Heat Waves & Guppy Appetites: How Warm Water Spells Trouble for Freshwater Life

Global warming is heating up freshwater habitats, and non-native fish are invading these places. Usually, scientists look at these issues separately, but they're both big threats to biodiversity. Fish are ectotherms, meaning their bodies are influenced by the temperature of their water. So, when water gets warmer, it can make fish hungrier and change how much food they eat. This is especially true for fish from warmer places that are now invading cooler waters. Plus, in fish with big differences between males and females, like the tropical guppy, warmer water can make males and females act differently towards their food.

Scientists did a lab study on tropical guppies (Poecilia reticulata Peters). They checked how much these fish eat mosquito larvae under different water temperatures, and how the size of the larvae affects the guppies' eating habits. They also looked at how being pregnant changes a female guppy's dinner time. Guppies ate more as the water got warmer, both males and females. But females ate more than males at any temperature. Warmer water also changed what size larvae females like to eat, while males didn't seem to care. Pregnant females ate even faster. So, when the water heats up, invasive fish like guppies can eat more and be pickier about their food. That means scientists need to consider both temperature and differences between males and females to understand how invasive fish can threaten local food chains.

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