N/A
The present invention relates generally to incubators for hatching fish eggs into larvae, and in particular, to an incubator system for fish eggs that are laid in jelly-like skeins.
Fish hatcheries use incubators to hatch fish eggs in an environment removed from predators and the variations in the natural environment that can increase mortality. A commonly used incubator is the so-called “Heath tray” which provides a set of shallow trays allowing water to sequentially flow downward through the trays, and within each tray upward through a false bottom over the eggs. An example early Heath tray design is shown in U.S. Pat. No. 2,982,246 hereby incorporated by reference.
While Heath trays work well for species such as trout and salmon to permit hatching of many eggs in a compact volume (high hatching density), they are less successful in species such as the yellow perch and Eurasian perch where the eggs are laid embedded in protective skeins or jellylike ribbons. In an incubation tray, these skeins can coil over themselves producing areas of anoxia within the skein and resulting in egg mortalities. Additional mortalities can occur if the egg skeins float to the surface of the tray permitting desiccation of the eggs.
The present invention provides a tray system suitable for use with fish laying eggs in skeins while providing good hatching density, promoting good water flow around the eggs, and reducing contact between the eggs and open air. The invention provides a set of cassettes that hold short lengths of skein flattened between opposed vertical meshes that provide exposure on both sides of the skein to upwardly flowing water. The regular form factor of the cassettes allows them to be closely stacked with small water flow gaps between them for high hatching density. The cassettes may be placed in a false bottom tray similar to that used in familiar Heath tray designs to be compatible with existing racks and hatchery layouts. A hanger system allows the cassettes to be removed and transferred to a larger tank prior to hatching.
More specifically, the invention provides an incubator for fish eggs skeins having a water-resistant cassette with a first and second frame each presenting a water permeable face. The first and second frames are adapted to move between an open state in which a fish egg skein may be uncoiled and placed between the first and second frame, and a closed state where the first and second frames flank the fish egg skein to resist coiling of the fish egg skein by the proximity of the water permeable faces of the first and second frames on either side of the fish egg skein. A clamp releasably holds the first and second portions in the second state.
It is thus a feature of at least one embodiment of the invention to provide a system for holding egg skeins in an uncoiled state exposed to water while allowing practical incubation density.
The water permeable faces may provide a lattice of water-resistant struts defining lattice openings having an area of at least one square centimeter.
It is thus a feature of at least one embodiment of the invention to minimize obstruction of the egg skein by the structure of the cassette consistent with the small-scale mechanics of the egg skein. It is another object of the invention to permit the cassette to be used during the hatching process allowing escape of the fish larva without undue interference from skein material trapped by the cassette.
In one embodiment, the water permeable face of the first frame may provide a peripheral border around a central opening comprising at least 50% of an area of the water-permeable face.
It is thus a feature of at least one embodiment of the invention to allow preferential clamping of the edges of the skein to reduce interference between the cassette structure and the water flowing around the skein.
In this case, the second frame may provide a lattice structure aligned with the central opening when the first and second frames are in the closed state.
It is thus a feature of at least one embodiment of the invention to provide a support resisting movement of the egg skein outside of the cassette when there is lateral waterflow through the trays. The cassettes may be oriented with respect to any such flow with the second frame downstream.
The water-permeable faces of the first and second frame in the closed state may be spaced apart by a gap of least one-half millimeter and provide protruding nubs extending into the gap to engage the fish egg skein.
It is thus a feature of at least one embodiment of the invention to separate the egg skein from contact over any substantial area with the cassette such as may reduce oxygen flow by using the nubs to provide extremely localized spacing.
The first and second frames maybe joined at one edge by a hinge to pivot respectively by rotation of the hinge between the open state and closed state.
It is thus a feature of at least one embodiment of the invention to simplify installation of egg skeins into the cassette retaining and stabilizing the cassette frames with the hinge allowing only a single angular degree of freedom.
The cassette may haves a neutral or negative buoyancy and in some embodiments may have a center of buoyancy urging the water-permeable faces into a vertical orientation in water.
It is thus a feature of at least one embodiment of the invention to promote submersion of the cassettes in the proper orientation in the event that they become loose from the frames or after a transfer from the trays into open tanks when they are unconstrained by the frames.
The incubator may further include a receiving tray having guides for slidably receiving opposed edges of multiple of the cassettes in the closed state with the water-permeable faces vertically oriented and the cassettes spaced apart parallel to each other for waterflow therebetween.
It is thus a feature of at least one embodiment of the invention to promote an extremely high density of egg skeins for reduced cost and resource usage.
The tray may provide an inlet receiving downwardly flowing water at one and discharging that water beneath the multiple cassettes for upward flow therebetween and may provide an outlet for receiving water after it flows between the cassettes to discharge that water to the inlet of a second tray positioned beneath the tray.
It is thus a feature of at least one embodiment of the invention to provide a stackable system for decreased space usage.
The second tray (and each tray in a stack) may be substantially identical to the first tray.
It is thus a feature of at least one embodiment of the invention to provide a low-cost and simple manufacture and stocking of the trays.
The incubator may further include a hanger providing a hook for pivotally attaching the hanger to a supporting structure, the hanger releasably attachable to the cassette to suspend the cassette with the water-permeable faces substantially vertical beneath the hook.
It is thus a feature of at least one embodiment of the invention to allow the cassettes to be transferred to an open tank during hatching.
These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention.
Referring now to
Generally, the water-permeable surfaces 17 provide a lattice or mesh structure sized to provide regularly spaced openings, for example, having an area in excess of 1 cm2, to provide good water flow through the frames 16 and to allow escape of larva when the cassettes 12 are transferred to a hatching tank to be described. In one embodiment, shown in
While both of the frames 16 may have identical structures, in one embodiment frame 16a provides a central opening 25 preferably at least 50% of the area of the front surface 17 that is surrounded by a border 29 of lattice structure. In this case, the border 29 operating with the surface 17 of the opposed frame 16b may clamp the edges of the skein 18 while the opening 25 provides unobstructed access to water. Both frames 16 may have an opening 25 but preferably frame 16b has a lattice structure with smaller openings over its entire surface to provide a backstop against distortion of the skein 18 under a slight horizontal flow of water expected during operation as will be discussed.
Desirably the cassette 12 may have a density that provides neutral or negative buoyancy in water, for example, through the use of a thermoplastic material having sufficient density or molded around weighting material or incorporating a weighted filler. The weighting of the cassette 12 may be distributed, for example, by increased weighting toward a bottom edge, so that when the cassette 12 is immersed in water it tends to orient itself with the water permeable surfaces 17 oriented vertically.
Referring also to
Referring now to
When the cassette 12 is closed with the frames 16a and 16b closely adjacent and latched, the inner surfaces 17 will be separated by a gap 31 of approximately 1 mm, a dimension being close to but slightly larger than the diameter of an egg 20. Nubs 26 on opposite frames 16a and 16b will align and closely approach each other with a gap 33 of approximately 600 μm to firmly retain the skein 18 and prevent it from contracting and coiling in upon itself. The size and shape of the nubs 26 operates in conjunction with the firmness of the eggs 20 and the dynamic qualities of the skein 18 to allow the eggs 20 to move away from the nubs 26 when the frames 16a and 16b are closed.
Referring again to
Flanking sidewalls 36 of the carrier 30, across the width of the carrier 30, may provide for internally extending, mutually opposed pockets 38 to receive, align, and retain the cassettes 12 just above the bottom edge of the carrier 30 to allow water to flow beneath the cassettes. One end of the carrier 30 provides an opening 28 through which water can enter for that purpose.
The width of the carrier 30 is sized to receive the 20 cm long longest dimension of the cassettes 12 and the length of the carrier is such as to allow multiple cassettes 12 to be inserted in parallel, spaced apart fashion with sufficient space between the cassettes 12 (for example, 1 to 2 cm) to allow the free flow of water therebetween.
The carrier 30 may fit within a generally rectangular tank 32 size to allow full submersion of cassettes 12 held in the carrier 30. The height of sidewalls 37 of the tank 32 are sized to allow complete submersion of the cassettes 12 when the carrier 30 is placed at the bottom of the tank 32 and the tank 32 filled with water, a dimension being slightly greater than the 10 cm height of the cassettes 12. A divider wall 41 of the tank 32 is adjacent to the opening 28 of the carrier 30 and provides a corresponding opening 42 aligned with opening 28. The opening 28 leads to a water-receiving compartment 48 forming one end of the tank 32. The water-receiving compartment 48 is open at the top to receive water flow 34a that may then pass through opening 42 in the divider wall 41, through opening 28 of the carrier 30, and upward through the cassettes 12. After passing upward through the cassettes 12, the water may then flow out of cutouts 43 in the wall 37 opposite wall 41. The height of the cutouts 43 is such as to encourage a circuitous path of the water flow 34b upward through the cassettes 12.
The tank 32 may be received by a tray 50 providing a surrounding trough 52 that may receive water flow 34c passing downward from the cutouts 43. This water flow 34d may then be conducted around the trough 52 to the opposite side of the tray 50 to exit through a drain port 54 that can be aligned with the water-receiving compartment 48′ of a tank 32′ identical to tank 32 described above, allowing identical multiple tanks 32 and trays 50 to be assembled in a stack with water pumped into the water-receiving compartment 48 of the uppermost tank 32 and extracted from the lowermost tray 50 to be recirculated. For this purpose, the tray 50 may provide for features allowing it to engage and nest with the upper edge of a lower tank 32.
Referring now to
Each of the above described components may be molded of a nonreactive thermoplastic for rust resistance and easy cleaning and sterilization.
Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context.
When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications, are hereby incorporated herein by reference in their entireties.
To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.
This application claims the benefit of U.S. provisional application 62/960,926 filed Jan. 14, 2020, and hereby incorporated by reference.
Number | Date | Country | |
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62960926 | Jan 2020 | US |