Rákok

Rákok are crayfish, a group of freshwater crustaceans belonging to the infraorder Astacidea within the order Decapoda. They comprise three main families: Astacidae, Cambaridae and Parastacidae, with numerous genera and species. Rákok are widely distributed in temperate regions and inhabit streams, rivers, lakes and ponds. They typically have a segmented body with a hard carapace and two large claws (chelae) on the first pair of legs, which they use for defense and feeding; the tail fan and walking legs aid in swimming and maneuvering.

Ecology and biology: rákok are omnivorous and opportunistic feeders, consuming plant matter, detritus, invertebrates and carrion. They are mostly nocturnal and some species burrow or aestivate during dry periods. They play a role in aquatic ecosystems by influencing vegetation structure, sediment turnover and nutrient cycling. Reproduction involves mating after molting, with females carrying eggs under the abdomen on swimmerets for several weeks; juveniles hatch and undergo several molts before reaching maturity.

Distribution and human use: rákok occur naturally in Europe, North America, Australia and parts of the southern hemisphere, depending on species. They are valued as a food source in many cultures and are kept in aquaculture and garden ponds. In many regions, crayfish fisheries are managed to prevent overharvesting and to protect native populations.

Threats and conservation: habitat destruction, water pollution and the introduction of non-native crayfish can threaten native rákok populations. Crayfish plague, caused by the oomycete Aphanomyces astaci, poses a particular risk to susceptible native species in some areas. Management often focuses on habitat protection, monitoring and controlling invasive species.