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Balaenoptera acutorostrata

2022-09-04 06:11:30 186

Balaenoptera acutorostrata Life habits and morphological characteristics

The body is short and thick, and is spindle-shaped. The maximum body length captured in the Yellow Sea is 8.60 meters for female whales and 7.91 meters for male whales; the average body length is 6.93 meters for female whales and 6.14 meters for male whales; the body length of adult female whales is longer than that of male whales. The average body length of whales captured in Dalian Qianhai is 7.28 meters for female whales and 6.92 meters for male whales. The average body length in the Haiyangdao fishing ground is 6.75 meters for female whales and 6.04 meters for male whales. The body length is 1.4 to 2.4 times the maximum body circumference. The head is small, and the front part of the body is fat and thick. From the thickest part of the head to the front, it is particularly sharp from the cheekbones to the tip of the snout. The two sides are symmetrical, and the front view is like an isosceles triangle. A low crest is formed on the midline of the jaw from the tip of the snout to the

Balaenoptera acutorostrata Distribution range and habitat

Widely distributed in Antarctic waters, the North Atlantic, North Pacific and Arctic Oceans, less in tropical regions. Distributed in the western Pacific coast of Japan, the Sea of ​​Japan and the Sea of ​​Okhotsk. In China, distributed in the waters near Beihai, Guangxi, Daya Bay, Guangdong, southern Taiwan Province, Fujian, Yinxian, Zhejiang, Zhoushan, Chongming Island, Shanghai, and the Yangtze River Estuary. The northern Yellow Sea is the main hunting area; the Yellow Sea side of Liaoning is the main fishing ground, and the Bohai Sea side can reach the Xiaolongshan waters.
Countries: Anguilla, Antarctica, Antigua and Barbuda, Argentina, Australia, Bahamas, Belgium, Bermuda, Brazil, Cape Verde, Canada, Chile, China, Cuba, Denmark, Dominica, Dominican Republic, Faroe Islands, France, French Guiana, Gambia, Greece, Greenland, Guadeloupe, Iceland, Indonesia, Ireland, Italy, Japan, South Korea, North Korea, Mauritania, Mexico, Morocco, Mozambique, Netherlands, New Caledonia, New Zeal

Balaenoptera acutorostrata Detailed Introduction

Minke Whale has two subspecies and is a small baleen whale of the genus Mysticetus.

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Minke Whale has 230 to 273 baleen pieces on each side. According to statistics of 38 individuals, the average is 253 pieces. The length of the entire whisker row is about 60% of the length of the skull. The whisker plate is a right triangle, generally about 17 cm high, and the highest is 21 cm in the middle and rear part of the whisker row. The base of the whisker plate is about 10 cm wide, and the middle is about 5 cm wide; the thickness can reach 1.8-2.5 mm. The whiskers are fine and soft, about 13 cm long, and 0.2-0.6 mm in diameter. The maximum spacing between the whiskers is about 5 mm, and the spacing at the proximal end is almost 1 times larger than that at the distal end. The length, width, thickness and spacing of the whiskers increase with the growth of body length. The whiskers and whiskers are yellow-white, and occasionally milky white. Some individuals have gray-black edges on the outer edge of the whiskers, which are generally 5 mm wide.

The baleen whale has 48-50 vertebrae. There are 7 cervical vertebrae, each separated. The number of lumbar vertebrae and caudal vertebrae varies. The vertebral type is usually C7+T11+L12+Ca18=48. The cervical vertebrae account for 5.5% of the total length of the spine, the thoracic vertebrae account for 21.2% of the total length, the lumbar vertebrae account for 36.1%, and the caudal vertebrae account for 37.2%. There are 11 pairs of ribs. The sternum is highly variable and is generally in the shape of a "cross". The shoulder blade is like an axe. The flippers have 4 fingers, and the finger type is: Ⅰ-3~4, Ⅱ-8, Ⅳ-7, Ⅴ-4. The waist belt bone is stick-shaped and slightly curved.

Most of the small whales swim alone. 10 to 20 individuals can be found in a small area, but they are scattered groups. Usually they do not swim in pairs, and only swim together for a short time during the estrus and mating period. The calf whales swim with the mother whale during the lactation period. The mist column emitted when breathing is thin and thin, up to 1.5 to 2 meters. Usually, it breathes 2 to 4 times each time it surfaces, with an interval of about 3 to 4 seconds each time, and an average stay time of 10 to 15 seconds on the surface. The diving time is short, and it surfaces again to breathe every 2 to 4 minutes. In 1955, when chasing a small whale in the north of Xiaohao Island in the Haiyangdao fishing ground, it was found that it breathed as many as 11 times in one time, and the diving time was about 10 minutes. After being frightened, it often does not breathe continuously, especially when it is chased for a long time and exhausted. It only breathes once each time it dives, and the diving distance is also short, only about 40 meters, and the diving direction is uncertain, so whaling ships are often confused by it. When it is not frightened or tired, it floats to the surface very lightly and steadily to breathe 3 to 4 times, and then slowly dives into the water. When diving, the body is very tilted, the head is exposed first, and then it dives down quickly, gradually exposing the back and tail peduncle, while bending the body to protrude the back and bend the tail peduncle sharply, and quickly disappears under the water, and the tail fin never appears above the water. When breathing, the body of the eel whale is exposed above the water more than other whales, and the back is exposed higher. The swimming speed is 5 to 7 nautical miles per hour (1 nautical mile = 1852 meters), and it can reach 10 nautical miles per hour when being chased and escaping.

The eel whale swims to low-latitude waters in winter and spring, and goes north to high-latitude waters in summer and autumn to feed. A group of eel whales that entered the East China Sea and the Yellow Sea through the Sea of Japan, some of them swam along the west coast of North Korea to the Haiyangdao fishing grounds, and can reach the coast of Dalian. From November to January and February of the following year, a small number of fish have arrived at the Haiyang Island fishing ground, forming the initial fishing season. They are distributed in the waters near China Haiyang Island, Zhangzi Island, Dahao Island, Xiaohao Island, Xiaochangshan Island, and Xiedao Island. The number gradually increases until mid-March. From April to June, more than 20 scattered individuals are often found, feeding and migrating in the waters near the islands, forming the peak fishing season. During this period, they are distributed in the waters east of Baihai Haiyang Island to the west, as far as the south of Guanglu Island and the outer sea west of Zhangzi Island, while there are fewer fish in the area from Dalu Island to Wangjia Island and the northeastern waters of Haiyang Island. After the end of June, they stay away from the offshore and appear in the deep waters southeast of Haiyang Island and migrate southward. Some of them go through the outer sea of Shidao and bypass Shandong Gaojiao to reach the Yanwei fishing ground, and some of them go north directly to the Haiyang Island fishing ground. Small eel whales appear in Shidao fishing grounds from November to February of the following year, and their number gradually increases after March. This sea area is a dry north-south swimming channel for small eel whales. In May and June, whales that migrate south from the northern Yellow Sea feed and raise their young in this sea area, forming an excellent fishing ground. In October of the previous year, very few whales can be found in Yanwei fishing grounds. Since mid-April, more small eel whales have swum here, and in May, a prosperous signal is formed, but the fishing season is very short, mainly distributed in the area from Chudao to Zhifu Island. Then continue to go north through Dazhushan and Yuandao to Dalian Qianhai. In early December, a small number of whales swam to Dalian Qianhai, and more small eel whales began to appear in mid-April. May and June are the peak fishing seasons, distributed in the waters from Sanshan Island to Lushun Longwangtang, with more in the coastal waters from Laohutan to Xiaoping Island. During this period, they were also found in the waters from Dalian to Xiaolongshan Island in Bohai. A small part of them passed through the central Yellow Sea and reached the outer sea of Qingdao and Haizhou Bay. After July, most of the young eel whales leave the northern Yellow Sea.

The young eel whales mainly feed on Pacific krill and small fish. The stomach contents are mainly sand eel, Pacific krill, Japanese anchovies, as well as bluefish, flat minnow, yellow crucian carp, small yellow croaker, eel, newt, yellow croaker, etc., and these fish are swallowed in small quantities.

The mother whale seems to have the characteristic of protecting the calf. There have been many encounters with mother and calf whales swimming together. From the small body length of the calf and the soft back mackerel that has not yet erected, it can be determined that it is a newborn baby whale. When the mother whale finds a ship approaching, it always prevents the calf from swimming on the side close to the ship. The calf may swim rapidly and jump continuously due to its small body and lack of strength. It was also found that when a newborn whale jumps and swims continuously for too long, the mother whale will rise and fall on the water surface and use its flippers to carry the baby whale. The mother whale is very attached to the baby whale. After the mother whale was captured, there was a situation where the baby whale crashed into the side of the ship several times and died.

In the Yellow Sea of China, the birth and mating period of the small whales are very inconsistent. Most of them are delayed for 3 to 4 months, and some can last for half a year. Usually after June, male and female whales can be seen swimming together, and the mating period is mostly between July and September. The minimum body length of a pregnant whale is 6.60 meters. The Yellow Sea small whales with a body length of more than 7 meters are generally sexually mature. The gestation period is 10 to 11 months. When the fetus is more than 240 cm long, all pregnant whales will secrete milk. The maximum body length of the fetus obtained is 255 cm. Some births have occurred in early April, and the peak period of birth is from May to July. Some births still occur as late as September. The Yellow Sea minke whale has only one reproductive period. The newborn whale is 250 to 270 cm long and generally weighs more than 150 kg. One litter is born each time. Two twins were caught in the Haiyangdao Fishery.

Due to its small size, the minke whale was not taken seriously in the world whaling industry in the past. With the decrease in the number of large whale species and the ban on hunting, the minke whale has become an important position, especially after the hunting of large whale species in Antarctica was stopped, small whales became the only hunting target, but due to the decrease in resources year by year, commercial fishing was stopped. In the North Pacific, the number of minke whale resources is also small. Japan caught more than 500 minke whales in the past year, and China caught more than 180 minke whales in the northern Yellow Sea, and the average annual catch is only dozens of minke whales. China stopped whaling in 1981. However, Japan and South Korea continued to hunt minke whales in the Sea of Japan and the southern Yellow Sea. South Korea's annual catch was as high as 800, and then the production dropped sharply until the International Whaling Commission decided to stop hunting in 1986.

Japan has long argued that only a few whales are facing the risk of extinction, and announced its withdrawal from the IWC in December 2018 and resumed commercial whaling. In response, anti-whaling countries and activists have expressed opposition, while local whaling groups are jubilant and held a ceremony to send ships out to sea.

Listed in the IUCN Red List of Threatened Species (IUCN 2018 ver 3.1) - Least Concern (LC).

Listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Listed in the List of Nationally Protected Wildlife in China - Level II.

In February 2021, it was listed in the List of Nationally Protected Wildlife in China - Level I.


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