Other students and colleagues of Don Kramer have investigated the risk of predation
by piscivorous fishes rather than birds. Robert Poulin has found that guppies did not
run a greater risk of being caught by oscars under hypoxia, probably because the
predatory oscars were just as affected by the lack of oxygen as their prey. In contrast,
Nancy Wolf has observed that giant snakeheads, Channa micropeltes, were more
successful at capturing dwarf gouramis, Colisa lalia, at 1 ppm than at 3 or 8 ppm,
because the gouramis had to leave the cover of submerged plastic plants to go near
the surface. The difference between the two studies may be that predatory air
breathers, such as snakeheads, are not as adversely affected by hypoxia as predatory
water breathers, such as oscars.22
Other students and colleagues of Don Kramer have investigated the risk of predationby piscivorous fishes rather than birds. Robert Poulin has found that guppies did notrun a greater risk of being caught by oscars under hypoxia, probably because thepredatory oscars were just as affected by the lack of oxygen as their prey. In contrast,Nancy Wolf has observed that giant snakeheads, Channa micropeltes, were moresuccessful at capturing dwarf gouramis, Colisa lalia, at 1 ppm than at 3 or 8 ppm,because the gouramis had to leave the cover of submerged plastic plants to go nearthe surface. The difference between the two studies may be that predatory airbreathers, such as snakeheads, are not as adversely affected by hypoxia as predatorywater breathers, such as oscars.22
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