Distribution of herbivorous fish is frozen by low temperature
Preferences of omnivorous fish for animal vs. plant diet are driven by temperature.
The number of herbivores in populations of ectothermic vertebrates decreases with increasing latitude. At higher latitudes, fish consuming plant matter are exclusively omnivorous. We assess whether omnivorous fish readily shift to herbivory or whether animal prey is typically preferred. Preferences of omnivorous fish for animal vs. plant diet are driven by temperature (see graph). In the mesocosm experiment with rudd (Scardinius erythrophthalmus) as a model organism, animal vs. plant diet was offered in three different ratios 1:1 (grey), 1:10 (blue), 1:400 (green) under three different temperatures (16, 20 a 24 °C). Plant matter was mainly preferred under the highest temperature with the highest amount of offered plants. Decreasing plant matter and increasing animal prey led to a decrease in observed herbivory. Rudd essentially consumed only animal prey at the lowest temperature in all three experimental concentrations because low temperature inactivates enzyme cellulase responsible for cellulose digestion.
Therefore, we addressed temperature as the key factor causing their absence at higher latitudes and discuss the potential poleward dispersion caused by climate changes. More details may be found in the following publication:
Vejříková I., Vejřík L., Syväranta J., Kiljunen M., Čech M., Blabolil P., Vašek M., Sajdlová Z., Chung S., Šmejkal M., Frouzová J., Peterka J. (2016). Distribution of herbivorous fish is frozen by low temperature. Scientific Reports 6. doi: 10.1038/srep39600.
