This chapter discusses the form, function, and locomotory habits in fish. Most fish swim by pushing back against the water with undulations of their body or their fins. Water is unfavorable in that it presents a yielding medium against which to push, and much energy may be wasted in making profitless eddies. Few species of fish walk on the bottom underwater with their paired limbs. On the other hand, those fish that make excursions out onto land usually have to resort to walking or skipping in some fashion, as the air provides an insubstantial medium against which their usual body undulations can act. Some fish are capable of brief aerial locomotion by passive gliding rather than by flying (and swim underwater by conventional body undulations). They are comparable to those restricted groups of mammals, amphibians, and reptiles that can glide but are not primarily adapted to this mode of locomotion. Only few fish (including the Gasteropelecidae and Pantodon ) can fly in the air by beating their wings. The formidable problems of simultaneous adaptations for locomotion, both in midair and underwater, have been overcome among the vertebrates only by diving birds such as loons.

1 - Form, Function, and Locomotory Habits in Fish

http://ieeexplore.ieee.org/iel5/5007879/5007912/05007924.pdf

Biological Rhythms

The purpose of this paper is to present a hypothesis on the nature of the schooling behaviour of fish based on an ethological investigation of schooling. Recognizing the disadvantages of a limited amount of data and of the use of different species for different parts of the study, the following tentative picture is suggested. Schooling may be considered an instinct as defined by TINBERGEN and is at a relatively low level in the hierarchical organization of behaviour. It has typical appetitive behaviour and a consummatory situation. A single fish separated from its school searches until perceiving a group of fish. It then approaches the group. In most cases vision is the only sense involved in this approach. If more detailed specific stimuli are then perceived (possibly through any of the sense organs) the fish ceases searching and remains with the school; if not, it soon leaves, and appetitive behaviour continues until the appropriate consummatory situation (being in a school of the same species) is attained. This hypothesis is based on the following points: 1. A school of fish is an aggregation formed when one fish reacts to others by remaining near them. 2. Typical features of Gasterosleits ticuleatus and Scardinius erythrophthalmus schools are: performance of the same activity at the same time by all fish, lack of aggressivcness between members and equality of rank of all members. 3. Blinded Scardinius fail to show typical schooling but remain in an area where odours from other Scardinius can be detected. This response may keep schools of this species from scattering widely at night. 4. Visual perception of a school of fish releases approach in single Scardinius and Pristella riddlei. 5. When presented with two different-sized schools of their own species single Gasterosteus, Scardinius and Leuciscus ntlilus prefer the larger to the smaller group. 6. A small Gasterosteus prefers six large to six small Gasterosteus. 7. A single Gasterosteus prefers a school of its own species to a school of Rhodeus amarus but shows no consistent preference when either Pygosteus pungitius or Leuciscus are presented together with Gasterosteus. 8. A single Pristella prefers a school of unoperated Pristella to a school with amputated dorsal fins. The dorsal fin with its conspicuous black patch is jerked more rapidly after alarm. This structure and its special movement may be considered a social releaser. 9. Increased feeding motivation leads to limited dispersal of a school of Gasterosteus. The head-down feeding posture is a signal attracting others in a school to a source of food. 10. Alarm causes an increase in density of a school of Gasterosteus. 11. With increasing reproductive motivation male Gasterosteus cease schooling and try to hold territories. Females disperse to a limited extent.

/pdf/some-aspects-of-the-schooling-behaviour-of-fish-4rg0l5cdof.pdf

Some Aspects of the Schooling Behaviour of Fish

Concise equations for the tangential, radial, and axial velocities as well as the water surface profile of air-core vortices at hydraulic intakes have been derived. The equations were developed by modifying the equation for tangential velocity originally proposed by Rosenhead in 1930. Laboratory experiments were conducted on strong air-core vortices near a water intake. The results indicate the equations agree with experimental measurements and are applicable to vortex motion in general. The equations for radial and axial vortex velocities contain an eddy-viscosity term, which should be proportional to vortex circulation. Dimensionless parameters describing the circulation and intake Froude numbers and the intake submergence are also used in the analysis. Using these equations, the depth and three velocity components of an air-core vortex at certain hydraulic intakes can be predicted. This information may be helpful to the practicing engineer in determining the submergence required to avoid air-entraining vortices at intakes.

Velocity of Air‐Core Vortices at Hydraulic Intakes

An investigation was conducted to study the onset of air-entraining vortices at a horizontal intake, with and without a bellmouthed entry, when the intake was projected into the experimental flume or mounted flush with the side wall. The basic non-dimensional parameters that govern the onset of vortices at a horizontal intake in model and prototype have been derived and determined experimentally. The results of measurements are given as a set of curves, which can be used for the design of a vortex-free intake and also for the selection of appropriate model scales. The results of the measurement showed that flow conditions in an air-entraining vortex is not affected by surface tension and the viscosity of the test fluid when the radial Reynolds number, and the Weber number are larger than 3x104 and 104 respectively. In this case the formation of vortices depends largely on circulation, submergence head and discharge into the intake. It was found that the bellmouth did not improve the performance of the int...

Similarity Of Free-Vortex At Horizontal Intake

https://science.sciencemag.org/content/sci/118/3064/321.full.pdf

Observations on the Daily Movements of Fishes.

Analytical and experimental studies were carried out to develop additional data on energy losses at a junction for systems operating in the Reynolds number range of between 10 and 10,000. The test pipe fittings were short-radius, galvanized screwed tees operated so as to produce both a combination and division of flow. The fittings were mounted in a 3/4-in. standard black iron pipeline with SAE No. 10 cylinder oil being circulated by a gear pump driven by a variable speed motor. The analytical phase of the program yielded fitting loss coefficients which can be used to estimate the energy loss due to the fitting over and above that due to straight pipe friction. It was concluded from an analysis of the results that the relationship between the loss coefficients and Reynolds number for pipe fittings can be represented by a family of curves similar in format to those of the Moody diagram for flow in straight pipes without fittings.

Junction Losses in Laminar and Transitional Flows

Effect of Viscosity on Vortex-Orifice Flow

Phenomenological explanations are given of the mechanisms associated with "nondisturbed" and "disturbed" flows in branching conduits, as well as straight ducts. Four categories of flow conditions are defined covering situations ranging from deep in the laminar regime (R less than 10) to high in the complete turbulent regime. Analytical concepts are reviewed and guidelines are presented for the construction of a standardized laboratory test apparatus. Protocols are presented to aid the design engineer in the calculation of energy losses in pipe flow resulting from fittings, with particular reference to the combining and dividing flows for pipe tees, branches, and manifolds. /Author/

James R. Villemonte

Papers

Observations on the Daily Movements of Fishes.

Junction Losses in Laminar and Transitional Flows

Effect of Viscosity on Vortex-Orifice Flow

Some Basic Concepts on Flow in Branching Conduits