Critical Population Density Triggers Rapid Formation of Vast Oceanic Fish Shoals

Abstract

Similarities in the behavior of diverse animal species that form large groups have motivated attempts to establish general principles governing animal group behavior. It has been difficult, however, to make quantitative measurements of the temporal and spatial behavior of extensive animal groups in the wild, such as bird flocks, fish shoals, and locust swarms. By quantifying the formation processes of vast oceanic fish shoals during spawning, we show that (i) a rapid transition from disordered to highly synchronized behavior occurs as population density reaches a critical value; (ii) organized group migration occurs after this transition; and (iii) small sets of leaders significantly influence the actions of much larger groups. Each of these findings confirms general theoretical predictions believed to apply in nature irrespective of animal species.

Feasibility of Acoustic Remote Sensing of Large Herring Shoals and Seafloor by Baleen Whales

“…The coefficients n, α, and β given in Table 1 are empirically determined [2] by least-square fitting between the measured and the modeled ambient noise levels as a function of measured wind speed during the OAWRS 2006 experiment [22] ( Figure A1). The instantaneous measurements of ambient noise vary with 5.6 dB standard deviation [26].…”

“…An OAWRS experiment was conducted on the northern flank of Georges Bank during the peak annual Atlantic herring spawning period in the Fall of 2006 [1,22,24]. The spatial distribution of herring was instantaneously imaged and continuously monitored [22].…”

“…Detection of large herring shoals and the seafloor is then investigated using theoretical and numerical methods developed for analyzing Ocean Acoustic Waveguide Remote Sensing (OAWRS) of fish shoals [21][22][23][24][25] given these active sensing parameters. Sensing resolution in cross-range is determined by spatial array theory and in range by incoherent energy analysis [1,2,[21][22][23][24][25][26], since evidence suggests temporally coherent auditory processing is unlikely [27,28].…”

“…Typical well documented scenarios during the herring spawning season on Georges Bank [1,2,22,24,25] are investigated to determine ranges up to which detection of large herring shoals and the seafloor is feasible for given whale acoustic parameters. Detection of large herring shoals and the seafloor is found to be highly dependent on local ambient noise conditions at whale locations, herring shoal distribution, baleen whale vocalization parameters such as time duration and source spectra, as well as oceanographic conditions including sound speed structure, bathymetry, and seafloor scattering amplitudes along the acoustic propagation path.…”

Optimal cooperative searching using purely repulsive interactions

“…This correlation is mainly due to the chemical signaling that is taking place, since dicty tries to avoid searching areas that were previously covered by avoiding the chemo-repellent areas left by other dicty cells, as well as moving toward chemo-attractive signals, where there may be a high local concentration of nutrients. Previous studies of short range interacting Brownian particles have been used to model biological systems such as transcription proteins sliding along DNA [18] and the swarming behaviors observed in birds and fishes [19][20][21].…”