European cisco

Adventure step • Meet the species

Overview

The European cisco is an elegant small whitefish belonging to the salmon family. With its streamlined body and silvery scales, it is perfectly adapted for life in the clear lakes of Northern Europe. The cisco typically reaches 15-25 cm in length, but in favorable conditions can grow up to 35 cm. The body is slender and elongated with a distinctly protruding lower jaw, meaning the lower jaw extends further than the upper jaw. This is an important identifying feature that distinguishes the cisco from other whitefish species. The back has a blue-green or gray-green tone while the sides and belly are silvery white. This fish has a fascinating life cycle closely linked to the seasonal rhythm of Nordic lakes. The cisco lives primarily in large, clear, and nutrient-poor lakes where it spends the summer months in the cool depths. It is a planktivore that filters small crustaceans and other microscopic organisms from the water with its closely-set gill rakers. During the bright summer nights, large schools of cisco can sometimes be seen hunting plankton at the surface, creating small rings on the water. Spawning is a dramatic spectacle that takes place in October-December when water temperatures have dropped to 2-6 degrees Celsius. Thousands of cisco gather over shallow water, often at sandbanks or shallow bays at depths of 1-10 meters. Females lay between 1,000 and 5,000 small eggs (about 1-2 mm in diameter) that stick to the bottom. Neither parent guards the eggs; instead, they are left to develop on their own through the cold winter. The fry hatch in April-May when the water begins to warm. The European cisco has great cultural and economic significance in the Nordic region. In Finland and northern Sweden, it has traditionally been an important food source, and smoked cisco remains a delicacy. The fish is also important as a food source for predatory fish such as pike, pikeperch, and burbot, as well as for terns and other fish-eating birds. Thanks to its abundant occurrence in many lakes, the cisco is a keystone species in Nordic freshwater ecosystems.