Steep reductions in the abundance of fish, shellfish, and other aquatic fauna in recent centuries are not restricted to animals that live in the sea: historical records show that species in rivers and lakes worldwide also experienced sharp declines. Yet the significance of these declines in freshwater species is frequently overlooked by natural resource managers, according to an article in the September 2009 issue of BioScience.
Authors Paul Humphries and Kirk Winemiller argue that as a result of this neglect of historical records, watershed planning is often built on estimates of baseline abundances of fish, freshwater mussels, and beavers that are much lower than actual past abundances. Planners consequently underestimate the likely far-reaching effects such animals had on their ecosystems before European colonization.
Although precise historical numbers cannot be known, written accounts dating from the 1600s suggest that abundances were much greater than they are today. Travelers and diarists reported rivers so full of fish that a spear thrown into the water only rarely missed one, salmon runs that spanned the whole width of a river, and fish so plentiful that they were used as pig feed.
Humphries and Winemiller point out that European colonizers in North America and Australia, in particular, could easily move inland from coastal communities to supplement their seafood with food taken from freshwaters. Then, within a few decades, they started constructing weirs and mills that impeded the migration of fishes and put further pressure on stocks. Stocks of fish and shellfish declined rapidly after colonization. The effects of this early loss of wildlife on the river ecosystems, the authors contend, has not been adequately considered.
Freshwater systems that have been little exploited seem to confirm the strong effects of fishing pressure in freshwater systems. Humphries and Winemiller cite the case of rivers in the Lake E
'/>"/>
| Contact: Jennifer Williams jwilliams@aibs.org 202-628-1500 x209 American Institute of Biological Sciences Source:Eurekalert |
Related biology news :
1. Shifting Sands highlights past, present and future of Maryland coastal bays ecosystem
2. Sand dollar larvae use cloning to make change, confound predators
3. Genome of simplest animal reveals ancient lineage, confounding array of complex capabilities
4. Baiji Dolphin previously thought extinct spotted in the Yangtze River
5. UC Riverside biologist receives prestigious MacArthur Fellowship
6. International team of scientists warns of climate changes impact on global river flow
7. Stronger EPA leadership needed to improve water quality in Mississippi River
8. UC-Riverside partners with Chinese university to address Chinas environmental problems
9. X-effect: female chromosome confirmed a prime driver of speciation
10. Tiny fish can yield big clues to Delaware River health
11. Scientists from the UGR prove that rivers do not act as barriers for groundwater flow
| Copyright © 2003-2012 Bio-Medicine. All rights reserved. ABOUT | CONTACT US | DISCLAIMER | PRIVACY POLICY | TERMS AND CONDITIONS |  |