Jenkins Laura E, Pierce Andrew L, Graham Neil D, Medeiros Lea R, Hatch Douglas R, Nagler James J
Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA.
Fishery Science Department, Columbia River Inter-Tribal Fish Commission, Portland, OR, USA.
Conserv Physiol. 2019 Jul 26;7(1):coz038. doi: 10.1093/conphys/coz038. eCollection 2019.
Many iteroparous fishes spawn after skipping one or more yearly cycles, which impacts recruitment estimates used for fisheries management and conservation. The physiological mechanisms underlying the development of consecutive and skip spawning life histories in fishes are not well understood. In salmonids, lipid energy reserves and/or growth are thought to regulate the initiation of reproductive maturation during a critical period ~1 year prior to spawning. The fasting spawning migration of summer-run steelhead trout () results in significant depletion of energy reserves during the proposed critical period for repeat spawning. To determine whether and when lipid energy reserves and growth influence repeat spawning, measures of lipid energy reserves, growth rate and reproductive development were tracked in female steelhead trout from first to second spawning as a consecutive or skip spawner in captivity. Plasma triglyceride (TG) levels and growth rate were elevated by 10 weeks after spawning in reproductive (i.e. consecutive spawning) versus non-reproductive (i.e. skip spawning) individuals. Muscle lipid (ML) levels, condition factor and plasma estradiol levels increased at later time points. The early differences in plasma TG levels and increases in growth rate are attributable to differential rates of feeding and assimilation between the groups following spawning. A year after spawning, plasma TG levels, MLs and growth rate decreased in consecutive spawners, attributable to transfer of lipid reserves into the ovary. During the year prior to second spawning, energy reserves and plasma estradiol levels were higher in reproductive skip spawners versus consecutive spawners, reflecting the energy deficit after first spawning. These results suggest that the decision to initiate ovarian recrudescence occurs by 10 weeks after first spawning and are consistent with the differences in energy reserves acquired following spawning being a consequence of that decision. This information will increase the success of conservation projects reconditioning post-spawning summer-run steelhead trout.
许多多次繁殖的鱼类会跳过一个或多个年度周期后产卵，这会影响用于渔业管理和保护的资源补充估计。鱼类连续产卵和间隔产卵生活史形成的生理机制尚未完全了解。在鲑科鱼类中，脂质能量储备和/或生长被认为在产卵前约1年的关键时期调节生殖成熟的开始。夏季洄游的虹鳟（）禁食产卵洄游会导致在提议的重复产卵关键时期能量储备显著消耗。为了确定脂质能量储备和生长是否以及何时影响重复产卵，在圈养条件下，跟踪了雌性虹鳟从第一次产卵到第二次产卵作为连续产卵者或间隔产卵者的脂质能量储备、生长速率和生殖发育指标。与非生殖（即间隔产卵）个体相比，生殖（即连续产卵）个体在产卵后10周血浆甘油三酯（TG）水平和生长速率升高。肌肉脂质（ML）水平、条件因子和血浆雌二醇水平在后期时间点增加。血浆TG水平的早期差异和生长速率的增加归因于产卵后两组之间不同的摄食和同化率。产卵一年后，连续产卵者的血浆TG水平、MLs和生长速率下降，这归因于脂质储备转移到卵巢。在第二次产卵前一年，生殖间隔产卵者的能量储备和血浆雌二醇水平高于连续产卵者，这反映了第一次产卵后的能量赤字。这些结果表明，卵巢再发育的决定在第一次产卵后10周就已做出，并且与产卵后获得的能量储备差异一致，而这种差异是该决定的结果。这些信息将提高恢复产卵后夏季洄游虹鳟的保护项目的成功率。
