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国内血統登録書から見たゴマフアザラシの飼育下繁殖の現状
寺沢 文男
新江ノ島水族館

要約
1） ゴマフアザラシ血統登録台帳21年分を用いて，飼育下繁殖個体の分析を行なった．内訳は，繁殖個体504頭（50.7％），保護個体461頭（46.4％），不明29頭（2.9％）であった．
2） 出生性比は，オス102対メス100でほぼ同じであった．
3） 両親の確定は52.6％（265頭）であった．
4） 1988年以降の死産，流産を含む年間の繁殖数の最多は1995年（37頭），最少は2006年（11）だった．
5） 出生月は，3月（259頭），4月（111），2月（32）の順で，6～8月では繁殖が見られず，9～12月の繁殖（25）は，出生時にすべて死亡して生まれた．
6) 出生数が多かったのは，3月下旬（113頭），3月中旬（95），4月上旬（76）の順であった．
7） 出生時の生存率は64.7％，1週間後では57.5％だった．1ヵ月後，3ヵ月後，6ヵ月後では54.4%，51.4%，50.3％，1年後は48.9％であった．
8) 繁殖（流産，死産を含む）の見られた43園館の生存率には差があり，それらを再分析した上で繁殖マニュアルを作成することが望ましい．

ABSTRACT
　Current status of captive breeding for spotted seals was surveyed through the Japanese Association of Zoo and Aquarium Studbooks from 1986 to 2006. This study was based on 504 animals born in captivity（ABCs）including stillborns and abortions.
　In 504 ABCs, there were 228 males（45.2％）, 223 females（44.3％）, and 53 animals of indeterminate sex（10.5％）．The sex ratio at birth for this survey excluding the animals of indeterminate sex was 102 males to 100 females.
　In 265（52.6％）out of 504 ABCs, the ABCs' parents were known. There were also 36.3％（183）cases of known mother and unknown father, and 11.1％（56）case of both parents unknown.
　The three most frequent ABCs were 259（184 survivals：75 deaths） in March, 111（89：22） in April, and 32（10：22） in February. Births did not occur from June to August. From September to December, 25 births occurred, but all were already dead at birth.
　There were 95 ABCs from March 11th to 20th, 113 from March 21st to 31st, and 76 from April 1st to 10th. The survival rate for these 11 days was 80.5％（91：22）, which was and better than the other two 10-day periods.
　Since 1988, the three most frequent years of birth for ABCs were 37 in 1995, 35 in 1996 and 31 in 1999. The smallest number for ABCs was 11 in 2006.
　The survival rate of ABCs at birth was 64.7％, and one week after birth it was 57.5％. It was more than 50.0％ for one, three and six months after birth, and less than 50.0% for one year after birth.
　A study was made in which the survival rate for ABCs was compared at birth, one month and one year after birth at 43 facilities. The creation of a standard manual for captive breeding of the spotted seal is suggested, because there is a difference in survival rates at each time stage at these facilities.