In virtually all of the studied scenarios, hunting by humans -- especially large-scale practices, like trawling -- outpaced nature-driven trait changes by over 300 percent. Now the question is: Are hunters permanently shaping animal populations, or do the observed changes reflect temporary demographic shifts rather than genetic evolution? Both, perhaps. "Some observed trait changes likely represent underlying genetic changes passed on from one generation to the next," Darimont explained. "In gill net fisheries, for example, evolution can favor smaller fish that pass through the mesh. Those smaller individuals are more likely to survive, reproduce and pass on genes for smaller offspring." "By contrast, some trait changes likely do not involve genetic changes, a process called plasticity," he added. "For example, shifts to earlier reproduction can occur because of an abundance of food being shared by a much smaller population of fish." Jeff Hutchings, a biology professor at Dalhousie University in Nova Scotia, told Discovery News that "we have known for some time that harvesting can affect the expression of various characteristics." He was surprised, however, by the magnitude of the difference between hunting-caused rates of change and those tied to other causes. "It is enormous," he said. Despite the apparent damage to ecosystems, Darimont said people could still turn things around. "In the context of human predation, if the goal is to minimize or eliminate harvest-induced changes, the key is to greatly reduce exploitation levels and to target the same size and age classes, that is, smaller and younger (prey), as natural predators do," he explained. Related Links: Treehugger.com: The Merits of Aquaculture |
advertisement
Put Discovery News on Your Site!
|
-
our sites
-
video
mobile
-
shop
-
stay connected
-
corporate
