BIOLOGICAL STUDIES ON THE FRESH-WATER SHRIMPS IN KOREA 4. The Ecology of Macrobrachium nipponensis (DE HAAN)

한국산 민물 새우류에 관한 생물학적 연구 4. 징거미의 생태

The fresh-water shrimp, Macrobrachium nipponensis (DE HAAN) is one of the largest of the shrimp species and one of the most important types fo protein food in fresh water fisheries. It can be found from Cheju island in the touth to Chung-ju in river or swamp, in the north. The breeding of these shrimps was studied by Chun and Yu (1967) and the relative growth was reported by author (1970a), but they did'nt provide other ecological features widely found in their natural environment. Shrimps were collected from the Nak Dong River, near Pusan, Korea once a month, from March to December 1963. The following is a summary of the results. 1. Larvae hatch from May to September, mainly in the month of July. 2. The average sex ratio ($male/female{\times}100$) is $62.9\%$ and goes down during the spawning season and rises from fall to spring season. 3. The minimum size of the female with eggs is aproximately 4.2cm in body length 3.5 gr in body weight, and 1.5 cm in carapace length. 4. Most shrimps of 5.75-7.75 cm in body length lay eggs. 5. The dorsal spines of the rostrum are 10-16(mode13) in number and the ventral spines of the rostrum are 1-5 (mode 3) in number.

낙동강산 징거미 Macrobrachium nipponensis의 생태적 제 특성을 조사한 결과는 아래와 같다. 1. 산란기간은 5월$\~$9월 사이이며 주 산란 시기는 7월이었다. 2. 성비 (숫컷/암컷$\times$100)는 연 평균 $62.9\%$이었으며, 산란기간 사이는 낮은 율이었고 동계에서 춘계 사이는 높은 율을 나타내었다. 3. 포란한 개체의 제일 작은 것은 체장 4.2cm 두흉갑장 1.5cm 체중 3.5g 내외였다. 4. 포란 미수의 출현율이 가장 많은 체장은 $5.75\~7.75cm$ 내외였다. 5. 상액각치수는 10개$\~$16개의 범위로서 13개의 범위로서 13개가 제일 많아 mode를 나타내었고, 하액각치수는 1개$\~$5개의 범위로서 3개의 출현율이 가장 많아 mode를 나타내었다.