Data from: Maternal effects in vulnerability to eye-parasites and correlations between behaviour and parasitism in juvenile Arctic charr

Hatchery-reared fish show high mortalities after release to the wild environment. Explanations for this include potentially predetermined genetics, behavioural and physiological acclimation to fish farm environments, and increased vulnerability to predation and parasitism in the wild. We studied vulnerability to <i>Diplostomum</i> spp. parasites (load of eye-flukes in the lenses), immune defence (relative spleen size) and anti-predator behaviours (approaches toward predator odour, freezing, and swimming activity) in hatchery-reared juvenile Arctic charr (<i>Salvelinus alpinus</i>) using a nested mating design. Fish were exposed to eye-fluke larvae via the incoming water at the hatchery. Fish size was positively associated with parasite load, but we did not find any relationship between relative spleen size and parasitism. The offspring of different females showed significant variation in their parasite load within sires, implying a dam effect in the vulnerability to parasites. However, the family background did not have any effect on spleen size. In the mean sire level over dams, the fish from the bolder (actively swimming) families in the predator trials suffered higher loads of eye-flukes than those from more cautiously behaving families. Thus, the results indicate potentially maternally inherited differences in vulnerability to eye-fluke parasites, and that the vulnerability to parasites and behavioural activity are positively associated with each other at the sire level. This could lead to artificial and unintentional selection for increased vulnerability to both parasitism and predation if these traits are favoured in fish farm environments.

育苗场人工繁育的鱼类在放归野生环境后死亡率居高不下。对此现象的潜在解释包括：先天遗传因素的影响、对养殖环境产生的行为与生理适应，以及在野外环境中更易遭受捕食与寄生生物侵扰。本研究采用巢式交配设计（nested mating design），针对育苗场繁育的幼年北极红点鲑（*Salvelinus alpinus*），探究其对复口吸虫属（*Diplostomum* spp.）寄生生物（即晶状体内眼吸虫负荷量）的易感性、免疫防御能力（脾脏相对重量）以及反捕食行为（对捕食者气味的趋近行为、静止行为与游泳活跃度）。研究人员通过育苗场的进水系统，使受试鱼类接触眼吸虫幼虫。研究发现，鱼类体型与寄生虫负荷量呈正相关，但未发现脾脏相对重量与寄生感染存在显著关联。不同母本的子代在同一父本组内的寄生虫负荷量存在显著差异，这表明母本效应对寄生虫易感性存在影响。不过，家系背景对脾脏相对重量并无显著影响。在整合母本信息的父本平均水平上，捕食者行为试验中表现更大胆（游泳更活跃）的家系子代，其眼吸虫负荷量显著高于行为更谨慎的家系子代。综上，本研究结果表明，鱼类对眼吸虫的易感性可能存在母系遗传差异，且在父本水平上，寄生虫易感性与行为活跃度呈正相关。若养殖环境对这类性状存在选择偏好，则可能会在无意中人工选择出更易遭受寄生与捕食的鱼类种群。