Fisheries Promotion Group, Higashidoori Village

Issue 6FISHERIES NEWSThe Seaside Flavor of Higashidoori

January-March 2018
Masu Salmon Fishing
Masu salmon is also calledspring salmon. The author
introduces its fishing.

Freshness Keeping ofMasu Salmon
The author shows how tokeep Masu salmon fresh ona fishing boat.

Sea Squirt Seed
Collection
Sea squirt seeds werecollected to distribute to afishermen’s group.

Kelp Reproduction
The author introduces thebiology and procedures for
producing kelp seedlings.

Keeping Squid FreshKeeping Squid fresh? Its
process and squid nervoussystem.

Masu Salmon Fishing ~What is “Hera-biki”?~
I accompanied “Hera-biki fishing” of Masu salmon this February. A Masu
salmon smolt travels to the Sea of Okhotsk in spring and grows there insummer. The fish grows big in the Sea of Okhotsk and migrates down to thewarm Tsugaru Strait and the Sea of Japan to spend winter. The Tsugaru Straitis known to be a good fishing spot of Masu salmon, and fishermen along thestrait catch the fish by a set-net, “Masu-nata” fishing or “Hera-biki” fishing.
The author introduces “Hera-biki” fishing in this article. “Hera-biki” fishing is
like flying a chain kite. A smooth and streamlined lip device “Hera” dives deep
into the ocean catching a water flow. Around 10 lures are attached to a mainline and 7 “Hera” devices. The 7 “Hera” devices deliver the lures to a target
depth where the salmon lives. The device “Hera” is surprisingly light, however,it dives to around 80m depth depending on the size. The lure is also light andattracts the fish by drifting in the water column. The fisherman hauled thefishing gear back and forth at his favorite spot, and waited for the bells on
the rod to ring. The fisherman stoped his boat and retrieved the gear slowly
onto the boat. We have to retrieve very carefully so we do not tangle thelines. This fishing needs a carefulness in every part of movements during
casting and retrieving. The author was too afraid to try it, and just stoodbehind him and took a picture of the fishing. It was his first day of Masu
salmon fishing in 2018. Although he said you could not expect any fortune
before we set out, we were very lucky to catch 17 fish. It was absolutely agood catch. The author wants to try it someday. It was the most interestingfishing method the author has ever seen. The author learned many things
about Masu salmon from him. After all the author realized that he dislikes
staying in a office all day long, and loves being out on the water.

Weird Sea Creature
A weird sea creature wascollected. What did it looklike??
Lures and “Hera”s1

Fisheries Promotion Group, Higashidoori Village

Issue 6Keeping Masu Salmon Fresh~Why is “Katsu-zime” important?~
Beside the fisherman who was fishing Masu salmon, the author
gathered pictures of the whole process of freshness keeping ofMasu salmon (Katsu-zime and blood draining) to make a freshness
keeping manual. Mr. Miyabe, researcher from Shimokita Food Reserch
Institute who is a bad sailor, demonstrated the process on the board
while showing his very pale face. After Masu salmon was brought onboard, we stored the fish in a tank until “Katsu-zime” was applied.
Then the Masu salmon was place on a cushion to prevent internal
bleeding during “Katsu-zime” process, and a sharpened knife
stabbed and cut a spinal cord and gills. The fish acted violently at
first and became immobile when the spinal cord was cut perfectly.
Then an artery at its tail was cut. Blood seeped from the tail. After“Katsu-zime” process was done properly, we placed the fish into
the ice seawater to drain blood. A recent study suggests that blood can be drained effectively in cold seawater
between 0-9 ℃. It took about 1.5 hours to drain blood perfectly. Therefore the researcher suggested that we canstore the fish in the tank until we come back from a set net fishing. But, for the “Masu-nata” and “Hera-biki”
fishing, we’d better take out the fish from the tank and store in an ice seawater around 0 ℃. We took out thefish from the tank after 1.5 hours of blood draining process and placed in an ice seawater to preserve the fisharound 0 ℃. The researcher recommended changing the bloody seawater once in a while or using flowing
seawater (< 9 ℃). We placed the fish in a box with a crashed ice partitioned by an urethan sheet to prevent thefish from touching with ice. Furthermore the fish was wrapped by a plastic sheet to keep the fish moist. The
researcher recommended removing internal organs and covering the whole body of fish with ice. If we process thefish in this manner, we can keep glittering scales, which beauty is valuable at the market, and bring out the
beautiful meat with the bright orange color which represents Masu salmon.
Cutting an artery at its tail.

Sea Squirt Seed Collection~What does Sea Squirt Seed look like?~
Sea squirt inhabits rocks in the ocean. It does not look like vertebrates likeus. However you may not believe it, it is a species of protochordates whichis said to be our ancestor. It has a vertebrae during its certain life stage
after hatching. A sea squirt spawns several times around the spring tidefrom the middle of November to the end of January. A sea squirt is ahermaphrodite and its gonad shows stripes with a white testis and greenish
Tadpole like larva
brown ovary. A sea squirt starts spawning around the spring tide in a tankin which water temperature has been kept around 10 ℃. It is mysteriousthat a sea squirt can recognize the spring tide even when it is reared in aVertebraetank. Sudden rise in water temperature also stimulates spawning. Its eggs
and sperms are released slowly or gushed out from its excurrent siphon.
Fertilized eggs drifting in the water column are collected in an egg
collection tank. The number of fertilized eggs are counted, and eggs are poured into a seed collection tank which holds acertain number of seedling ropes calculated from the number of eggs. Eggs undergo cleavage, and tadpole like larvae hatchout 2 days later. The tadpole like larvae have a vertebrae at its tail and swim or drift in the water column. Its head attaches
to the seedling rope and its tail part is absorbed and disappears within a few days. The larvae grow up on the rope andmetamorphose into tiny sea squirts. The baby sea squirts are reared in a tank for a month and moved into the ocean
afterwards. They come to look like a sea squirt as we see them at a supermarket in August.

Testis(white)
Ovary(Greenish brown)

Releasing eggs and sperms
from excurrent siphon

2Fisheries Promotion Group, Higashidoori Village

Issue 6

Biology of Kelp ~Seedling production~
Kelp has received a good reputation in its taste among edible seaweeds for a longtime, and it has been an important food source for sea urchin and abalone. Sincekelp has also been an important fisheries resource in this village, fishermen have
deployed a kelp culture set called “Tate-nawa” into the ocean to increase its
biomass. However people may not know much about its reproduction and seedproduction in a tank, therefore the author introduces these in this article fordeepening the understanding of kelp. From October, brown algae species including
kelp develop a chocolate brown patch called “sorus” which holds zoospores on thesurface of kelp. We collect the kelp which sorus developed widely, wash it with UVsterilized water and dry it in the shade for a few hours. After drying we wrap itwith paper and leave it for one night. Next morning we unwrap and soak the kelpin cold UV sterilized water. This process stimulates the kelp to release manyzoospores. After just an hour, the water turns light brown with zoospores. We pour a certain amount of this zoospore water
into a 30L tank holding UV sterilized water, and place seedling frames which have a string coiled neatly inside them.
Zoospores drift in the water and attach onto the string within one night. We start providing light and nutrient from the next
day of zoospore collection. We change the water, provide a certain amount of nutrients, and adjust the intensity of thelight and aeration weekly. The zoospores sprout and grow up on the string. The string turns into dark brown after a monthof culturing. We can see tiny kelp seedlings about 1 mm long under a microscope. The cultured kelp seedlings are wrappedaround a rope and thrown into the ocean to increase the biomass. It is said that a kelp stock is abundant in a year when
winter is very cold. We anticipate a good catch of kelp this year since we have had a very cold winter in 2018.

Sorus

ZoosporewaterSeedlingframes

Keeping Spear Squid Fresh ~What is “Ika-Kattyaki”??~

A keeping squid fresh workshop was held at Shiranuka Fishing Port on
January 31. Mr. Miyabe, as mentioned in a Masu salmon article,lectured a process to keep freshness of squid. You may be surprisedby hearing “Katsu-zime” of squid. A squid also has a sophisticatednervous system. Owing to the nervous system, it can change its color
instantaneously depending on surroundings. In this workshop, welearned “Katsu-zime”of squid by using a device called “Ika-kattyaki”
which was invented by an emeritus professor from the School ofFisheries Sciences, Hokkaido University from which the author
graduated. A squid has a pair of nerves called “giant axon” at its
joint between the head and the body. Once the nerves are cut by thedevice, its body turns transparent and immobile instantaneously
because the signal from brain which controls its body movement andcolor is shut down. By cutting the nerves, we can delay the decomposition of components which indicates freshness, andkeep the freshness of its body parts for longer periods. We can also keep the freshness of its head by cutting a pair ofnerves which extend toward each tentacle from brain. The color of the squid turns white and the freshness of squid
deteriorates faster when it touches ice and other squids directly in a box. Therefore it is recommended using a special tray
called “Ika tray”. The tray has 8-10 partitions depending on makers to place each squid in a partition. It is said that thefreshness of “Katsu-zime” squid is kept much longer in the tray than in a normal box. The author thinks that this techniquewill spread among fishermen once a market for “Katsu-zime” squid is established.

Cutting a nerve using“Ika-kattyaki”

Rest in a tankTurns transparent
instantaneously
Placing in a “Ika tray”

3Fisheries Promotion Group, Higashidoori Village

Issue 6Column “Weird Sea Creature, Pyrosomes”
The author received a picture of unknown sea creature that looks like atransparent sea cucumber which a fisherman in Noushi captured from a Greenlingtrap on February 2. It did look like a transparent sea cucumber at first sight,
however, it looked weird once I looked at the picture carefully. I forwarded thepicture of this weird sea creature to Asamushi Aquarium like before when thepure white sea cucumber was collected last October. The next morning, Mr.
Kushibiki at the aquarium replied to the author that this sea creature might be atype of Pyrosomes. The author went to touch it that morning, and it was rather
hard, as opposed to soft like a sea cucumber, and immobile. It was also light andseemed suspend in the water column. It became clear that it is a type ofplankton. Mr. Kushibiki who is very enthusiastic about sea creatures drove 2hours from snowy Aomori city to get this weird sea creature for his interest inrearing in the aquarium. He said that it was to be exhibited if it was still alive.
The author searched for the information about it, and found that this sea creature inhabits warm and tropical waters. A large numberof this sea creature were found and caused big trouble to fishing industries in the North Pacific last year. Unlike a white sea cucumber
collected last year, this creature seems to bring nothing but trouble. This sea cucumber like creature is not an individual but anassemblage of small individuals of pyrosomes. Some of the pyrosomes coexist with luminous bacteria, and they glow in the ocean. The
biology of the pyrosomes is still unknown. The author caught a glimpse of mysterious and fascinating underwater world of marineorganisms. He also hopes that this weird sea creature is exhibited at the aquarium to convey the mysterious and fascinating world ofmarine organisms. The author was fascinated by this mysterious marine organism.

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