The present invention relates to fish pot bait as indicated by the preamble of claim 1. The present invention relates further to a method for manufacturing of said fish pot bait as indicated by the preamble of claim 13 and use of said fish pot bait as indicated by the preamble of claim 20.

Background

Fish pot fishing is a widespread form of fishing commercially as well as in leisure fishing. There are fish pots adapted to various fish species and pots adapted shell fish. Common for all fish pots, baits are being used to capture the fish and shellfish. For most marine species, fresh baits in the form of herring, squid etc. are used. Normally it is desirable to have the fish pots placed in the sea for several days. The natural baits deteriorate rapidly in the sea and eventually cease to attract fish and shellfish. Our studies show that baits from herring, squid etc. leak out the odours in a timespan of about 2 days while the optimal pot fish bait should have a useful lifetime of at least 1 day, preferably more than 7 days and in some cases at least 14 days.

Fresh or frozen baits have a very short useful lifetime in the fish pots. The baits deteriorate rapidly in the water and subsequently cease to attract fish and crabs. In addition, handling of fresh or frozen bait is not practical if cooling and freezing are required. Furthermore, it is not sustainable to use fish edible for human consumption as bait.

Tropical areas

In tropical areas fish and shellfish often are captured with traps and fish pots in shallow water reefs and brackish water reefs. Fish pots are also used to capture deep-sea fish in these areas. Most fish pots and traps used in the tropics are designed for fishing in the reefs, in rocky areas and on coarse sea bottom. The species being fished include squid and crustaceous animals as well as snappers, luvars, sea bass, parrotfish, surgeonfish, squirrelfish, angelfish, tropical mountain lobster and others. Fishing with fish pots is widespread in mangrove creeks and river mouth areas for different crabs (mud crabs, swimmer crabs, spanner crabs, etc.), adult shrimps (mud shrimps, yellow shrimps, etc.) and a number of offshore shrimps. Different types of squid are also captured in most tropical waters.

Subtropical and tempered areas

A selection of fish, squid and crustaceous animals are captured with traps and fish pots in these areas, which encompass everything from near-coast species like eel, terapons, wrasse, sea bass (barramundi), breams, croakers, and crabs like rock lobster and species living in deeper waters and snappers, trevallies, squid, hermit crabs, and shrimps. Colder waters

There is a lot of fish pot catching in the northern Atlantic Ocean, the English Channel and the northern Pacific Ocean even if not as widespread as in the warmer areas. Cod, cusk or ling are often caught with fish pots and there is substantial fishing for lobster, marine crayfish, whelk, and edible crab in the English Channel and outside the west coast of France. King crab, snow crab, lobster and shrimps are caught outside the coast of Alaska. Today, there is widespread fishing in the Barents Sea for king crab and snow crab. Along the coast of Norway edible crab, lobster, shrimps, ballan wrasse, and whelk are caught with fish pots. In addition, there is a desire to use large fish pots with long resident time to catch cod. For this kind of fishing pots, it is desirable that leakage from baits is ongoing for a long time and most preferred leakage for a period of 3 to 4 weeks.

In total there is a pot fish catch of fish and crabs exceeding 1.5 million tons per year.

Odours for use in fish pots

The use of attractants for fishing and catching of fish and other marine species is well known in a number of contexts; attractants being substances that have an attracting influence on the marine species in question— in combination with means that serve to determine the rate of release of attractant, so that it lasts for a certain time period.

This is also relevant for fish pot fishing to which the present invention is directed. In this context, it is known that baits for crustaceous animals, in particular lobster, which includes a pelletized carrier comprised by ingredients intended for extended useful lifetime in seawater. The pelletized carrier is mixed with attractants and a fish oil for prolonged release of the attractant. The pelletized carrier can comprise different kinds of meal, cf. US patent 6 555 144 Bl.

Furthermore, from US patent application No. 2013 0118 055 Al a lobster trap in the form of a "cake" is described, comprising a mixture of animal collagen, water, gelatine, gelling agent, fish meal, and fish oil, moulded and cured to a cylindrical cake.

Norwegian patent No. 341 329 discloses an improved fish pot bait comprising use of hydrated lime. Lime brings about that the bait has a high pH, which can present challenges when handling the bait during manufacture and use. The amount of attractant leaching over time can be adjusted by changing the relative amounts of the components from which the bait is made. Different fish pot baits which show different amount of attractant leaching over time have a very different composition. Also this issue can present challenges when handling the bait during manufacture and use.

US patent application No. 2004 0216 357 A1 discloses a spinner with a bait which can comprise gypsum and which has a pH which is about neutral. The bait is substantially well to handle during manufacture and use. Leaching of attractant over time is referred to as controlled compared with bait which surface is sprayed on with attractant. Leaching over a longer time period than 60 minutes is not disclosed, which renders the bait from the spinner scarcely appropriate for crab fishing.

The PCT publication WO 2015 191 136 A1 discloses a bait which can comprise gypsum and which has a pH which is about neutral. The bait is substantially well to handle during manufacture and use. The amount of attractant leaching over time can be adjusted by changing the relative amounts of the components from which the bait is made. Different fish pot baits which show different amount of attractant leaching over time have a very different composition. This issue can present challenges when handling the bait during manufacture and use.

Objective

It is an objective of the present invention to provide an alternative to known means for control of release rate of attractants for fish pot baits, which means should be effective, inexpensive and not significantly affecting the aqueous environment or the handling of the fish pot bait.

More concrete, it is an objective to provide a fish pot bait which includes alternative means for controlling the release rate of attractant. Typical applications are for catching cod and other fish species, crabs and shell fish as well as species mentioned above in relation to tropical, subtropical and colder waters. The bait should also be well suited for catching lobster, snow crab and king crab.

The present invention

The above mentioned objectives are fulfilled by the present invention as defined by claim 1.

According to another aspect of the invention, it relates to a method for fish pot fishing as defined by claim 13.

Finally, the invention relates to use of fish pot bait as defined by claim 20.

Preferred embodiments of the invention are disclosed by the independent claims.

It should be understood that what is here referred to as the environment is water, and more specifically seawater (saline water). Use of gypsum as substance to control the release rate of attractant to the environment and thereby to attract crab, shell fish and fish, has proven very effective in practice. Use of organic metal salt in addition to gypsum but in considerable lower amount can contribute to adjust the release rate of the attractant. The organic metal salt is partly or wholly manufactured by mixing at least one corresponding acid with one corresponding alkaline metal salt.

As attractant in the present invention, hydrolysed bi-products or extracted odours from fish- or shellfish production is typically used, as well as ground bi-products directly. We also consider the use of bi-products from other food production relevant, like chicken production, cattle like e.g. casein, and vegetable sources like for example yeast and algae, micro-algae as well as macro algae. In our tests we have used bi-products from shrimps, snow crabs, cod, coalfish, mackerel and herring.

Typically, the bait according to the present invention comprises odours (attractant) adapted to different marine species and a carrier for the attractant. The attractant can comprise a mixture of odours recovered from marine resources. The carrier, which in the present case comprises gypsum, is 100% environmentally friendly.

In accordance with the present invention, a bait useful for pot fishing is provided, said bait leaking odours at a rate that can be controlled in accordance with the species of interest to catch. The bait is sustainable and does not cause any external effects. By adding different odours, the bait will be effective for different species of fish, crabs, etc. When odours recovered by hydrolysis or extraction are combined with carrier in the form of gypsum and organic metal salt, a paste is formed that can be moulded, extruded or in other ways shaped to bait of adequate sizes. The paste is dried in air with or without heat.

Attractants that are used are most typically bi-products from the fishing industry. These are typically products which are not used for production or further refinement in any form. The present invention, however, is not restricted to a particular type of attractant, but to a certain type of carrier for the attractant.

Social value

An improved catching yield is obtained when using the present invention. The fish pot bait according to the present invention can be used for more than 1 day and preferably more than 7 days. This implies a more efficient fishing and the possibility of allowing fish pots stand for a week rather than 1-3 days. There is no need for cooling/ freezing which reduces the costs and C02 emissions. In the new bait, odours from bi-products from fishing production may be used. Reduction in the use of fresh or frozen baits will be environmentally friendly, strengthen the fish stocks, and allow an effective use of scarce marine resources.

More detailed about the invention

Figure 1 shows leakage rates versus composition. In fish pot fishing, controlling the release of odours and the ability to adapt odours to different species of fish and crabs are the most important features in order to achieve efficient catch. The new fish pot bait opens for an entirely new way of controlling the release of odours to attract fish/crabs into fish pots and other traps. Use of bi-products from the fishing industry combined with gypsum and organic metal salt provides a possibility of controlling release of odour. This is done by adjusting the amount of gypsum and organic metal salt in the bait. During tests, we have experienced that the bait is effective for more than 3 weeks. According to the present invention, it is used in a weight ratio between gypsum and organic metal salt in the range from 250:1 to 3:1, more preferred about 100:1 to 4:1 and most preferred 50:1 to 5:1.

Experimentally Examples of the composition of bait according to the present invention are shown in Table 1. The baits are manufactured by mixing gypsum, lime (hydrated lime Ca(OH)2) which is selected as alkaline metal salt and citric acid, which is selected as organic acid. The ratios are given in Table 1. Thereafter attractant is added. A fish pot bait is achieved, which is easily workable during manufacturing and physically stable in use. The leaching time is controlled by the amount of organic metal salt. Calcium citrate is the organic metal salt in the examples and is formed from lime and citric acid.

Table 1: Composition of bait [%] according to the present invention

Leaching of attractant from the bait follows a first order decay for the residual amount of attractant which is left versus time. Experience teaches that a first order decay down to 30% residual amount of attractant (typically 70% leached attractant) is good enough for a successful fishing. In order to evaluate the leaching from baits with different leaching rates the leaching down to 30% residual amount is primarily compared. Figure 1 shows leaching studies of bait with different leaching rates. Examples 1, 2 and 3 in Figure 1 show that the leaching rate of attractant can be adjusted to the time frames which are relevant for the use of the invention. Changes in the composition of baits with significantly different leaching rates are small.

The ratio between gypsum and organic metal salt is selected to typically 12:1 in order to obtain a leaching of attractant up to typically 70% total leaching after 30 hours.

The ratio between gypsum and organic metal salt is selected to typically 25:1 in order to obtain a leaching of attractant up to typically 70% total leaching after 72 hours.

The ratio between gypsum and organic metal salt is selected to typically 5:1 in order to obtain a leaching of attractant up to typically 70% total leaching after 120 hours.

Table 2 shows a selection of organic metal salts and their solubility in water as g/L at typically 25°C if not specified different. The metals in the metal salts are selected from but are not limited to Ca, Mg, Al, Zn and Fe. Other organic metal salts can be used in the invention.

¹¹ warm water

Table 2: Selection of organic metal salts and their solubility in water [g/L],

Organic metal salts with a solubility lower than 0.1 g/L are depicted as insoluble in Table 2. The solubility of organic metal salts will have influence on the stability of the bait and therefore on the release of attractant within a given period of time. Use of an organic metal salt with relatively high solubility in water will generally lead to a bait with lower stability when applied in water compared to use of an organic metal salt with relatively low solubility in water.

Organic metal salts which can be used in the present invention are typically manufactured by mixing at least one corresponding acid with one corresponding alkaline metal salt at room temperature or elevated temperature. Appropriate acids can be selected from but are not limited to citric acid, gluconic acid, oxalic acid, benzoic acid, C1-C24 carboxylic acid, sorbic acid, p- hydroxybenzoic acid, lactic acid, malic acid, fumaric acid, tartaric acid, metavinic acid, maleic acid, ascorbic acid, aspartic acid, gallic acid, substituted and unsubstituted hydrochinone, adipic acid, succinic acid, glutamic acid, 4-hexyl resorcin, alginic acid, polymers and copolymers of acrylic acid. For multi-base acids with more than one mole of acid functionality per mole of acid, the acid may be partially converted into acid derivatives selected from esters and salts. Corresponding basic metal salts may be selected from but are not limited to hydroxides, oxides, oxide hydroxides, carbonates, hydrogen carbonates, silicates. The person skilled in the art will come up with suitable combinations of corresponding acids and corresponding basic metal salts. Organic metal salts which are insoluble or insoluble in water are particularly suitable for carrying out the invention.

The solid content of the attractant is preferably between 40 and 50 %, more preferably about 45 %.

The content of gypsum in the bait is in the range of 60-80 % by weight calculated by the weight of the bait, more preferably 62-74 % by weight.

The weight ratio of attractant to gypsum is in the range of 1:10 to 6:10, more preferably about 3:10. In order to adjust the pH value in the fish pot bait, the fish pot bait may contain an

(stoichiometric) excess acid in a suitable amount.

The fish pot bait may additionally contain 1-10% by weight of lignin to improve its workability and mechanical properties.

Further extension of the leakage time can be achieved by the use of a coating of a PVA polymer foil of desired thickness.

The bait can be used as is in standard bait bags or in PVA plastic bags used as bait bags. These are bags with holes to ensure circulation with the surrounding water, that being micro-holes or larger holes.