Fish Swimming 2013
Dr. Paolo Domenici
The Fish Swimming course was taught for a sixth time at Friday Harbor Labs this summer. The course is typically very international as it has attracted students from more than twenty countries around the world over the years. This year we had twelve students, coming from the USA, Canada, the UK, Brazil, Australia, Italy, Spain, Denmark and France. The first part of the course was lecture based, and students were introduced to the principles of fish swimming, in terms of hydrodynamics and kinematics, as well as to the energetics of exercise and to behavioural and ecological aspects of fish locomotion. In the second part of the course, students worked in groups of three. Each group developed a project, which was discussed with the instructors. Under the instructors’ supervision, students set up the projects, carried out the experiments, the data analysis, the statistical analysis, and wrote the project reports. This year the students came up with four challenging projects, all of which gave interesting results:
Tyron Lucon Xiccato (U Padua, Italy), Julie Nati (U Glasgow, UK), and Felipe Rocco (U Sao Carlos, Brazil) investigated the effect of acute hypoxia on staghorn sculpins' behavioral lateralization. Preliminary work by this team showed that this species of sculpin is right-lateralized, i.e. individuals tend to turn most often to the right when facing a barrier. This type of lateralization is known to be due to functional asymmetries in the brain and to be an advantage in fish and other animals, because it allows them to have high cognitive performance when multitasking. The team found that after exposure to acute hypoxia, sculpins lost their lateralization, having equal probability to turn left or right when facing an obstacle. This implies that hypoxia may have an effect on brain functional asymmetries in intertidal fishes like sculpins, which are often subject to fluctuating environmental conditions.
Lauren Nadler (James Cook U, Australia), Stephanie Snyder (Scripps Inst. Oceanography, USA), and Jeppe Bayley (U Aarhus, Denmark) looked at two aspects of respirometry in their project. In the first part of their experiments, they examined three methods for exposing fish (shiner perch) to hypoxia while measuring oxygen consumption using respirometry. Preliminary analysis indicates that the most consistent results were produced by a long acclimation period (minimum of 12 hours) and intermittent-flow respirometry. Trials conducted using short acclimation periods (1 hour) and closed respirometry produced highly variable results in terms of indicators for hypoxia tolerance, likely due to the accumulation of CO2 and wastes that occurs with this method. In the second part of their project, the team looked at the calming effect of schooling behavior and its effects on hypoxia tolerance. Preliminary analysis indicates that the presence of conspecifics did not exert a calming influence on the focal individuals nor did it increase hypoxia tolerance, though further analysis on kinematic variables and ventilation frequency is still underway.
Julie van der Hoop (MIT/Woods Hole Oceanographic Institution, USA), Margaret Byron (UC Berkeley, USA), and Karlina Ozolina (U Manchester, UK) examined the effect of different levels of flow turbulence on swimming energetics and kinematics in shiner perch. While previous studies have shown increases in metabolic demand associated with swimming in more turbulent flow regimes, this group found consistent results showing the opposite, where all individuals expended more energy when swimming in more controlled, straightened flow. It is known that some fish are able to harness energy from fluctuating water movements to decrease energy expenditure for swimming. Though it is still under investigation, the group hopes to find how these individuals are able to change their kinematics in response to different flow conditions to increase swimming efficiency.
Ana del Pozo Cano (U Murcia, Spain), Marie Durollet (U La Rochelle, France) and Morten Bo Søndergaard Svendsen (U Copenhagen, Denmark) studied the effect of the time of day on the escape response in staghorn sculpins. First, fish displayed nocturnal daily activity during a 24 h cycle under a natural photoperiod of 15 h Light: 9 h Darkness. Later, the escape response to a mechanical stimulus was investigated at 4 different times of day (at 1:30, 7:30, 13:30 and 19:30 h). Sculpin escape response depended on the time of day since lower responsiveness and longer travelled distance occurred at night, although no statistical differences between times of day were found in some escape response parameters, such as directionality (fish always escaped away from the threat), escape latency and turning rates. These results suggested the elusiveness of sculpins is reduced during their active phase (at night), but when they do respond to the startling stimulus, their night-time fast-start performance in terms of travelled distance is greater compared to other times of the day.