Hybrid metachronal rowing augments swimming speed and acceleration via increased stroke amplitude

Numerous aquatic invertebrates use drag-based metachronal rowing for swimming, in which closely spaced appendages are oscillated starting from the posterior, with each appendage phase-shifted in time relative to its neighbor. Continuously swimming species such as Antarctic krill generally use “pure metachronal rowing” consisting of a metachronal power stroke and a metachronal recovery stroke, while burst swimming species such as many copepods and mantis shrimp typically use “hybrid metachronal rowing” consisting of a metachronal power stroke followed by a synchronous or nearly synchronous recovery stroke. Burst swimming organisms need to rapidly accelerate in order to capture prey and/or escape predation, and it is unknown whether hybrid metachronal rowing can augment acceleration and swimming speed compared to pure metachronal rowing. Simulations of rigid paddles undergoing simple harmonic motion showed that collisions between adjacent paddles restrict the maximum stroke amplitude for pure metachronal rowing. Hybrid metachronal rowing similar to that observed in mantis shrimp (Neogonodactylus bredini) permits oscillation at larger stroke amplitude while avoiding these collisions. We comparatively examined swimming speed, acceleration, and wake structure of pure and hybrid metachronal rowing strategies by using a self-propelling robot. Both swimming speed and peak acceleration of the robot increased with increasing stroke amplitude. Hybrid metachronal rowing permitted operation at larger stroke amplitude without collision of adjacent paddles on the robot, augmenting swimming speed and peak acceleration. Hybrid metachronal rowing generated a dispersed wake unlike narrower, downward-angled jets generated by pure metachronal rowing. Our findings suggest that burst swimming animals with small appendage spacing, such as copepods and mantis shrimp, can use hybrid metachronal rowing to generate large accelerations via increasing stroke amplitude without concern of appendage collision.

Swimming Performance of Four Carps on the Yangtze River for Fish Passage Design

Anthropogenic engineered structures alter the local ecological connectivity of river and survival habitat of native fishes. The swimming performance is critical for establishing fish passage or fish habitat. This study evaluated the swimming performance of four carps (black carp, grass carp, silver carp and bighead carp) with smaller body lengths (1.0–9.0 cm) in a swimming flume. The results showed that the critical and burst swimming speed (m/s) of the four carps increased with the increased body length, and the relative (critical and burst) swimming speed (the critical and burst swimming speed divided by the body length, BL/s) decreases with body length. The critical and burst swimming speed of each species at two individual length groups (1.0–5.0 cm, 5.1–9.0 cm) was significantly different (p < 0.05), and the water velocities in fish passage should be less than the fish burst swimming speed. The results further provided the swimming performance data of juvenile carps and provided technical reference for the construction of fish passage and the restoration of ecological habitat.

Morphometry and burst swimming in six continental fish species from Costa Rica

Introduction: Current research of fish locomotion is focused on creating better underwater vehicles and how environmental stress factors modify swimming. Objective: To study the relation of morphometric characteristics with burst swimming in six representative species of continental fishes from Costa Rica. Methods: We measured total length, standard length, height and area of the tail of 38 individuals from six species. We used a Kruskall-Wallis test and a Boxplot graphic to compare species; and a PCA test to identify body variables that influence swimming. A Non-Metric Dimensional Scaling (NMDS) test was done for species and position in the water column. Results: The fastest swimming corresponded to A. nigrofasciata (9,29cm/s), while S. salvini (1,65cm/s) was the slowest. Burst swimming speed is influenced by body size and tail type, and differed with position in the water column, being surface species the fastest. Conclusions: Morphological and ecological characteristics determine differences in burst swim.

A Classification Method for Fish Swimming Behaviors under Incremental Water Velocity for Fishway Hydraulic Design

In fishway design, the combination of fish swimming behaviors and suitable fishway hydraulic characteristics increases the fish passage efficiency. In this study, the most representative grass carp among the “four major Chinese carps” was selected. Under conditions similar to the time period for feeding migration, juvenile grass carps were targeted to study the swimming characteristic indicators (i.e., critical and burst swimming speeds) and swimming behaviors that were closely associated with fishway hydraulic design using the incremental water velocity method in a homemade test water tank. (1) The study results reveal that both the absolute critical (Ucrit) and burst (Uburst) swimming speeds increased linearly with increasing body length and both the relative critical (U’crit) and burst (U′burst) swimming speeds decreased linearly with increasing body length. There existed a quantitative relationship between Uburst and Ucrit, which could facilitate the fishway hydraulic design. (2) This study analyzed the effects of water velocity changes on fish swimming behaviors and proposed a classification method for four fish swimming behaviors—swimming freely, staying, dashing at a long distance, and dashing at a short distance—of tested fish during the process of adapting to water velocity changes interspersed with one another. The entire swimming process under the incremental water velocity was divided into four stages. (3) This study suggests that the maximum water velocity of the mainstream in a fishway using grass carp as the major passage fish should not exceed 52–60% Uburst at stage 1. For the high-water velocity areas of a fishway, such as vertical slots and orifices, the optimal water velocity should not be higher than 76–79% Uburst at stage 2 and should absolutely not exceed 90–96% Uburst at stage 3.

Swimming performance of sauger (Sander canadensis) in relation to fish passage

A lack of information on the swimming abilities of sauger (Sander canadensis), a highly migratory species particularly sensitive to habitat fragmentation, may inhibit the design of effective passage structures for this species. Passage success, maximum ascent distances, and maximum sprint velocities of sauger were estimated in an open-channel flume over a range of water velocities (51, 78, and 92 cm·s−1) and temperatures (10.0, 14.3, and 18.3 °C) to assess swimming performance. Passage success was high (91%) over all test velocities, as was the maximum instantaneous burst velocity (219 cm·s−1). Water temperature and body size had little effect on swimming performance. Sauger transitioned from steady, sustained swimming to unsteady, burst–glide, or steady burst swimming at 97 cm·s−1. Sauger were capable of sustained sprints of 124 cm·s−1 over 15 s duration in a swim chamber. Results suggest passage structures with water velocities less than 97 cm·s−1 should provide high probability of successful passage of adult sauger, whereas structures with water velocities exceeding 219 cm·s−1 may be impassable.