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Golden Apple Snail Eggs On Japanese Water Fern Stems At Bo Lac Lake, Dong Que Commune - Tam Dao


Figure 3.4: Golden apple snail eggs on Japanese duckweed stems at Bo Lac Lake, Dong Que Commune - Tam Dao


Figure 3.5: Golden apple snails in a rice field being harvested at Viet Xuan commune , Vinh Tuong district.

The distribution density of golden apple snails in rice fields and water surface areas is very different in each locality and in the same locality but in different areas and different times of the year. The main breeding period of snails is in the summer, so when the fields are planted with young rice seedlings in the crop season, there are the most baby golden apple snails in the fields and the density is at its highest at this time, some fields can count up to thousands of baby snails.

Figure 3.2: Relationship between rice field area and area damaged by golden apple snails

(Data)

melon

on the results of the investigation of 122 local agencies and organizations

you are the boss​​​

and through surveys by the Center for Natural Resources and Environmental Protection in 2010 and compared with the area of ​​unused land according to the Statistical Yearbook 2009). Chart 3.2 shows the level of damage by golden apple snails on the total rice land area of ​​each district. Accordingly, the districts with the largest area damaged by golden apple snails, ranging from 40 - 50% of the area, are Binh Xuyen, Lap Thach, Yen

Lac, Lo River.

3.2.3. Current status of Japanese duckweed (Eichhornia Crassipes )

Japanese water hyacinth (scientific name: Eichhornia crassipes ) is also known as water hyacinth, water hyacinth, or water fern, is an aquatic, herbaceous, floating plant, belonging to the genus Eichhornia of the family Pontederiaceae .

Japanese water fern grows about 30cm high with round, green, smooth and glossy leaves. The leaves roll together like flower petals, the leaf veins are arched, the petioles swell like foam bubbles to help the water fern float on the water surface. The three sepals are like three wings, the water fern roots look like feathers, black in color, hanging down to the water, sometimes up to 1m long. The flowers grow in clusters at the top of the water fern, the flowers are uneven, light green with a hint of purple; the sepals and corolla are the same color, attached to each other at the base, the upper petals have a yellow spot, 6 stamens, 3 long stamens and 3 short stamens. The upper ovary has 3 cells containing many ovules - bearing fruit. The flower stalk stands upright, bringing the flower up above the leaf cluster, usually blooming in the summer.

Japanese water fern originated from South America, introduced to Vietnam around 1905, possibly for ornamental purposes or as food for livestock and poultry, so in Vietnamese it is called Western water fern, and also called Japanese water fern because some people think that water fern was brought from Japan, Loc Binh is because the leaf stalk swells like a vase, Phu Binh is because it floats on the water surface. Under favorable conditions, this species can double its area in about 10 days and is now widely distributed in freshwater bodies in Vietnam.

In Vinh Phuc province, Japanese duckweed is the type of duckweed that grows with the largest area and is almost uniform and widespread throughout the province. They are distributed in most public water bodies, mainly in lagoons, canals and stagnant ponds. Even in private fish ponds, they grow very well, requiring a lot of labor to maintain the necessary area without causing an outbreak. The survey results on the questionnaire show that many households do not know the harmful aspects of Japanese duckweed, only know some small benefits: contributing to water purification, being a place for fish to spawn or being food for livestock, etc.

In fact, in addition to the small benefits, Japanese duckweed grows on a large scale in many places, making human efforts to limit it very difficult. Japanese duckweed in many places has blocked the flow, competed with many plants in the water, reducing biodiversity, and also prevented the diffusion of oxygen from the air into the water, causing fish to suffocate, etc.

The presence of Japanese duckweed in districts and towns according to statistics is relatively regular according to the commune ratio, only Tam Duong district has the smallest ratio (40%).

The current status of Japanese duckweed area in districts and towns is shown in detail in Table 3.3 below.

Table 3.3: Current status of Japanese water fern in Vinh Phuc province in 2010


Status


Location


Number of Organizations

survey

Number of agencies and organizations

function with invaded area

harm


Area of ​​encroachment

(ha)

1

Tam Dao District

10

9

23.37

2

H. Song Lo

17

14

50.0

3

Phuc Yen Town

8

7

28.0

4

Vinh Tuong District

25

24

30.0

5

Tam Duong District

10

4

30.0

6

Vinh Yen City

5

5

60.0

7

Yen Lac District

13

13

30.0

8

H. Lap Thach

20

19

50.0

9

Binh Xuyen District

14

13

1,375.04


Total

122

108

1,676.41


Infestation rate


88.52

%


Maybe you are interested!

(Data)

melon

on the results of the investigation of 122 local agencies and organizations

you are the boss​​​

and through surveys by the Center for Natural Resources and Environmental Protection in 2010).

Out of 122 communes and Tam Dao farm, Tam Dao National Park were surveyed, the number of communes identified to have Japanese duckweed distributed is 108, accounting for 88.52%. The area with Japanese duckweed surveyed is 1,676.41 ha. However, this area is not even in the districts, especially Japanese duckweed has a particularly high area in Binh Xuyen district up to 1,375.04 ha, accounting for 82.02% of the total area surveyed. Although the distribution area is not as large as the golden apple snail, Japanese duckweed is dangerous because its density when appearing is extremely thick, can completely cover the water surface with 60-70 plants/m2 ( medium plants) or 50 plants/m2 ( large plants) and spread continuously over a long and wide water surface area. This causes aquatic plants in the area where Japanese duckweed lives to be almost completely overwhelmed, they grow weakly and gradually degenerate. Animals, mainly fish, also develop quite difficultly due to suffocation and lack of light. In villages where household livestock is developed (eg: Keu village - Dao Duc commune - district

In Binh Xuyen, most of the village ponds are silted up and Japanese duckweed grows strongly, making the ponds shallower and completely unusable for aquaculture.

Comparison of aquaculture water surface area with Japanese duckweed invasive area in 2010 is shown in chart 3.3.



Figure 3.3: Relationship between surface area

aquaculture and​​​​​


(Data)


melon

Area invaded by Japanese duckweed

on the results of the investigation of 122 local agencies and organizations


you are the boss​​​

and through surveys by the Center for Natural Resources and Environmental Protection in 2010 and compared with unused land areas according to the Statistical Yearbook 2009). Based on the chart, we see that Japanese duckweed is present in all districts and towns, but not large compared to the area used for aquaculture. Only Binh Xuyen district has an area of ​​Japanese duckweed invasion larger than the aquaculture area. The reason is that Japanese duckweed not only grows in aquaculture areas but also

developed in rivers, streams, canals and rice fields throughout the district.


Figure 3.6: Japanese Water Fern at Mui Bridge, Thanh Tru Commune, Vinh Yen

Figure 3.7: Japanese Water Fern at Dam Vac, Tich Son Ward, Vinh Yen


3.2.4. Current status of distribution, area and density of other alien species in the province

a. Red-eared slider turtle (Trachemys scripta elegans)

Figure 3.8: Red-eared slider turtles are raised at Que Huong restaurant in Ngo ward.

Authority - Vinh Yen

The red-eared slider ( Trachesmys scripta elegans) or red-striped slider is perhaps the most famous and easily identifiable slider turtle. Its shell is smooth and slightly curved, with yellow stripes down its back and a patch of red and sometimes yellow just behind its eyes.

The scientific name is Trachemys scripta elegans, the red-eared slider is an animal belonging to the order Testudinata , class Reptilia , the turtle's homeland is in North America, concentrated in the Mississippi River valley from northern IIIinois and Indiana to the northern Gulf of Mexico, Texas and Alabama, and possibly even wider. Due to its beautiful morphology and high adaptability, the red - eared slider is sold as a pet. In our country, the red-eared slider has appeared for about 10 years now and is bought as a pet, mostly in Hanoi and Ho Chi Minh City.

Ho Chi Minh City. However, until now there has been no official document from the authorities allowing the import and breeding of this turtle species.

The red-eared slider is an exotic animal that has recently appeared and become well-known. They are omnivorous, aggressive animals that can swallow all fish and aquatic animals that are smaller than them. The slider can carry salmonella bacteria that cause typhoid fever in humans and is listed in the 206th global species list and is among the 100 most dangerous species in the world.

Red-eared sliders are a new alien species introduced into the province. At the time of the survey (July 2010), more than 99% of the population did not know about this species and the number of turtles counted was less than 10. The turtles surveyed were scattered in households in districts such as Song Lo, Vinh Yen city, etc. Turtles were found in natural water bodies. However, when the police force participated in the survey and capture, up to October 2010, according to report No. 246/BC-PC49 dated September 7, 2010 of the Vinh Phuc Provincial Environmental Police on the number of turtles discovered and destroyed in Vinh Yen city. The number of turtles counted in the city alone was 62. Red-eared sliders captured during this period were mainly concentrated in pet stores. According to an additional survey by the Center for Natural Resources and Environmental Protection, temples and shrines with lakes or wells are places where red-eared sliders are released and thrive. The province has a total of 121 communes, each of which has at least one communal house or pagoda and often has a pond or lake in the complex. A survey of some clusters shows that on average each communal house or pagoda has about 4 sliders. Thus, it is estimated that the number of sliders in the temple and shrine area alone is nearly 500 individuals (this number may be many times higher because the number that can be seen during the survey is often smaller than the actual number, and reproduction helps sliders increase in number). Due to spiritual factors, sliders in general and sliders in particular are rarely killed by people in Vinh Phuc, so when they escape into natural water bodies, they are likely to spread rapidly.

b. Snail ( Achatina fulic)

The snail family (Achati-nidae) has many types, the most common is the flower snail (also known as the ghost snail) with the scientific name Achatina fulica , a terrestrial species, originating from Africa. This alien land snail species entered Vietnam in the 1960s. This type, about 2 years old, has an average weight of 50-

60g, individual: 140g, the largest snail is the Achatine Achatina species, found in Africa, the largest has a length from antennae to tail: 39cm, weighs 900g.

This is a wild species, during the day they hide in holes, bushes or burrow into the ground. When night falls, they appear and destroy trees and crops. Snails are a type of mollusk, with a large, thick shell. The head has 2 tentacles (antennae), the whole body is enclosed in a shell covered by a layer of mucus. Snails prefer to live at the base of damp trees, mainly in the mountains of Tam Dao district and Song Lo district. In the natural environment during the dry season, they can sleep for many months, but just a shower of rain (usually in spring), they will wake up and operate normally.


Figure 3.9: Snail

Vinh Phuc is also home to snails and has become a familiar creature often found in home gardens and vegetable fields, they are harmful to banana gardens, vegetable gardens, beans and other crops. Snails are so widely distributed that some localities have given very large estimates of snails, specifically: Yen Lac district is estimated to have an area of ​​up to 603.21 hectares of snails, Lap Thach is 56.5 hectares, Vinh Tuong is 20.61 hectares, ...

Snails usually breed in March and they damage gardens and vegetables the most in the summer months. Thus, it can be said that snails are also a common harmful alien species in Vinh Phuc province. Its harmful effects have been known through the damage reported by people, so if there is propaganda and a campaign to capture them, snails are also an easily limited creature.

c. Five-color plant ( Latana camara )

The five-color plant belongs to the verbena family. The plant originated in Central American countries, and later spread to the Far East, Mangat, and New Caledonia. In New

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