惠东幼年绿海龟的洄游规律及觅食地选择

Satellite-Tracking Reveals and Highlights:Migration Route and Key Foraging Sites for Headstarting Juveniles(Chelonia mydas)from Huidong National Sea Turtle Reserve,China

绿海龟(Chelonia mydas)为全球性濒危物种、我国Ⅰ级重点保护野生动物。栖息地保护是野生绿海龟保护的一种极为重要和有效的保护策略,但我国幼年绿海龟的生活习性及其栖息地分布尚不明确,故开展相关洄游行为及栖息地分布研究意义重大。2011至2015年间,将6只来自广东惠东海龟国家级自然保护区人工培育2~14 a的幼年绿海龟,分为夏季组(n=3)及冬季组(n=3),在其背甲上安装追踪器。其中,2只个体分别安装了美国Wildlife Computers公司生产的追踪器SPOT5-AM-S181C和SPOT5-AM-S244A,另外4只个体安装美国Telonics公司生产的TAM-2639追踪器,然后在出生地放归。利用全球ARGOS系统实施全天候的追踪监测,地理坐标数据的筛选及分析在卫星追踪分析工具软件(STAT)上完成。6只个体4年共获得有效位点397个,其中,包括前期研究获得的有效位点62个。相关有效位点输入免费软件Maptool,通过GIS图层叠加、汇总生成洄游路线图。研究结果用以揭示我国幼年绿海龟的洄游规律。使用SPSS软件t-检验统计冬夏两组海龟间的个体大小及洄游速度是否存在统计学差异。冬季组、夏季组绿海龟的背甲曲线长(CCL)分别为(48.9±8.65)cm和(59.07±7.64)cm,组间无显著性差异(t=1.527,df=4,P=0.202)。追踪期平均(66±47)d,追踪路程(1653±1585)km(n=6)。平均最小洄游速度,夏季组为(1.63±0.22)km/h(n=3),冬季组为(0.67±0.12)km/h(n=3),夏季组明显较冬季组高(t=6.726,df=4,P=0.003);夏季及冬季分别游往台湾和海南两个方向,主要沿大陆架140 m等深线以内海域洄游,所有个体的洄游路线及方向均与同期海流大致相同,活动范围与近海渔场及开发区域高度重叠,与早期野外调查结果一致。仅冬季组观察到定居及归巢行为,越冬场分布在越南昏果岛及我国海南岛东部;越夏场则分布在福建至浙江一带,主要分布在近岸或近岛20 m等深线以内浅海,为底栖大型海藻、海草床或珊瑚礁的集中分布区。研究结果揭示,惠东人工培育幼年绿海龟放归后可正常洄游、觅食和适应野外环境,在东海、南海之间作季节性定向洄游的趋势十分明显,觅食地沿我国大陆架沿岸及附属海岛分布,进一步印证了我国近海绿海龟洄游廊道的存在。建议把北部湾、琼州海峡、海南东部、广东、福建、浙江及台湾沿岸及附属岛屿的海洋保护地整合优化,制订国家海龟栖息地名录,组建海洋类型国家公园保护网络,同时深入开展国际及地区间的保护合作,加强绿海龟及其觅食地和洄游廊道这些重要栖息地保护,使海龟整个生命周期得到有效和完整的保护。

The green turtle(Chelonia mydas)is a globally endangered species and listed as ClassⅠof protected animals in China.Habitat conservation is an important and effective conservation strategy for this species.However,the habits and habitat of juvenile green turtles in China are not clear yet.We six tagged juvenile green turtles aged from 2 to 14 years old from the Huidong National Sea Turtle Reserve of China with six satellite transmitters,including two American Wildlife Computer trackers(Spot5-AM-S181C,n=1;Spot5-AM-S244A,n=1),and four Telonics trackers(TAM-2639)(Table 1)between 2011 and 2015.We released them in the summer(n=3)and in the winter(n=3).The global ARGOS system was used to carry out an all-weather tracking and monitoring,and the geographic coordinate data were filtered and analyzed using the satellite tracking and analysis tool(STAT)software.We obtained a total of 397 effective locations for the four years(including 62 obtained from previous studies).GIS layers were then generated and overlaid with MapTool software to reveal the migration of juvenile green turtles.The SPSS software t-test was used to determine statistical difference between the two season data on individual size and minimum travel speeds The curve carapace lengths(CCL)in the turtle released in winter and in summer were with 48.9±8.65 cm(n=3),and 59.07±7.64 cm(n=3),respectively,with no difference between the two groups(t=1.527,df=4,P=0.202).The average tracking period was 66±47 d(n=6),and the tracking distance was 1653±1585 km(n=6).The average minimum travel speed in the summer group was 1.63±0.22 km/h(n=3),which is longer than those turtles in winter group(0.67±0.12 km/h,n=3;t=6.726,df=4,P=0.003).They migrated to Taiwan in summer and to Hainan in winter,along and within the 140 m isobath of the continental shelf.The migration directions of all individuals were as same as the monsoon currents of the sea during the same period(Fig.1).Homing behavior was observed only in the winter group(Fig.2).The over-winter sites were mainly distributed in Con Co Island of Vietnam and the eastern part of Hainan Island,whereas the over-summer habitats were located between Fujian and Zhejiang,but all were within the 20 m isobath and with concentrated distribution of macro-algae,seagrass beds,or coral reefs.The activity area overlapped with the offshore fishing ground and other development areas,which was consistent with the results of previous research.The captive juvenile green turtles could migrate normally,forage,and adapt to the wild environment after being released,and they tended to migrate seasonally between the East China Sea and South China Sea.The foraging sites are primarily distributed along the coast of the continental shelf and affiliated islands of China,which further confirms the existence of migratory corridors for green turtles offshore of China.We suggest integrating and formulating marine national parks off the Beibu Gulf,Eastern Hainan,Guangdong,Fujian,Taiwan and Zhejiang Marine Nature Reserves,strengthening international and regional cooperation to protect the natal grounds,foraging grounds,migratory corridor,and other habitats of green turtles,to ensure effective protection of their life cycle.