Kanagawa Updates & Photo Topics Top

To Japanese page

Purple Sea Urchins Growing on Cabbage of Kanagawa


Due to the influence of recent years’ global warming, vegetable eating fish of southern hemisphere, such as rabbitfish and sea urchin, are increasing in the sea of Kanagawa.  They eat up marine algae that grows in clusters along the coast bringing about serious damage called “isoyake”, or shore burning.  Seaweed like Ecklonia cava is also wiped out causing a decrease in the number of turban shell and abalone which feed on it.  This phenomenon is dealing a heavy blow to fisheries.  Purple sea urchin is one of the causes of shore burning.  Having small edible part (gonads, or reproductive organ), purple sea urchin has been only considered as the object of extermination.  

Photo: Purple sea urchins feeding on cabbage


Another problem facing us is treatment of vegetable waste.  As Miura Peninsula is a major production center of Japanese radish and cabbage, large amount of cracked cabbage and outer leaves are also generated, which do not fit for sale and only to be discarded.


In order to solve these problems at the same time by utilizing the unwanted purple sea urchin and vegetable waste, Kanagawa Prefectural Fisheries Technology Center started experiments to give various kinds of local products to purple sea urchins two years ago.  Among about 20 kinds of food given, including Japanese radish, broccoli and tuna, they particularly preferred cabbage.  80 sea urchins finished one cabbage in only three days.


Based on this result, the Center started working on development of farming technology to grow purple sea urchins with large and tasty gonads in short period by giving waste cabbage and other vegetable of the Miura Peninsula.

Photo: Experiment result


Before the experiments, the edible part weighed 2 to 3% of the entire weight.  After feeding them on cabbage for two months, it grew to 12%, 17% at the maximum, of the entire weight on average.  Furthermore, it tasted sweeter and much less bitter than the ones now commonly seen in the market.


From FY2017, Fishery Technology Center starts working with Keikyu Aburatsubo Marine Park and Prefectural Marine Science High School on development of technologies to cultivate fully stuffed and delicious purple sea urchins as many as possible through various ways.




For Revival of Miura Pearl --- Governor Visited the Farming Site 


Did you know that Miura of Kanagawa Prefecture was a place connected with pearl?  It is said that Miura is where pearl culture technique was first developed in Japan.  Pearl culture was conducted by Kanagawa Prefectural Government (K.P.G.) and other entities for a period after WWII(ローマ数字の2), but did not become established as an industry at that time.


In recent years, however, in the Koajiro Gulf, many sectors are working together for revival of Miura pearl cultivation and development of marine education materials. 


As part of this project, Kanagawa Prefectural Marine Science High School began producing seeds and seedlings of Pinctada, a pearl oyster, last school year and started teaching pearl cultivation this year.


Photo: Governor trying nuclei insertionIt takes two to three years to grow Pinctada.  Various creatures like barnacles, oysters and algae stick to Pinctada while they are cultivated in the sea.  Regular cleaning of their shells is one of the important works because attached creatures will prevent Pinctada’s growth.   When the shellfish is grown to a certain size, a nucleus, which is to become a pearl, is implanted.  Harvest time is about six months later.


Photo: Talking about the importance of regional resourcesGovernor Kuroiwa visited the farming site and tried nuclei insertion with the students.  Under the instruction of NPO Koajiro Pearl Growers, they conducted the delicate work seriously.  Following the work, participants joined a meeting and talked about the importance of regional resources.  Kanagawa Prefectural Marine Science High School will continue offering a wide range of knowledge from marine creatures to pearl culture to the studnts through practical training like this.   They are aiming to develop human resources to pass on the techniques to utilize regional resources, and nurture regional community.






For comments/questions on this page, please contact theInternational Division.

End of content