Large fish occupy a very important economic role with a major segment of the commercial fishing industry dedicated to catching them. On a per fish basis large fish also have a much higher value than small or medium-sized fish and thus represent a much more significant investment. It is crucial to properly cool and store them after catching so that they can later be sold at full value and safely consumed. Let’s take a look at some common large fish, special considerations when cooling and storing large fish, and best methods and practices.

Types of Large Fish and Their Role

The term “large fish” is fairly subjective in that it might mean different things to different fishermen and there may not be a clear cutoff between large and medium-sized varieties. However, for the most part the many species of tuna and marlin are considered to be large fish, along with other sizable fish such as mahi mahi, halibut, and cod to name just a few.

Large fish are very popular in part because large fillets of meat can be harvested from them and make ideal steaks. Smaller pieces of meat may also be used for a variety of dishes and even fish byproducts such as oil may generate value. As such large fish are important to the economy of coastal towns all over the world.

Special Considerations for Cooling Large Fish

To understand how best to cool large fish it is necessary to understand the ways that large fish vary from their small or medium counterparts. First, large fish have very thick bodies and their meat is often beneath layers of insulating fat. That increased thickness and insulation results in much slower cooling times than are seen with small or medium sized fish. Thus it is important for fishermen to act quickly and efficiently to begin the cooling process immediately after the fish are caught.

While the thickness and insulation are a drawback for rapid cooling, the preservation of large fish does have a significant advantage over the preservation of smaller species: surface area. Relative to their weight, large fish have a much smaller surface area than littler fish. This is easy to understand when one considers that for small fish nearly all of their meat is right beneath the surface; whereas for large fish much of the meat is deeper and further away from the skin surface. The reason that this is so significant is because surface areas are the most vulnerable to spoilage, thus giving the large fish an edge in preservation.

Another advantage for large fish cooling is that just as their larger, thicker nature slows down the cooling process it also slows down the rewarming process. Thus large fish hold onto low temperatures for longer once they reach suitable levels. On the downside, however, is the fact that because large fish are so big there is also more of a risk of a temperature gradient existing with some parts of the fish cooler or warmer than others. By contrast small fish typically cool uniformly through and through.

Preparing the Large Fish for Cooling and Storage

The considerations mentioned above mean that it is much more difficult to adequately cool large fish by merely placing ice against their outer surface. Instead it is recommended that prior to placing them in the hull and icing them, the large fish first be gutted. This of course removes undesirable mass that does not need to be cooled, but much more significantly it creates another major access point for the ice or chilled seawater. Once the fish have been gutted their bellies can be directly filled with ice, thus providing cooling from both their internal and external surfaces.

Cooling with Flake Ice and Chilled Seawater

Research data from the Food and Agriculture Organization of the United Nations (FAO) shows that only two types of commonly used cooling methods are effective enough to rapidly cool large fish within the time window needed for safe preservation: chilled seawater (CSW) and flake ice. As such these two methods should be used on commercial vessels.

Semco understands the vital role large fish play in the economic lives of our fishing clients. We are committed to providing top quality, dependable cooling and storage systems that are great for use with large fish. All of our systems are custom designed to best fit the needs of the particular client. Let us help you keep your large fish cool and fresh.