JPH0320209B2 - - Google Patents

Description

[Detailed description of the invention] (A) Industrial application field This invention generates a weak electric current between dissimilar metals in seawater by combining steel and aluminum alloy and utilizing the potential difference between dissimilar metals. This invention relates to a breeding reef for breeding abalone that increases the abalone collection effect and settlement rate by utilizing it.

(B) Conventional technology Conventionally, abalone propagation blocks have been designed to attract abalone by cultivating seaweed that serves as food for the abalone, and by creating a feeding area. Since it is a living organism, we take advantage of its properties to create a shadow area (also known as a shadow area, the area where the sun's rays pass through the ocean and are not exposed to it).
The main aim is to manage and cultivate abalone resources by increasing the surface area of the abalone, creating a habitat for abalone, and promoting their settlement. Concrete blocks etc. have been devised and used.

However, it has become clear that the concrete blocks currently in use are not a good environment for marine life, such as fish and shellfish (especially young ones), due to the elution of strong alkaline components unique to concrete. .

Although this is not the only cause,
Abalone is no exception, and has the drawback of low aggregation and settlement rates.

This is due to the fact that the proportion of fish farms for breeding and artificial abalone stocking projects that are being carried out as part of the so-called cultivation fishery promotion, ``from fisheries that catch fish to fisheries that are cultivated and fished,'' as part of coastal fishery promotion measures, has decreased. ,
This is one of the major reasons why abalone stocks are not increasing.

Therefore, there is a strong need to develop breeding reefs that are more suitable for resource management type fisheries and have a higher collection effect and settlement rate than conventional breeding blocks.

(C) Problems to be Solved by the Invention The present invention attempts to solve the drawbacks of the currently used breeding reefs for breeding abalone, which have low abalone agglomeration and settlement rates, from the following point of view. It is something.

This has long been based on observations of the behavior and ecology of abalone in the natural world when they interact with coastal marine steel structures and steel materials in the sea. Taking advantage of the ecology of abalone, in which abalone collects in the cathode and is difficult to escape without being affected by This invention is a breeding reef suitable for resource management type fishing that can increase effectiveness and settlement rate.

(D) Measures to solve the problem For a long time, many cases of abalone growing on steel materials under the sea have been reported.

Many of them have almost no seaweed growth,
Adhesion to steel materials has been observed even when exposed to transmitted light.

In the natural world, this phenomenon of condensation on steel materials occurs due to the countless potential differences on the metal surface when the steel material comes into contact with an electrolyte called seawater, even if the material is the same metal that appears to be homogeneous at first glance. A weak current (called a corrosion current in this case) is generated by the so-called local battery action.
In order to confirm the behavioral ecology of abalone in response to this weak electric current, we conducted the following aquarium experiment for about 6 months.

To give an overview, Experimental Example 1 First, we investigated the growth of abalone on three types of concrete plates: concrete plates with the same shape, steel plates coated with resin to prevent corrosion currents, and bare steel plates that are prone to corrosion currents. .

The results are average values calculated per 10 abalones, with approximately 2.3 individuals growing on concrete plates, approximately 3.0 individuals growing on resin-coated steel materials, and approximately 4.7 individuals growing on bare steel materials. This is the result.

Experimental Example 2 Next, we conducted experiments on two types of corrosion currents: corrosion currents generated by local battery action such as in bare steel materials, and weak currents artificially generated using the potential difference between steel materials and aluminum alloy anode materials. I compared the settlement status of the same abalone as in Example 1 and during the same period.

In this case, if the surface area of the steel material is smaller than the surface area of the aluminum alloy anode material used, the potential of the steel material will be cathodically polarized to the potential of the anode material used, the potential difference between different metals will become small, and almost no current will flow. Since it was not possible to use the same shape as in Experimental Example 1, the experiment was conducted using larger steel materials and changing the shape.

The results are the minimum and maximum average values per 10 abalone individuals, and the number of settlements on bare steel is approximately 3.2 ~
4.0 individuals and 6.0 to 6.8 individuals settled on the steel material used as the anode material, which was about twice as many when a weak electric current was generated artificially.

The current density generated in this case was 0.1 A/m ² , but it was also found that if the current density (A/m ² ) was lowered, the steel material would corrode, and abalone would not grow in areas with severe corrosion. did.

Also, if a weak current is artificially generated,
Abalone only collects and settles on the cathode (steel material), and once it has settled, it is difficult to escape, and the settlement is conspicuous in places where there is relatively little sunlight. It was observed to be a sexual creature.

Based on such experimental results, in order to solve the drawbacks of conventionally used concrete blocks, etc., we have developed an example of the structure of the growing reef of the present invention, the required current density (A/m ² ), and the generated current. To explain how to calculate: (a) Attach the aluminum alloy anode 2 to the steel growth reef 1 (see the drawing) (b) The required current density (A/m ² ) is determined by the conditions of the sea area where the steel growth reef is deposited. The value is 0.15A/m ² ~
The range shall be 0.08A/ ^m2 .

The reason is that when steel reefs corrode,
It is necessary to prevent the corrosion of abalone because it reduces the area where abalone is attached and the rate of settlement.

These underwater corrosion prevention techniques for steel materials are already established and known techniques, and by applying these techniques, corrosion can be prevented.

In other words, since the anti-corrosion potential of steel in the sea is -0.77V with respect to the saturated calomel electrode, corrosion can be prevented by cathodically polarizing the steel to -0.8V, and the current density required for this purpose is Just do it.

The required current density in this case varies depending on the sea conditions such as seawater in the sea area where the steel reef is to be deposited, but in general, the value is
A value suitable for the various conditions of the sinking area may be selected within the range of 0.15A/m ² to 0.08A/m ² .

(c) Calculate the current generated from the anode in the following order.

Total surface area (As) of steel materials used for growing reefs
seek. (cm ² ) Total surface area (Aa) of the anode material installed on the growing reef
seek. (cm ² ) Find the water contact resistance (Rs) of the steel material using the following formula.

Rs=0.266×ρ/√ ρ: Seawater resistivity (usually 25 to 30Ω-cm) Calculate the water contact resistance (Rs) of the anode material using the following formula.

Ra＝0.266×ρ／√ ρ: Same as Find the total resistance (R) in the circuit using the following formula.

R=Rs+Ra+Rw Rw: Resistance when a conductor, etc. is used in the circuit (generally 0Ω) In the formula, the larger the steel surface area, the closer Rs≒0Ω, and R≒Ra.

Find the effective potential difference (ΔE) between the steel material and the anode using the following formula.

ΔE = Potential of steel − Potential of anode Potential of Γ steel material (bare) (non-current potential) Approximately -0.6V (based on saturated calomel electrode) Potential of Γ aluminum alloy anode Approximately -1.05V (based on saturated calomel electrode) The current flowing from the anode is calculated from the following formula.

I=ΔE/R (A) The current flowing from the anode initially has a large ΔE, so the generated current is large, but the potential of the steel material is polarized in the negative direction depending on the amount of current supplied, so the generated current becomes small and stable. do.

Therefore, in this case, it is necessary to cathodically polarize the potential of the steel reef to around -0.8V to prevent corrosion, so it is okay to calculate ΔE=0.25V.

The generated current density is determined by the following formula.

Current density (A/m ² ) = Generated current / Total surface area of the growing reef As can be seen from the above, the current generated there depends on the total surface area in contact with water of the steel growing reef and the total surface area in contact with water of the anode material used. This determines how much current will flow, and the generated current divided by the total surface area of the steel is within the range of 0.15A/m ² to 0.08A/m ² and based on the conditions of the sea area where it will be deposited. Just make it equal to the set value.

(E) Effect When a growing reef made using this configuration and method is submerged in seawater, an electric current flows from the anode (aluminum alloy) to the cathode (steel growing reef) using seawater as an electrolyte.

As mentioned above, the generated current is large immediately after energization, but as the cathode polarization progresses, the current becomes weak and stable, and it is also possible to prevent corrosion of the growing reef.

(F) Example When the cultivated reef of the present invention was deposited in an actual sea area and its effects were confirmed, the following points were particularly taken into consideration.

Firstly, there is almost no growth of seaweed or abalone growth in the submerged area, and secondly,
Two conditions were set for the experimental reef: it had a structure (see drawing) with as few shadow areas as possible and received as much transmitted light as possible.

Furthermore, of the two experimental reefs, one was made to undergo corrosion (leaving bare steel), and the other was anodized so that an artificially weak current (current density 0.08A/m ² ) was generated. It was decided to install and sink it.

The purpose of this study was to confirm the effectiveness of this reef in an environment where abalone abalone aggregation and settlement conditions are extremely poor, and to confirm the effectiveness of applying a weak electric current.

Therefore, in the area where the seabed was previously sandy, we created a breeding ground by combining concrete blocks and natural stones for breeding, which was effective.
For the past few years, we have selected an area where the sea has been deserted, and there is no growth of seaweed or abalone growth, so much so that we cannot confirm it through diving surveys, and we have decided to place the reef on top of the existing concrete blocks. , two units were sunk at a depth of approximately 5 m, separated by a distance of approximately 50 m.

Regarding the results of the investigation after the installation, we will give an overview of the results, with No. 1 being a reef grown using bare steel that generates corrosive current, and No. 2 being a reef grown with a weak electric current artificially passed through it. The result of abalone settlement after about one month after being deposited was 7 individuals on the No. 1 nursery reef.
There were 12 epiphytes on the second day. At this time, No. 1 was in a red rust state, and No. 2 was black and no corrosion was confirmed.

Approximately 3 months after depositing, the results showed 12 individuals in No. 1,
In addition to the 25 abalones that settled on No. 2, the number of abalone that congregated and settled on the existing block directly below the breeding reef was No.
Five individuals were confirmed at No. 1 and 13 individuals at No. 2.

At this time, the corrosion of No. 1's growing reef was progressing and red rust was starting to appear in many places, so aluminum alloy anodes were installed. No corrosion was confirmed in No. 2. Approximately 20 days after the anode was attached to No. 1, the anticorrosion effect of No. 1 was confirmed.

Approximately 6 months after sinking, 27 individuals were confirmed to have settled on No.1 and 31 individuals on No.2. twenty one
There were 28 individuals at No. 2.

Regarding existing blocks other than those around the main breeding reef,
The situation was almost the same as before, with only some epiphytes observed on the block hangers.

Regarding the collection and settlement status of plants other than abalone, approximately 6
I will only report after several months have passed, but the sea urchins
16 individuals were confirmed in No. 1 and 11 individuals in No. 2.

In addition, it was observed that when a weak electric current was applied to seaweeds, the settlement of useful seaweeds such as Ulva and Kelp was better than on the existing blocks.

However, the growth of useless seaweed (miscellaneous algae) was also observed.

(G) Effects of the invention The results described in the examples show that even in a poor environment for abalone, by passing a weak electric current, it is possible to increase the abalone concentration effect on the steel reef that is the cathode part. It is said that the settlement rate is improved and it is difficult to escape (the reason for this has not yet been determined physiologically).
The significance of the present invention has been demonstrated, and the present breeding reef is more suitable as a resource management type breeding reef for breeding abalone than conventional concrete blocks for breeding.

Furthermore, since this reef is made of steel, its shape and structure can be freely changed to suit various conditions.

For example, (a) In order to improve the settlement rate by taking advantage of the nocturnal nature of abalone, it is possible to increase the number of shaded areas, and to improve the abalone collection method (diving, hook fishing, etc.). You can freely change the shape and structure.

(b) Abalone can be easily combined with the growth of useful seaweed, and can be freely combined with natural stone or various concrete blocks as needed.

(c) Shapes and structures suitable for the ocean conditions and seabed conditions to be submerged can be freely created.

In this way, it has many advantages over conventional concrete blocks, etc.

Furthermore, the number of anode materials is determined by the total surface area of the steel material of the growing reef and the anode material used, but even if it is installed in several locations, the purpose can be achieved with almost no effect, and the consumed anode material can be easily replaced.

Furthermore, in carrying out the present invention, the following method will be used to manage and manage abalone resources better than before.
Easy to grow.

In order to grow abalone as large as possible and increase production, it is important to secure feed, and it goes without saying that it is necessary to secure feed that is correlated with the number of abalone inhabited.

Therefore, it is easier to manage the resources by depositing the main breeding reef in sea areas where seaweed beds for food have already been secured, since the effect of attracting and epiphyting the reef is higher than in the past.

Furthermore, by combining this breeding reef with established forest facilities for food and marine forest facilities, it is possible to develop large-scale managed breeding grounds, and it is easier to systematically manage and grow resources than in the past.

In addition, the growth of useless seaweed and barnacles on abalone can cause a decline in the survival rate of abalone and cause them to escape, so if such growth is observed, remove the metal fittings (scraper) as early as possible early in the morning. The effects of the cultivated reef can be regained by removing unnecessary materials such as peeling them off from the cultivated reef and maintaining and managing them, making resource management easier than in the past.

[Brief explanation of the drawing]

The drawing is a perspective view showing an example of the present invention. 1 is a steel growing reef, 2 is an aluminum alloy anode.

Claims (1)

[Claims] 1 A steel breeding reef for breeding abalone that uses a steel breeding reef as a cathode and an aluminum alloy as an anode to which a weak electric current is passed in seawater.