Instead, watersheds need a good mix of steep, cold-running streams and slower, meandering streams of warmer water to keep options open for salmon adapted to reproduce better in one setting than the other, new research shows.
Preserving that sort of varied landscape serves not just salmon, it provides an all-summer buffet that brown bears, gulls and other animals need to sustain themselves the rest of the year.
"In any one stream, salmon might spawn for two to four weeks," said Peter Lisi, a University of Washington doctoral student in aquatic and fishery sciences, who studies the Wood River watershed in southwest Alaska.
"Animals like coastal brown bears and Glaucus-winged gulls gorge themselves at one stream for a few weeks and then just move to another stream that might have water temperatures a few degrees warmer and therefore support salmon populations that spawn at a later time," he said. "It's easy for animals to move when such streams are as little as a mile or two apart."
A whole network of streams, some colder and some warmer, provides what Lisi and Daniel Schindler, UW professor of aquatic and fishery sciences, call "hydrological diversity." Such diversity more than triples the time predators have access to salmon in a summer, from just a few weeks to more than three months in the watershed studied.
The researchers' paper on landscape attributes that influence spawn times will be presented Aug. 8 in Portland, Ore., during the Ecological Society of America’s annual meeting.
"Both Glaucus-winged gulls and brown bears have very short growing seasons at high latitudes. Salmon are a key resource that allows these species to fatten up and achieve the necessary annual growth in this short period of time," Schindler said. "A complex landscape results in streams of differing temperature so salmon populations don't spawn at the same time. Predators and scavengers have a much longer window of accessibility."
"We knew that salmon are an important seasonal resource for lots of predators and consumers. However, there is little appreciation for the importance of biological diversity within salmon for these consumers."
The response of salmon to hydrologic diversity is what makes stocks viable over time and will probably make them better able to respond to climate change, Lisi said. Instead of focusing narrowly on flow regimes or trying to decide which individual streams and rivers to protect, a better goal would be to protect a wide range of hydrologic conditions, the co-authors said.
"Biological diversity within salmon stocks has important benefits to terrestrial ecosystems," Schindler said. "This scale of variation in hydrology, geomorphology and biological diversity is often swept under the rug and dismissed as unimportant in activities such as river restoration, projections of climate impacts and fishery management."
The paper, part of a session on linkages between aquatic and terrestrial systems, also describes how biological diversity in returning salmon are linked to the pollination of a flowering plant, something no other group has described.
Populations of kneeling angelica, 3-to-6-foot plants loaded with clusters of tiny white blossoms, don't all bloom at the same time, even though sun and weather conditions might be uniform across a watershed. Instead, these streamside plants have evolved to bloom approximately 10 days after salmon typically arrive at a particular stream.
It takes about that long for salmon to start to die, many of which are killed by bears or die naturally after spawning. Blowflies lay eggs on the carcasses and the result is a population boom of maggots to take advantage of all the dead salmon. Those maggots emerge as adult blowflies the next summer just in time for the salmon run. Before laying their eggs, the blowflies swarm kneeling angelica flowers to feed on nectar, spreading pollen at the same time.
Previous research has looked at direct connections to plants, such as roots taking up nutrients when salmon carcasses decay, Lisi said. This is an indirect consumer pathway.
"Kneeling angelica are among the last plants to bloom. It's fall, everything else is dying, most of the insects are gone but these plants hold out for the arrival of salmon," Lisi said.
The work is funded by the Gordon and Betty Moore Foundation, National Science Foundation and Western Alaska Landscape Conservation Cooperative through the U.S. Fish and Wildlife Service.For more information:
Schindler, email@example.com, 907-842-2534Suggested websites
Sandra Hines | Newswise Science News
Road access for all would be costly, but not so much for the climate
10.07.2020 | Potsdam-Institut für Klimafolgenforschung
Innovative grilling technique improves air quality
01.07.2020 | Fraunhofer Institute for Building Physics IBP
Biochemists at Martin Luther University Halle-Wittenberg (MLU) have used a standard electron cryo-microscope to achieve surprisingly good images that are on par with those taken by far more sophisticated equipment. They have succeeded in determining the structure of ferritin almost at the atomic level. Their results were published in the journal "PLOS ONE".
Electron cryo-microscopy has become increasingly important in recent years, especially in shedding light on protein structures. The developers of the new...
New insight into the spin behavior in an exotic state of matter puts us closer to next-generation spintronic devices
Aside from the deep understanding of the natural world that quantum physics theory offers, scientists worldwide are working tirelessly to bring forth a...
Kiel physics team observed extremely fast electronic changes in real time in a special material class
In physics, they are currently the subject of intensive research; in electronics, they could enable completely new functions. So-called topological materials...
Solar cells based on perovskite compounds could soon make electricity generation from sunlight even more efficient and cheaper. The laboratory efficiency of these perovskite solar cells already exceeds that of the well-known silicon solar cells. An international team led by Stefan Weber from the Max Planck Institute for Polymer Research (MPI-P) in Mainz has found microscopic structures in perovskite crystals that can guide the charge transport in the solar cell. Clever alignment of these "electron highways" could make perovskite solar cells even more powerful.
Solar cells convert sunlight into electricity. During this process, the electrons of the material inside the cell absorb the energy of the light....
Empa researchers have succeeded in applying aerogels to microelectronics: Aerogels based on cellulose nanofibers can effectively shield electromagnetic radiation over a wide frequency range – and they are unrivalled in terms of weight.
Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic...
07.07.2020 | Event News
02.07.2020 | Event News
19.05.2020 | Event News
13.07.2020 | Physics and Astronomy
13.07.2020 | Life Sciences
13.07.2020 | Life Sciences