Sockeye salmon catches often add up to half of the value of Alaska's total salmon fishery, and the so-called reds dominate the season's early fisheries starting in mid-May.

But sockeye catches so far range from record-setting highs at Bristol Bay to record lows nearly everywhere else.

For example, the Copper River sockeye harvest of just 26,000 is the lowest in 50 years. At Kodiak, just 212,000 sockeyes were taken through July 6, making it the weakest harvest in 38 years. Sockeye fishing at Yakutat has been closed due to the lowest returns in 50 years; likewise, fishermen at Chignik also have yet to see an opener.

Sockeye harvest levels at Cook Inlet and the Alaska Peninsula also are running well below average.

Fishery scientists suspect the downturns are due to the warmest sea-surface temperatures ever recorded running from 2014-2016, which likely depleted food sources before the sockeyes returned from the ocean this year as adults.

At the other extreme, the early sockeye run at Bristol Bay set records for some of the best catches ever. By July 6, fishermen at the Nushagak district had four harvests that topped one million reds per day, including a record 1.77 million fish taken on July 1.

Salmon trackers

Anyone can easily track Alaska's daily and weekly salmon catches with two free sources.

The Alaska Deptartment of Fish and Game's "Blue Sheet" updates salmon catches daily for every Alaska region from May through September. Through June 6 it showed that just over 22.2 million salmon had been taken so far — 16.5 million sockeyes, nearly 5 million chums, 91,000 chinook, 8,000 coho and 636,000 pink salmon.

ADF&G also provides a weekly in-season summary and catch tally by region. The harvests are graphed to show the progression of catches for the fishing season, with comparisons to the previous year and five-year averages. The timing charts can be customized by region, area, district or fishery and salmon species.

Another Alaska salmon source is the harvest summary done weekly by the McDowell Group for the Alaska Seafood Marketing Institute. It also shows catches by species and region with comparisons to the previous year's catch.

As of July 5 the summary showed that the pace of Alaska's salmon harvest was about 25 percent below the same time last year, an improvement from the previous week. Sign up for the summary by contacting Garret Evridge at garrette@mcdowellgroup.net.

Fish watch

Lots of fishing is going on besides salmon all summer across Alaska.

Cod, pollock, flounders and other whitefish are being hauled in from the Gulf of Alaska and Bering Sea.

The Dungeness crab fishery in Southeast is ongoing, with a summer harvest pegged at 2.25 million pounds.

A red king crab fishery is underway at Norton Sound with a limit of 290,282 pounds.

Golden king crab along the Aleutians opens Aug. 1 with a 6.3 million pound harvest.

Lingcod fisheries continue in portions of Prince William Sound and the Panhandle. Shrimp fisheries also are ongoing in both regions.

Scallop fisheries opened across Alaska on July 1 with a total take of 265,000 pounds of shucked meats.

The Dutch Harbor food and bait herring fishery opened July 1 with a catch quota set at 1,810 tons.

For halibut, 47 percent of Alaska's 17-million-pound catch has been taken so far with less than 9 million pounds remaining. For sablefish, about 15 million pounds are left in the nearly 26 million pound quota. Both fisheries run through Nov. 7.

In other fish news

The Alaska Board of Fisheries will hold a special meeting on July 17 in Anchorage to address several emergency management petitions, including hatchery production in Prince William Sound, sockeye failures at Chignik, Kodiak and the Alaska Peninsula and gillnet chum fishing on the Yukon.

Finally, President Donald Trump's trade war with Alaska's top seafood buyer, China, went into effect on July 6.

A 25 percent tariff will be imposed on Chinese imports of Alaska salmon, pollock, cod, herring, flatfish, Dungeness crab, sablefish, geoduck clams, mackerel and more. That's on top of existing tariffs ranging from 5 to 15 percent.

China purchased 54 percent of Alaska's seafood exports last year, valued at $1.3 billion.

Ferry science

The state ferry Columbia now has more than six months of data since it began testing the waters for acidity last fall from Southeast Alaska across British Columbia to Bellingham, Washington.

The weekly testing is part of an unprecedented Alaska-Canada collaboration to learn how increasing ocean acidity affects regional fisheries.

"Nowhere in the world is there a ferry system that's outfitted with CO2 sensors running that scale of a transit. It is really exciting," said Wiley Evans, the technical lead for Canada's Hakai Institute who rigged the 418-foot ferry to suck up water samples while it is underway.

The samples are measured automatically for oxygen, temperature, salinity and carbon dioxide which indicates the acidity of the water.

"We're trying to understand the time and space patterns in surface ocean CO2 chemistry near shore. In this area, it's extremely data-poor, Evans said."

The project aims to discover how ocean acidity levels change seasonally, and where there are hot spots or refuges from corrosive waters.

Off-kilter ocean chemistry makes it hard for marine creatures — and the micro-organisms they feed on — to form shells, among other things. The ferry information can help scientists estimate the rate at which acidification is occurring in near-shore waters.

Preliminary ferry data point to an extremely variable seascape in which the surface water is primarily corrosive in fall and winter, representing the most vulnerable time of year for species sensitive to ocean acidity.

When spring arrives, two primary factors create a change: the phytoplankton bloom removes CO2 from the water through photosynthesis, and the water gets warmer, making conditions more favorable for shell production.