Fishing – trapping – and vermin destroying – Fishing – Gathering or catching device with conveyer to boat
Reexamination Certificate
2000-05-31
2002-02-05
Ark, Darren W. (Department: 3643)
Fishing, trapping, and vermin destroying
Fishing
Gathering or catching device with conveyer to boat
C114S255000, C043S009200
Reexamination Certificate
active
06343433
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an apparatus for live harvesting of an aquatic target species at depth and bringing it to a collection point at the surface of a waterbody in a manner which substantially reduces the mortality rate. In addition, this apparatus permits ready separation, either or both at the surface collection point, or during transportation to the surface collection point, of live target and any non-target species harvested simultaneously from the waterbody and facilitates the reintroduction of the non-target species at depth to the waterbody.
BACKGROUND OF THE INVENTION
Conventional practice for the mass harvesting of relatively small aquatic target species such as shrimp is usually accomplished by using trawl nets, or the like, which are towed behind a trawler. These nets catch both the target and non-targeted or by-catch species indiscriminately. As the volume of bio-mass is compressed into the collection end, or cod end, of the trawl net as it is moved through the water body, a high mortality of both target and by-catch species results. In addition, this compression and the subsequent lifting movement of the filled net from depth to the surface of the water body and its transportation onboard the trawl boat results in additional mortality and inflicts damage to the target species resulting in a decrease in quality.
Public pressure and regulation now require that more attention to be paid to limiting the mortality rate of the by-catch, since much of it is made up of juveniles of commercially valuable species. The mortality of such juvenile by-catch species is the result of compaction and suffocation in the cod-end of the trawl net during netting, and as the net is hauled onboard the trawler and the inability to survive the temperature differential of the water from the point of catch to the point of release at the surface of the water body.
Without intending to be limiting, it is an object of this invention to transport both target and by-catch species live to a container at the surface of a water body along with a constant volume of water from the depth at which the species were caught.
Again without intending to be limiting, it is a further object of this invention to provide a means of escapement for by-catch species during the transportation of by-catch and target species to the surface.
Again without intending to be limiting, it is a further object of this invention to provide a means of separating target and by-catch within the surface container and returning the by-catch directly to depth to thereby reduce mortality.
Further, this invention overcomes inherent difficulties where the target species and by-catch species are quite similar in size and where the by-catch species is an endangered species.
Applicant is aware that many bodies of fresh water have in the past seen the introduction of nonindigenous aquatic organisms intended as an additional forage source for indigenous sport fish. In some cases the introduced species has resulted in dramatically adverse changes to the aquatic ecosystem and has become a direct competitor for available food resources, placing the indigenous species in even greater peril. Such has been the experience with the introduction of
Mysis relicta,
a.k.a. Opossum shrimp or Mysis shrimp as a food source for
Oncorhynchus nerka kennerlyi
a.k.a. Kokanee, land-locked sockeye or silver trout. Control of the Mysis shrimp population through an aggressive harvesting program is therefore seen as a major component of a plan to protect what has become, in some lakes, an endangered species, namely the Kokanee.
In the prior art Applicant is aware of U.S. Pat. No. 3,768,193, which issued Oct. 30, 1973 to London for a Brine Shrimp Harvesting Apparatus. London discloses a method of using a elongated housing containing a rotatable internal screw, mounted on a raft, for removing shrimp concentrated on a net at the surface of a water body. Applicant is further aware of U.S. Pat. No. 5,361,528 which issued Nov. 8, 1994 to Peacock for a Trawling System and Trawl Device for Shrimp. Peacock discloses a device having angularly adjustable opposed elongated arms for trawling over the seabed. Water pressure as the trawl is moved over the seabed forces shrimp to the outer extremities of the elongated arms where they can be drawn to the trawl boat by onboard pumps.
What is neither taught nor rendered obvious from the prior art, and which is an object of the present invention to provide is an apparatus which permits ready separation, at the surface collection point, of live target and any non-target species harvested simultaneously from a body of fresh water and which facilitates the reintroduction of the non-target species to the waterbody at a depth where the water temperature is generally the same as where they were harvested thereby reducing mortality of the non-target species.
SUMMARY OF THE INVENTION
The present invention relates to a device for harvesting a target species, which in this example is, but not limited to, a variety of fresh water shrimp, separating from the target species any non-target species, such as juveniles of a commercially valuable sport fishery species such as Kokanee salmon which have been inadvertently and simultaneously harvested and releasing the non-target species back to the same depth and water temperature at which they were caught.
The device of the present invention includes a trawl net and a catch boat each being towable by a trawler by separate towing lines or cables so as to be movable concomitantly through the water by the trawler. A catch drawer is mounted within the catch boat for selective vertical movement relative thereto by a means for selective vertical movement of the catch drawer in relation to the catch boat. A conduit connects the cod-end of the trawl net to a forward end of the catch drawer. The conduit permits both target and by-catch species to be freely carried through the conduit along with a constant volume of water, which is funneled through the conduit as the trawl net is pulled through the water.
A pump or other means maintains the surface level of water in the catch drawer below the surface level of the lake or other large body of water in which the device of the present invention is situate.
A series of removable nets or screens are positioned within the catch drawer for separating target and by-catch species. A means is provided to convey by-catch organisms from the catch drawer to a layer of cooler water below the surface of a waterbody generally at the trawl net operating depth.
In an alternative embodiment, a by-catch separating device is positioned downstream of the trawl net to provide means whereby escapement of by-catch species is naturally encouraged. The by-catch separating device is a short tubular section having an internal baffle or screen comprising a plurality of parallel, spaced apart members secured therein and biased against the incoming water flow. The internal baffle creates a downstream chamber wherein by-catch organisms unable to pass through the spaced apart members are directed toward one side of the separator which contains an escape aperture. A source of illumination is fixed externally of the separator in proximity to the escape aperture as an attractant to encourage by-catch to egress the downstream chamber through the escape aperture.
The members comprising the internal baffle or screen may be flexible, such as of nylon strings, and are generally parallel and spaced apart sufficiently so as to permit passage therethrough of all the target species. Where the lower size range of non-target species approximates target species size, a further separation is possible by placing a further by-catch separating device in series upstream of the primary. The internal baffle of the secondary separator, in order to separate out smaller by-catch, has the spaced apart members positioned closer together. Such separation will still permit a reduced quantity of smaller sized non-target organisms to be brought to the catch boat along with the intended target spe
Ark Darren W.
Edwards Antony C.
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