Conserving arctic char
Arctic char come in many forms. This variety, as well as the other characteristics of char, present a number of conservation challenges.
Arctic char are long-lived, and in lake populations in northern areas, individuals may live over 30 years. Anadromous populations typically live 20 years or more, which is still long in comparison with other fishes. Arctic char reach sexual maturity as late as age 10, and in northern areas where productivity is low, may reproduce only every second year or even less frequently. Despite their long lives, the total reproductive output of arctic char, and thus their potential for sustainability, may be quite limited.
All arctic char spend the first few years of life in freshwater. After that, anadromous fish begin the process of transition to the marine environment, and eventually spend each summer feeding in the sea and each winter in freshwater. In theory, this adaptation allows the fish access to the productive ocean, and in fact anadromous char are larger at the same age than their freshwater counterparts and produce more and better quality eggs. For these reasons, anadromous char are typically regarded as more productive and thus capable of supporting greater levels of exploitation. This may not be true, however, especially as anadromous char require multiple habitats widely separated in space.
Spawning habitat is usually in short supply, and for char inhabiting rivers, overwintering habitat can be very limited. In northern Alaska and Canada, for example, spawning, rearing, and overwintering sites all correspond to the same perennial springs which feed the mountain rivers used by Dolly Varden char. Downstream of these areas, the rivers freeze to the bottom. Thus, the entire population of char must survive in relatively small volumes of water for eight or nine months each year. While lake populations of char likely lead relatively stable lives, anadromous fish are susceptible to disturbances in their various habitats. These factors combine to reduce the ability of char to withstand disturbances, whether from humans or from natural causes, as each successive impact takes a significant toll on the fish’s ability to survive and reproduce.
Char are important in the Arctic for their evolutionary significance as the only freshwater fish in high latitudes, for their ecological role as a top predator and intermediate prey, and for the extent of their use by humans. This last factor can greatly complicate conservation efforts because fishing for sea-run char may take individuals from several stocks without being able to determine relative levels of exploitation. Fishing in rivers and lakes can mean that the same stock is targeted more than once during the year. The importance of char to household, sport, and commercial uses makes effective management more complicated and, hence, more essential.
Our knowledge of char is still limited in relation to the great diversity of types of char, their population characteristics and dynamics, and the effects of fishing and of indirect impacts such as pollution and climate change. To conserve char effectively, more research is needed in these areas, and in particular, greater attention to the methods used in the management of such a complex species group.
James D. Reist, Fisheries and Oceans Canada, Winnipeg, Canada. From the CAFF publication, Arctic Flora and Fauna, www.caff.is