三亚近海诺亚砗磲分布特征及底质对其外套膜颜色的影响

文章调查了三亚近海蜈支洲岛 (主要受旅游扰动影响)和三亚珊瑚礁国家级自然保护区 (包括亚龙湾、鹿回头半岛和东西瑁岛, 主要受非法捕捞影响)的诺亚砗磲 (Tridacna noae)分布、密度、种群结构及影响因素, 结果显示: (1)亚龙湾和蜈支洲岛海域诺亚砗磲密度最高, 分别为2.00×10–2和1.92×10–2 ind./m2, 显著高于东西瑁岛和鹿回头半岛海域 (P<0.05)。蜈支洲岛诺亚砗磲群体主要分布于2—4 m水深, 亚龙湾群体主要分布于6—8 m水深; (2)在蜈支洲岛海域, 壳长<5 cm、5—<10 cm、10—<15 cm和≥15 cm四种规格诺亚砗磲均有分布, 表明该海域种群结构稳定; (3)诺亚砗磲主要分布于活珊瑚区, 其次为礁石区, 砂石区极少; (4)诺亚砗磲外套膜RGB参数值与周边底质颜色均呈现显著地相关性 (P<0.05), 其中蜈支洲岛群体RGB参数相关系数低于三亚珊瑚礁国家级自然保护区群体。综上所述, 与旅游扰动相比, 非法捕捞是影响砗磲种群结构和外套膜颜色的主要因素。研究可为砗磲保护策略制定提供参考。

DISTRIBUTION AND THE INFLUENCE OF SUBSTRATE ON ITS MANTLE COLOR OF GIANT CLAM TRIDACNA NOAE IN COASTAL WATERS OF SANYA

Giant clam is one of the most important bivalves, and performs a significant ecological role in maintaining the balance of coral reef ecosystem. In China, giant clams are distributed in the Penghu Islands and south of Hainan in the South China Sea. Since the 1990s, the giant clam population surrounding Hainan Island has been greatly reduced, of which fishing and marine tourism are considered as the two main factors. In order to evaluate the influence of illegal fishing and marine tourism on giant clam population, this paper studied the distribution, density and population structure, as well as their influence factors, of Tridacna noae at Wuzhizhou Island (WI) (mainly affected by marine tourism) and Sanya Coral Reef National Nature Reserve including Yalong Bay (YB), Luhuitou Peninsula (LP) and Dongmao-Ximao Island (DXI)], which are mainly affected by illegal fishing in coastal waters of Sanya. Our study showed that (1) the densities of T. noae in YB and WI were 2.00×10–2 and 1.92×10–2 ind./m2, respectively, which was significantly higher than that in LP and DXI (P<0.05); Moreover, the depth of T. noae distribution in WI was mainly 2—4 m below mean sea level, while the depth of T. noae distribution in YB was 6—8 m below mean sea level. (2) Four sizes of T. noae (shell length of <5 cm, 5—10 cm, 10—15 cm, and >15 cm) were found in WI, indicating that its population structure in this sea area was reasonable. (3) The favorite substrate of T. noae was the living coral reef, followed by the rock, then the sand. (4) There was a significant correlation in RGB values between T. noae mantle and background colors (P<0.05), and a stronger correlation was observed in Sanya National Coral Reefs Reserve group. In summary, illegal fishing significantly affected the distribution and mantle color of T. noae, compared to marine tourism. This result will help the giant clam conservation.