Calculation of search volume on cruise-searching planktivorous fish in foraging model.

Search volume of cruising planktivorous fish was calculated based on its detailed behavior Th examine the factors influencing search volume, a series of experiments were conducted by varying ambient conditions, such as structural complexity light intensity and turbidity Pseudorasbora parva were used in experiment as predator and Daphnia pulex was selected as prey The shape of scanning area of P parva showed elliptic and the search volume changed drastically depending on ambient conditions. Compared with the results of previous foraging model, the search volumes of the fish under previous study were larger (1.2 to 2.4 times) than those from our study These results on the changes in feeding rate can be useful in determining microhabitat requirement of P parva and othercyprinids with a similar foraging behavior The calculated search volume is compared with other foraging model andthe effect of zooplankton-planktivore interactions on aquatic ecosystem is discussed.

Effects of stream hydraulic conditions on foraging strategies of false dace, Pseudorasbora parva, in the lentic ecosystem.

The effects of current velocity on the foraging behavior of false dace, Pseudorasbora parva, were examined in a zero velocity (stagnant) condition, and at four flow rates (5, 7, 11 and 16 cm per second). In stagnant water, the fish displayed a cruise-searching pattern, but they used a drift-feeding foraging tactic in flowing water. The shape of the transverse field of reaction field was elliptical in the stagnant condition, whereas their downward regions were restricted under the flowing conditions. The fish had a blind spot oriented directly in front of their reaction field. Although the relative swimming speed (with considering the against current velocity) increased with increasing flow velocity, the absolute search speed (ignore the against current velocity) showed about 1.2 fish body length per second at stagnant water and low flow velocity. The results of feeding rates showed stop-and wait (driff-feeding) foraging strategy is more efficient in flowing water because prey drift directly towards the fish and prey easily detected.

Effects of environmental conditions and prey size on locomotion behaviors of planktivorous fish.

The locomotion behavior of Pseudorasbora parva was observed in laboratory under various light intensity, turbidity, structural complexity and zooplankton size, focusing on swimming speed and time of search, approach, and attack. At low prey density, the satiation level affected the swimming speed only slightly. The search speed was nearly constant regardless of the satiation level to reduce the swimming energetic cost when opportunities of encountering prey were low. However, the attack and approach speeds slightly decreased with satiation. With increasing visual and swimming conditions, the approach speed increased markedly, but the search and attack speeds did not. Although the time for the approach and attack to capture a prey did not change much with decreasing swimming and visual conditions, the search time significantly increased to compensate for the decreased swimming speed.