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“长江女神”白鱀豚疑似现身 已“功能性灭绝”9年(图)

2016-10-06 12:35:59   中国江西网 作者:佚名

1992年,我国在湖北建立了两个国家级自然保护区,分别是“长江天鹅洲白鱀豚国家级自然保护区”和“长江新螺段白鱀豚国家级自然保护区”,此外还建立了安徽铜陵白鱀豚养护场,实施白鱀豚的就地保护和迁地保护。

1980年,渔民捕获的一头受伤白鱀豚被送到中国科学院水生生物研究所,在人工环境下存活了23年之久,成为世界淡水豚类人工养殖时间最长的之一。

人工繁殖研究的重要成果是“淇淇”。1986年,人们好不容易捕获一头雌性白鱀豚,尝试让其与“淇淇”交配。这只白鱀豚当时尚未成熟,就在等待它性成熟期间,它不幸患肺炎死亡。2002年,世界上唯一一头人工饲养的白鱀豚“淇淇”去世。

灭绝与否言之尚早

白鱀豚是否已经灭绝?王丁教授的回答给大家带来一线希望:“仅凭这几次考察的结果并不能下白鱀豚已灭绝的定论,因为首先我们的考察并非24小时不间断,而是每日8小时工作;其次,我们的考察并没有覆盖全部水域;第三,我们的考察采取抽样法,既然是抽样,自然不可能看见每一个个体。”

王丁教授表示,判定一个物种功能性灭绝主要看两个指标:种群稀少,功能丧失,对周围生态影响微小;数量下降至无法保证种群繁殖的需要。

据他介绍,根据世界自然保护联盟的标准,一个物种持续50年未发现,才可宣告“灭绝”。白鱀豚在2004年还有被发现的记录,说它灭绝言之尚早。联盟还规定,确定一个物种灭绝必须连续考察整个分布区,在该物种一个生命周期内未发现存在才算灭绝。白鱀豚一般可活30年,确认灭绝必须30年内连续对其生存状况进行考察。

白鱀豚濒危四大原因

资料显示,收集到的白鱀豚标本中90%以上的死亡是由于人类活动直接造成的。

首先,酷捕滥捞经常误杀白鱀豚,或导致白鱀豚食物匮乏。专家说,一方面沿江人口飞速增长,渔民对鱼类需求越来越大,以鱼为生的白鱀豚能够得到的食物越来越少。另一方面,渔民捕捞作业对白鱀豚的误伤屡见不鲜。据不完全统计,由于捕捞作业误伤死亡的白鱀豚几乎达到死亡总数的一半。加上一些不法之徒大量使用炸鱼、毒鱼、电打鱼、迷魂阵等有害手段,令白鱀豚的生存雪上加霜。1987年在长江死亡的一头白鱀豚身上,竟有103处血淋淋的大小伤口。

其次,繁忙的水上交通威胁白鱀豚的安全,航道的日益繁忙使其生活空间越来越小。船舶的噪音污染将白鱀豚的正常生活打乱,干扰了它们的声呐系统,造成白鱀豚被船舶螺旋桨打死的惨剧。在收集到的死亡白鱀豚标本中,有的头骨粉碎,有的被拦腰斩断。

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