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125 posts in Research

Fish that learn migration from their elders are more susceptible to fishing

Many fish species repeatedly migrate from feeding areas to spawning areas, and their migration pathways could be innate or learned. Two possible models are examined for learning of these migration pathways: the Diffusion Model holds that fish head to spawning site near where they themselves hatched; while the Go With the Old Fish Model involves young fish joining schools of older fish, and learning migration pathways from the older fish. 

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How to get great science out of citizen science

Citizen science is when members of the public directly work with scientists on a particular question or issue. Participation can range from a large number of single interactions to repeated and complex sampling that requires substantial training. A new paper now explains how to train participants, validate the collected data, and produce rigorous scientific papers from the outcomes. Key highlights include the need to increase the quality of data when designing a project, and to apply quality control afterwards to check for issues with the collected data. 

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Oysters and eelgrass help each other out under increasing carbon dioxide levels

Increasing human output of carbon dioxide results in higher temperatures and in ocean acidification—the lowering of ocean pH and other chemical changes. Oysters are threatened by ocean acidification, while eelgrass may benefit from the higher carbon dioxide levels in the water. A new laboratory study asks whether culturing Pacific oysters (Crassostrea gigas) together with eelgrass (Zostera marina) can help both out. 

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Intensive use of lake water affects freshwater food webs

Many lakes are important sources of water for agriculture and other purposes, while also supporting diverse ecosystems. In a new study, a comparison is made between the food webs of two natural lakes that were dammed early in the 20th century. The neighboring lakes are nearly identical except that one (Lake Keechelus) experiences rapid drawdown of water beginning early summer while the other (Lake Kachess) remains fuller and fluctuates less in water height during summer, but is lowered to a lesser extent beginning early fall. 

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LIME: a new model for assessing the status of data-poor fisheries

Formal stock assessments are conducted for many large and valuable fisheries, but these typically require reliable catch data, estimates of trends in fish numbers, and age data from caught fish. In data-poor fisheries, these kinds of data are not available, resulting in difficulties in assessing whether they are overfished or sustainably fished. Now a new model called LIME has been developed that accounts for variability in recruitment (the number of baby fish produced each year), and can assess status from samples of the lengths of fish in each year, together with whatever additional information is available. 

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Fish and chips: DNA analysis on a chip can separate endangered wild steelhead trout from hatchery steelhead trout

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. 

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Steepness, lakes, and forest cover are the main factors influencing salmon-stream temperatures

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. 

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Traditional knowledge about polar bears adds to climate change evidence in Greenland

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. 

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Predicted impacts of ocean acidification on fisheries on the U.S. west coast

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. 

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Stretching out supplies of fish food to aquaculture species

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. 

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