South Australian Research and Development Institute and Aquafin Cooperative Research Centre, Lincoln Marine Science Centre, PO Box 1511, Port Lincoln, SA 5606, Australia.
Vet Parasitol. 2010 Oct 11;173(1-2):107-15. doi: 10.1016/j.vetpar.2010.06.007. Epub 2010 Jun 15.
Peaks in epizootics of sea lice (mostly Caligus chiastos) and blood flukes (Cardicola forsteri) among Southern Bluefin tuna (Thunnus maccoyii) appear to coincide with the onset of an increased mortality. The mortality event occurs 6-12 weeks after T. maccoyii have been transferred into static ranching pontoons from the wild. However, to date available data on parasite occurrence before commercial harvesting begins, are scant. This research gathered epizootiological data from weeks 4 to 13 post-transfer, for 153 T. maccoyii sampled from two research and four commercial pontoons. Counts of both parasites in the research pontoons reached levels far heavier than previously documented in ranched T. maccoyii. For sea lice, the prevalence in most pontoons was 100%; the highest intensity reached 495 individuals, and mean counts at the peak of the infection exceeded 265 lice per fish. Almost all of the 5407 individual lice counted were identified as adult C. chiastos (89.44% female, 10.14% male); adult females of two other species were also present, C. amblygenitalis (0.13%), in addition to an undescribed species, C. sp. (0.04%). Lice counts were correlated positively with gross eye pathology scores (r(s,151df)=0.3394, p=0.0000), negatively correlated with condition index (r(s,151df)=-0.5396, p=0.0000), and positively correlated with plasma cortisol (r(s,131df)=0.3906, p=0.0000) and glucose (r(s,131df)=0.2240, p=0.0096). For the blood fluke, prevalences were less uniform than those of sea lice, with lower rates of infection at the beginning (ranging from 10% to 40%), reaching 100% mid-study, and declining again (40% in one pontoon). The highest intensity reached 441 individual flukes. Fluke counts were negatively correlated with plasma haemoglobin (r(s,151df)=-0.2436, p=0.0051) and positively with lysozyme (r(s,151df)=0.3013, p=0.0019). Fluke counts were also correlated with sea lice counts (r(s,150df)=0.3143, p=0.0000). Peaks in these epizootics occurred near the onset of elevated mortalities, which started after 7 weeks of ranching.
在南方蓝鳍金枪鱼（Thunnus maccoyii）中，海虱（主要是 Caligus chiastos）和血吸虫（Cardicola forsteri）的流行高峰似乎与死亡率的增加同时出现。这种死亡率事件发生在金枪鱼从野外转移到静态牧场浮筒后 6-12 周。然而，迄今为止，在商业捕捞开始之前寄生虫发生的数据很少。这项研究从转移后的第 4 周到第 13 周收集了 153 条南方蓝鳍金枪鱼的流行病学数据，这些鱼来自两个研究和四个商业浮筒。在研究浮筒中，两种寄生虫的数量都达到了以前在养殖南方蓝鳍金枪鱼中从未记录过的水平。对于海虱，大多数浮筒的流行率为 100%；最高强度达到 495 只，感染高峰期的平均计数超过每只鱼 265 只虱子。统计的 5407 只虱子中，几乎全部被鉴定为成年 C. chiastos（89.44%雌性，10.14%雄性）；此外，还存在两种其他物种的成年雌性，C. amblygenitalis（0.13%），以及一种未命名的物种，C. sp.（0.04%）。虱子数量与总眼病理评分呈正相关（r(s,151df)=0.3394，p=0.0000），与身体状况指数呈负相关（r(s,151df)=-0.5396，p=0.0000），与血浆皮质醇呈正相关（r(s,131df)=0.3906，p=0.0000）和葡萄糖（r(s,131df)=0.2240，p=0.0096）。对于血吸虫，流行率不如海虱均匀，感染率在开始时较低（范围为 10%至 40%），研究中期达到 100%，然后再次下降（一个浮筒中为 40%）。最高强度达到 441 只吸虫。吸虫数量与血浆血红蛋白呈负相关（r(s,151df)=-0.2436，p=0.0051），与溶菌酶呈正相关（r(s,151df)=0.3013，p=0.0019）。吸虫数量也与海虱数量相关（r(s,150df)=0.3143，p=0.0000）。这些寄生虫的流行高峰出现在死亡率升高的初期，死亡率升高始于牧场养殖 7 周后。
