Many populations of native steelhead trout in the Pacific Northwest US are threatened by disease, habitat loss, poor ocean survival, and genetic mixing with hatchery steelhead trout. Steelhead are a form of rainbow trout that migrate out to the ocean when young, and return to spawn, just like many salmon species. Hatchery-produced steelhead have lower survival in the wild because they become less afraid of predators; one of the resulting concerns is that interbreeding between hatchery and wild steelhead will erode the natural fitness of wild steelhead and hinder their recovery. 

Salmon returning to streams and lakes in Southeast Alaska are affected greatly by water temperatures both in winter and summer, and these temperatures are projected to increase given climate warming. Changes in water temperature affects the time it takes for salmon eggs to hatch and emerge, and the timing of salmon returning to each stream, as they seek to avoid dangerous peak stream temperatures. 

Interviews with 25 Inuit polar bear hunters in East Greenland provide a wealth of knowledge about changes in sea ice, warming, and polar bear distribution and trends. Evidence of climate change reported by the hunters included receding glaciers, higher temperatures, and the loss of sea ice. These changes made it harder for them to access sea ice, because dog sledges are no longer safe given wide patches of open water during months when sea ice used to be safe to travel over. 

Ocean acidification is the a suite of chemical reactions in the ocean caused by climate change that include higher levels of carbon dioxide and lower pH levels, caused by human emissions of carbon dioxide into the atmosphere. A new model now projects the impacts of ocean acidification from California to Washington, finding that species declined most in the southern regions, but economic impacts were highest in the northern regions. 

Some types of aquaculture-raised (farmed) fish and crustaceans rely on wild-caught fish as feed for omega-3 fatty acids and micronutrients. But with the rapid and continuing rise of aquaculture, and the natural limits to the supply of forage fish (anchovies, herring, and their relatives), eventually this supply of feed will be exhausted. A new study now highlights ways in which the supply of fish food can be eked out further by: (1) reducing the proportion of feed that is based on wild-caught fish and switching to crop-based diets such as soy; (2) increasing catches of forage fish to maximum sustainable levels, adding 30% more catch compared to 2012 levels; (3) eliminating the addition of wild-caught feed to non-carnivorous farmed species; (4) eliminating forage fish from pig and poultry diets; (5) using trimmings from the processing of other wild-caught species as food for farmed fish; and (6) increasing the efficiency of farmed fish production. 

Polar bears rely heavily on sea ice to search for prey, and in Baffin Bay between Canada and Greenland, such ice-associated searching halts during ice-free months. However, since 1979, higher temperatures have resulted in the ice-free season in this region increasing by 12 days per decade in this region. Now, satellite-tags placed on 81 polar bears in Baffin Bay reveal that polar bears greatly reduced the area in which they forage between 1991-95 and 2009-15, by as much as 70% in summer. 

A new study examines the overall environmental effects of eating different kinds of foods, comparing the energy required, greenhouse-gas emissions produced, release of nutrients harming water quality, and compounds causing acidification; and also looking at freshwater demands, and the use of pesticides and antibiotics. The review examined 148 life cycle analysis documents that cover the complete impacts of each food production source from start to finish. 

A new genetic analysis of Pacific cod has identified more than 6000 genetic markers, and demonstrates that their DNA diverges steadily with distance, which is termed “isolation by distance”. The results allow researchers to identify where Pacific cod are caught to within 220 km, even if the unknown Pacific cod come from a population that was not included in the original analysis. 

Sablefish is a highly valuable wild-caught fish on the west coast of North America that can also be easily cultured in aquaculture facilities. However, when reared at high densities in pens, disease outbreaks can be a problem, especially a bacteria that causes a disease named furunculosis. A new study examines the effectiveness of a vaccine developed by the company AquaTactics, to test whether this vaccine protects against furunculosis when injected into fish, or when the fish are immersed for one minute in a vaccine solution. 

Many scientific fields require long-term monitoring of regions using sensors that are fixed in place, such as weather stations or acoustic stations that monitor fish abundance. These sensors produce high-quality streams of data in time, but typically over a small proportion of the study area. A long-standing sampling design problem is calculating how many sensors should be deployed to accurately estimate amounts of monitored variables such as rainfall.