_T Γ _TSH ROWTH AΠΠK ERATION AND DENSTTY-INCREASING APPARATUS _ The present invention relates to apparatus for and methods of accelerating the growth rate of fish, such as salmonoids and the like, (and wherein the term "fish", is generically employed to apply to all types of fish, eels, crustacia etc., exhibiting growth development characteristics as hereinafter described), being more particularly directed to the provision of novel dark resting zones and pluralities of intermediate feed zones in pools and the like (the term "pool" being generically employed herein to mean any volume of water having means for confining the fish therein, whether hard walls or nets or cages).

Underlying the invention is the discovery of the remarkable fish growth rate acceleration effects that can be produced by blocking all light from a substantial portion of the surface of a pool, but with illuminated feed regions provided external to the dark or shadow zones or areas caused by the blocking of shielding—such regions occupying either or both of peripherally surrounding regions or interior regions of the light-blocking appartus. Water-contacting light-opaque covers are preferably employed for the light blocking; and preferred control of illumination of the feed regions is effected beyond daylight hours in up to 24-hour cycles. Under such conditions, it has been found that the fish, such as

salmon fry or parr, and later smolt developing therefrom and more mature fish, relax in columns in the dark zones, and dar into the illuminated feed regions for food at will, over a 24-hour or other extended period, without competition, disfiguring one another, or agitation, thereby resulting in startling acceleration of growth rate and increase of feasibl densities of fish in the pond. As an example, in Scotland, with normal environmental water (not artificially heated) ove a five-month period from May to September, salmon parr were found to have grown 25 more than similar parr in open or tent-covered ponds, during daylight illumination hours only, and 150% with 24-hour illumination of the feed regions; and that a doubling of the number of fish that could be accommodated in the pond could be safely attained. Acceleration of the period required to smolt has thus been effected, and growth rate acceleration of maturing salmon has also been observed to take place.

In accordance with the present invention, it has also been discovered that very significant improvement in increasing the useable densities of fish in ponds of predetermined size can be effected while obtaining such accelerated growth rate phenomena, with the aid of improved floating and submersible cover designs and, if desired, with tiers of the same within the pond.

An object of the invention, accordingly, is to provide a new and Improved apparatus for and method of salmonoid and other fish growth rate acceleration that significantly increase the densities of fish that may be simultaneously grown in pools.

A further object is to provide novel submersible covers and tiers of covers useful in such methods or processes.

Still another object is to provide a multiple-cover apparatus that can be used to train the fish to live and feed thereunder, so that if the apparatus is moved to other surroundings, the fish immediately adapt to the same in view of the familiar "home" provided by the covers.

Other and further objects will be explained hereinafter and are more particularly delineated in the appended claims. In summary, however, from one of its important aspects, the invention embraces a method of accelerating the growth of fish including salmonoids and the like, that comprises, stocking a volume of water with fish; circulating the water around the pool with feed; blocking ^' light Impinging upon the water over a substantial surface of the volume from entering a downwardly extending zone to provide in the same, dark superposed rest areas wherein the fish remain in dense stacks; and transmitting light at

predeter ^' mined unblocked regions of the said surface to expo the feed In the water thereat to fish resting in said dark zone and able to view therefrom the unblocked light-illuminated feed regions.

In another aspect, in summary, the invention provides apparatus for accelerating the growth of fish, including salmonoids and the like, within a volume of water containing the fish, comprising light-opaque cover means provided with means for supporting the same submerged withi the pool; and the cover means having a plurality of open regions spaced along its surface interemediate light-opaque regions of the cover; said light-opaque regions producing d zones within the pool underneath the same for the fish to remain in quiet, and with said open regions providing acces to and visibility for feed immediately thereunder. And fr still another viewpoint, the invention includes a method of training fish, including salmonoids and the like, to live I dense masses at spaced regions of a pool, that comprises, stocking a pool with such fish; submerging a tier of successively vertically spaced light-blocking covers in the pool to provide dark zones under the covers in which the fi may learn to rest in tight stacks; and illuminating from ab feed regions of the pool outside the dark zones but lateral visible to the fish resting therein.

The invention will now be described with reference to the accompanying drawing, the single figure of which is an Isometric view of a preferred apparatus for practicing the method or process of the invention, with parts broken away to illustrate ^' details of construction.

Referring to the drawing, a pool P is illustrated as provided with a water inlet 1, directed to inject water at an angle to the vertical to circulate the same about the pool, and with a central vertical exit tube 3, the open upper mouth of which is disposed at or just below the water level W of the pool, and the lower end of which is provided with an exit strainer 3^« The pool (hard-walled or net-confined) is stocked with fish, such as, for example, salmon parr. Pish feed is periodically dropped into the pool at F, as by a timed solenoid-operated shutter, as is well known, with the feed circulated around the pool by the moving water.

At the top of the pool, a light-opaque cover Co is shown preferably provided, as of an inverted cup type, contacting the water to provide a dark shadow area or zone thereunder over the major portion of the pool.

Taking further advantage of this light-blocking or shielding cover phenomenon before described, the present invention employs a submerged cover C of light-opaque material, illustrated as of generally circular contour, and

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specifically as of an Inverted cup of rusto-conical shape, with the tube 3 passing axially through the center of the conical cup and its top central opening 6'. Where the cover Co is also used, it is usefully aligned with the cover C. T underwater cover C, extending also over a major portion of t cross-section of the pool, is supported by legs 2 and define dark rest areas or zones D between the underside of the cove and below. Peripherally surrounding the cover C (and Co) Is an uncovered annular region 6 which, like the central openin 6', is illuminated by light L transmitted from above the poo and renders the feed circulating therein clearly visible to the fish as they rest in the dark shadow zones D under the covers. Through control of the illumination after daylight hours, including up to 24-hours of continuous illumination, the fish have been found to feed more continually; and, in view of the dark zones D, rest therein after darting out for the feed, without agitation or hostile competition or mutual attack and disfigurement.

It has been discovered, however, that by providing along the surface of the cover C, a plurality of spaced narr open regions, illustrated as transversely spaced slot openin S in the cover, each shown extending substantially radially along a directrix of the cone, and circumferentially spaced

therealong, additional narrow feed zones are created external to and intermediate the much larger-area and wider dark or shadow zone regions that enable significantly improved density populations to be used; and, because of the geometry, keep the cover relatively clean in prolonged useage.

If the top cover Co is not used, the opaque cover C is the first cover to block the light from above and produce the dark regions, and the openings S will be additional illuminated feed regions. The width of the narrow slot openings S is preferably tapered, diverging towards the periphery of the cover C but terminating short thereof. With this construction, it has been observed that the feed circulated by the water inflow at 1 gradually sinks and rests on the upper surface of the cover C. The Illuminated or unblocked slots or narrow regions S divide or border or are laterally external to the much larger light-blocking regions or segments of the cover and the dark zones formed thereunder. The circulating currents slowly move the feed around until if falls off the edges of the slot openings S and into illuminated view immediately thereunder to the fish resting quietly in the adjacent dark zones D (illuminated from L if the cover Co is not used, or visible as silhouette illumination looking laterally toward 6 or 6 ' if the cover Co is used). The fish then readily gobble the feed with little

movement and with out agitation or hostile competiton, and re-position themselves in the dark rest zones D; Startingly this segmented slot construction has enabled, in some cases, at least a quadrupling of the density of fish that can be maintained in the pool, for a given pool size and width and oxygen flow rate, with the fish assuming an almost unbelievable solid stacked mass In the dark zones D.

Further to this end, it has been found that a tier of similar covers can be used to divide the pool into a plurality of vertically spaced dark zones. In the drawing, second similar submerged cover C is thus shown aligned belo the cover C, with the upper surface of the cover C supporti the legs 2 of the upper cover C, and the legs 2' of the lowe cover C supported on the pool bottom, thereby defining lowe dark zones D in the space between the lower surface of the lower cover C and the pool bottom. In land-based pools, simple resting of the legs 2, 2" may be sufficient; but the tier structure may be otherwise supported, with legs attachable to lower covers or otherwise unitarily fastened. Preferably, the slots S' in the lower cover C are offset or staggered from those in the cover C, as shown in the drawing, for the feed efficiency purposes later explained; and the closely packed, vastly increased fish mass density in the set of dark zones D under each cover thus greatly Increases the

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effective fish production feasible in the pool— ll with the before-described accelerated growth phenomena. A significant saving of feed that would otherwise drop to the bottom and be lost is attained by such off-setting or staggering of the slots S, S' of successive submerged covers C, C, etc., since feed that is not eaten in dropping through a slot S will then fall on the surface of the lower cover, and then gradually be circulated to a slot S' for exposure to the fish below cover C; and so on for further covers in the tier employed.

In the case of salmon parr in a fresh water pool of about 2.5 meters in diameter and volume of 45 cubic feet and water flow rate of 10 gallons/min., covers as above described were found to enable a parr density of 2.25 lbs./ft.3, as com¬ pared with the normal or customary density of 1.5 lbs./ft.3, currently generally employed in such pools; with a growth rate of about 3 cm. per summer month, as compared with about 1.3 cm. per month with the submerged cover system of the invention; and with substantially zero disfigurement, as compared with about 25 in uncovered pools. While these results enable more rapid and greater volume of smolt production, the acceleration phenomenon of the invention has also been found to continue in the salt-water maturing of the salmon, as well.

The invention also has particular application whe fish, such as salmon parr and the like, are ultimately to b placed In relatively large volumes, as In pools defined by nets in salt water sometimes called sea cages, for maturat after reaching the smolt state in fresh water walled pools. Apart from the important increased density feasible with accelerated growth In the fresh water pools, it has been fo that the tiered vertically spaced submerged covers, particularly if first used in the smolting pools, will accustom or train the fish to live primarily in the dark zo In closely packed stacks and with contentment, feeding continually without hostility at the slot openings and at t illuminated regions beyond the borders of the opaque portio of the cover. When smolting has occured, accordingly, and is time to transfer the fish to much larger maturation pool such as large net-confined volumes in the sea or even large land-based pools, by transferring the tiered-cover "home" ( a similar one) to the larger pools (Including cages within term "pool" as before explained), the new surroundings do n appear "new". The fish acclimate immediately and continue their rapid growth and heavy density tendencies under the familiar submerged cover or covers, improving the efficienc of their maturing process in the larger maturation pools. feed-efficient staggered slot arrangement in successive

covers, oveover, is particularly desirable in net-confined sea pools or cages where much feed Is lost by natural ^" circulation out of and dropping through the nets.

While the invention has been described with reference to a preferred circular frusto-conical configuration, clearly other geometrical contours may be employed, as may intermediate opening regions bordering or external to the dark regions of other than radial orientation; tiers of more than two submerged covers may also be used, and in some instances need not be in alignment; and the covers may, in certain applications, be only partly rather than totally submerged. The •invention, moreover, is useful, as before mentioned, with other fish such as trout, eels and Crustacea, exhibiting similar resting, feeding and growth characteristics and behavior; such and further modifications as will readily occur to those skilled in this art, being considered to fall within the spirit and scope of the invention as defined in the appended claims.