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California – Where Have All the Albacore Gone?

 

Computerized tags implanted into albacore tuna record the water temperature, depth, and internal temperature of the fish every 30 seconds. Southwest Fisheries Science Center photo courtesy of John Childers.

If an albacore swims more than 60 miles off the southern California coast and no one is looking for it, does that mean it's not there?

Good question. And one that no one will probably be answering anytime soon.

Especially California fishermen. Most of the central and Northern California fleet heads north to fish the productive waters off the Oregon and Washington coasts. Ironically, the fleet is not taking advantage of the abundant albacore.

"Fewer people are fishing for albacore this year," said Wayne Heikkila, of the Western Fishboat Owners Association. "Salmon prices are good and that's kept a lot of people from switching back to albacore."

Most of the north of California albacore action is taking place between Coos bay and the Columbia River, between 40 and 100 miles offshore, Heikkila continued.

As for California albacore, "They were really rare this summer," he said.

"There were some off of Eureka and Crescent City, but they were a smaller age class. California hasn't seen many albacore for seven or eight years. You have to go back to 2005 or 06, when there were some off of Monterey."

Even the scientists don't have an answer to the Mystery of the Missing California Albacore.

"The albacore didn't show up in California this year," said John Childers, resident expert in all things albacore at NOAA's Southwest Fisheries Science Center (SWFSC). "It's been ten years – there haven't been enough fish in quantities to supply commercial boats, at least in southern California.

"Central California gets a little better – there have been some good sport catches out of Monterey and Santa Cruz. There were a few schools, but not anything substantial enough to attract 30 or 40 boats."

There may not be one simple explanation.

Once upon a time, fishing for albacore was a predictable business. So predictable that albacore scientists T. Otsu and R.N. Oshida developed a model that gave a good description of the albacore's migrations along the US West Coast.

Otsu and Uchida's 1963 classic 'Model of the migration of albacore in the North Pacific Ocean', which developed a model of North Pacific albacore migration throughout their life cycle, is cited by John Childers and SWFSC colleagues Stephanie Snyder and Suzanne Kohin in a 2011 scientific report, 'Migration and behavior of juvenile North Pacific albacore'.

Childers and his colleagues are involved in an extensive albacore tagging and tracking program in an effort to divine the mysteries of the migrations and movements of albacore along the US pacific coast.

"Their model hypothesized that albacore from ages 2 to 5 migrate from the coast of Oregon (in October) and from the coast of Japan (in June) to an area centered at 40°N, 180°," says Childers' report, referring to Otsu and Oshida's work.

"According to their model, upon which they conclude that North Pacific albacore constitute a single stock, the fish stay in that offshore area until February or March and then migrate either to the coast of southern California or Baja California, Mexico (arriving in August), or to Japan (arriving in May).

"While their model has been widely accepted and has served as the basis for other related studies, some uncertainty remains about the migratory patterns and population structure of North Pacific albacore."

This model seemed to work as it jibed with the fishermens' observed behavior of the albacore.

"Historically, there have been periods of up to 25–30 years when the fishery was confined mostly to California waters, followed by periods of 15–20 years when the fishery shifted to waters principally centered off Oregon, Washington and British Columbia, Canada," state Childers and his colleagues in their report.

The first crack in Otsu and Oshida's model came in the 1970's when Childers and colleagues observe that "Tagging studies conducted by SWFSC and the industry research group AFRF indicated that two sub-stocks may exist along the west coast of North America based on limited mixing and different growth rates between albacore caught either north or south of 40º N."

So much for the single stock hypothesis. But that still does not explain why there are no albacore – at least not enough to make it worthwhile for the fleet to head for sunny southern California.

"It's probably a combination of environmental factors and food availability," says Childers. "Maybe the water temperatures are a little cooler off southern California and it's slightly warmer up north. The weather patterns this year seem to have changed."

Albacore are known for their schooling behavior. There are signs that may be changing a little as well.

"This year, the fish didn't school up into large schools late in the season and feed on the surface," said Childers, who just returned from an albacore tagging trip to Oregon and Washington. "Most fish were spitting up small squid and myctophids (lantern fish) from the mesopelagic layers. They would migrate up in the evening. This year we observed almost nothing on the surface – which was really strange. "

Water temperatures may have something to do with why Oregon and Washington are the hip places to hang out – as Childers and colleagues point out in their report.

"Several previous studies have linked the horizontal movements of albacore to oceanographic conditions," the report states. "By combining in situ oceanographic data with conventional tag data and catch data, it has been shown that young albacore have a preference for sea surface temperatures (SSTs) between 15º and 18ºC.

"Using more advanced remote sensing capabilities to link SST and ocean color data to concurrent albacore commercial fishery catch data, the areas with highest albacore catch off Central and Northern California were found to be related to coastal upwelling boundaries; high concentrations of albacore were found on the oceanic side of the upwelling boundaries in the warmer (>16ºC), blue (<0.3 mg/m3 chlorophyll) water ...

"In addition, the distribution of albacore in the North Pacific was found to be concentrated around the transition-zone chlorophyll front," Childers notes. "Albacore catch was greatest where chlorophyll levels were approximately 0.2 mg/m3. Higher catch rates have also been linked to areas of high eddy kinetic energy in the Central and Western North Pacific."

Perhaps those areas of high kinetic energy have moved a few hundred miles north. Or not.

The fact remains that no one really knows exactly why the albacore aren't hanging out in commercially valuable numbers in California – especially southern California waters – these days.

Maybe it's just a new twist on the traditional 25-year cycles. The reason could also be tied to the fact that there have been very few professional fishermen working California waters, especially southern California water, for albacore for almost a decade.

"Back in '68, there were about 2,300 individual boats going out," said Wayne Heikkila, whose association represents about 300 boat owners. "Now there are maybe 600 or 700. A lot of guys have retired, their kids don't want to follow in their footsteps – there are no new people getting into fishing. The number of boats keeps going down."

"The tonnage hasn't decreased so much over the last 40 years," he said. "The landings are still coming in between 10,000 and 20,000 tons. The boats are more efficient."

Infrastructure is probably another factor in the dearth of fishermen along the California coastline, says Heikkila. Many California ports don't have the facilities to handle the catch when the boats come in.

John Childers and his team at NOAA's Southwest Fisheries Science Center are working hard to solve the many migratory mysteries of the wandering albacore. The key to solving the mystery is more and better data about the albacore and its eating and migratory habits, says Childers.

Tagging is the way to gain the data. Childers uses computerized tags that he and his colleagues implant into the abdomens of the albacore. The tags are programmed to record the water temperature, depth, and internal temperature of the fish every 30 seconds. The tags also record light levels several times a day to give an idea of the fish's location.

The scientists go out late in the season on working boats to tag albacore. They have to cut the live fish open, implant the tag, then sew it back up and release the fish back in the water.

"Our recovery rate on the tags is about four or five percent," said Childers. "People catch the fish and find the tags. There is a reward for turning them in. Most of the ones we get back come in about a year after the fish were tagged."

Advances in electronic tagging technologies have enabled more detailed investigations into juvenile albacore behavior and their habitat use," states Childers' report. "The ability to track individual fish, both vertically and horizontally, over a broad range of oceanographic conditions provides greater insights into the relationship between the environment and their behaviors.

"Historically, the thermocline was thought to act as a barrier to the vertical distribution of juvenile albacore, thus confining their movements to the upper mixed layer ... however, acoustic tracking studies overturned this hypothesis.

"Observations of juvenile albacore diving behavior were combined with concurrent in-situ environmental measurements in the vicinity of tracked animals to demonstrate that juvenile albacore spend substantial time below the thermocline, particularly during the day.

"While acoustic tracking methods provide highly detailed information, the duration of tracks tends to be short and sample sizes are often too limited to make inferences about large-scale movement and habitat."

The tags used by Childers and his team are marvels of modern micro-electronics. One of the tags is the TDR-Mk9 archival tag. It is about 1.5 inches long and is designed to study seals, penguins, fish and other marine animals. This mini-micro tiny computer measures depth, temperature, and light-level, and also differentiates wet or dry conditions. It is suitable for both external attachment and internal implantation.

The tags have given the scientists in-depth looks and information at the albacore's deep diving and migratory behavior that would be impossible to gain without the tags. Archival tags were used to study the seasonal movements, migration patterns and vertical distribution of juvenile North Pacific albacore.

Between 2001 and 2006, archival tags were deployed in North Pacific albacore in two regions of the Northeast Pacific – off Northern Baja California, Mexico and Southern California – and off Washington and Oregon. Twenty archival-tagged fish were recovered with times at liberty ranging from 63 to 697 days.

The tag studies paid off from the beginning. One of the mysteries the tags shed some light upon was the diving habits of the albacore. The depth range of the tagged albacore exceeded 1,150 m – only nine of the 20 fish dove deeper than 400 m. With the exception of one fish that migrated to coastal Japan, dives to greater than 400 m were always brief; the maximum duration of any dive below 400 m in the eastern Pacific was 32 min. In general, albacore exhibited a diurnal diving pattern, spending more time near the surface at night than during the day.

The SWFRC team continues tagging albacore very late in the season, and gathering loads of data to crunch and analyze from the small percentage of fish they tag. Maps and charts and graphs are generated from that data that help Childers and his colleagues understand almost everything that can be understood about albacore.

Information from the tags is supplemented with even more data that Childers and his team gather from necropsies they perform on the albacore in their brand-spanking new laboratory at SWFRC headquarters in San Diego.

Computerized tags implanted into albacore tuna record the water temperature, depth, and internal temperature of the fish every 30 seconds. Southwest Fisheries Science Center photo courtesy of John Childers.

Otolithic microchemical analysis is a procedure that involves cutting the largest of the fish's tiny ear bones crosswise. This reveals the built-up rings – like a tree's rings – the chemical makeup of those rings tell the story of the waters the fish has lived. Otolithic analysis tells many tales of the albacore that would otherwise remain untold and unkown.

Except why not many albacore have been found off the coast of California – especially southern California – in recent years.

Childers hazards a guess – maybe it's not that there aren't any albacore – maybe it's because not enough boats are looking far enough out. "There could be a lot of fish outside the range of the smaller fishing boats – about 60 miles out.

"It's amazing how much we don't know about these fish. We have so much technology at our disposal – yet we are just scratching the surface.

 
 
 
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