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The new fishing - purse seining really big "fish"
Last Post 05/13/2020 03:02 PM by 79 pmooney. 0 Replies.
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79pmooney

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05/13/2020 03:02 PM
Purse seining - an old form of fishing involving a mother vessel and small boat that tows a net hanging from a buoy-ed line out around a school of fish and back to the boat. A line around the bottom of the net is tightened, forming a "purse. The net is then pulled in toward the boat and lifted around a block hung on an yard, swung in and lowered onto the deck

Now this project is somewhat larger. No tightening around the bottom of the net, this fish doesn't dive. And it is a little too big to pick up. 125,000 tons perhaps. Instead it will be towed to port with two 1000'' ships.

The fish? A large Antarctic iceberg. To be towed to South Africa for drinking water. One of the world's best salvage experts is pursuing the idea. He lives in Cape Town so he is very familiar with the need (and getting a little tired of the 13 gallon/person ration that's been going on for years now), He's looking at towing a net of a new super rope, Kevlar-like, neutral buoyancy and not affected by cold, around a typical "tabular" iceberg (say 1000m X 500m X 250m deep, roughly rectangular and flat). The small boat will be an ocean going tug and the mother, two 1000' supertankers. The net will be 2 miles long and 60' deep, costing $25 million.

Once caught, the berg will be towed very slowly 1600 miles to Cape Town where it would provide the city 20% of its water for a year.

Crazy, crazy! There will be environmental impacts. (Probably far less than desalinization which creates a nice toxic brew.) But the real issues is our over-population of the planet and overuse of resources. As a sailor, naval architect and with my experience in fish boat design and stability, I find this truly fascinating.

I worked in the '90s for Marco shipyard in Seattle. The yard that developed the Power Block in the '50s, a hydraulic block to pull the heavy seine nets onboard. Power Blocks revolutionized purse seining. Previous to that, the nets were pulled in by hand. Large crews, very hard and dangerous work. Now, the industry was beyond purse seining when I worked for Marco. (Still done for sardines, tuna and salmon but demand for new boats was basically zero.) Our boats were trawlers (I have very mixed feelings there), long liners (cool boats) and Being Sea crabbers - vessels that worked in very nasty weather. Not the very high waves and winds of the Southern Ocean that this venture see, but still. I wrote the stability reports for the crabbers, that if adhered to, the boat should be coming home. Every winter a few didn't. In the small marine community of Seattle, we all heard. And I regularly prayed one of mine wouldn't make the news. I knew that the limits I spelled out on pots they could carry were not always adhered to. (One small ling crab pot - 8' X 8' X 6', 600 pounds before bait or crabs. 10X and 800 pound for a big one. 100 pots in good weather for a 100' crab boat. These would be stacked 4 deep or more on the big, flat aft deck of the boat to leave Dutch Harbor, Aleutian Islands. Alaska in January. If a storm came up, the netting and steel pipe of the pots would ice up, adding weight and windage up high. My reports spelled out far fewer pots for icing conditions. Fewer pots, less money for the year for the entire crew. You know how that goes.

I've seen icebergs from a sailboat. "Little" Arctic ones. I took a photo of one roughly the dimensions of the proposed above, only in feet, not meters. 1/30th the size! And still big enough to make our biggest aircraft carriers look like lightweight toys.. Also had one appear out of the fog when were sailing at speed dead ahead. Quite exciting! (Both were between the Labrador coast and north tip of Newfoundland.) We watched (and heard) a very tall one blow apart. It was a long ways off but it looked and sounded like an explosion. That trip we used iceberg debris for both cooler ice and for our drinks. (Those explosions are very useful. People pay $40/pint for 5000 year old water for their drinks. We rounded it up with buckets.)

I"m going to be watching how this plays out. Of course, now it is mostly money and politics.

Ben
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