大黄鱼耳石锶标志技术

利用六水合氯化锶进行大黄鱼(Larimichthys crocea)幼鱼耳石的标记,探讨了锶元素对大黄鱼幼鱼耳石的元素指纹标记效果,分析了锶元素标记对大黄鱼幼鱼生长和存活的影响。结果表明:(1)阶段性倍增饲养水体中锶离子浓度可使标记组个体在特定耳石区段的Sr/Ca比值显著提升,形成与对照组个体和野生个体在该耳石区段Sr/Ca比值的显著差异(P0.01),标记组、对照组和野生个体在该耳石区段的Sr/Ca比值分别为(3.58±1.09)mmol/mol、(1.73±0.08)mmol/mol和(1.09±0.35)mmol/mol。此区段形成的Sr/Ca比值峰值可视作标记组个体的耳石锶元素人工标记。(2)标志组和对照组大黄鱼幼鱼的生长速率和存活率均无显著性差异(P0.05),表明此项标记技术对受标个体的生长和存活状况不会产生显著负面影响,可用作大黄鱼增殖放流鱼苗的规模化标记手段。

Strontium marking on otolith of Larimichthys crocea

Enhancement and release of <i>Larimichthys crocea </i>has become more and more important because of continual decline in its resources. The traditional method of marking was not suitable for the larvae of <i>Larimichthys crocea</i>. In order to effectively evaluate itseffect of the enhancement, it has been a top priority to build a scale method of marking which is suitable for the larvae of <i>Larimichthys crocea</i>. The paper studied the effects of hexahydrate strontium chloride on otolith marking, growth and survival of <i>Larimichthys crocea</i>, aiming to improve the applicability of this marking technique in tracing <i>Larimichthys crocea</i> for a better evaluating of its effect of the enhancement. The experiment selected 4 groups'' the larvae of <i>Larimichthys crocea </i>that were hatchery-reared, each group had 2000 larvae of <i>Larimichthys crocea</i>. Two groups were immersed by hexahydrate strontium chloride, and others were used as control groups. Before the experiment, we respectively selected 50 larvae in 4 groups to compare their difference of body length and body weight. During the experiment, we recorded the number of deaths per day so that we compared their difference of survival rate. After they were experimented 7 d and 50 d, we randomly selected 15 larvae in 4 groups, respectively. We compared their difference of growth by biological determination, and we used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze the otolith of strontium distribution features. The results showed that fish exposed to increased levels of strontium had higher strontium-calcium ratio in the given part of the otolith relative to those of control and wild fish. The higher strontium-calcium ratio in the given part of the otolith was located by 0.65 to 0.80 mm far away from the core area of the otolith. The strontium-calcium ratios in the given part of the otolith for the marked, control and wild fish were (3.58&#177;1.09) mmol/mol, (1.73&#177;0.08) mmol/mol, and (1.09&#177;0.35) mmol/mol, respectively. They had extremely significant difference (<i>P</i><0.01). The higher otolith strontium-calcium ratio could be used as elemental fingerprint in identifying marked fish. In addition, there were no significant difference in survival rate among marked and control fishes by the statistical test (<i>P</i>>0.05), indicating that immersion in water enriched in strontium did not negatively affect the survival rate of marked fish. In terms of growth, after experimented for 7 d, the average of body length and body weight of marking group and control group were (19.43&#177;2.67) mm and (0.11&#177;0.05) g, and (19.64&#177;1.99) mm and (0.12&#177;0.04) g, respectively. After experimented for 50 d the average of body length and body weight of marking group and control group were (44.76&#177;4.15) mm, (1.82&#177;0.55) g, and (43.26&#177;4.71) mm, (1.62&#177;0.53) g, respectively. The body length, body weight and their relationship were tested according to statistical methods. We found that there were no significant difference (<i>P</i>>0.05), implying that strontium did not negatively affect the growth of marked fish. Our results suggested that immersion in water enriched with strontium could be an effective means of marking hatchery-reared <i>Larimichthys crocea</i>for stock enhancement. The means could provide solid fundament for the evaluation about scientific and reasonable enhancement and release.