Swimming Behavior of Individual Zooplankters During Night-Time Foraging.
Abstract
Amatzia Genin, Jules Jaffe, Duncan McGehee developed a method for automatically tracking individual plankters swimming through the imaging volume, and applied the method to track approximately 280,000 animals. Net samples indicated that most of the acoustic targets tracked were euphausiids in the 11-13 mm range. This was supported by target strength measurements coupled with an acoustic scattering model for euphausiids based on the distorted-wave Born approximation. Total movement of the animals was treated as the sum of two components: (1) an average component shared by all the animals, due in the horizontal dimension to currents and in the vertical dimension to internal waves, and (2) a random component due to the behavior of the individual animals. The average horizontal speeds measured acoustically agreed with measurements from a current meter mounted on the mooring. the random component of euphausiid movement was isotropic in three dimensions with the distribution of velocities in each dimension approximated by a zero-mean Gaussian random variable whose standard deviation depended on the time of night. One data set was dominated by small fish. Here the random behavior was not Gaussian, and was probably affected by the presence of the sensor. A Monte Carlo simulation of euphausiid behavior was made by applying velocities from a zero-mean Gaussian distribution to thousands of individuals, and filtering the modeled movement through a mathematical model of fish TV. This yielded a set of model-based observations that agreed with the in situ measurements.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 29, 1998
- Accession Number
- ADA358435
Entities
People
- Duncan E. Mcgehee
Organizations
- Woods Hole Oceanographic Institution