WO1988008665A1

WO1988008665A1 - Raceway culturing of fish

Info

Publication number: WO1988008665A1
Application number: PCT/US1988/001600
Authority: WO
Inventors: Clifford W. Long
Original assignee: Fisheries Engineering Research And Development Co.
Priority date: 1987-05-12
Filing date: 1988-05-11
Publication date: 1988-11-17
Also published as: AU1794188A; GB2211383A

Abstract

Fish are cultured in one or more flumelike watercourses, bounded by a raceway (10) or a plurality of raceways (110A-E). The rate of water flow is such that the fish swim substantially continuously to maintain position, and the fish are so numerous that they are too close together to assert territorial rights. Water is preferably supplied from and returned to a surrounding natural or man-made body of water, which also preferably floats the physical raceway apparatus, enabling water depth adjustment. Water enters via a well enclosure (11, 111) at the upstream end, as by upwelling, passes through the watercourse, sweeping waste materials along, and leaves via a weir-like enclosure (19, 119) at the downstream end, within which such waste is collected. Fish so cultured survive well and grow rapidly and uniformly.

Description

RACEWAY CULTURING OF FISH

TECHNICAL FIELD

This invention relates to culturing fish close together in watercourses defined by "raceway" structures within which the fish swim substantially continuously to maintain position.

BACKGROUND OF THE INVENTION

Fish-raising or "pisciculture" is now being adopted as an effective way of providing healthful high-protein food of uniform kind and quality. In contrast, fish caught naturally vary greatly in age, size, and quality. Moreover, fishing is becoming increasingly expensive and less certain of success, in large part because of past over-fishing and environmental disturbance. Nor can such fishing meet the increasing demand for quantity and uniformity of product.

Conventional culturing of fish occurs in natural or manmade bodies of water under quasi-natural conditions, subject to predation and disease. More controlled environments are represented by net-pens, within which fish are confined at a necessarily low concentration, and hatchery raceways, usually located near a spring or similar source, from which water is diverted to flow through such raceways at intermediate speed conducive to somewhat higher concentration or density of fish. Maintaining fish free of infection and injury under such conditions is very difficult, and--although uniformity is usually better than in a conventional catch--the fish still compete vigorously for food, whereupon the superior ones become increasingly larger, much as in the wild.

Prior use of raceways is illustrated by Jones in U.S. Patent 4,516,528, wherein water is aerated in an inclined raceway having blocks to "tumble" the water to aerate it, and an underwater spillway for removal of solid wastes along with the effluent water. Collins in U.S. Patent 4,267,798 shows a geothermally heated raceway for fish, snails, or similar animal life (also plants), with harvesting of the products aided by a counter-current catch-box movable therealong, plus flow-induced removal of waste. Designs of floating raceways are reported by Heard and Martin in the Marine Fisheries Review issue of March 1979, page 18 et seq. Endurance training of fish at various water flow rates is discussed by Michel Besner in a 1980 doctoral dissertation at the University of Washington and references cited therein, but his experimental results have not had any effect upon commercial fish culturing.

There is an increasing need for improving fish culture, whereupon the present invention is directed to meeting that need, not so much by perfecting the existing procedures, but rather by going contrary to--indeed violating--many accepted principles and practices.

DISCLOSURE OF THE INVENTION

In general, the objects of this invention are attained by culturing numerous fish in flume-like structures--called

"raceways"--intercepting the surface of a surrounding body of water, in which the raceway preferably floats. The fish are confined too closely together to assert territorial rights.

The rate and volume of flow are so great that the fish must swim to maintain position, as inflowing water is continually replacing the water already in the raceway. Fish excrement, uneaten food, and other contaminants are swept downstream and are removed appropriately. The resulting fish are healthier, larger, more uniform, and better to eat than most fish caught in the wild or raised in net pens ever could be.

A primary object of the present invention is to improve fish culturing so that more of the food requirements of the world's rapidly increasing population can be readily met.

Another object of this invention is to supplement--not to replace--much of the world's agriculture by aquaculture, namely pisciculture, as required to provide adequate food.

A further object of the invention is to raise healthy, more uniform fish than obtained in previous fish culturing. Yet another object is to provide apparatus designed to aid in accomplishing the foregoing objects.

A still further object is to attain the foregoinggoals more economically than less is accomplished in the prior art. Other objects of the present invention, together with means and methods for attaining the various objects, will be apparent from the following description and the accompanying diagrams of a preferred embodiment, which is presented by way of example rather than limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

For convenience of illustration, the raceway apparatus of this invention is apportioned initially among successive sheets of drawings of barely overlapping successive upstream and midstream and downstream portions--each shown in several or more views--to illustrate a single raceway. Added sheets illustrate multiple raceway apparatus and features for use in both individual and multiple raceways.

Fig. 1 is a side sectional (i.e, bisected lengthwise) elevation of an upstream end portion or well of an individual embodiment of raceway apparatus according to this invention;

Fig. 2 is a transverse sectional elevation of the same apparatus portion, taken at II-II on Fig. 1; and

Fig. 3 is a plan of the same taken at III-III on Fig. 1. Fig. 4 is a side sectional elevation (partly overlapping Fig. 1) of the midstream portion of such raceway apparatus of this invention;

Fig. 5 is a transverse sectional elevation of the midstream apparatus of Fig. 4, taken at V-V thereon; and Fig. 6 is a plan of the same, taken at VI-VI on Fig. 4. Fig. 7 is a longitudinal sectional elevation of a downstream end portion (overlapping Fig. 4) of the same raceway apparatus of this invention;

Figs. 8, 9, 10, and 11 are transverse sectional views of the downstream apparatus of Fig. 7, taken at spaced intervals as similarly indicated thereon; and

Fig. 12 is a plan of the same downstream apparatus taken at XII-XII on Fig. 7.

Fig. 13 is a side sectional elevation of auxiliary means useful in the foregoing individual, or in subsequently multiple, raceway apparatus of this invention; Fig. 14 is a transverse sectional plan of the apparatus of Fig. 13, taken at XIV-XIV thereon; and

Fig. 15 is a plan view of an apparatus component of the two preceding views. Fig. 16 is a side sectional (i.e, bisected lengthwise) elevation of an upstream end portion of a multiple-raceway apparatus embodiment of this invention;

Fig. 17 is a plan view of the apparatus of Fig. 16;

Fig. 18 is a side sectional (i.e, bisected lengthwise) elevation of the apparatus, taken at XVIII-XVIII on Fig. 17;

Fig. 19 is a detail sectional end elevation of a feature of Fig. 18;

Fig. 20 is a fragmentary endwise sectional elevation of a plurality of the component raceways of Figs. 17 to 19; and Fig. 21 is a schematic representation of connection of raceways as shown fragmentarily in Fig. 20.

DETAILED DESCRIPTION OF THE INVENTION

Figs. 1, 2, and 3 show flow introduction pool or well 11, as the upstream portion of individual raceway apparatus embodiment 10 of the present invention, respectively from the side, end, and top--Figs. 2 and 3 being sectional views, as already indicated. This portion and preferably all of this raceway apparatus is preferably within a surrounding body of water, whose surface the raceway intercepts and whose surface level is denoted occasionally by a small unnumbered triangle. Midstream portion 15 (the raceway proper) is partly visible at the right in this view, whereas downstream portion 19 is not shown here. The well has sidewalls 24 flanked at their top edges by the upper surface of walkway decking or platform 34, which is supported at each side on cylindrical floats 38 (three shown at each side). The well has at its far upstream end intake door 21 (bottom-pivoted) whose doorway is covered by flat screen 22, Bottom 23 of the well has nearby intake opening 25 with cylindrical inlet screen 26 thereunder. Supported above such platform by any suitable means (not shown) is motor 27A, whose drive shaft 27B passes through an opening in the decking and terminates in gearbox 27C from which propeller 27D is driven by a short intervening shaft. Propeller 27D turns (in a vertical plane) in such a direction as to draw water into the well through screen 22 over the top edge of the pivoted door (if open) and/or up through both cylindrical screen 26 and bottom opening 25. Alternative or supplemental propeller 27D' (shown in broken lines) turns horizontally above cylindrically screened opening 25 and is connected to similarly supported overhead motor 27A' through gearbox 27C' and drive shaft 27B' in like manner. The water drawn into well 11 by either (or both) of such propellers exits therefrom into the open upstream end of the raceway proper, through one or both of removable bar screens 13.

Pair of vertical tracks 42 are supported by platform 34 plus braces 43 at opposite sides between the downstream end of well 11 and adjacent upstream end of raceway 15--together with a like pair of both at the downstream end of the raceway and adjacent upstream end of waste collection lagoon or catch basin 19 (Figs. 4, 6, 7). The tracks connect to mechanical, electromechanical, hydraulic, or pneumatic lifting apparatus (not shown here) to enable the level of raceway 15 to be changed relative to the prevailing water level, as suggested in broken lines, or perhaps even (not shown) to be raised clear of the water. Sliding panels 17 at each end rise too, to close off well 11 and catch basin 19.

The raceway proper comprises a flexible band of durable plastic material stretched taut into U-shaped cross-section by attachment to metal frames 33 supported at their edges by vertical tracks 42, which support bar screens 13 at both upstream and downstream ends. Metal stringers (hidden) fit into sleeves 14 along each upper edge of the raceway material between the frames and support its weight. Removable cover 5 is conveniently in the form of multiple lengths of open-mesh, relatively rigid material shaped like an inverted channel with its side edges extending down along the raceway edges. The raceway has at its opposite ends pairs of upstream and downstream bar screens, as shown in elevation in Fig. 5. One screen in each pair is enough to retain the fish when the other screen in such pair is removed for cleaning or repair. Both the cover and the bar screens have mesh sizes effective to exclude flying and swimming predators from the raceway.

Fig. 7 shows, in longitudinal section, and Fig. 12 shows in plan, flexible waste collection lagoon or catch basin 19 through which the water from the raceway exits over weirlike downstream end 29. Intermediate Figs. 8, 9, 10, and 11 are successive transverse sections of the catch basin viewed in the upstream direction. The rectangular U-shaped section at the entering end in Fig 8 transitions gradually to a concave (upward) outline in Fig. 9, then into a V-shaped one in Fig. 10, and finally into a larger V-shape in Fig. 11.

The enlarging cross-section of the catch-basin increases the volume and thereby slows the water flow rate, ensuring settling out of most undissolved solid wastes. The bottom edge 37 angles downward to a lowest point, at which waste outlet line 30 (cut away in Fig. 7) connects to convey such waste onshore to a collection station or similarly suitable destination. Filter 40, which is suspended removably from the platform near the top of the end wall, collects ammonia and perhaps other dissolved or free gaseous contaminants and is removable for renewal or regeneration, as noted below.

Fig. 13 shows in sectional elevation air-lift apparatus 150, suitable for use in well 11 (along with or instead of the apparatus of Figs. 1 to 3). This view features open-top cylindrical intake housing 151 having screened inlet end 126 at its bottom. Hollow shaft 157 from motor 127, mounted by suitable means (not shown) above the water level, has at its bottom end hollow propeller 159. Just beneath the motor this shaft has air-inlet openings 153 into which arrows point to suggest the inflow of air thereinto. The trailing edges of the propeller have openings 158 therein, from which bubbles are rising. Indeed, the water in the interior of housing 151 is filled with air bubbles from the propeller ail the way to the top, where it overflows into the raceway itself. Apparatus in foregoing Fig. 13 and/or in the subsequent views is designated, to the extent it is similar to apparatus already shown and described, by reference numerals higher by one hundred (sometimes with a suffix) for such corresponding components, while dissimilar components are marked with other three-digit numbers in the one hundred series.

Fig. 14 is an enlarged sectional plan taken through the junction of hollow propeller 159 with hollow shaft 157, whose clockwise rotational direction is indicated by arrows. This view shows openings 158 along the propeller's trailing edges. Fig. 15 is a further enlarged view of propeller 159, its supporting hub 155 at the bottom end of the shaft, and also openings 158 in the trailing edges--with exemplary bubbles. Fig. 16 shows, rather schematically and predominantly in transverse or endwise sectional elevation, multiple-raceway embodiment 100 of the present invention, including air-lift system 150 of the several preceding diagrams just described and a couple additional air-lift systems transversely of well portion 111 bounded by sidewalls 142 at both left and right. Shown are five raceways: 110A, 110B, 110C, 110D, 110E--seen only end-on, without screens, supports, etc. Visible above the water level are three airlift motors, 127, 127', 127"--with respective drive shafts 157, 157' 157" extending down to screw propellers 159, 159', 159" within cylindrical housings 155, 155', 155" of respective air-lift units 150, 150', 150". Fig. 17 shows rather schematically in plan such multiple raceway embodiment 100, featuring well portion 111 at the left and collection lagoon or catch-basin portion 119 at the right, joined by raceways 110A, 110B, 110C, 110D, and 110E, but with pairs of screens 113A, 113B, 113C, 113D, 113E at the left between the well and the respective raceways, and at the right between the respective raceways and the catch basins. Walkways 134 flank the first and last raceways and intervene between each pair of adjacent raceways. Fig. 18 shows same raceway apparatus 100 in longitudinal medial section, featuring well 111 with air-lift system 150' at the left, collection lagoon 119 at the right, and central raceway 110C (partly cut away to conserve space) in between. Features of lagoon or catch-basin 119 in Fig. 18 are denoted by reference numerals one hundred higher than those of lagoon 19 previously shown--and are not necessarily mentioned here. Joined to the under side of raceway HOC, just to the left of its junction with collection lagoon 119, is air-lift system 160C, which differs from the 150 type of such system simply by replacing the submerged propeller (plus shaft and motor) with side inlet 168C for compressed air. Air is furnished by motor-driven compressor 165 supported on one of the walkways (see Fig. 17) above the water surface, through air tube 166C. The bottom of housing 161C is closed rather than screened.

Fig. 19 is a detail transverse view of cover 162C over the top end of housing 161C where it joins raceway 110C. The cover may be removed manually or be provided with suitable lifting or other opening means (not shown) when desired to connect the raceway interior with the housing interior.

Fig. 20 shows in transverse sectional elevation raceway 110C, whose air-lift housing 161C is filled with air bubbles, joined to like air-lift housing 161B (bubble-less) of raceway 110B by transverse header 165 of similar cross-section. Fish in raceway 110B are entering housing 161B and proceeding down into and through the header into the bottom of housing 161C and up through it out into raceway 110C. The light weight of the air-in-water mixture induces a flow of water through the header from the dense all-water contents of housing 161B (which is not receiving compressed air). Both covers 162B and 162C have been removed to enable the water to flow--and the fish to go readily with the flow--out of raceway 110B and into raceway 110C. The flow dissuades the fish from entering the non-moving contents of such housings not opened at the top, or elsewhere in the header.

Fig. 21 shows schematically interconnection of raceways 110A, 110B, 110C, 110D, 110E by air-lift housings 161A, 161B, 161C, 161D, 161E and header 165. At the right of the raceway assembly the header continues to the right as indicated by the arrow, such as to a location onshore or elsewhere, where water may be removed, whether by air-lift or pump means for harvesting or otherwise gathering the fish. The apparatus of this invention does not require any exotic materials or methods of construction, or any more than ordinary skill for persons in the construction trades to pick suitable materials and form them into the desired shapes. Ordinarily skilled persons, however, would not be likely to select a flexible polymeric material for the raceway walls and bottom, though in practice such a material with a smooth surface to protect the fish from abrasion is a good choice, such as polyester-reinforced chlorinated polyethylene, about a millimeter thick. The generally rectangular end-frames to form it into a U-shaped outline preferably are made of light-weight metal, such as aluminum, as are the stringers that fit into the lengthwise edge sleeves in the raceway material and support it. Either material is also usable for the lagoon. The bar screens at the ends of the raceway preferably are made up of round vertical metal rods or tubes several millimeters in diameter and suitably spaced to retain the fish to be confined therein, plus somewhat heavier horizontal cross or reinforcing members. Placing a pair of such bar screens at each end of the raceway proper enables a screen to be removed for cleaning, etc. The mesh size of the intake screens for the well is smaller, in order to exclude small fish and other undesirable animals or plants that also may be present in the surrounding water. Preferred screen materials include stainless steel and thermosetting plastics.

The electrical equipment is also conventional and runs on a.c. power from any available source, such as a public utility, which may be supplemented by a backup generator on site driven by a combustion engine fueled by gasoline, diesel fuel, etc. The drive motors may be a.c.-powered, or they may operate from rectified d.c. with battery backup. Multiple motors and backup facilities are desirable to permit removal of a unit for maintenance without interruption of operations and because the fish could not survive long in the event of interruption of raceway water flow. The mesh cover may be opened to introduce the fish from overhead. The fish may be fed through the mesh with the cover open or closed closed. The cover composition resists not only the elements but also any attempts by predatory birds or other animals to get at the fish. Metal is a good choice, but lighter polymeric plastic or textile meshes, preferably with an added core wire, can be substituted for all-metal meshes.

The raceway apparatus itself is preferably located in a body of water, such as a lake or an estuary, from which water is readily drawn and into which it is easily discharged. The raceway defines a watercourse at least about five times as long as it is wide or deep, is conveniently one to two meters wide and deep, and at least about ten to a dozen meters long. The walls of the raceway intercept the water surface at such level as to provide adequate wetted volume for fish confined in the raceway, and are adjustable for depth as described. Alternatively, such adjustment of the depth may be achieved by rolling the walls around the lengthwise stringers, while maintaining a sufficient end seal to contain the fish, as by detaching the ends of the raceway proper from the U-frames and substituting brushes on the frames to engage the ends and thereby contain the fish.

The outlet filter for adsorbing gaseous contaminants may be a modified gabion containing natural or artificial zeolite or like material, so as to capture ammonia, usually dissolved in ionic form. A preferred material comprises the mineral clinoptilolite, which can be regenerated very economically with salt water. See, as an example, a 1981 Seattle Aquarium Technical Report (no. 7, p. 92) article by Bruin, Nightingale and Mumaw, entitled "Bio-Engineering for Fish Culture."

The weirlike overflow edge at the downstream end of the collection lagoon or catch basin is of such height and width as to accommodate outflow therefrom without raising the water level in the raceway unduly. The indicated filter means for removing gaseous contaminants, such as ammonia, may take any of many forms, and the foregoing illustration is schematized for simplicity of the showing. Operation of the apparatus of this invention will become readily apparent from the foregoing description and drawings. The motor(s) normally drive(s) the propeller(s) to upwell the underlying water, whether directly or by air-lift, enough to flow the water through the raceway at desired velocity. The upwelling water flows through the first pair of vertical screens and into the raceway proper, through the raceway, and out through the second pair of such screens, into the catch basin, mostly through the suspended filter, and finally over the basin's weir-like end out into the surrounding body of water. At high flow rates the filter pivots to allow water to escape around or under it, if and as preferable.

Water flow should be sufficient to replace the raceway water frequently enough to maintain a healthful concentration of oxygen, also to bring about a complete volume turnover not less than once every ten minutes and preferably at least once every several minutes. The flow rate should induce the fish to swim substantially continuously. Such flow also should convey solid waste, such as excrement or uneaten food, into the lagoon for collection and removal. A suitable flow rate is at least about several meters per minute and about a fish length per second--preferably at least about one-tenth meter, and about one and one-half fish lengths, per second.

It will be apparent that, as the fish grow larger, their oxygen demand increases, as does their swimming ability. The increased oxygen requirement is preferably met by increasing the water flow rate--and the water depth. The fish densities of this invention usually require flowing through the raceway at least once every several minutes a volume of water equal to the wetted volume of the raceway. Filters for ammonia at the outlet end may be suspended likewise at spaced intervals

(in series and/or parallel) to cope with increased fish size.

The fish are raised or "grown out" from fingerling size, until they reach a suitable size for marketing. Their food requirements also increase over such period and are met by an increase in duration or frequency of feeding, with increased

Quantities of feed--which itself may be conventional. Conventional net pens for fish culture rely upon tidal or other low flow rate or diffusion of water to supply oxygen to the fish and to disperse waste materials, resulting in an unacceptable incidence of disease in the fish and degradation of the environment, which cannot renew itself satisfactorily even at the low fish concentrations in such enclosures. A density from about ten to a dozen kilograms per cubic meter (about 3/4 pound per cubic foot) of fish is a good level for a net pen--but only a fraction of what this invention employs free from significant disease or mortality and productive of highly uniform growth and condition of the resulting fish.

Standard hatchery raceways may be an order of magnitude higher than net pens in fish concentration or density, but even their water volume exchange or turnover time usually approximates twenty minutes, and their flow rate only about a centimeter per second (about several hundredths foot per second). They are unsuitable for fish a couple dozen or more centimeters in length. Hence, they similarly fail to provide operating conditions most characteristic of this invention. Conventional wisdom in the culturing of fish holds that the higher the density of the fish, in whatever enclosure, the lower the rate of growth, the food conversion ratio, and survival rate. However, at low densities the more vigorous fish exercise territorial rights and commandeer more of the available food, resulting in greater non-uniformity than is desirable. Such fish must be graded periodically--increasing a likelihood of disease and injury from excessive handling.

The present invention contravenes conventional practice by subjecting fish at high density in a raceway to high rates of water flow and high frequency of water replacement or turnover. The fish have to swim vigorously to maintain their position, thereby improving musculature, foregoing contesting injuriously for territory or food, and developing much more uniformly than otherwise. The environmental loading drops significantly below that of hatchery raceways and net-pens by reason of waste collection and removal, enabling water to be returned to the environment and be re-used subsequently. The methods and apparatus of the present invention are useful with a wide range of fish, such as varieties of salmon (e.g., coho and sockeye) and trout (e.g., rainbow). Whereas salmon prefer cooler temperatures, rainbow trout can be raised in water at moderate temperature. Although other methods of providing the necessary water may be used, the method of choice at this time is induced upwelling, both for its economy and for the localized control it affords over the resulting temperature of water to which the fish are exposed. It can tap cooler stratified layers than are normally present near the surface, even in lakes whose depth is limited to a half dozen meters or so. Of course, deeper estuarial waters often have an even more sharply defined thermocline to be tapped in this manner. Appropriate control of temperature enables additional fish and possibly other types of marine animals to be raised or "grown out" likewise.

Air-lift provision of water for the head-end of raceways according to this invention has an added advantage over screw propulsion without air-lift in enabling smaller propellers to be used at even lower speeds, thereby reducing electric power requirements and costs. Injection air-lift in transferral of fish from one raceway to another or to a harvesting location is superior to prior art methods because the fish essentially swim from one place to the other without interposition of net or human hands or other handling device, minimizing injury.

Raceway apparatus for use according to this invention preferably floats in the surrounding body of water, thereby eliminating or minimizing the need for anchoring. Adjustable supports, such as the illustrated tracks between raceways and their flotation means, or the suggested roll-up means for the flexible raceway material, are helpful in enabling the depth of water in the raceway to be decreased, as when adding or harvesting fish, or to be increased, as when the growing fish reσuire more volume. This invention facilitates life-cycle culturing of fish from fingerling size to marketing size in a single facility. Thus, a batch of fingerlings of appropriate quantitity and type is placed in a raceway appropriately adjusted in depth so that its volume confines the fish to the desired density. As the fish grow, the raceway depth is increased gradually, to increase the volume of water in the raceway and thereby to maintain or adjust the desired fish density. When the volume is at or near the maximum available in the raceway, some of the fish (e.g., half of them in number) are transferred from that initial raceway to another raceway, and both raceways are adjusted in depth to continue the desired fish density. Alternatively, the initial raceway may be emptied entirely of fish into two other raceways similarly adjusted, and a batch of fingerlings introduced into the initial raceway as before.

As time goes on and the fish get increasingly larger, the number of raceways to accommodate them increases also, necessitating additional transfers to a greater number of raceways. Because the fish swim readily from one raceway to another interconnected to it, as via the illustrated air-lift method and apparatus, the transfer process is not detrimental to their health. The water flow rate and volume are adjusted to suit whatever fish are in a given raceway at a given time.

INDUSTRIAL APPLICABILITY It will be apparent that this invention provides a fish "factory" wherein fish can be produced in whatever marketable size is desired. Properly controlled conditions result in low injury and mortality rates, high quality and uniform size of product, hence a high economic yield (i.e., high profits). marketplace is most receptive to such a food product, so such pisciculture will expand into an industry of gigantic size.

Despite presentation of preferred apparatus embodiments of the invention, additional variants in both structure and use have been suggested above. Other modifications may be made, as by adding, combining, subdividing, or deleting parts or steps, while retaining at least some of the advantages and benefits of this invention--which itself is defined in the following claims.

Claims

THE CLAIMED INVENTION

1. Pisciculture process characterized by the steps of confining numerous fish within a flumelike watercourse so closely as to preclude them from exercising territorial rights, and flowing water therethrough from end to end so rapidly as to require the fish to swim to maintain position, substantially continuously for at least several months.

2. Pisciculture process according to claim 1, wherein the fish are substantially uniform in size and type.

3. Pisciculture process according to claim 2, wherein the fish remain substantially uniform in size throughout.

4. Pisciculture process according to claim 1, wherein the density of fish per cubic meter of wetted volume is at least about one hundred kilograms.

5. Pisciculture process according to claim 4, wherein the density of fish per cubic meter of wetted volume is several hundred kilograms.

6. Pisciculture process according to claim 1, wherein the rate of water flow is at least about several meters per minute, and about one fish length per second.

7. Pisciculture process according to claim 6, wherein the rate of water flow, per second, is at least about onetenth meter, and about one and one-half fish lengths.

8. Pisciculture process according to claim 1, wherein the wetted volume of the body of water is at least about five times as long as it is wide or deep.

9. Pisciculture process according to claim 8, wherein the wetted volume is at least about one to two meters wide and deep and at least about ten to a dozen meters long.

10. Pisciculture process according to claim 1, including upwelling water at and into the upstream end of the watercourse from a surrounding natural or man-made body of water.

11. Pisciculture process according to claim 10, wherein the water is upwelled by injecting air into a column of water underlying and connected at its top to such watercourse.

12. Pisciculture process according to claim 11, wherein air is so injected via a hollow shaft from atmosphere to outlet openings in a propeller rotating at the bottom of such column of water.

13. Pisciculture process according to claim 1, including slowing the rate of water flow at the downstream end of the watercourse by increasing its cross-sectional area.

14. Pisciculture process according to claim 13, including collecting undissolved solids near the downstream end of the watercourse and conveying them away therefrom.

15. Pisciculture process according to claim 14, wherein the solids comprise fish waste and uneaten food.

16. Pisciculture process according to claim 10, including collecting a dissolved gaseous composition near the downstream end of the watercourse and removing it therefrom.

17. Pisciculture process according to claim 16, wherein the dissolved gaseous composition comprises ammonia.

18. Pisciculture process according to claim 17, wherein the ammonia is adsorbed onto a zeolitic material.

19. Pisciculture process according to claim 18, wherein the zeolitic material includes mineral clinoptilolite.

20. Pisciculture process according to claim 1, including outflowing the water from the downstream end of the watercourse into a surrounding natural or man-made body of water.

21. Pisciculture process according to claim l, including upwelling water at the upstream end of the watercourse from a surrounding natural or man-made body of water, and outflowing the water from the downstream end of the watercourse into the surrounding body of water.

22. Pisciculture process according to claim 1, including so confining numerous fish within a plurality of such flumelike watercourses, and relocating fish, initially confined in one such watercourse, into more than one such watercourse as they grow.

23. Pisciculture process according to claim 22, wherein the fish are so relocated by interconnecting a first such watercourse, from which fish are to leave, with a second such watercourse into which fish leaving the first are to enter.

24. Pisciculture process according to claim 23, wherein the respective watercourses are interconnected via adjacent underlying columns of water connected respectively thereto and cross-connected to each other at their bases.

25. Pisciculture process according to claim 24, including injecting air within the column of water connected to the overlying watercourse into which fish from the other watercourse are to enter.

26. Pisciculture process according to claim 24, including harvesting the fish by interconnecting to a conduit leading away therefrom to a harvesting location the bases of one or more such columns of water connected to respective overlying raceways.

27. Fish cultured according to the process of claim 3.

28. Fish cultured according to the process of claim 5 and characterized by a lower incidence of mortality than are fish cultured at lower density that is characteristic of net pens.

29. Fish cultured according to the process of claim 7 and characterized by greater size than fish raised at lower flow rates that are characteristic of hatchery raceways.

30. Fish cultured and harvested according to the process of claim 26.

31. Pisciculture apparatus comprising raceway means having opposite sides and an interconnecting bottom bounded by continuous surfaces and having upstream and downstream ends bounded by discontinuous surfaces; such continuous surfaces and discontinuous surfaces being effective to confine fish within the raceway means, and such discontinuous surfaces also being effective to permit passage of water and particulate solid waste therethrough; and means to induce rapid water flow into the upstream end and through the raceway means and out the downstream end.

32. Pisciculture apparatus according to claim 31, including waste-removal means adjoining the downstream end.

33. Pisciculture apparatus according to claim 32, wherein the waste-removal means includes a catch-basin for collecting particuiate waste from the water passing therethrough, and conduit means for conveying such collected waste elsewhere.

34. Pisciculture apparatus according to claim 32, wherein the catch-basin increases in transverse cross-section in the water flow direction, whereupon the water flow rate decreases and the particulate waste swept from the raceway by the water flow drops to the bottom under the influence of gravity.

35. Pisciculture apparatus according to claim 32, wherein the waste-removal means includes a filter for collecting dissolved gaseous waste from the water passing therethrough.

36. Pisciculture apparatus according to claim 35, wherein the gaseous waste comprises ammonia, and the filter comprises zeolitic material.

37. Pisciculture apparatus according to claim 35, wherein the zeolitic material comprises mineral clinoptilolite.

38. Pisciculture apparatus according to claim 31, wherein the apparatus is surrounded laterally and underneath by a body of water, some of which is removed temporarily by the means for inducing flow of water through the raceway means.

39. Pisciculture apparatus according to claim 38, including at the downstream end of the apparatus weir-like means over which water from the raceway means returns to the surrounding body of water.

40. Pisciculture apparatus according to claim 38, wherein the apparatus floats in such body of water.

41. Pisciculture apparatus according to claim 40, including supporting means effective to raise and lower the raceway means relative to the water level and thereby alter the depth of water in the reaceway means.

42. Pisciculture apparatus according to claim 31, wherein the flow-inducing means includes a well communicating with the upstream end of the raceway and an adjacent body of water.

43. Pisciculture apparatus according to claim 42, including propeller means in the well for upwelling water from the adjacent body of water into the raceway.

44. Pisciculture apparatus according to claim 43, wherein the propeller means has a hollow shaft communicating with the ambient atmosphere above the surface of the water in the well and includes a propeller having openings communicating with its hollow shaft and adapted to release air therefrom into the adjacent water as the propeller rotates therein.

45. Pisciculture apparatus according to claim 31, comprising a plurality of such raceway means located side by side, and means interconnecting the respective raceway means.

46. Pisciculture apparatus according to claim 45, wherein the interconnecting means comprises cylindrical housings enclosing columns of water underlying the respective raceway means and connected respectively thereto, and header means cross-connecting the cylindrical housings to each other at their bases.

47. Pisciculture apparatus according to claim 46, including means for injecting air within the column of water enclosed by any of such cylindrical housings.

48. Pisciculture apparatus according to claim 46, including means for harvesting the fish including a conduit connected to such header and leading away therefrom to a harvesting location.

49. Fish cultured in the apparatus of claim 31.

50. Fish cultured in and harvested from the apparatus of claim 48.