Lock up your goldfish! Fish are on spiders' menus worldwide


Don’t tell your guppies, but fish eating spiders can be found on every continent apart from Antarctica, a new study has found.

While most spiders are insectivores, it is well documented that bats, birds, mice, amphibians and reptiles are also occasional prey items — but now it seems fish may be high on the menu of far more spiders than previously believed.

Researchers looked deeper into reports of fish predation, which up to now have been based largely on anecdotal evidence or from just a few locations. The results show that spiders from five families have been observed catching and eating fish in the wild with three more seen to do so when given the opportunity in laboratory conditions.

The fish eating behaviour of the Diving bell spider (Argyroneta aquatica) is well documented but this study focused on semi aquatic species which inhabit the edges of streams, swamps and ponds, grabbing fish by walking on the water surface or in some cases swimming and diving to snatch their unsuspecting fish supper.

Powerful, fast-acting venom and enzymes allowed them to take fish up to twice their own size with the largest observed prey item being a 9cm/3.5in goldfish from a pond in Australia. However, it seems that fish may be occasional 'super-size' treats rather than regular fodder as the majority of the spiders' diets was made up from insects.

The fish eating spider hot-spot was found in the wet lands of Florida where they feast on Mosquito fish, but two UK species of raft spider (Dolomedes fimbriatus and D. plantarius), are known to occasionally take small fish such as Sticklebacks.

For more information, see the paper: Nyffeler M, Pusey B.J (June 2014) Fish Predation by Semi-Aquatic Spiders: A Global Pattern.

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