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Merit McCrea – WHEELHOUSE SCOOP

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Friday, February 22, 2019
The inside story: two tackle manufacturers
Wednesday, April 10, 2019
Errata


Tagging Giants
This past Saturday, the Balboa Yacht Club hosted the CCA-Cal Orange County Chapter for an evening with Dr. Barbara Block, perhaps the world’s leading authority on bluefin tuna, along with Paul Fruchbom of Stanford’s Hop­kins Marine Station, Monterey Bay. Block was there to present her lab’s latest findings with respect to Pacific bluefin tuna and her ongoing projects.

drbarbarablock
DR. BARBARA BLOCK, preeminent bluefin tuna expert, before the packed room at the Balboa Yacht Club bluefin seminar put on by the CCA-Cal Orange County Chapter this past Thursday.


The house was packed as some 140 attendees joined for an information-filled evening all about one of our favorite subjects, giant tuna. The event drew many of the best known in SoCal recreational fishing. CCA National Director of State Development Robert Taylor came all the way from Houston, Texas.


The evening started with a few words from CCA-Cal ED Wayne Kotow and CCA-Cal State Board and Hubbs SeaWorld Research Institute Chair Bill Shedd, President of AFTCO.


After an awesome buffet, the audience settled in for a hearty helping of info on bluefin migration, biology, life history, international fisheries and a side of comparative Atlantic bluefin data.


Block began her work on the big tunas, targeting the Atlantic sub-species. It was initially thought, rather conveniently, to be of two major stocks, a Western Atlantic and Eastern Atlantic population.


This was convenient because it meant the U.S. and European nations weren’t in competition, as each had their own fish. The Atlantic info is a great place to start because research is at least 10 years ahead of work on our North Pacific subspecies, amply illustrating the multi-national dynamic at play here too.


Currently there are thought to be 5 sub-stocks of the Atlantic tunas — like tribes or races or breeds — each with their own physical traits, each using the environment in different ways. Some parts of these sub-stock’s home ranges overlap while others don’t.


One group forages off the middle of our Atlantic seaboard, migrating east to forage off the European Coast and moving into the Mediterranean Sea to spawn. Another stock forages along the northern fringes of our Atlantic seaboard, extending into Canadian waters.


It’s this stock that spawns in the Gulf of Mexico and grows to be the largest of all — sometimes attaining weights of 1,500 pounds or more. While it’s simplest to think of these groups as always keeping to their own kind, there’s likely some level of intermixing like West Side Story, no matter how much disdain exists between different stocks.


For Atlantic bluefin fisheries, these findings meant all nations had to own up to the fact the fish they were seeing and hammering — whether off the Carolinas, or Great Brittan or Spain or Italy — were actually the same fish. No one could claim they had their own barrel of fish after Block’s and other’s tagging work amply illustrated they were all dipping from the same barrel.


At the same time, Nova Scotia’s giants were indeed a different breed. But Gulf of Mexico harvesters shared with Nova Scotia.


Here in the Pacific, we just don’t fully know yet how the Pacific bluefin gangs work out — Jets vs. Sharks, Crips and Bloods. We kind of know where bluefin are, and at least a couple of places where they spawn.


Just like all bluefin — warm blooded to some degree, the bigger ones prefer cooler waters, because they can, while smaller ones are somewhat restricted to areas where they can retreat to warmer surface waters as they need to.


Block had lots of slides showing both bluefin tagging and the results of tag data. They included day-by-day plots of bluefin positions on a map of the Pacific. There were also depth-by-time plots showing when fish did most of their deep diving.


Block pointed out that the fish we’re catching range from the tip of Baja, north to Washington seasonally, and offshore out to 400 miles, following food and water temperature. We’re seeing fish as old as 8 years, she believes. So far, Block’s hypothesis is that this tribe matures much later than the 3 to 5 years as previously thought.


She’s holding with the idea that the older fish run west to spawn in the Orient and stay — actually, mostly getting caught soon after.


So how does her lab get these data? There are two principal types of tags the lab has developed. One is an archival tag, which records things like light levels, time, temperature and pressure. The tag can keep recording until its battery runs out or memory is full, usually several years.


But that kind of tag is implanted internally and has a small external light sensor. The fish has to be caught, the tag noticed by someone and turned in to be read, with data downloaded and such.


In the Atlantic, Block’s people noticed there were certain dark areas they never got a tag returned from, despite there being a robust local bluefin fishery.


A second type of tag was developed — a “popup” archival tag, one which is anchored to the fish, but self releases after a set number of weeks or months, floats to the surface and uploads all its data via satellite.


A side note here: radio waves don’t go through water well at all, maybe just an inch or two, but that’s what carries data through air and space best for the least power. So far there’s no way to get real-time data from tuna.


Sometimes a combination of acoustic signals through water to a buoy and a satellite uplink from the buoy is used. However, the through water link is at max, a half kilometer. So, a network of buoys located no more than a kilometer apart would be required for real-time fish data.


This is great for seeing your favorite white shark show up at your favorite beach, yet not so practical for tracking a tuna swimming across the Pacific.


With these pop-up tags, in the Atlantic it was soon discovered that the dark areas were places where local fishermen most likely ****-canned any tags they found in fish they caught, rather than turning them in for the reward.


It’s been mostly archival tags deployed so far here in the Pacific, many of them, from the deck of the Shogun. Despite getting a scary-large fraction of a total of over 800 archival tags back — almost half, few have shown fish in the southernmost of the two known spawning areas — off Taiwan.


Block’s latest thrust is to include more satellite pop-up tags in the tagging mix, as was done in the Atlantic. But the big challenge is their cost at roughly $6,000 a copy.


This means not only coming up with the tags, but having to be highly selective as to the fish they get put on. The fish would have to be a big one, big enough to haul the tag around with little extra effort. It would have to have been landed fairly quickly, not battled to exhaustion, yet controllable on deck. The live landing, surgery and data taking would have to go off flawlessly.


As you might guess, it’s going to take a lot of financing and fishing. If you’re interested in further info on Block’s Tag-A-Giant program, there are opportunities to participate, even fish with her crew for those with plenty of experience in catching big bluefin. https://tagagiant.org/


Block wrapped up her pre­sentation with the preliminary results of one of her grad-student’s work, analyzing global open ocean industrial fishing fleet locations. Not surprisingly, the 200-mile radius off the U.S. was relatively fleet free. That’s our claimed EEZ or exclusive economic zone, which no other nation has access to.


Foreign fleets fishing here need permits (only a few Canadian albacore boats) or they might “go dark” on their AIS feed (Automated Identi­fication Service) and poach our waters.


Mapping the Pacific fishing fleets showed high concentrations of long-line and other fishing boats filling the open ocean outside our waters. No matter how hard we hold back our own fishermen and women in the name of conservation, when it comes to offshore critters, the real issue today is less how much fish we catch, but how much foreign-caught fish we import.


Go to www.marinetraffic.com to see the global fishing fleet in real-time. Fishing boats are orange. Check out the Far East and equatorial waters especially.


There are trans-national fisheries management organizations. U.S. fisheries managers work hard within them to compel sustainable harvest levels internationally. Yet, one of the biggest problems remains industrial level Illegal, Unreported and Unregulated or “IUU” fishing, as it’s called.


Into the weeds with science: The way daily fish location is calculated from daylight data is by measuring day length and timing.


By knowing dawn and dusk one can calculate midday — local noon. By knowing the global z time/GMT at local noon, one derives how far east or west the fish was (longitude), very accurately.


By knowing the day of the year and the day length, one can tell how far north or south the fish was (latitude). So you can see the kinds of errors that might be involved (overcast in the morning, etc).


Some error sources can be mitigated in modeling. For example, data shows depth, so light attenuation due to depth can be dealt with. Correlating satellite-observed SST patterns at the time with the SST recorded by the tag further refines latitude and provides a reasonable fix within 1 degree of the real location.


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Merit McCrea is saltwater editor for Western Outdoor News. A veteran Southern California party boat captain, he also works as a marine research scientist with the Love Lab at the University of California at Santa Barbara’s Marine Science Institute. He can be reached at: merit@wonews.com. 


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