Salmon survive best when the water is cooler along the coast and warmer farther out. Colder La Ni帽a conditions have also led to higher salmon counts. Right now, that鈥檚 exactly what鈥檚 happening. But things will likely change over the summer.
鈥淭he next few months look pretty good. However, things are expected to change. A lot of the warm water we鈥檝e seen the past couple of years is not gone completely. It鈥檚 just not at the surface,鈥� says Brian Burke, a research fisheries biologist with NOAA Fisheries.
The mixed messages the ocean is sending for salmon survival could be frustrating for fisheries managers, who are trying to figure out how many fish will return to fresh waters.
Warm water may come close to the coastline this July through September, which spells trouble for salmon in the ocean.
Salmon Challenges
Burke outlined some of the challenges salmon may face in the ocean at .
More good news for salmon: they had a lot of good food to eat in the ocean in 2020. Small aquatic crustaceans, known as copepods, were abundant last year. Copepods are often used as an indicator of salmon survival in the ocean. For salmon, the northern species of copepods are what Burke calls 鈥渃heeseburgers of the sea.鈥�
鈥淭he good news is that 2020 was actually really good, from the copepod perspective,鈥� he says. 鈥淚t was one of the highest biomass anomalies of northern (copepod) species that we鈥檝e seen.鈥�
The southern copepods, which often thrive in warm waters, are smaller and not as good a food source, according to Burke.
He says there鈥檚 a huge data gap in understanding what happens to salmon in the ocean: a lack of information on predators. From birds to marine mammals 鈥� like sea lions 鈥� to other fish, scientists don鈥檛 know what the biggest threat to salmon survival might be.
鈥淧redators and prey in the ocean are critical, particularly predators. I think it鈥檚 the number one thing we should be (studying) right now,鈥� Burke says.
Long-term forecasts are more dismal. But it鈥檚 not all doom and gloom. There are some steps fisheries managers should take to help salmon as conditions become harsher.
Burke says there will be a lot more warming trends over the next 30 years. That means more much like The Blob, which warmed a large amount of water from 2014 to 2016. He says predictions show a "dramatic increase in the probability and severity of marine heat waves."
shows climate change could threaten salmon throughout their lives. Those effects 鈥� mostly bad and a tiny bit good 鈥� could vary at different times.
For example, snowpack that melts more quickly could provide more cool water for rearing salmon. (That's not to say climate change is all good news for salmon inland. It definitely isn't.) The research suggests salmon are most sensitive to climate change in the ocean when their survival could be drastically imperiled.
鈥淲e鈥檙e expecting up to a 90% decline in the abundance (of salmon), just due to (the marine) stage,鈥� Burke says.
Ocean conditions are 鈥渟wamping鈥� a lot of the freshwater efforts put into saving salmon, he says.
鈥淭hese climate impacts are happening now, and they鈥檙e going to continue. This isn鈥檛 something that we can keep putting off. This isn鈥檛 a 40-, 50-years down-the-road problem. This is a problem right now,鈥� Burke says.
Climate change will bring a 鈥渧ery dramatic impact鈥� on the numbers of spawning salmon.
Snake River Basin
Looking at specific runs of wild spring-summer chinook in the Snake River basin, the numbers could drop off significantly. For example, the small numbers of fish in Camas Creek, east of Boise, quickly dip below 50 fish, which researchers have dubbed the 鈥渜uasi-extinction threshold.鈥�
Other runs that have more spawning fish right now have more of a buffer.
鈥淲e definitely don鈥檛 want fish going below that level for a couple years in a row,鈥� Burke says.
The research assumed a status quo in salmon management and looked at several different rates at which the climate could change, depending on how much heat-trapping emissions are released into the atmosphere.
鈥淭his isn鈥檛 what鈥檚 going to happen. It鈥檚 what could happen, if we don鈥檛 take further action,鈥� Burke says.
He says there are things that can 鈥� and should 鈥� be done now to help manage salmon survival.
What happens in different parts of a salmon鈥檚 life, can set them up for success in some of the more difficult stages.
For example, when fish grow well in an estuary, they can often survive better in the ocean. (That is, unless there are a lot of predators looking for fat fish.) So, he says, restoring and conserving estuary habitat and managing predators could be some of the ways management could help salmon survival in the ocean.
鈥淭he idea that there鈥檚 nothing we can do (to help salmon survive) in the ocean, is just not true. There are things. We need to clarify those things, certainly,鈥� Burke says. 鈥淲e need to develop those ideas further. But there are things we can do to improve marine survival.鈥�