Mariani P, MacKenzie BR, Visser AW, Botte V
Individual-based simulations of larval fish feeding in turbulent environments
MEPS 347:155-169 | Full text in pdf format

 

Videos 1 & 2: simulated feeding processes under calm water conditions
robocod_1a.mpg (8MB), robocod_1b.mpg (6.2MB)
Videos 3 & 4: simulated feeding processes under turbulent water conditions
robocod_2a.mpg (2.7MB), robocod_2b.mpg (5.8MB)
Video 5: cod larva feeding in turbulence cod_turbulence_MK00.mpg (880KB)
NOTE: for the MPEG file it is recommended to set the play speed of the media-player to 'slow'

 

Individual-based model (IBM) simulations appear to be naturally suited for virtual reality technology. A virtual fish mimicking the behavior of a cod larva is used to show the encounter, pursuit and capture processes used in the individual-based simulations of cod feeding in turbulence. We ran the model, storing information about the trajectories of both predator and prey. Using the model outputs we derive the timing of the encounter, pursuit and capture process of a cod larva feeding on passive moving prey. We then reconstructed the feeding processes in calm and turbulence water using information to recreate the virtual environment implemented in the model. Moreover, we also provide a video (Video 5) of the behavior of a cod larva feeding in turbulence as observed by MacKenzie & Kiørboe (2000).

 

 

Video clip 1 shows the feeding in calm water while Video clip 3 shows the feeding process when turbulence (Â = 10^-6 m² s^-3) is considered. The point of view in the videos is that of the fish, as the camera is positioned on the head of the larva, while in Video clips 2 & 4 the camera is positioned outside the numerical box.

 

Green items are the prey and they are moving only when turbulence is added (Video clips 3 & 4). Note that we show in red the target prey, i.e. the prey that will be encountered, chased and captured by the cod larva. A black sphere is used to represent the cod larva (Video clips 2 & 4), while the surrounding sphere has a radius equal to the perception distance R = 1 cm.
Two additional panels are shown in the video. The lower right panel shows the top view (x- and y-axes) of the relative trajectories of the 2 particles (predator and target prey), while the lower left panel shows the relative distance (as function of time in seconds) between cod and the target prey item. The black line representing the distance turns to red when the cod starts to pursue the prey. The dashed line is equal to the predator reactive distance (R = 1 cm).

 

Note that in these simulations we used a prey concentration of 100 l^-1 in order to have encounter, pursuit and capture events in a short period of time. This concentration is 10-fold higher than the concentration used in the present study and makes short searching (i.e. swimming) events possible. As a result, the produced videos are shorter and smaller in size than if we had used 10 prey l^-1.

 

Video clip 5 shows a real cod larva feeding in a turbulent laboratory environment. This video is extracted from the dataset used by MacKenzie & Kiørboe (2000) for the analyses of turbulence-feeding interactions in cod larvae. Note that while exposed to moderate turbulence in this particular video, the larva uses its fins and tail to keep its position in the water while waiting for prey to be advected by the small scale velocity. The video shows 2 successful encounters, pursuits and captures.

 

LITERATURE CITED

 

MacKenzie BR, Kiørboe T (2000) Larval fish feeding and turbulence: a case for the downside. Limnol Oceanogr 45:1-10