|
Vol. 43 No. 2, 2004
Potential Use of Extremely High Biomass and Production of
Copepods in an Enclosed Brackish Water Body in Lake Nakaumi, Japan, for
the Mass Seed Production of Fishes
Shin-ichi
Uye1,*, Shinobu Nakai1 and Moriyuki Aizaki2
1Graduate
School of Biosphere Sciences, Hiroshima University, 4-4-1 Kagamiyama,
Higashi-Hiroshima 739-8528, Japan
2Faculty of Life and Environmental Sciences, Shimane
University, Matsue 690-8504, Japan. Tel: 81-852-326582. Fax:
81-852-326598. E-mail: aizaki@life.shimane-u.ac.jp
Shin-ichi
Uye, Shinobu Nakai and Moriyuki Aizaki (2004) We found extremely
high abundance, biomass, and production rates of mesozooplankton in an
enclosed brackish water body (called the Honjo District) in Lake
Nakaumi, Japan, during a 2-yr investigation. To the best of our
knowledge, the overall biomass mean of 71.0 mg C m-3 is one of the
highest values recorded so far anywhere in the world. Copepods
dominated the zooplankton community in terms of abundance (94.4%) and
biomass (83.4%). Zooplankton biomass and production rates were twice as
high in Honjo District as those in adjacent Lake Nakaumi, although the
phytoplankton chlorophyll α concentration was twice as low. Two reasons
for the enhanced zooplankton standing stock in Honjo District might be
the development of weak benthic deoxygenation and lower numbers of
planktivorous fish. We propose to use zooplankton as a food source for
the intensive mass seed production of finfish. By our conservative
estimate, exploiting 10% of the daily zooplankton production (or around
2.5% of the biomass) of Honjo District would allow the production of
5.6 million red sea bream (Pagrus
major) or Japanese flounder (Paralichthys
olivaceus) seeds, and 15.4 million ayu (Plecoglossus altivelis) seed fish
annually.
Key words: Brackish
water ecosystem, Lake Nakaumi, Eutrophication, Mass seed production of
fish, Economic value.
*Correspondence: Tel: 81-824-247940. Fax: 81-824-227059.
E-mail: suye@hiroshima-u.ac.jp
|
