In the first broad study of its kind, a group of scientists from Taiwan and USA leaded by Chih-hao Hsieh (assistant professor in the Institute of Oceanography, National Taiwan University) have found that the effects of climate change are being felt across a wide ensemble of fishes. These results are highlighted in the April issue of Nature.
Their study, to be published in an upcoming issue of the journal Global Change Biology is based on fish data from the California Cooperative Oceanic Fisheries Investigations, a program that has monitored the marine environment of the California Current for nearly 60 years. They studied 34 open-ocean fish species. Among their findings, the researchers describe a significant increase in the population of 25 fish groups between a 1951-1976 cold period and a 1977-1998 warm period. They also found that fish species that typically migrate vertically in the marine water column underwent a geographic shift northward to colder waters that wasn't seen in fish that don't migrate vertically. This may be because the upper layers of the water column warmed considerably more than deeper levels, leaving the bottom dwellers less impacted. Migrating species would have sensed the warming more readily and moved in response.
The researchers also found that groups that typically reside in the far open ocean shifted closer to shore between the cold and warm period, and species that normally reside in coastal areas moved even closer to shore. It's almost like seeing ocean invaders come into the coast, and these ad hoc mixed ecosystems could potentially have large ecological and commercial consequences.
Open ocean fishes that were rarely studied due to their low economic values may in fact provide important clues signifying how marine organisms responding to climate variations. The interactions found between oceanic and coastal-neritic species also imply that the anthropogenic disturbance, e.g. fishing, could have profound indirect effects on other components of the marine ecosystem. Long-term ecological surveys proved to be essential for marine management and conservation.
Reference and websites
Hsieh, C. H., H. J. Kim, W. Watson, E. Di Lorenzo, and George Sugihara.
Climate-driven changes in abundance and distribution of larvae of oceanic fishes in the southern California region. Global Change Biology.
Nature Research Highlights (Nature Magazine, 459: p142,