In northern Australia the lesser salmon catfish (Neoarius graeffei) are being studied more closely since mice have mysteriously appeared in their bellies. It’s uncommon for Australian freshwater fish to consume terrestrial vertebrates, so the presence of spinifex hopping mice (Notomys alexis) in the bellies of catfish is an interesting phenomena. The Centre for Fish and Fisheries Research at Murdoch University in Perth, Australia delve deeper into the mysterious finding.

Ashburton River Study
Erin Kelly and her research team recently published their findings on the strange catfish and mice phenomena in the Journal of Arid Environments. For their study they took a sample of 18 lesser salmon catfish from the Ashburton River in northern Australia during the early dry season. Out of the lesser salmon catfish sampled, 44% had remains of spinifex hopping mice within their stomachs. And surprisingly the mice constituted about 95% of their stomach content, revealing that the lesser salmon species of catfish will consume large quantities of the terrestrial vertebrate when available.
 
Their research suggests that lesser salmon catfish are opportunist creatures that prefer to eat terrestrial vertebrates, such as mice, when given the chance. But this begs the question… how were the catfish able to feast on the spinifex hopping mice? Their name suggests that they get around by hopping, but it’s not part of their normal behaviour to intentionally spend time in the water. Kelly hypothesizes that heavy rainfall has unintentionally caused the mice to enter the Ashburton River. Mice often live in burrow systems in small colonies, and heavy rain may have collapsed or flooded one or multiple burrow systems along the river’s edge. This could explain how the mice entered the river system and why a large quantity of mice have been found in the bellies of the catfish.
 
Ecological Impacts
Peter Lisi, an aquatic ecologist at the University of Wisconsin-Madison, says that it still remains unclear and inconclusive how the catfish have access to the mice, how often this phenomena occurs, and at what scale the mice support the river’s food webs. Although more research needs to be done on the phenomena, Lisi sees these big meals for catfish as ecologically relevant. 
 
Some catfish are known to ambush pigeons at the water’s edge, but overall land vertebrates are not part of a regular catfish diet. The lesser salmon catfish in particular is known to eat mainly aquatic invertebrates and plants, and during floods in the wet season they also eat fruit and terrestrial insects. The lesser salmon catfish is a common species found in dryland rivers of north-western Australia and can weigh up to 1.5 kilograms and grow up to half a metre long. Since they’re prevalent in waterways such as the Ashburton River, it’s important to observe their diets in order to better understand the local ecosystems.
 
Kelly says that north-western Australia is predicted to face longer periods of drought and more intense rainfalls because of climate change. The changes in flooding patterns could largely alter the river ecosystems and their food webs. If the mice are indeed falling into the rivers because of intense flooding, then their population may face more danger in future flooding events.
 
Because of climate change, weather patterns are become more unpredictable all over the globe. It’s important for ecosystems to be continually monitored to observe and understand the changes and challenges climate change poses all around us. Not only are humans faced with issues of flooding and drought, but wildlife and ecosystems are also at risk of becoming endangered or even destroyed.