Scientists from NOAA's National Marine Fisheries Service report a significant decline of endangered white abalone off the coast of Southern California in the journal Biological Conservation.
"Since 2002, we have been surveying white abalone off San Diego using an underwater remotely operated vehicle (ROV)," said Kevin Stierhoff, research fisheries biologist at NOAA's Southwest Fisheries Science Center in La Jolla, and lead author of the journal article. "In the absence of fishing, we hoped to see the population stabilize or increase. However, our latest assessment using data collected in 2008 and 2010 indicates that the white abalone population has continued to decline by approximately 78 percent over the last ten years."
The abalone breeding strategy does not work well when their population densities get too low.
These results confirm predictions made by scientists in 2001 suggesting that wild populations had dwindled to levels that were too low to support successful reproduction, and that as animals died of natural causes, a new generation would not emerge to replace them. White abalone are "broadcast spawners," projecting eggs and sperm into the water column at the same time for fertilization. If there is not a suitable partner close by, it is unlikely any offspring will be produced.
"Unfortunately we have continued to see white abalone grow larger, older and further apart with no evidence of significant numbers of offspring for the last ten years," said John Butler, a research biologist at NOAA's Southwest Fisheries Science Center and co-author of the article. "While it could be the juveniles are hiding or too difficult to see, it is more likely that the species is just failing to reproduce."
The scientists see a need for captive breeding programs, or else the species will not survive. Wow.
|Share |||Randall Parker, 2012 July 08 06:59 PM Trends Extinction|