Effects of photothermal manipulations on the artificial reproduction of barbel, Barbus barbus (Actinopterygii: Cypriniformes: Cyprinidae): a pilot study

The effects of photothermal manipulations on the artificial reproduction of female Barbus barbus (L.) (age 6+, 0.3–0.8 kg body weight) were studied under controlled conditions. The experiment was preceded by a 3-month period of wintering (Light/Dark hourly regime 9L : 15D–13L : 11D; temperature 8–12°C). The experiment commenced when the photoperiod was changed promptly from 11L : 13D to 14L : 10D. As the experiment progressed, the photoperiod gradually changed to 16L : 8D. After 50 days of photostimulation, water temperature was increased from 12 to 17°C within 24 h, and stabilized for the next 14 or 22 days. When photothermal stimulation was completed (65 or 73 days, respectively), fish were treated with mGnRH-based ovulating agent Ovopel. The ovulation rate amounted to 33% and 22%, respectively for the shorter and longer stimulation time (difference insignificant at P ≤ 0.05). Longer photothermal stimulation resulted in lower variability of latency time, higher relative weight of stripped eggs, and higher relative working fecundity. The undesirable effect was the triggering of oocyte resorption in 11% of females

Developmental temperature affects phenotypic means and variability: A meta‐analysis of fish data

Fishes are sensitive to their thermal environment, and face an uncertain future in a warming world. Theoretically, populations in novel environments might express greater levels of phenotypic variability to increase the chance of surviving – and eventually thriving – in the new conditions. Most research on the effect of the early thermal environment in fish species focuses on average phenotypic effects rather than phenotypic variability, but to understand how fishes will respond to rising temperatures we need to consider both the average response of the population, as well as the breadth of individual responses. Here we present the first meta-analysis on the effects of developmental temperature in fishes. Using data from 43 species and over 6,000 individual fish, we show that a change in developmental temperature induces a significant change in phenotypic means and variability, but differently depending on whether the temperature is increased or decreased. Decreases in temperature (cool environments) showed a significant decrease in phenotypic means and no change in phenotypic variability. Increases in temperature (warm environments) showed a non-significant increase in phenotypic means, and a marginally significant increase in phenotypic variability. Larger increases in temperature saw greater increases in phenotypic variability, but no increase in the mean phenotypic response. Together, our results suggest that fishes exhibit both directed and stochastic developmental plasticity in response to warming temperatures, which could facilitate or accelerate adaptation to a changing environment