Department of Biology, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Department of Production Biology, Nofima AS, Tromsø, Norway.
PLoS One. 2024 Oct 15;19(10):e0311735. doi: 10.1371/journal.pone.0311735. eCollection 2024.
A successful control of sexual maturation is crucial for year-round production of lumpfish juveniles destined as cleaner fish in Atlantic salmon aquaculture. This study investigated the combined effects of photoperiod and temperature manipulations on sexual maturation and spawning in lumpfish females. Lumpfish juveniles were exposed to simulated natural and nine-month compressed annual photoperiods, with subsequent temperature elevation. Body weight (BW), condition factor (K), gonadosomatic index (GSI), ovarian development, plasma levels of 17β-estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT), and spawning were assessed. Compressing the natural photoperiod caused a clear increase and decrease in GSI, T, 11-KT and E2 towards and during the spawning period. Before the temperature elevation, GSI, T, 11-KT, E2 and ovarian development were advanced in the compressed photoperiod. After the temperature elevation, GSI, T, 11-KT and E2 fluctuated more in the compressed photoperiod, while in the natural photoperiod, E2 declined, and GSI, T and 11-KT increased. Spawning was advanced by 1 month in the compressed photoperiod compared to the natural photoperiod. Temperature elevation led to higher levels, earlier peaks and declines of T, 11-KT or E2 in both photoperiods, and advanced spawning by 1.5 months in the compressed photoperiod compared to the natural photoperiod. Temperature elevation also led to increased ovulation recruitment and increased cumulative weight of spawned eggs in the natural photoperiod. Compressing the natural photoperiod and elevating temperature can thus advance sexual maturation and spawning in lumpfish females. Due to the lower amounts of spawned egg weights in the high temperature compressed photoperiod, further studies on effects of photoperiod and timing of temperature manipulations on spawning, fecundity and egg quality could optimize the photothermal manipulations on lumpfish broodstock.
性成熟的成功控制对于全年生产作为大西洋鲑鱼养殖中清洁鱼的鳕鱼幼体至关重要。本研究调查了光周期和温度处理对鳕鱼雌性性成熟和产卵的综合影响。鳕鱼幼体暴露于模拟自然和九个月压缩年光周期下，随后温度升高。体重（BW）、条件系数（K）、性腺指数（GSI）、卵巢发育、血浆 17β-雌二醇（E2）、睾酮（T）和 11-酮睾酮（11-KT）水平以及产卵情况进行了评估。压缩自然光周期导致 GSI、T、11-KT 和 E2 在产卵期之前和期间明显增加和减少。在温度升高之前，在压缩光周期中，GSI、T、11-KT、E2 和卵巢发育提前。在温度升高之后，在压缩光周期中，GSI、T、11-KT 和 E2 波动更大，而在自然光周期中，E2 下降，而 GSI、T 和 11-KT 增加。与自然光周期相比，压缩光周期中的产卵提前了 1 个月。温度升高导致两种光周期中 T、11-KT 或 E2 的水平更高、更早出现峰值和下降，并使压缩光周期中的产卵提前 1.5 个月。温度升高还导致自然光周期中排卵募集增加和产卵总重量增加。因此，压缩自然光周期和升高温度可以促进鳕鱼雌性的性成熟和产卵。由于在高温压缩光周期中产卵重量较低，进一步研究光周期和温度处理时机对产卵、繁殖力和卵质量的影响可以优化对鳕鱼亲鱼的光热处理。
