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Like Temperature, Egg Size, Oxygen Levels Also Critical for Salmon

https://swfsc.noaa.gov
Water flowing over a gravel riffle in the Sacramento River

New federally funded research shows water temperatures, egg size and oxygen levels are all critical for baby salmon.

Credit https://swfsc.noaa.gov
Winter-run Chinook salmon embryos (like the ones shown above) hatch from their egg capsules after more than a month-long development period buried in gravel nests.

Scientists were trying to pin down why salmon eggs raised at the same temperature in a laboratory had much higher survival rates than those hatched in the Sacramento River. According to the author, existing scientific models have shown that water temperatures in the river haven’t been high enough to kill young salmon since at least 1996. Yet scientists have also blamed warm river temperatures for killing more than three quarters of all young salmon in certain years. 

Scientists from the National Oceanic and Atmospheric Administration and the University of California at Santa Cruz discovered that size matters. Larger salmon eggs, it turns out, need more oxygen than smaller ones. That oxygen is delivered by water. The more water, the faster it moves. The faster it moves, the more oxygen is delivered.

Winter-run Chinook, it turns out, face a special challenge. They evolved to lay larger eggs to take advantage of colder waters of the Sacramento’s headwaters. Those areas, however, are inaccessible due to Shasta Dam.

Results of the study were published in the journal Ecology Letters.