Magic Baby Shower: the Observation of Releasing Red Craw Crab Zoea in Koajiro Forest 小網代の森

So, about my recent adventure with Koajiro Forest 小網代の森 in Miura Peninsula 三浦半島. Do you remember my post on July 15, 2016? I joyfully noticed I would go to see crabs to release their babies to the high tide sea. It was an annual “invitation only” occasion, the observation of baby crabs, aka zoea, released by their red craws crab mums (Chiromantes haematocheir) アカテガ二放仔観察会. Kanagawa Green Trust 公益法人かながわトラストみどり財団 and NPO Koajiro Activities Coordination Council NPO法人小網代野外活動調整会議 organize this event for 4 nights in July-August every year under full or new moon. Each night, only lucky 50 people are allowed to join. As the observation event is held in sea, even if a storm does not hit our region directly, when weather brings rough water to the shore of Koajiro Forest, the meeting is cancelled. We must apply to attend the event: only one application is accepted by a person per year. There always is a draw for tickets. Please calculate the probability of obtaining a ticket when the average number of application for a night is 200. By the way, August and September are storm months for Japan. On August 26, 2016, I regretfully reported in my post a super typhoon destroyed my hope to meet baby crabs of Koajiro Forest.　The event was called off. *Sigh*





Since 2016, I’ve annually cast lots for the gathering. Result? 1 lose, and 2 cancellations by typhoon (including 2016). This year, I changed the strategy. To maximize my odds for the ticket, (1) we must intentionally choose a week night expecting the number of application smaller than for weekends, and (2) the choice of the day must have the least probability for a typhoon to come to Japan, i.e. the earliest schedule of the event. This year, such day was August 1st, New Moon. Hurrrrrrrrrrrrrah! I hit a jack pot! Not only I get the permit, August 1st this year had a clean sky of 30°C with very calm wind from the Pacific Ocean. Koajiro Forest was damned hot and humid. But crabs were fine.







Aside from Japanese oak wilt attacks, the environment surrounding Koajiro Forest has been changed this summer. It seems to me the City of Miura 三浦市 has decided to make the Forest one of the major tourism attractions. The traffic light to the entrance of the Forest was named “Koajiro Forest Entrance” this July. On June 9 they opened an information desk near Hikihashi Entrance 引橋入口 of the Forest. Though the brochures and videos provided down there is in Japanese, city staff are stationed, and I hope they could provide some information in foreign languages. (Please try 😉) Bonus: the info desk is in the second floor of a large supermarket called Beisia Miura ベイシア三浦. You can procure your meal there before entering the Forest. For the observation event, we started from this information desk with mini-lecture about red craws crabs, zoea releasing, and meaning of this annual event in Koajiro Forest that is very near to the downtown Tokyo. We then entered the Forest before sunset, went down the board walk to Enoki Terrace えのきテラス. (The map of Koajiro Forest is here.) At low tide, we normally go to the tideland from the Terrace to see crabs dancing on the sand. Red craws crabs do not live there, or release their zoeas in this spot. In any case, with high tide, the dancing stage for crabs is under water. We were chaperoned to another beach. (I won’t tell you where. Please apply for the event!) There were reeds (Phragmites australis) almost to the edge of seashore. This was a place hidden from the hiking road. Casual visitors are not allowed to enter there. And so, red craws crabs can come safely every summer, meandering the jungle of reeds to the sea.





When you take a bus ride from
Misakiguchi Station 三崎口 of Keikyu Line 京急,
this #1 stop is the place you have to go first.





Second stop from Misakiguchi Station
is Hikihashi Bus Stop where





We can find Beisia Miura.
The info desk for Koajiro Forest resides in the second floor.





Mini-seminar before entering the Forest






Beisia Miura has a free parking.
As long as the store is open,
you can park your car here to visit Koajiro Forest.





Newly named cross road, “Koajiro Forest Entrance.”





There is this sign when we cross the traffic light.
Please simply go straight.





The road goes down to the forest, and





The entrance to Koajiro Forest, with a map.





As long as you follow the board walk,
you cannot lose your way.
And PLEASE DO NOT DEVIATE from the board walk.
Human stomping is the most damaging
for the ecosystem in a forest.
Thank you.





Getting darker …



Red craws crab has a very peculiar life cycle as sea crab. They don’t like sea actually. The adult crabs spend almost all their life in a forest that must be by the sea. They even do not bother if water near their nest is fresh. But, just for several nights of high summer under full or new moon, and so with high tide, female red craws crab enters sea and releases babies from her belly. If she lives near the highest altitude area of Koajiro Forest, the creature walks roughly 1.2km with babies on her stomach. It’s astonishing. After the delivery in sea, a matured female is ready to fertilize next batch of eggs. Male crabs are waiting, also on seashore, for the females coming back baby-less, to mate and to continue their DNA in the next generation. Fertile eggs hatch on the belly of a mum and baby crabs, called zoea, cling to the mum’s stomach. Mothers come to visit the seashore again, vibrate their body to release zoeas. Once they leave from mum’s protection, zoeas swim in the sea for a while, eating smaller planktons for about a month to grow as megalopa. When red craws crab babies are in zoea stage, they are only 0.5mm tall with 4 legs. A toddler megalopa is about 2mm tall with 8 legs like their parents, but without craw. Before winter comes, megalopas turn into grade-schooler tiny crabs of about 4mm. They return to the forest and spend 2 years to be adult red craws crabs, about 5cm wide. According to the lecture, a female red craws crab in Koajiro lets loose 30,000-40,000 zoeas per night. Typically, they let loose zoeas 3 times in summer, so that she is a mother of roughly 150,000 babies. Out of these zoeas, only 1 or 2 individuals reach to adulthood for procreation. In sea they are eaten by bigger creatures, like fishes. Young crabs in the forest are always in danger of being a meal for animals, of desiccation on land, and from tramping of merry human tourists. Life of a crab is not at all easy. *Sigh*





A dusk of Koajiro Bay with New Moon …


“Please do not turn on your flash light before the creature enters the sea. Never. Crabs run away with your light. Also, please keep quiet. Even a slight commotion can frighten them, and they will not come here tonight.” Mr. Ichisaki of Kanagawa Green Trust gave us orientation. At around 18:30 of August 1, we softly went into the sea knee-deep; carrying good boots is the MUST for this event. We then stand and wait quietly in water, facing to the bushes of reeds expanding along the water’s edge. We strained our eyes for crabs in dark seashore of Koajiro. I understood why a far-away typhoon can cancel the meeting. Calm waves came towards and went away from us. I could feel the sand beneath my foot was shifting. Mr. Ichisaki warned us if we were in poor shape we could easily feel sea-sickness while concentrating to find the creature. According to Yabe and Kishi (2001)* red craws crabs in Koajiro start to release their zoeas roughly 20 minutes before the sun-set, suddenly increase their activity at sun-set which reached to its max 30 minutes after the sundown, and end their discharge by 30 minutes after the peak. Surprisingly, it was exactly so on August 1, 2019. Mr. Ichisaki whispered behind us “The sun has set,” and “30 minutes past” as a cue. The sun set at 18:45. “Look! One came!” “Wow, she really vibrates her entire body …” “Is this whitish smoke around her sand or zoeas?” 30 minutes later, our small conversation became like “This side of a rock is very congested.” “Hmmmmm, she’s very quick, but this one is hesitating quite a while if she can do it.” “Difference in personality?” “For crabs?” “Hey, it seems to me there is a kind of route for crabs coming out from the reeds.” “Yeah, indeed ...” It was for less-than-90-minutes, but so amazing adventure. 2 years later, only 2 zoeas will come back here as parents. How long have these crabs kept their “tradition” of baby farewell in Koajiro Forest? It must be far longer than humans use to this place …


* Kazuhiro Yabe and Yuji Kishi. Time characteristics in zoea releasing of Chiromantes haematocheir in Koajiro. Keio University Hiyoshi Bulletin: Natural Science, 30, 75-82, 2001. 矢部和弘、岸由二。「小網代におけるアカテガ二の放仔活動の時間特性」慶應義塾大学日吉紀要・自然科学、30：75-82、2001。





To the beach!





We were facing toward reeds.





She’s an early riser.





Mr. Ichisaki with his stop watch.
The staff was stationed in case medical emergency.
So, even if you could not swim, rescuers were behind you.





She’s releasing her babies.





The place is getting congested …


A person from Koajiro Activities Coordination Council captured zoeas in his plastic wine glass and showed it to us. The cup looked like a magic potion of Harry Potter where tiny twinkling stars were dancing inside vivaciously. Cute. And marvelous. Hey kids, you get bigger, you promise? Releasing zoeas in the sea is very important moment for red craws crab as species to continue. Before, when there were lots of forests reaching to the seashore, Japan had many places for the crab to thrive. People also took their existence for granted even to allow the creature for nests inside their houses. In the 21st century Japan, the condition is different. There are not many natural forests along with tideland by sea for red craws crabs. The majority of such places were deforested and dried up for reclamation of whatever human purposes. In any case, when a bay is in the vicinity of megalopolis Tokyo, the environment of tidelands and forests has experienced serious pollution during industrialization of the nation. Many crabs went into extinction. Though, with some miracle, Koajiro Forest facing to Sagami Bay 相模湾 has survived with crabs. Now it’s receiving an attack of Japanese oak wilt. How can we treasure this wondrous ecosystem so near to the Megalopolis downtown?






Magic goblets of baby crabs in Koajiro


You can see You Tube video here about the observation event last year. I guess Green Trust will upload this year’s event eventually as well. By the way, till the end of September near Enoki Terrace we can enjoy flowers of Hemerocallis fulva L. var. littorea (Makino) M.Hotta . This flower was once ubiquitous along the beach near Tokyo, but now very rare because of theft and Tsunami on March 11, 2011. Corporate money and volunteers plant the seedlings and protect their habitat in Koajiro. The Trust and the Council will welcome both CSR money and volunteers to expand their activity. If you think you can help, please enquire at the Information desk in the 2nd floor of Beisia Miura.






This year’s first flowers of
Hemerocallis fulva L. var. littorea (Makino) M.Hotta in Koajiro.


If you find an environmental issues, like Japanese oak wilt, in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター


657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/


If you sighting is in the northern part of City of Yokohama, the office you may call is

Office for Northern Parks, City of Yokohama 環境創造局公園緑地部北部公園緑地事務所
Phone: 045-353-1166
FAX： 045-352-3086
ks-hokubukoen@city.yokohama.jp


Or for the southern part, the address to call is

Office for Southern Parks, City of Yokohama 環境創造局公園緑地部南部公園緑地事務所
Phone： 045-831-8484
FAX： 045-831-9389
ks-nambukoen@city.yokohama.jp

We Really thank you, for your kindness to rescue our forest!

Biohazard: Japanese Oak Wilt in Kanagawa Prefecture ナラ枯れ病

In March Last year, I attended a seminar held by researchers for Kanagawa Natural Environment Conservation Center. One of the topics was about Japanese oak wilt, presented by entomologists. Japanese oak wilt is disease of oak trees caused by Raffaelea quercivora virus carried by insects called Platypus quercivorus. So, the presentation was by entomologists. Platypus quercivorus is monogamous ambrosia beetle. Platypus quercivorus has fashionable pockets on their back where they nurture Raffaelea quercivora. The bugs dig lots of tunnels within trunks of oak trees and mate. The female lays their eggs inside their home-sweet-home tunnel. While they are busy in their home, their back rubs the surface of the tunnel, and infects the tree with the virus. Viruses multiply rapidly, which is a good thing for the insect family as their diet consists almost solely of the Raffaelea quercivora. Her eggs soon hatch and the baby worms eat voraciously the virus as their parents. Happy insect-family life. It is a death knell for mighty oaks.

Fashionable back of Platypus quercivorus

Platypus quercivorus is a beetle having a big family life. Their nest within an oak has several egg chambers for thousands of babies. i.e. The bug loves to dwell in a large, established oak. They need at least 30cm of diameter for raising their offspring. Once a parent beetle infests an oak with Raffaelea quercivora, the virus spreads within a body of the tree like cottony mold. It clogs vascular cambium of the oak rapidly, just like blood clots for heart attack, stroke, et al. Big tree has big cambium that can somehow keep a space for water and nutrition to flow if the amount of such liquid is not much, like during rainy season in Japan with moderate temperature. Though, when Japanese summer temperatures skyrocket to 35°C+ with 80%+ humidity, trees get thirsty at once and needs lots of fluid circulating within their body. If Raffaelea quercivora blocks such vital “endocrine system,” large oaks dehydrate and become starved to death rapidly. The researchers for the Centre warned us, “With severe infestation, very large and tall oaks can be blasted within few weeks, even if they looked healthy and vigorous with rich green leaves during rainy season. Japanese oak wilt attacks a tree drastically.”

This photo was taken in Koajiro Forest on August 1^st,
 a bit early to observe autumn leaves in Kanagawa Prefecture.
 The tree was blasted by oak wilt.

Worse, the story does not end here. Tiny worms of Platypus quercivorus with lots of tasty Raffaelea quercivora grow briskly and leave soon parents’ home in masse as adults. A young male immediately tries finding a mate and emits pheromone to attract partners of different DNA. It calls for another flock of Platypus quercivorus to this forest, and move to another oak to build their new nest in droves. Japanese oak wilt would spread rapidly within the forest when the place has lots of established trees of Quercus family, like Quercus serrata, and Quercus acutissima. It is said that the first massive infestation inJapan was recognized in the western part of archipelago around 1990. Since then, the disease devastated the forests in the western Japan, including Kyoto 京都. It now marches to the east.

Another example from Koajiro Forest

Basically, Platypus quercivorus is common in the jungle of South-East Asia, like Vietnam. They are comfortable in tropics. Japan may have had home for Platypus quercivorus for centuries, but within a limited area. It’s no more. The climate change with warmer Japanese winter and lots of rain during spring (like this year) may have provided ideal conditions for the bug to proceed further north. And/or, it would be the result of our neglect of forests. For Platypus quercivorus to have nests, they need large oak trees. When our ancestors used firewood as household energy to cook, to warm, to prepare bath, etc. they coppiced oak trees every 10-15 years to harvest their logs. It was rare to find an oak tree of 30cm of diameter in Japanese villages. In colder places, it could take 50 years for a tree to be that big. Yeah, maybe Platypus quercivorus has lived in Japan for ages, but it was not easy for them to find a suitable home to multiply. Now, no more. When fossil energy replaced firewood in the 1960s, traditional usage of forests was abandoned. An oak forgotten in a forest since the 1960s is nearing 60 years old in 2019. They are big and tall enough for Platypus quercivorus to make holes for thousands of baby worms. Platypus quercivorus of the 21st century Japan find themselves living in a gorgeous place to procreate. The stage is ready for a forest of oaks to die massively. As the disease is caused by virus, once a tree is infested hopelessly, we have to

1. Cut the tree and uproot it entirely to remove the infested body completely.
2. The logs, leaves, etc. must be moved from the site promptly to be incinerated perfectly.
3. The soil where the tree stood should be sanitized entirely.

You see? Once the affected area becomes large, it’s impossible for humans to control the situation.

Also in Koajiro on 1 August 2019, damned hot summer.

In 2017, the Office of Kanagawa Prefecture started to receive reports of Japanese oak wilt attacks in Hakone 箱根 and Miura Peninsula 三浦半島. And so, there was an urgent seminar topic in early 2018. Recently, I’ve been to Koajiro Forest 小網代の森 in Miura Peninsula, aghast to find extensive oak wilt. (More for my adventure in that Forest next week!) When I first posted my blog about Koajiro Forest (on July15, 2016), there was a talk to nominate such royally-loved forest for the 35th National Park of Japan. (It is said that the former Emperor and Empress 上皇 are planning to visit there again with their grandkids before long). I’m not sure if such ambition has any progress now with lots of died oak trees standing here and there. According to a person from the Koajiro Activities Coordination Council NPO法人小網代野外活動調整会議 who guided us at that time, the Prefecture hastily came to the forest and cut the infected trees along the board walk and brought out the logs, leaves, etc. for incineration. There remained rather sorry scenes very near for the visitors to observe. The typical evidence of disease was clear. The remained roots have lots of holes whose mouth is covered by wood powders. Peeled off barks of dying oaks are scattered without mercy. I presume the scientists are caught in a dilemma there. To stop infestation they have to sanitize the place. But Koajiro Forest is proud of its biodiversity and extensive natural underground water system within its tiny 70ha area. If humans chemically treat the soil, even if a bit, what would happen for the creatures, other than Platypus quercivorus, living in the entire forest? It’s a serious problem.

A killing field for oaks

Then, few days later, I found a Quercus acutissima with wood powder in none other than our be-loved Niiharu Citizen Forest 新治市民の森. EMERGENCY. I panicked. I consulted with my seniors of Niiharu Lovers, and called the City Office for my sighting. The chairman of Niiharu Lovers has officially requested the municipality to tackle the problem promptly … Compared with the remnants of oaks in Koajiro Forest, the Niiharu’s oak has, it seems to me, fewer holes, and powder. The crown of the tree was still alive at least a week ago. I hope, I really hope, we have yet time to stop the disease to spread …

Niiharu’s sick oak.
 But it still has green crown.
 We may well be able to save it …

A typical sign of infestation.
 Lots of holes at the bottom of large tree covered by frass.

If you find an environmental issues, like Japanese oak wilt, in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/


If you sighting is in the northern part of City of Yokohama, the office you may call is

Office for Northern Parks, City of Yokohama 環境創造局公園緑地部北部公園緑地事務所
Phone: 045-353-1166
FAX： 045-352-3086
ks-hokubukoen@city.yokohama.jp

Or for the southern part, the address to call is

Office for Southern Parks, City of Yokohama 環境創造局公園緑地部南部公園緑地事務所
Phone： 045-831-8484
FAX： 045-831-9389
ks-nambukoen@city.yokohama.jp

We Really thank you, for your kindness to rescue our forest!

Emergency II: Naomi’s PC is broken

Naomi’s 9 years old Dell Vostro has reached her final leg, and all the data for my unposted blog is currently frozen in her …

I hope I can recover it within a week …　😖

Meanwhile … please enjoy your happy summer in forests!

Best regards,😟

Naomi

Second baby swallows of the same nest this year!

Let’s be Samurai! Whetting sickles for forest volunteers

We forest volunteers have a rule for standard attire when we do forestry. It’s to minimize the risk of injury. Shoes should be sturdy enough, and preferably with protective toes and soles against falling objects on foots. Covering arms and legs is the MUST to protect limbs during the activity with saws et al. Leather hand gloves are indispensable as it can prevent the tools from slipping. And helmet. Forest can be a precarious place where broken twigs, boughs, etc. could fall down on our head unexpectedly. Safety helmet is literally a life-line for us forest volunteers. Caution: “It is highly recommended not to wear imported helmets in Japan.” Trade restriction? Oh, no. Euro-American made helmets often do not have a chin strap. It would be OK without it in a flat forest floor of continents. In contrast, during our activity, it’s so easy for us tumbling down precipitous hills of Japanese forests. Do you remember the episode of my injury last year? I dropped 3m below and broke my right wrist. If I was unlucky enough I would have broken my skull è death. At that time, my helmet was at least secured enough to cover my head. Thank God, honestly.

That hurts …

Because of this very aggressive (?) gear, once we put a waist belt dangling saws, scissors, and/or machete over this special costume, we feel a sort of elation. Hey, in the 21^st century Japan when can we legitimately enjoy our style with edged tools on our waist, just like samurai with swords? It is whispered that a person can change his/her personality once s/he carries saw in a forest. It could be a reason we are so fascinated by Jason, Friday the 13^th … (by the way, I don’t like that film.) Coming to the issues of swords of samurai, sharpness was decency for them even when they did not engage in a combat. To some extent, for us forest volunteers polish of our tools is beyond the etiquette. For one thing, dull edge of a saw is a recipe for severe injury. Besides, tackling forestry tasks with stupid devices is really a waste of energy (physical and mental) and time. So, taking care of our instrument is one of the most important things we have to do.

This,

and this.

Having said that, (1) our saws are often not that expensive, and (2) we do not have skill to whet saw. Confession. I’ve never sharpened my saw. After use, I simply clean my gear, and spray mineral oil to stop rusting. When time comes, I visit my nearby home center and bought a replacement, in less than 2000 yen ($20). Very interestingly, filing blades of motorized chainsaw is far easier. I’m doing it regularly. It has a guiding gage, easy to use sharpener, etc., you see? I’ve felt this situation somehow uneasy. So, one day, I attended a training session to learn “how to sharpen hand tools for forestry.” They did not tell us the way to file saw, but I’ve learned how to whet single edged sickles. I cannot declare I’m now an expert for this … but I have a kind of peace of mind thanks to this lesson. Here is what I’ve studied;

1. Before anything, preparation is necessary. DO wear gloves. Cotton work gloves with cleats are the best, as we work with water. Cotton gloves tighten our grip when wet, so that we can be prevented from injury by slipping a grindstone. Also, before start working, we have to submerge whetstones in fresh water for at least one or two hours. Reason? Sharpening stones for our hand tools are made of sedimentary rocks or tuff. They have lots of tiny cavity inside. We have to fill these spaces with water that can smooth the movement of filing.

A popular whetstone.
 Black side is normally used,
 and the red side is for a finishing touch.

Can you see air bubbles coming out during the submersion?

2. Position the prepared stone over the front side of the ENTIRE sickle, not only to the blade. Move the stone along the entire sickle, in a same direction. NEVER going back and forth. ONE WAY, please.

Before the procedure …

3. It will create a shining trace of the stone at the outer edge of the sickle. It’s the sign of right way.

4. The backside of the sickle would have burrs. Using the stone, we just “wipe” them gently. NEVER grind the backside.

Er, well, if your sickle has so many chips in a blade, do sharpen your blade from the back until the chips are gone. Then, whet the front as above.

Admitting, some needs more elaboration from the back …

After whetting, spray mineral oil, and they are ready. We don’t have to stick to mineral oil. EX olive oil will do the same, but it could be more expensive. 😉

It’s a popular spray of mineral oil.

The work was very meditative … We have to concentrate on the task for avoiding injury from the sharpened blade. Also, too much polishing could wear down the entire tool. Stop at the best moment is the key. Focus, focus, focus … The result I could get from the task was strangely satisfying. I realized why there are many scenes in samurai movies where Japanese swashbucklers take care of their swords while in a contemplative conversation. Ah-ha. Yep, polishing your swords, even if they are not for samurai, but for forest volunteers of the 21^st century, is VERY rewarding, especially when we’re stressed out in a rat race. Let’s sharpen our “knives” to relax more! … Plash, plash, plash, … (It sounds bizarre … subversive …)

Done!

If you find an environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657

Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/