Analysis of the internal arrangement of individuals within crustacean aggregations (Euphausiacea, Mysidacea)

The hydrodynamic disturbances of two species of krill: implications for aggregation structure

“…Fig.1 indicates that the NNDs are in the range of less than two body lengths for these data. Consistently, the NNDs from previous laboratory studies of schooling krill range from 0.4 to three body lengths (O'Brien, 1989;Kawaguchi et al, 2010). Because the hydrodynamic perturbation of E. superba is present at a distance of less than four body lengths, the potential cue is within the range of schooling individuals.…”

“…Although data are not available on the internal arrangement of aggregations for this species, E. pacifica has a more vertically oriented flow field whereas E. superba has a horizontally oriented flow field that could contribute to the long layering noted in schools of the polar species versus the vertical migratory behavior of the temperate species. Euphausia superba have been reported to school in aquarium during the day (O'Brien, 1989;Strand and Hamner, 1990;Kawaguchi et al, 2010) and in the natural environment during the day and night (Hamner et al, 1983). The length of a school is reported to be up to 100m (and larger for superswarms) (Tarling et al, 2009), and the schools tend to be narrow in one dimension such that an individual is only a few meters from clear water (Hamner et al, 1983;Hamner, 1984).…”

“…Because the hydrodynamic perturbation of E. superba is present at a distance of less than four body lengths, the potential cue is within the range of schooling individuals. Individuals positioned to the side of juvenile E. superba have a smaller NND (less than one body length) than individuals in front of or behind the krill (one to two body lengths) (O'Brien, 1989). O'Brien (O'Brien, 1989) reports that E. superba often swim at the same elevation as their neighbors, i.e.…”

Influence of physical and biological mesoscale dynamics on the seasonal distribution and behavior of Euphausia superba in the antarctic marginal ice zone

“…Euphausia superba are sensitive to variation in food availability (Hamner et al 1983) and changes in risk of predation (Hamner 1984, O'Brien 1987b. In one experimental study, the structure of krill swarms did not appear to change in response to water flow but rather to behaviorally induced mechanisms, such as food and predators (O'Brien 1989). In another study, krill were induced to swarm in a tank when a model of a predator was introduced (Strand & Hamner 1990).…”

Energetic cost of position-holding behavior in the planktonic mysid Mysidium columbiae

“…Since there are energetic costs associated with maintaining these aggregations, both in terms of increased metabolic costs associated with swimming behavior to overcome turbulence and currents, and in terms of decreases in food availability within densely packed swarms and 'E-mail. buskey@utmsi utexas edu schools, it seems reasonable to assume that the zooplankters must accrue some adaptive advantage from these aggregatlve behaviors The suggested adaptlve values of swarmlng and schooling behavior In planktonic myslds include protection from predators (O'Brien R Ritz 1988, Ritz 1991, facilitation of m a t~n g (Clutter 1969), and maintaining posltion In the envlronment (Clutter 1969, O'Brien 1988, Ritz 1994 Mysid schools have been extens~vely studied ( e g Clutter 1967, 1969, Mauchline 197 1, Wittman 1977, O'Brien 1988, 1989, Modlln 1990, 1993 but much remains to be learned about these active crustaceans with sophisticated sensory capablllties and complex social intelactlons While inany species of mysids are associated with the benthos durlng the day, Mysldium spp are predominantly holoplanktonic (Emery 1968, Mauchline 1980) The m y s~d M y s~d i u r n colurnbiae is usually found in the shaded aleas near mangroves (Steven 1961), ~t 1s also found In the vicin~ty of coral reefs, mainly in areas protected fiom stlong curlents (Emery 1968) It has well developed compound eyes that are thought to have limited visual acuity but swimming speed and respiration rate to examine the highly developed movement perception (Waterman metabolic cost of position-holding behavior. 1961, Buskey unpubl.).…”