Salmonidae

Many salmon species face a multitude of often devastating threats, including overfishing, habitat degradation (e.g., as a result of mining, timber cutting, agriculture, and urbanization), obstruction of migratory routes (e.g., by dams and hydroelectric plants), and interbreeding and other ecological interactions with hatchery-raised salmon (IUCN 2009).

In addition to these threats, salmon face additional challenges caused by rapid climate change (Battin et al. 2007; Crozier et al. 2008; IUCN 2009). For example, because the developmental rate of salmon is directly related to water temperature, it is possible that increasing temperatures could cause the more rapidly developing juveniles to enter the ocean before their planktonic food source has reached sufficiently high levels to sustain them (IUCN 2009). Increased water temperatures could cause other problems as well. Areas of particularly warm freshwater can present a thermal barrier to migrating salmon that then requires additional energy to navigate around. Such barriers can also delay or even prevent spawning. As air temperatures warm, much of the snow that feeds the river systems is expected to melt earlier. In many cases snow is predicted to be replaced by rain. This will lead to a reduction in the summer flows of many rivers, coupled with an increase in freshwater inputs during the winter. A reduction in summer flow levels will serve to increase water temperatures further and is likely to reduce the overall habitat available to salmon. Increased winter flows are likely to scour the river beds, disturbing nests and causing physical damage to both salmon eggs and juveniles. Coupled with an increase in freshwater inputs is an increase in the sedimentation of river and stream beds. Such sedimentation is likely to reduce the amount of gravel substrate available for spawning and to smother both eggs and juveniles (IUCN 2009).

Because salmon inhabit diverse habitats, and a single species may live in both freshwater and marine habitats during different parts of its life history, the impacts of climate change may be very complex and highly dependent on both the particular species and local geography and ecology. Predicting the specific effects of climate change on salmon in their marine environment is especially difficult as a consequence of our limited knowledge of the marine habits of salmon, combined with uncertainties about how marine habitats will be affected by climate change.

Some salmon populations at higher latitudes may actually benefit from warmer temperatures through increased productivity. It is possible that a warmer climate could make new spawning habitats available, as has been observed in parts of Alaska. Rapid climate change is likely to lead to unexpected consequences and shifts in ecosystems and fisheries, and humans will need to be prepared to adapt to these new conditions (IUCN 2009). Some evolutionary response on the part of salmon to changing environmental conditions is to be expected, but these environmental changes might produce conflicting selection pressures in different life stages, which will interact with plastic (i.e., nongenetic) changes in complex ways that are very challenging to predict (Crozier et al. 2008).

Distribution: Northern Hemisphere, but widely introduced in cold waters for sports and aquaculture. Many are anadromous, spending part of their life at sea, but returning to freshwater where all species spawn in a gravel bed in rivers or streams; most fish die after spawning. Small cycloid scales. Gill membranes reaching far forward, detached from isthmus. Axillary process on pelvics. Last three vertebrae directed upward. No spines. Adipose fin present. Attains 1.5 m (maybe 2 m) maximum length. Highly valuable in sport and commercial fisheries. There is disagreement about the status of some species and genera.

Animal / pathogen
colony of Saprolegnia parasitica infects epidermis of Salmonidae

Salmonidae (trout) preys on:
Asellus
Valvata
herb
Chironomidae
Daphnia
fry
Penaeidae
Mugilidae
Actinopterygii
zooplankton
detritivore
Percidae

Based on studies in:
Scotland (Lake or pond)
Scotland, Loch Leven (Lake or pond)
USA: Florida (Estuarine)

This list may not be complete but is based on published studies.