Funa-zushi (crucian carp sushi) (鮒寿司)
Funa-zushi, a local specialty of Shiga Prefecture, is a type of nare zushi (fermented sushi) made with crucian carp. Nigoro buna (Carassius auratus grandoculis) which is an indigenous species of Lake Biwa is mainly used. Both male and female fish are used but female with roe command higher prices.
The following is a recipe commonly used.
The season for funa-zushi begins around April, and to make it you first remove the scales and gills from some nigoro buna (other crucian carp varieties can be used as substitutes) and then split its belly to gut it, keeping the ovaries, if present, intact. After stuffing the fish cavity with salt, transfer the fish to a barrel, put a small lid directly over the fish with a weight placed on top of it, and then store the barrel in a cool place.
The foregoing process is referred to as 'shiokiri.'
After preserving in salt for approximately three months, remove funa from the barrel, wash salt off with water and soak in water to remove excess salt. The process of removing salt is complete when the fish has a slight salty taste and it is time to stuff funa with the rice and salt mixture. Some recipes call for rice malt or sake to accelerate fermentation. Put the stuffed fish in a barrel alternating every other layer with rice whereby there is rice inside the fish cavity and also on either side of the fish. Some people add water to the barrel during this process. Put a small lid directly on the top of the food, place a weight on the lid and keep the barrel in a cool place.
The barrel is stored until the end of the same year at the minimum or it may be kept one to as long as two years depending on the person. Inside the barrel, lactic fermentation prevents decomposition of funa while amino acid enhances the flavor of fish.
When the brine that forms has risen to above the fish as a result of the volume of the solid part of the fish having been reduced, which causes an unpleasant odor to be emitted, the funa is removed from the barrel.
Generally, it is said that, when funa-zushi is ready, the rice is removed and only the fish is eaten but since many local residents eat the fish together with the fermented rice of paste-like consistency, one needs to be careful as to how much rice should be taken off the fish. Fish is usually served sliced and arranged on a dish. There are various ways of enjoying funa-zushi such as eating as is and adding to the bowl of rice in hot tea as a topping.
Since funa has hard bones, the fish is slow-simmered and the bones are removed when prepared as sashimi but, after being cured for about one year, the bones in funa-zushi, which is uncooked, become tender enough so that one may not find them overly objectionable. Additionally, as the rice completely disintegrates approximately after two years of curing, it is said that those who cure funa-zushi for three to four years repeat the layering of the fish and rice using the fresh batch of rice halfway.
Due to the strong sour taste and odor caused by lactic acid fermentation, funa-zushi is not for everyone but it may be more appealing to the palate of those who are unfamiliar with this food if served with a bowl of rice in hot tea. The fermented fish roe resembles natural cheese and is fairly good eating. Various methods of packaging such as vacuum packing have been tried to contain its strong smell to promote sales.
Due to its time-consuming and labor-intensive recipe and the dwindling number of funa and nigoro buna, that are most suitable for making funa-zushi, caused by various factors including the decreased reed fields, deteriorating water quality, destruction of breeding grounds by concrete embankment and fish of foreign origin in the lake, the price of these fish species has steeply risen to several thousands of yen each in recent years and, in some cases, funa-zushi is made with gengoro buna (Carassius cuvieri) and gin buna (Carassius langsdorfii) in substitution for funa and nigoro buna. Additionally, some attempts have been made to make the fermented sushi with black bass or blue gill based on the similar recipe as that for funa-zushi.