Gossamer webs and silken threads are what most of us associate with spiders. But that is just part of their story. The wonderful world of spiders is as complex as their webs. Interestingly, not all spiders have eight eyes, not all spiders build webs or wait to ambush their prey. Some of these highly skilled and diverse creatures, like fishing spiders, even catch fish and other invertebrates.
In Cooch Behar, West Bengal, wildlife photographer Ripan Biswas captured some rare and stunning images of a species of fishing spider (Nilus albocinctus). Every monsoon evening, Biswas went to a seasonal swamp near his home to photograph insect life. On one such walk he came across a peculiar spider poised on top of vegetation. It had a fish almost as large as itself in its mouth. What Biswas saw was a fishing spider or fish-eating spider in action (Nilus species, earlier classified as Thalassius). A semi-aquatic spider, the Nilus albocinctus belongs to the Pisauridae family commonly known as nursery web spiders. Pisauridae spiders closely resemble wolf spiders, and are also called hunting spiders.
The swamp area he visited was used for paddy cultivation during the summer, and come monsoon it brims with insect life. Biswas hadn’t seen these water-loving spiders before. Over the next three years that he documented their lives, he managed to photograph them hunting fish only three or four times. “There are several species of fishing spiders but sighting them while they are actually eating a fish is extremely rare,” he says.
This spider is often found near water, preferring shallow water sources like forest streams, swamps, and wetlands. Running water contains more dissolved oxygen than still water because more contact with the air allows more oxygen to mix into the water. In swamps and ponds, these opportunistic hunters have been observed taking advantage of the low oxygen levels which require fish to come up to the surface in search of oxygen-rich water. “This could also explain why I have often seen these spiders hunt at night,” Biswas adds, “At night the oxygen levels reduce even more.” Dissolved oxygen levels tend to drop at night as aquatic photosynthesis is light dependent.