Fish lice

Fish lice (Branchiura) represent a subclass of small parasitic crustaceans that inhabit fresh and salt water. Often referred to as "argulids," they are significant pests in aquaculture, causing economic losses by harming stock in commercial fish farms and ornamental pond environments.

Taxonomically, they are classified under the subphylum Crustacea, within the subclass Branchiura, which consists of a single order Arguloida and one family, Argulidae. The genus Argulus is the most prominent, containing several species that parasitize a variety of commercial fish species worldwide.

These parasites primarily infest freshwater fish such as carp, trout, and various species of ornamental fish. They attach themselves to the host using specialized suction cups and feed on the fish's blood and mucosal tissues, leading to severe stress, weight loss, and in extreme cases, the mortality of the host.

The life cycle of Branchiura is direct and does not require an intermediate host. Adult females lay eggs on solid substrates such as rocks or aquatic vegetation. After hatching, the larvae must find a host within a few days to survive and develop into adults. The duration of the life cycle is highly dependent on water temperature, which explains why infestations peak during the summer months.

Damage caused by fish lice is visible as localized skin lesions, ulcers, and hemorrhages where the parasites have been feeding. These wounds create entry points for secondary bacterial or fungal infections. Effective control measures include

• mechanical removal of vegetation in ponds;
• draining and drying ponds between production cycles;
• application of approved chemical treatments;
• maintaining high water quality to boost fish immunity.