Today, "Nam O" refers to an ancient fishing village located at the southern gateway of the former Dai Viet, situated by Da Nang Bay. It is home to a renowned traditional fish sauce-making craft. The reputation of Nam O fish sauce has made its way into folk songs and proverbs, such as: "Nam O fish sauce, Xuan Thieu anabas testudineus fish" and "Nam O fish sauce, known everywhere", "Nam O fish sauce has a strong aroma, wherever I go, I remember the scent of home". 

On August 27, 2019, the Ministry of Culture, Sports and Tourism issued Decision No. 2974/QD-BVHTTDL recognizing "the craft of making Nam O fish sauce from the two wards of Hoa Hiep Nam and Hoa Hiep Bac, Lien Chieu District, Da Nang City as a national intangible cultural heritage". 

Regarding sensory characteristics, Nam O fish sauce has a dark amber color, a salty taste, a lingering and intense sweet aftertaste, and a distinctive mild aroma. 

In terms of quality, Nam O fish sauce has a total nitrogen content of 20 g/L or higher, an amino acid nitrogen content of more than 43.5% compared to the total nitrogen content, and an ammonia nitrogen content of less than 14.2% compared to the total nitrogen content.  

 

Figure 1. Nam O Fish Sauce 

The uniqueness of Nam O fish sauce comes from the harmonious combination of natural geographical conditions and the centuries-old production methods of the fish sauce makers. 

Having endured through the years, the fish sauce making craft in Nam O has maintained and preserved its traditional techniques to create a product with its own unique characteristics. Nam O fish sauce is processed using black anchovies and salt as its primary ingredients. These anchovies are a type of fish that lives in the upper layers of the sea and are caught by the local people in the waters off Da Nang from February to March of the lunar calendar (the Southern fishing season) and from July to August of the lunar calendar (the Northern fishing season). 

During the Southern fish season, as it approaches the warm, sunny summer with little rain, the seawater in the Da Nang area has a higher salinity, resulting in firmer flesh of the black anchovy (fish). To achieve a moderate saltiness in the fish sauce, a smaller amount of salt is needed for curing the fish. Based on their experience in production, fish sauce makers in Nam O have determined the ideal curing ratio for the Southern fish season to be 3 parts fish to 1 part salt. 

During the Northern fishing season, due to the early onset of the rainy and storm season in Da Nang, the flow of river, stream, pond, and lake water into the sea increases, reducing the salinity of the seawater. As a result, the flesh of the black anchovy is less firm compared to the Southern fishing season. To prevent spoilage during salting, the amount of salt used for curing the fish needs to be increased. Through experience in production, fish sauce makers in Nam O have discovered that the salting ratio for the Northern fishing season is 2.5 parts fish to 1 part salt.  

 

Figure 2. Black anchovies catch and mix the fish with salt 

Due to its geographical proximity to the Ca Na (Ninh Thuan) and Sa Huynh (Quang Ngai) regions, Nam O fish sauce makers have historically used salt sourced exclusively from these two areas, a tradition that continues to this day. 

The selection of fish ingredients affects the color of fish sauce. Due to the use of fresh black anchovy with minimal impurities and relatively uniform size (approximately 95% black anchovy), and sufficient salt, Nam O fish sauce has a brownish-amber color. 

In fish sauce production, the mixing stage and the fermentation time influence the color of the fish sauce. In Nam O, the main ingredient is black anchovy and salt is added to the earthenware jars only once at the beginning of the fermentation process. The fish mixture is pressed down during the first 3 months, and then mixed for the remaining time to ensure the bones and flesh of the fish dissolve evenly. After the fermentation period (from 12 to 18 months), the sauce is considered ready when it has a brown-amber color and is then filtered.  

Figure 3. Mixing fish sauce in Nam O 

Due to its geographical location on the coast of Da Nang Bay, it is advantageous as a dock (port) for boats to anchor and gather fresh black anchovy to be promptly fermented whenever the fish are caught. 

Nam O fish sauce is bottled within the geographical area. 

Geographic area: Nam O 1, Nam O 2, Nam O 3, and Xuan Thieu sub-quarters of Hoa Hiep Nam ward; and Kim Lien sub-quarter of Hoa Hiep Bac ward, Lien Chieu district, Da Nang city. 

Source: Bảo hộ chỉ dẫn địa lý "Nam Ô" cho sản phẩm nước mắm 
Translator: Nguyễn Hải Phong