Patent Description:
Advances in aquaculture in general and fish farming in particular, and improvements in technology, have enabled significant progress to be made to efficiently address increasing world demand for fish product at lower costs. Developments in fish farming reduced the risks associated with overfishing indigenous fish populations. In particular, open-ocean aquaculture employing fish cages or fish pens, have found some recent success. Large fish pens suitable for aquaculture applications are known in the art aid for the efficient and bio-responsible cultivation of food sources. Typically, in open-ocean aquaculture large fish pens are positioned a distance offshore in deeper and lesssheltered waters where ocean currents are relatively strong. The fish pens are stocked with young fish or fry, and the fish are fed and maintained until they reach maturity. The fish pens provide a habitat and protection for the fish. Similar fish pens are also used for freshwater aquaculture, for example, in larger freshwater bodies of water.

A common problem in conventional commercial aquaculture fish pens is the safe identification and removal of ill and deceased fish within the system. When fish in a commercial fish pen die or become debilitatingly ill, the deceased or ill fish (referred to in the art as "morts") will initially have a negative buoyancy and sink to a bottom end of the fish pen. However, after a time the morts may become neutrally buoyant and then positively buoyant due to gasses generated therein. If morts are not regularly removed they may become very difficult to identify, isolate, and separate from the healthy fish population. Mort collection in an open ocean fish pen is a significant and time-consuming task requiring the regular (e.g., daily) deployment of divers tasked with removing morts. Typically, safety protocols require raising the fish pen to a maximum elevation to minimize the maximum diving depth required for the divers. Manual removal of morts in conventional fish pens requires divers to enter the fish pen, identify and collect morts in mesh bags, and then either swim the filled mesh bag back to a retrieval vessel, or attach the bag to a safety line to be hauled to the retrieval vessel. Risks to the divers include the possibility of underwater predators being drawn to the area by the morts.

There are clear benefits to quickly identifying, isolating, and removing morts. By identifying and retrieving morts the cause of death can be timely determined, and appropriate corrective measures implemented to prevent or reduce the loss of additional fish. For example, if a mort is found to be inflicted with a pathogen for which a protective treatment is available, early administration of the treatment can be implemented. If the cause of death is determined to be related to food or other product provided to the pen, then corrective measures may be timely implemented. In addition, removing the morts reduces the time that the mort is among the healthy fish population, thereby slowing or preventing the spread of pathogen(s) in the population. Even if a natural, non-pathogenic cause of death is responsible, it would be advantageous to remove morts from the population for general health maintenance of the fish pen and to avoid undesirably attracting predators to the area of the fish pen.

Innovations in fish pens employing a center spar buoy or center cluster of spar buoys are disclosed in <CIT>, and in <CIT>. Loverich et al. discloses a mobile pen for growing fish or shellfish wherein a central vertical spar buoy is surrounded by one or more horizontal rim assemblies. A mesh/netting extends from an upper end portion of the spar buoy outward to the rim assemblies, and then inward from the rim assembly to a lower end portion of the spar buoy, defining the primary interior volume <NUM> for the fish. More recently, <CIT> discloses a spar buoy fish pen assembly with a deployable system for segregating a population of fish within a fish pen, and/or for crowding the fish into a smaller space, for example, to facilitate treatment or harvesting operations.

<FIG> shows a front view of a vertical spar fish pen <NUM> disclosed in <CIT> Gace et al. discloses a fish pen having a central spar buoy <NUM> supporting an enclosure defined by a netting assembly <NUM>, and suitable for use in open-ocean fish farming, for example. A mortality trap ("mort trap") <NUM> is attached to a lower end of the spar buoy <NUM>. The mort trap <NUM> is configured to receive and isolate morts from the remaining fish population in the fish pen <NUM>. An external extraction hose <NUM> extends from the mort trap <NUM> external to the fish pen <NUM>, to facilitate removal of morts from the mort trap <NUM>. The mort trap <NUM> may also be configured to facilitate the harvesting or extraction of healthy live fish from the fish pen <NUM>.

In an exemplary embodiment the spar buoy <NUM> includes one or more interior spaces (not shown) that can be selectively filled with water or with air (or another gas). It will typically be desirable to raise the fish pen <NUM> at least partially out of the water, for example to facilitate fish pen cleaning, inspection, maintenance, upgrade, and/or repair. In a current embodiment, the fish pen <NUM> is configured with, or configured to engage, an air pumping assembly (not shown) such that air may be pumped into chambers in the spar buoy <NUM>, displacing sea water and thereby increasing the buoyancy of the spar buoy <NUM>. The spar buoy <NUM> may therefore raise the fish pen <NUM> partially out of the water. The spar buoy <NUM> may be connected to an anchor or ballast member (not shown) to maintain the vertical orientation of the spar buoy <NUM>. In some embodiments the spar buoy <NUM> may be configured to allow the user to flip the fish pen <NUM> to selectively raise either end of the fish pen <NUM> out of the water. It will also be appreciated by persons of skill in the art that raising the fish pen <NUM> may also be beneficial when harvesting fish from the fish pen <NUM>, for example, to crowd the fish into a smaller volume within the fish pen <NUM>.

A rim assembly <NUM> is disposed around the spar buoy <NUM>. The rim assembly <NUM> in the exemplary embodiment is formed from a plurality of tubular segments assembled into a polygonal or circular configuration. The rim assembly <NUM> in the embodiment of <FIG> is disposed generally perpendicular to the spar buoy <NUM>. In some embodiments the buoyancy of the rim assembly <NUM> is adjustable. For example, the rim assembly <NUM> in cooperation with the spar buoy <NUM> may be configured to be filled with air, water, or a combination of air and water, to produce a desired fish pen <NUM> buoyancy, or to reorient or invert the fish pen <NUM>, e.g., by asymmetrically changing the buoyancy of the rim assembly <NUM>.

The rim assembly <NUM> is attached to the spar buoy <NUM> with a plurality of tension members <NUM> that extend between a lower spokeline ring <NUM> and the rim assembly <NUM>, and a plurality of tension members that extend between an upper spokeline ring or cone <NUM> and the rim assembly <NUM>. The rim assembly <NUM> includes a plurality of spaced-apart guides, pulleys, or flanges <NUM> that are configured to engage respective tension members <NUM>. The flanges <NUM> provide attachment or engagement points for the tension members <NUM>, and may also be used to anchor the fish pen <NUM>, and/or to gang or interconnect a plurality of fish pens <NUM>. In some embodiments, the fish pen <NUM> may comprise more than one rim assembly <NUM>. For example, the fish pen may have two or more parallel and spaced-apart rim assemblies <NUM>.

The cone <NUM> is connected near an upper end of the spar buoy <NUM>. In the current embodiment, the cone <NUM> is attached to the spar buoy <NUM> through a plurality of longitudinal rails <NUM> fixed to, or co-formed with, an outer surface of the spar buoy <NUM>. The rails <NUM> preferably include a plurality of spaced attachment positions such that the axial location of the cone <NUM> is adjustable.

There remains a need for improvements in fish pen construction. For example, in contained fish pen populations it is desirable to remove or separate sick or deceased fish from the healthy population quickly, in order to prevent harm to the healthy fish. It would be beneficial to isolate morts quickly, to maintain the health of the remaining population. It would also be beneficial to identify and remove morts quickly, to be able to determine the cause of death and, if appropriate, take corrective measures.

<CIT> discloses a mort trap comprising a slide, an upper ramp having an outer edge that is fixedly attached to an inner edge of the slide, a retaining chamber being located below a bottom end of the upper ramp and having an opening, a lower ramp and a purge pipe fluidly connected to the retaining chamber. <CIT> discloses a mort trap comprising an upper receiver portion having an upper edge configured to engage a fish pen, an upper ramp having an outer edge that is fixedly attached to a lower edge of the upper receiver portion, a retaining chamber being located below a bottom end of the upper ramp and having an opening, a lower ramp and a purge pipe fluidly connected to the retaining chamber.

As used herein, "morts" is defined to mean deceased or ill fish, and in particular deceased or ill fish in a fish pen assembly, and a "ramp" is defined to mean a component providing an elongate surface that slopes, i.e., a surface that slopes downwardly.

<FIG> is a front view of a fish pen assembly <NUM> in accordance with the present invention, including a mort trap <NUM> that may be installed, for example, at or near a lower end of the fish pen assembly. The fish pen assembly <NUM> includes a vertical spar buoy <NUM> and a rim assembly <NUM> that extends around the spar buoy <NUM>. In a currently preferred embodiment the mort trap <NUM> may be positioned at any location along the full height of the spar buoy <NUM>, for example to receive morts when an intermediate nursery net or the like (not shown) is installed/deployed in the fish pen <NUM> to reduce the occupied volume of the fish pen <NUM>. The rim assembly <NUM> is attached to the spar buoy <NUM> with a first plurality of tension members <NUM>, for example cables, that connect the rim assembly <NUM> to an upper end portion of the spar buoy <NUM>, and a second plurality of tension members <NUM> that connect the rim assembly to a lower end portion of the spar buoy <NUM>. A netting assembly <NUM> is connected to the spar buoy <NUM> and the rim assembly <NUM> to define a working volume for the fish enclosure. In some embodiments the fish pen assembly <NUM> includes a system, for example a pumping system (not shown) for changing the buoyancy of the spar buoy <NUM> and/or the rim assembly <NUM> to controllably change the buoyancy of the fish pen assembly <NUM>, such that the fish pen assembly <NUM> can be moved between a submerged position wherein the fish pen assembly <NUM> is submerged below the water surface, and a raised position wherein a significant portion of the fish pen assembly <NUM> is disposed above the water surface. In some installations one or more anchor assemblies (not shown) are provided to secure the fish pen assembly <NUM> in a desired location. In some installations a plurality of fish pen assemblies <NUM> may be interconnected or otherwise maintained in close proximity to each other, and may share a centralized operating infrastructure, for example, feeding, monitoring and/or control systems.

The fish pen assembly <NUM>, in this embodiment, includes a mort slide <NUM>, e.g., a false bottom, installed inside a lower portion of the fish pen <NUM>. In the current embodiment the mort slide <NUM> extends only partially around the spar buoy <NUM>, for example, about half way around the spar buoy <NUM>, as seen most clearly in <FIG>. In some embodiments a slide may be configured to extend fully around the spar buoy <NUM>. The false bottom mort slide <NUM> has an upper end <NUM> fixed to or otherwise abutting, the netting assembly <NUM> and an opposite end <NUM> that engages an upper ramp <NUM> of the mort trap <NUM>, as discussed below. The mort slide <NUM> is configured to guide morts that engage the slide <NUM> as they descend through the fish pen <NUM> such that the engaged morts are captured in the mort trap <NUM>, preventing these morts from sinking into a region adjacent to the mort trap <NUM>. For example, the mort slide <NUM> in a current embodiment is made from an ultra-high-molecular-weight polyethylene (UHMWPE). UHMWPE has mechanical characteristics similar to high-density polyethylene (HDPE), and is resistant to acids, alkalis, and many organic solvents. It has a very low coefficient of friction and is self-lubricating. Suitable UHMWPE fibers include fibers marketed under the trademark DYNEEMA®, registered to DSM High Performance Fibers B. Corporation, Netherlands. The false bottom mort slide <NUM> may be a netting be made from a fiber-reinforced composite material, such as fiberglass, having a relatively low sliding friction coefficient to facilitate the morts sliding into the mort trap <NUM>. Optionally, the slide <NUM> may include a water-insoluble lubricant on its surface to facilitate the engaged morts to continue their descent to the mort trap <NUM>.

A purge pipe, for example a riser <NUM> extends from the mort trap <NUM>, and in the present embodiment is attached to the spar buoy <NUM> with one or more fastening clamps <NUM> with spacer members <NUM> (see also, <FIG>). As discussed below (e.g., see <FIG>) a pumping system may be provided to transport morts from the mort trap <NUM> to a location at or near the top of the fish pen assembly <NUM>, thereby eliminating the need for divers to conduct regular manual recovery of the morts.

<FIG> shows a detail view of the mort trap <NUM> connected to a bottom portion of the spar buoy <NUM> and the slide member <NUM>. The slide <NUM> is fixedly attached to an upper ramp <NUM> of the mort trap <NUM> located on one side. Refer also to <FIG> showing a perspective view of the mort trap <NUM> (connected to the riser <NUM>), and to <FIG> showing a sectional view of the mort trap <NUM>.

The mort trap <NUM> is generally annular with a central aperture <NUM> that is sized and configured to receive a lower end portion of the spar buoy <NUM>. Other configurations are contemplated, as will be apparent to persons of ordinary skill in the art. For example, the mort trap may alternatively be configured to attach to, and extend below, a lower end of the spar buoy <NUM>, or to be formed integrally with the spar buoy. In a currently preferred embodiment the annular mort trap <NUM> is configured to be installed at one or more intermediate locations along the spar buoy <NUM>. For example, the annular mort trap <NUM> may be installed at a location above the midpoint along the length of the spar buoy <NUM> for use with an intermediate nursery nets and harvest systems (not shown) that may be installed to reduce the occupied volume of the fish pen <NUM>.

The mort trap <NUM> includes the upper ramp <NUM> having a radially outer edge that is fixed to a lower end of the slide <NUM> such that morts descending along the slide <NUM> are directed by the slide <NUM> onto the upper ramp <NUM>. An inner edge <NUM> of the upper ramp <NUM> curves upwardly to engage and guide received morts as they slide down the upper ramp <NUM>. The upper ramp <NUM> includes left and right ramp sections that slope downwardly from a central portion located near the riser <NUM> towards a corresponding one of two spaced-apart entry ports <NUM> to a retaining chamber <NUM> located below the upper ramp <NUM>. The upper ramp <NUM> is configured to receive morts, directly or from the slide portion <NUM>, and to guide their continued descent toward the entry ports <NUM>. The retaining chamber <NUM> is generally semi-annular with space-apart openings at each end. A pair of lower ramps <NUM> are positioned opposite the upper ramp <NUM> and are configured to receive descending morts from the upper ramps <NUM> and to receive morts descending from elsewhere in the fish pen <NUM>. The lower ramps <NUM> slope downwardly in opposite directions towards a corresponding one of the entry ports <NUM> to the retaining chamber <NUM>. The retaining chamber <NUM> is therefore configured to receive morts from the lower ramps <NUM>.

Pliable curtains or live fish excluders <NUM> on either side of the retaining chamber <NUM> are configured to permit descending morts to enter the retaining chamber <NUM>, and provide a visual deterrent to discourage live fish from entering the retaining chamber. For example, in a current embodiment the live fish excluder <NUM> comprises an upper frame, door flap with weights at the bottom of the door. The door flap (either solid or in strips) may be, for example, <NUM> (. <NUM> inch)- <NUM> (. <NUM> inche) or more in thickness. A plurality of holes may be placed at intervals along a lower edge of the door and weighted blocks may be selectively installed. These tunable features of the assembly allows for specific movement of the door to both allow morts to enter the containment area, throughout a multitude of environmental conditions (e.g., water current, pen position in the water column, etc.), while visually and physically inhibiting living or well fish from entering the retaining chamber <NUM>. The live fish excluders <NUM> preferably are configured to allow live fish that are able to breach the excluder to exit the retaining chamber <NUM>. It is contemplated that in some embodiments the retaining chamber may have a vertical dimension greater than the vertical dimension of the entry ports <NUM> and/or a transverse dimension greater than the transverse dimension of the entry ports <NUM>, thereby providing a retaining chamber with a large volume relative to the size of the entry ports <NUM>.

As seen most clearly in <FIG>, the riser <NUM> includes an end connector portion <NUM> that fluidly connects the riser <NUM> to the retaining chamber <NUM>, such that morts in the retaining chamber <NUM> can pass into the riser <NUM>.

Referring now also to <FIG>, illustrating in diagram one embodiment of a mort transport system using an air pump <NUM> configured to facilitate the transport of morts from the mort trap <NUM> upwardly through the riser <NUM> to a discharge hose <NUM> located at or near an upper end of the fish pen assembly <NUM>. The transport system facilitates removal of the morts from the mort trap <NUM>.

In this embodiment an air pump <NUM> is configured to inject air into the riser <NUM> periodically or on command. It is contemplated that the mort trap <NUM> may be purged without raising the fish pen assembly <NUM> to the surface, for example, providing a discharge hose <NUM> that extends from the fish pen assembly <NUM> to a remote collection location. For example, in one embodiment an elongate discharge hose <NUM> may extend through one or more intermediate node buoys (not shown) to an arterial collection station located away from the fish pen <NUM>. For example, a plurality of fish pens <NUM> may discharge morts to a single collection station. In other embodiments, the fish pen <NUM> may be raised to the surface prior to discharging morts.

In this embodiment air is injected into the riser <NUM> near a lower end of the riser <NUM>, to produce a buoyancy-driven upward flow through the riser <NUM>. The buoyancy-driven upward flow draws water and morts from the mort trap <NUM> and transports the morts to the discharge hose <NUM> (see <FIG>).

In another embodiment a water pump is connected to the riser <NUM> and configured to selectively generate a flow through the riser <NUM> towards the discharge hose <NUM>.

Claim 1:
A mort trap (<NUM>) assembly for a fish pen (<NUM>) comprising:
a slide (<NUM>) configured to receive descending morts in the fish pen, the slide having an outer edge configured to engage the fish pen and an inner edge; and
a mort trap comprising:
an upper ramp (<NUM>) having a top end and a bottom end, the upper ramp having an outer edge that is fixedly attached to the inner edge of the slide;
a retaining chamber (<NUM>) located below the upper ramp, the retaining chamber located below the bottom end of the upper ramp, the retaining chamber is a semi-annular chamber with spaced-apart openings at each end, wherein the upper ramp has a right and a left ramp section that each slope to a corresponding entry port (<NUM>) of the annular retaining chamber;
a lower ramp (<NUM>) having a top end spaced away from the upper ramp, and a bottom end located at a bottom of each entry port; and
a purge pipe (<NUM>) fluidly connected to the retaining chamber,
wherein the upper ramp is configured to receive morts from the slide, and the lower ramp is configured to receive the morts from the upper ramp and to direct the received morts towards the entry ports.