall ice to cool. Along the same the lines a trip that goes further out to sea may need more ice than a closer-to-shore trip since it will be more difficult to cut a long distance trip short if capacity is met early or if something else happens.

Consider the Storage Conditions

Finally, the storage conditions on the boat are also a crucial factor for calculating the amount of ice needed. If the storage hold is well insulated and double lined it will hold in cool temperatures and keep out warm temperatures vastly more effectively than a non-insulated hull and will thus not require as much ice to get the job the done. The type of ice being used is another important factor.

Semco understands how important it is to have a trustworthy and reliable cooling system in place on board fishing vessels. We manufacturer and install industry-leading systems and equipment that can be customized to fit the space considerations, capacity needs, and other specs of our clients. We are committed to providing outstanding ice and cooling systems.