THE big beasts are doomed. That’s the bleak message from a marine biologist who has found that body size is an excellent predictor of which fish species are likely to become extinct. And he says the same rule should apply to land animals, insects and even plants.
Nick Dulvy from the University of East Anglia in Norwich was frustrated that few people seemed to have noticed that many fish species are disappearing from the oceans. “Counting fish is an impossible task, so I wanted to find another way of predicting which species were most vulnerable,” says Dulvy.
Luckily, fishers boast about their prize catches, so there is good data on the maximum body size of thousands of fish species. Dulvy studied the data for 230 species of skate and found that most of those known to be disappearing fastest, such as the common and barndoor skate, are also among the largest. He believes the study has revealed several other species at risk, such as the smooth skate of New Zealand and the big skate of California.
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On land, large species like rhinos, tigers and the great apes are famously endangered. Some scientists say their smaller, less celebrated cousins such as wildcats or monkeys are at equal risk. But Dulvy’s work suggests that the big animals are more vulnerable.
“Obviously people prefer to hunt large species. But large species also tend to mature later and have lower reproductive rates, so they are less able to replace the numbers killed by man,” he says.
Dulvy thinks biologists will continue to count land animals to pinpoint vulnerable species. But his prediction could be especially useful for elusive sea creatures, about which we know very little. “It will allow us to decide which species to investigate first.”