Fish Processing You are what you eat, and the quality and edibility of the fish you bring home says a lot about you. Treating the fish so that it tastes as good as possible, and stays fresh for longer, displays admirable skill and shows respect for the fish. And when you consider all the time and effort you put in to catch a few keepers – and the strict bag limits in force these days – proper fish care is just plain common sense.
Fortunately, the basics of fish care are pretty straight forward. In this article I'll explain the science, the law and address a furphy or two.
ICED OR ALIVE?
The traditional method of processing a fish is to bleed it (depending on the species) and immerse it in a brine slurry. However, more anglers are now opting to keep their fish alive in a livewell so they can process their catch later. This can be a good option, but there are some regulations to bear in mind if you want to do this.
First of all, it’s illegal in Queensland to retain live coral reef fin fish. The only exceptions are if you’re planning to put the fish in an aquarium, or if you intend to immediately return it to the sea.
Second of all, it can be a legislative minefield to fillet or remove the head of fish in Queensland until you get them ashore. The minimum length of a fish fillet that can be carried aboard your boat is 40cm, and the skin and scales have to be left on. You also can’t return a fillet to the boat after it’s been taken ashore. There are some exceptions to the rule, and you can find out more at www.dpi.qld.gov.au/28_3054.htm.
Because of the hassle involved in adhering to these on-water filleting regulations, most offshore crews simply ice all the fish down and leave processing until they get ashore. This saves confusion and constant referral to the rule book.
GUT IN OR OUT?
When storing unfilleted fish, there has been a lot of discussion about whether or not to leave the gut in. The theory is that the less flesh that gets exposed to the air the better (and that scales serve as a form of protection to the outer surface). Likewise, because an un-gutted fish will be thicker, it will be less susceptible to freezer burn and therefore last longer.
Unlike hot-blooded animals where the gut is removed to get rid of the heat, fish are cold-blooded. That means when they’re immersed in a cold environment, the low temperatures will generally control bacterial growth.
Having said that, gutting and gilling breaks the skin and risks exposing the fish to bacteria that can spoil the flesh. The decision of whether to gut or not is just one you’ll have to make yourself.
SLURRY
Adding salt to a slurry of ice and water (or using a seawater and ice brine) lowers the temperature at which the water freezes. Salt makes ice melt more slowly, and the temperature of the water will drop. The end result is a saltwater brine in a two-phase (liquid and solid) mixture that quickly chills down fish.
Fish cools faster in an ice slurry because there are no air pockets, as there would be | 
