Data from: Direct effects of microalgae and protists on herring (Clupea harengus) yolk sac larvae

This study investigated effects of microalgae (Rhodomonas baltica) and heterotrophic protists (Oxyrrhis marina) on the daily growth, activity, condition and feeding success of Atlantic herring (Clupea harengus) larvae from hatch, through the end of the endogenous (yolk sac) period. Yolk sac larvae were reared in the presence and absence of microplankton and, each day, groups of larvae were provided access to copepods. Larvae reared with microalgae and protists exhibited precocious (2 days earlier) and ≥ 60% increased feeding incidence on copepods compared to larvae reared in only seawater (SW). In the absence and presence of microalgae and protists, survival and growth trajectories of yolk sac larvae were similar and digestive enzyme activity (trypsin) and nutritional condition (RNA-DNA ratio) markedly declined in all larvae directly after yolk sac depletion. Thus, microplankton promoted early feeding but was not sufficient to alter survival and growth during the yolk sac phase. Given the importance of early feeding, field programs should place greater emphasis on the protozooplankton-ichthyoplankton link to better understand match-mismatch dynamics and bottom-up drivers of year class success in marine fish.

本研究探究了微藻（microalgae，Rhodomonas baltica）与异养原生生物（heterotrophic protists，Oxyrrhis marina）对大西洋鲱（Clupea harengus）仔鱼从孵化至内源（卵黄囊）期结束阶段的每日生长、活力、生理状况及摄食成功率的影响。实验设置了添加与不添加微浮游生物（microplankton）的两组卵黄囊仔鱼培育体系，每日均为各组仔鱼提供桡足类（copepods）作为摄食饵料。与仅以海水（seawater, SW）培育的仔鱼相比，添加微藻与原生生物的培育组仔鱼对桡足类的摄食起始时间提前2天，摄食发生率提升≥60%。无论是否添加微藻与原生生物，卵黄囊仔鱼的存活轨迹与生长轨迹均无显著差异；且在卵黄囊耗尽后即刻，所有组仔鱼的消化酶活性（digestive enzyme activity，核心检测酶为胰蛋白酶trypsin）与营养状况（nutritional condition，以RNA-DNA比值（RNA-DNA ratio）表征）均显著下降。综上，微浮游生物可促进仔鱼的早期摄食，但不足以在卵黄囊阶段改变其存活与生长状况。鉴于早期摄食的重要性，野外调查研究应更加重视原生浮游动物-仔鱼营养联系（protozooplankton-ichthyoplankton link），以更好地解析海洋鱼类的匹配-失配动态（match-mismatch dynamics）及年群成功（year class success）的上行调控因子（bottom-up drivers）。