Wednesday, July 18, 2007

Making Lemonade

Barb Block from the Shogun Expedition. We spent a few days hunting bluefin and scored some nice albacore fishing and a fantastic view of a blue whale mom and calf. We continue to have challenges getting bluefin to bite our live sardines. One reason may be because the bluefin are feeding on anchovy bait balls -- schools of anchovies driven to cluster by larger fish attacking them -- and getting them to switch to sardines is a challenge. A second reason may be that the fish were boat shy from the commercial fishing efforts in the region.

We decided to change our tactics. We headed to Ensenada, Mexico, to work with the ranchers at Maricultura del Norte, a spectacular bluefin ranch that catches wild bluefin and holds them in pens. We went down to the pens where in previous years the ranch helped our scientists release small bluefin tuna for our archival tagging study .

The ranch owners allowed us to approach a pen and “fish” from the stock. While it sounds easy to execute this “fish in the barrel” effort, it takes careful planning to catch a live bluefin and safely transfer the fish from the pens to the wells flowing with seawater on the Shogun. Captain Bruce and Sean were the fishers; they used a line and circle hook. They caught the fish and transferred each fish to a seawter sling. Luis Rodriguez and Ty Brandt from the Tuna Research and Conservation Center removed the hook and passed the fish to researchers Andy Seitz and Kurt Schaefer who motored in a Zodiac over to the Shogun swim step, where Dan and Jake lifted the fish to the deck of the shogun. We measured each fish and placed it in the “slammer” -- the back bait well on the Shogun. It was quite the operation.

We sampled several fish by placing small tissues in liquid nitrogen -- a quick way of super-cooling muscle samples -- for a new national NOAA-funded aquaculture project we have started in collaboration with the fish ranchers. We hope to develop several genomic markers for conditioning that will help establish the health and aerobic status of bluefin in captivity. All and all, it was a fun day with innovative techniques made possible by the ever versatile crew aboard the F/V Shogun. ABOARD THE F/V SHOGUN, off Ensenada, Mexico.

Sunday, July 15, 2007

Watchful or Busy? Bluefin Ignore Bait

Barb Block from the Shogun Expedition. Bluefin tuna must have good vision. After all, they warm their eyes with counter-current heat exchangers that keep the temperature of their retinas warmer than the water around them.

That's just one hypothesis as to why they won’t take our live baits, even when we present them on 20-lb fluorocarbon fishing line.

In the old days -- 1999 -- when we were collecting live tuna, our team would only use heavy gear for any size bluefin to reduce stress on the fish. Now, we use anything we can. Today, we worked the same waters we’ve pretty much been in the entire trip to find bluefin tuna na├»ve enough to bite our large sardine baits. We are pleased to tell you all that we did get 3 more bluefin in the 15-20 lb size range in our wells. But we felt a minor bit of frustration as every school of bluefin we approached either did not leave the anchovy bait ball it was on or barely noticed our sardine baits.

We know that the fish we are trying to collect -- young 2-year-old bluefin tuna -- were born in waters off Japan and swam across the Pacific this year to these waters. The archival tagging data shows that once they're here, most of these fish will ply our California Current waters for up to 3 to 4 years before they return to the western Pacific, presumably to spawn in the warm waters off southern Japan.

Some of the fish we’ve tracked, as small as 30 pounds, will swim back and forth across the Pacific and move to the Emperor Seamounts when production in the California Current is low. This confounds all our theories. For now, we’re focused on finding more bluefin of collecting size, and with the promise of good weather tomorrow, we hope to snatch a few more fish from the sea. I’m thinking smaller baits...and wondering how one rigs an anchovy. ABOARD THE F/V SHOGUN, Off San Diego, California.

Saturday, July 14, 2007

Tunabago

Barb Block from the Shogun Expedition. We decided to take the 8 bluefin tuna we caught yesteray to shore to load on the Monterey Bay Aquarium’s specially designed truck to send the tuna up to the Tuna Research and Conservation Center (TRCC). Because the small bluefin tuna are so valuable to our year-round research program, we need to move them quickly from the open sea to the lab. After the tuna arrive, our team will put these bluefin through their paces. These fish -- the “Lance Armstrongs of the sea” -- will reveal the secret of their athleticism to our students.

So, the Shogun carried its research load of fish to Scripps Institution of Oceanography’s MARFAC facility, where a specially built Tunabago truck was waiting to receive the bluefin. Andy Seitz, a former technician at the TRCC and now a researcher, got the nod to hop into the wells to remove the bluefin. Andy, who's living in Alaska these days, opted out of using a wet suit, and quickly removed the bluefin from the wells and placed them into the vinyl sling filled with seawater.

Each tuna was carefully lifted to the deck, where Mike Lipnick and I put into each fish pit tags that carry an identification number. The fish were quickly carried up to the truck and placed inside the seawater filled tank.

The fish looked super in the transport tank. The tank is kept at the cooler end of the bluefin tuna’s comfort zone. As they go in I love to see them light up as they swim around in the tank mouth’s gaping opening. It's a sign of their continuous need for oxygen.

The Tunabago drove to Monterey, and within nine hours of leaving the dock all 8 fish were reported to look great swimming in our tank at TRCC.

We were back fishing by noon and spent the day hunting for more bluefin. Sure enough, we found a school. Captain Norm’s excitement was palpable as he called out: “Get ready on the bait tank!”

Despite all the live sardines we threw overboard, the bluefin ignored everyone’s baited hooks and continued to feed on a large bait ball. We were all disappointed. This picky nature of the bluefin -- the difficulty of attracting them from their rich natural forage to our lines -- has frustrated us for years. It makes me appreciate how each fish we do catch and tag or capture is so valuable to our research efforts.

Hopefully, they’ll bite again tomorrow. ABOARD THE F/V SHOGUN, Off San Diego, California.

Friday, July 13, 2007

The Perfect-Size Bluefin


Barb Block from the Shogun Expedition. I'm happy to report that the Shogun, the Tuna Research and Conservation Center (TRCC) team, and the Monterey Bay Aquarium team have taken the jinx out of Friday, the 13th. We found the perfect bluefin tuna for collection.

Captain Norm put us on a school that was chowing on a bait ball of small sardines. The Shogun crew quickly tossed out a lot of live sardines. We all snapped into action and put out our 30- to 50-pound test lines with barbless circle hooks and voila! -- we had hook-ups on small bluefin. The swim step team (Ty and Luis, our TRCC techs) who had been drilling on albacore were quick to step into action. They rapidly placed live bluefin into the vinyl stretchers. Fish were coming in from both directions. Then the fish were rapidly placed into the hands of a deck team who guided the fish into the Shogun's wells, which are filled with aerated seawater. The fish were the perfect collection size of 18 to 25 pounds. We have 8 fish on board so far, and we’re continuing to look. We'll head into shore to unload tomorrow morning at the dock. ABOARD THE F/V SHOGUN, Off San Diego, California.

Thursday, July 12, 2007

Bluefin Tuna and the New Moon

Barb Block from the Shogun Expedition. The wind and seas came up a bit today as we searched around for baby bluefin tuna.

A small sport fishing boat from San Diego had reported catching a handful of the collectable-sized bluefin in waters just offshore so we worked the area all day long. We had a nice stop on a small school of albacore late in the day, but found no bluefin. We think that the weather may have pushed the fish down.

But it's the phase of the new moon and we now know, from the data retrieved from more than 180 satellite tags returned to us by anglers, that the bluefin are very responsive to the moon phases: they are up closer to the surface both day and night during the new moon. In fact, when they dive, they go down to the top of the thermocline -- that's the layer of water where the temperature rapidly decreases as you go deeper -- and spend most of the day foraging between the surface and the thermocline.

That's why we’re out right now. I think we have a higher chance of encounters with the bluefin during these new moon periods. I have high hopes for Friday the 13th. The photo is Stanford graduate student Dan Madigan on his first tuna fishing trip with the team. ABOARD THE F/V SHOGUN, Off San Diego, California.

Wednesday, July 11, 2007

First Day - Signs of Life


Our first day out at sea and conditions have looked very good. Just a few hours out of San Diego, and we've got great weather, the right water temperatures for Pacific bluefin tuna and waters rich in bait. Good signs of ocean life are everywhere -- sea lions, seabirds, spinner dolphins, and fish jumping. Today we found a large school of albacore tuna and fished through them for several hours. We practiced drilling the team through tag and release operations.

To tag the fish, we have to catch them on a line with a barbless circle hook, then move them onto the swim step where a team puts the fish in a sling and hands it up to a second team on board the vessel. We then move the fish into the surgery station where Kurt Schaefer or Barb Block places an archival tag into the tuna.

Over several expeditions, we’ve tagged over 386 Pacific bluefin. The two bluefin that were tagged today were 97 and 110 cm in length -- exactly what we hoped for. A smaller fish of 65 cm was loaded on board for our live bluefin collection. After today's start, we have high hopes for the next few days.

Tuesday, July 10, 2007

A Summer Tradition: Going after Pacific Bluefin

The team from the Tuna Research & Conservation Center of Stanford University and the Monterey Bay Aquarium headed out Tuesday on the F/V Shogun, a long-range sport fishing boat out of San Diego. We have a dual mission at sea - 1) to tag Pacific bluefin tuna and 2) to collect Pacific bluefin for our laboratory studies.

We’ve been implanting archival tags inside the body cavity of bluefin in the Pacific since 2002. To date we’ve placed approximately 400 archival tags in the Pacific. We’ll be working off San Diego, where the Pacific bluefin have just begun to show up.

Our laboratory studies focus on the aerobic performance of bluefin tuna. These fish, whose tags have shown they swim across the entire Pacific to Japan and back to California in a single year, are the Lance Armstrongs of the sea. They have a superior level of cardiac performance and, on this trip, we have 4 physiologists with us to study the tunas. If we succeed in collecting some for the trip up to the tuna center, we’ll be examining the capacity of the energetics of the bluefin tuna.

The photo above is from our previous trip, and we expect to take many more like this over the next 10 days.