Common loon

The common loon (lat. Gavia immer) belongs to the order Gaviiformes and the family Gaviidae. While not a traditional crop pest, the common loon is considered an avian pest in the aquaculture industry due to its specialized diet consisting primarily of fish, which directly competes with commercial fish farming operations.

The biology of the common loon is characterized by its reliance on deep freshwater bodies for foraging and nesting. These birds are highly specialized predators, capable of deep-water diving, which allows them to hunt effectively throughout the entire water column. Their presence in or near commercial ponds often leads to severe depletion of stocked fry.

In commercial aquaculture, the common loon causes significant economic damage by predating on fingerlings and juvenile fish. As these birds are efficient hunters, they can decimate a large percentage of stock in a relatively short period, particularly during the initial stocking phases. This leads to reduced biomass production and direct loss of investment in hatchery operations.

The damage caused by these birds is not limited to fish consumption. The constant presence of a predator causes significant stress to the fish population, resulting in decreased feeding activity and slower growth rates. Furthermore, loons may act as vectors for the transmission of various aquatic parasites or diseases between different ponds, further compromising the sanitary quality of the aquaculture system.

Integrated management strategies are necessary to mitigate the impact of the common loon on aquaculture facilities:

• Exclusion systems, such as overhead netting, are the most effective method for smaller, high-value nursery ponds.
• Acoustic deterrents that use predator calls to mimic threats and discourage birds from landing.
• Visual deterrents including reflective tapes, decoys, and strobe lights to create an unwelcoming environment.
• Habitat modification, including clearing vegetation along pond banks to reduce nesting opportunities for the birds.