Phytoplankton Preferences of Young Silver Carp,Hypophthalmichthys molitrix, in Hypereutrophic Mesocosms during a Warm Season

Abstract

The feeding behavior of age-1 silver carp, Hypophthalmichthys molitrix (Val.), on phytoplankton species in a shallow hypereutrophic lake was studied in enclosures from 22 May to 18 September, 1997. Over the experimental period, the filter-pore sizes of the fish and the total biomass of the phytoplankton in each enclosure changed little with time. The fish biomass in each enclosure increased with time, while the percentage of weight gain correlated negatively to the stocking density, due perhaps to competition for prey. Analysis of gut contents of silver carp showed a strong similarity between the algae in the foregut and the algal communities in the water and this was significant (pC0.05) for the enclosure with a low fish density. There were weak relationships between the sizelshape of phytoplankters and the selectivity of fish on them (~0 . 0 0 1 , p>0.5). Silver carp fed unselectively when cyanobacteria populations were high, even though the selectivity index for diatoms was slightly higher than those for cyanobacteria, green algae, and cryptomonads.

A Review of Nontraditional Biomanipulation

“…Summed from 30 field enclosure (microcosm or mesocosm) experiments managed on silver or bighead carp conducted in various water systems since 1975, the average success rate of nontraditional biomanipulation is about 63% (19 of 30 case studies [29,33,38,42,44,68,70,100,103,104,105,106,107,108,109,112]) and nine experiments indicate fish did not significantly suppress phytoplankton [27,38,43,47,101,108,110,113], and planktivorous fish have no effects in other studies [44,89] (Table 1). Here we consider management to be successful if total algal biomass is suppressed after fish introduction.…”

Seasonal Variations of Planktonic Ciliates with Reference to Their Prey in a Shallow and Eutrophic Korean Stream

“…However, predators such as fish (Kim et al 2003), ciliates (Takamura et al 1966 and, and zooplankton display remarkable preferences for various phytoplankton species. Our results suggest that prey selection of ciliates can be broadly divided into two types.…”

Bacterium and Fish-Mediated Morphological Changes of the Toxic CyanobacteriumMicrocystis aeruginosa

“…(Fukushima et al 2001, Kim et al 2003. To date however, no studies have been conducted on the grazing activities of 0. latipes or T. albonubes, due perhaps to their susceptibility to toxic algae and their relatively restricted habitats.…”