La. Hansson et al., Biomanipulation as an application of food-chain theory: Constraints, synthesis, and recommendations for temperate lakes, ECOSYSTEMS, 1(6), 1998, pp. 558-574
The aim of this review is to identify problems, find general patterns, and
extract recommendations for successful biomanipulation. An important conclu
sion is that the pelagic food chain from fish to algae may not be the only
process affected by a biomanipulation. Instead, this process should be view
ed as the "trigger" for secondary processes, such as establishment of subme
rged macrophytes, reduced internal loading of nutrients, and reduced resusp
ension of particles from the sediment. However, fish reduction also leads t
o a high recruitment of young-of-the-year (YOY) fish, which feed extensivel
y on zooplankton. This expansion of YOY the first years after fish reductio
n is probably a major reason for less successful biomanipulations. Recent,
large-scale biomanipulations have made it possible to update earlier recomm
endations regarding when, where, and how biomanipulation should be performe
d. More applicable recommendations include (1) the reduction in the biomass
of planktivorous fish should be 75% or more; (2) the fish reduction should
be performed efficiently and rapidly (within 1-3 years); (3) efforts shoul
d be made to reduce the number of benthic feeding fish; (4) the recruitment
of YOY fish should be reduced; (5) the conditions for establishment of sub
merged macrophytes should be improved; and (6) the external input of nutrie
nts (phosphorus and nitrogen) should be reduced as much as possible before
the biomanipulation. Recent biomanipulations have shown that, correctly per
formed, the method also achieves results in large, relatively deep and eutr
ophic lakes, at least in a 5-year perspective. Although repeated measures m
ay be necessary, the general conclusion is that biomanipulation is not only
possible, but also a relatively inexpensive and attractive method for mana
gement of eutrophic lakes, and in particular as a follow-up measure to redu
ced nutrient load.