Method for farming cephalopods

Abstract

The present invention provides a method for farming cephalopods in a group in an artificial rearing environment, the method including farming the group of cephalopods so that, in a predetermined period immediately after hatching of the cephalopods, the group is not merged with other groups, or even if merged with other groups, the number of merging does not exceed three times.

Description

Cephalopod farming methods

[0001] The present invention relates to a method for cultivating cephalopods.

[0002] Animals belonging to the class Cephalopoda of the phylum Mollusca, such as squid and octopus (hereinafter sometimes referred to as "cephalopods"), are widely eaten because of their unique texture and flavor, as well as their high nutritional value.

[0003] Due to high demand and high commercial value, attempts have been made to cultivate cephalopods (see, for example, Non-Patent Document 1). Non-Patent Document 1 discloses various findings regarding the cultivation of several major cephalopods, including the commercially valuable bigfin reef squid. For example, Non-Patent Document 1 discloses findings regarding the maintenance and management of broodstock for cultivation, hatching, water quality management and feed during cultivation, etc.

[0004] Cephalopod Culture, edited by Jpse Leglesias, Lidia Fuentes, Roger Villanueva, Springer Publishing, pp. 315-348.

[0005] However, conventional methods such as those described in Non-Patent Document 1 have not been able to sufficiently increase the survival rate of cephalopods in an artificial rearing environment. Therefore, an object of the present invention is to provide a cephalopod farming method that can sufficiently increase the survival rate of cephalopods in an artificial rearing environment.

[0006] The present inventors have conducted extensive research to achieve the above object, and have newly discovered that when raising a group of cephalopods in an artificial breeding environment, the survival rate of the cephalopods can be significantly increased by minimizing the number of groups of cephalopods that merge with other groups, leading to the completion of the present invention.

[0007] The present invention aims to solve the above-mentioned problems advantageously by providing a method for cultivating cephalopods, which comprises cultivating a group of cephalopods in an artificial environment without allowing the group of cephalopods to merge with other groups, or limiting the number of mergers to three or less, for a predetermined period of time from immediately after hatching. This method can sufficiently increase the survival rate of cephalopods in the artificial environment.

[0008] [2] Here, in the method for cultivating cephalopods according to [1] above, it is preferable that the cephalopods are not allowed to merge with other shoals different from the shoal for a predetermined period of time immediately after hatching.

[0009] [3] In the method for cultivating cephalopods according to [1] or [2] above, the school of cephalopods is preferably a school including cephalopod individuals that have hatched together.

[0010] [4] In addition, in the method for cultivating cephalopods according to any one of the above [1] to [3], it is preferable to cultivate the cephalopods while running seawater over them.

[0011] [5] In the cephalopod culturing method of [4] above, it is preferable that the temperature of the seawater is 15°C or higher and 30°C or lower.

[0012] [6] In addition, in the cephalopod culturing method according to any one of [1] to [5] above, it is preferable that the total number of cephalopods is 200 or less over the predetermined period.

[0013] [7] In addition, in the cephalopod farming method according to any one of [1] to [6] above, it is preferable that the cephalopods are squids or cuttlefish, which have a habit of forming schools.

[0014] [8] In the cephalopod farming method of [7] above, it is preferable that the cephalopods are squids belonging to the family Dolomitidae, among the group of squids that have the habit of forming schools.

[0015] According to the present invention, a method for cultivating cephalopods can be provided that can sufficiently increase the survival rate of cephalopods in an artificial rearing environment.

[0016] 1 is a bar graph showing the age at survival for each group, and a graph plotting the average survival rate for each 7-day period when the mice were reared from 0 to 91 days of age.

[0017] Hereinafter, an embodiment according to an example of the present invention will be described in detail.

[0018] (Cephalopod Cultivation Method) The cephalopod cultivating method of the present invention is characterized in that, when raising a group of cephalopods in an artificial rearing environment, it includes rearing the cephalopods in such a way that, during a predetermined period immediately after hatching, the cephalopods are not allowed to merge with other groups different from the group described above, or, if merged, the number of mergers is limited to three or less. That is, the group that has been artificially reared from the beginning is designated as group A, and other groups different from group A (e.g., groups B1, B2, ... B5) are not allowed to merge with this group, or, if other groups are merged, the number of mergers is limited to three or less, thereby minimizing mixing of group A with other groups. Although it is unclear why such a method can increase the survival rate of cephalopods in an artificial rearing environment, it is presumed to be due to the fact that cephalopods can be highly social. In other words, by "fixing" the multiple individual members of a group immediately after hatching, excluding a decrease in the number of individuals due to death, and minimizing the entry of new individuals into the group, it is believed that stress that may arise from conflict between individuals can be suppressed and the probability of events that may reduce survival rates, such as cannibalism, can be reduced. In the cephalopod farming method of the present invention, it is most preferable to raise cephalopods as a so-called independent group without merging with other groups for a predetermined period of time immediately after hatching. Even if other groups are merged with the group that has been raised from the beginning to form a mixed group, it is preferable that the number of mergers be two or less, and more preferably one or less. In this way, by minimizing the merger of other groups with the group that has been raised from the beginning, the survival rate of cephalopods can be further increased. As a result, it is believed that it will be possible to raise cephalopods for generations. In this specification, "other groups" refers to "other groups" that hatched at different times and / or in different environments from the group that hatched together.

[0019] Here, cephalopods include animals belonging to the class Cephalopoda of the phylum Mollusca, and specifically refers to a taxonomic concept that includes squid, octopus, nautilus, etc. The cephalopod farming method of the present invention is particularly applicable to cephalopods, particularly those with a schooling habit. More specifically, the cephalopod farming method is particularly applicable to squids and cuttlefish, which belong to the class Decapoda of the subclass Cephalopoda of the phylum Mollusca and have a schooling habit. In particular, the Japanese flying squid (Todarodes pacificus) has a schooling habit and is particularly applicable. Furthermore, many species of squids in the families Loliginidae and Ommastrephidae, which are classified as squids, also have a schooling habit and are particularly suitable for application. Examples of squid in the family Sepiolidae include the bigfin reef squid (Sepioteuthis lessoniana), the common spear squid (Heterololigo bleekeri), and the long-finned swordtip squid (Uroteuthis edulis), which are known to have a schooling habit. Among these, the cephalopod farming method of the present invention is particularly suitable for the bigfin reef squid. In the following explanation, the cephalopod will be described as the "Bigfin Reef Squid." Here, the bigfin reef squid is a species of squid belonging to the genus Sepiolidae, family Sepiolidae, of the genus Sepiolidae. Bigfin reef squid is a large species found along the coast of Japan and is popular for consumption. Bigfin reef squid is said to be the most expensive of all squids, and the large white squid type is particularly expensive and is mainly used in sushi restaurants and high-end restaurants.

[0020] <Characteristics> Generally, the body length of the bigfin reef squid is approximately 40-45 cm. Large specimens can reach a body length of over 50 cm and weigh over 6 kg. The bigfin reef squid's body is rounded, with semicircular fins along the edge of the body. The appearance of the bigfin reef squid is somewhat similar to that of a cuttlefish, but its carapace is thin and transparent. Mature, reproductively active males have scattered short white horizontal stripes on their backs, while females have indistinct horizontal stripes, which generally serve as an indicator of sexual differentiation. The distribution of bigfin reef squid is widespread, centered around the equator, from Japan to northern New Zealand, and from Hawaii to South Africa. The average lifespan of a bigfin reef squid is approximately one year. Furthermore, as is evident from their distribution, bigfin reef squid tend to prefer relatively high water temperatures.

[0021] <Water temperature and water quality> The temperature of seawater when rearing bigfin reef squid is preferably 15°C or higher, more preferably 20°C or higher, preferably 30°C or lower, and even more preferably 26°C or lower. If the water temperature is above 30°C, there is a risk that the eggs will not hatch. Furthermore, by setting the water temperature to 26°C or lower, the hatching rate can be increased. By setting the water temperature to 15°C or higher, more preferably 20°C or higher, predation by bigfin reef squid can be promoted. By setting the water temperature to 20°C or higher, the hatching rate of bigfin reef squid can be increased. For example, under conditions where the water temperature is 25°C, bigfin reef squid eggs will hatch in about one month.

[0022] Furthermore, it is preferable that the seawater used when raising bigfin reef squid is free-flowing seawater. Furthermore, it is preferable that seawater is supplied to and discharged from the aquarium so that the free-flowing seawater creates a water current within the breeding tank. In this way, the tank can be kept clean at all times. Free-flowing seawater is also economical as it does not require electricity for water temperature control, etc. Furthermore, when cultivating bigfin reef squid in their habitat, the squid can be raised in the seawater of their natural environment, which provides a good growth environment. Bigfin reef squid may also be raised in a fish pen.

[0023] Spawned eggs typically hatch after a developmental stage spanning approximately three to four weeks. For eggs hatched from a mass of eggs laid on the same spawning date, the time required from the start of hatching to the end of hatching is typically approximately one week. In this specification, the date on which hatching begins is referred to as the hatching date. Here, the cephalopod school reared using the cephalopod farming method of the present invention is preferably a school containing cephalopod individuals that hatched together. Specifically, in this specification, "cephalopod individuals hatched together" refers to multiple cephalopod (Volvoviviparous squid) individuals hatched at the same time in the same breeding tank (including a fish tank; the same applies hereinafter). Such multiple individuals may be individuals hatched from eggs spawned by a single female. By rearing such hatched individuals together for a predetermined period of time immediately after hatching, stress caused by interactions between individuals can be reduced and survival rates can be increased. The predetermined period of time from immediately after hatching may be, for example, the rearing period until the farmed Volvoviviparous squid are shipped. In another aspect, the predetermined period may be the period until the hatched individuals are transferred to a tank for rearing mature individuals. The rearing period until the farmed bigfin reef squid is shipped is not particularly limited and can be changed as needed, but may be, for example, from 90 days to 200 days.

[0024] It is preferable to feed hatched cephalopod larvae (juvenile squid, in the case of bigfin reef squid) a combination of dead bait and live bait for a period of 20 to 100 days from the date of hatching. Feeding live bait requires more labor than feeding dead bait, making it less convenient. For this reason, it is preferable to transition to dead bait as soon as possible, but completely transitioning to dead bait in a short period of time, such as one week, may impair the survival rate of the bigfin reef squid. Therefore, in one aspect, it is preferable to increase the survival rate of the bigfin reef squid by transitioning to dead bait after a relatively long transition period as described above.

[0025] <Breeding> Because bigfin reef squids have a habit of jumping out of the water, in order to increase their survival rate, when breeding bigfin reef squids, it is preferable to select the height of the tank and the water surface so that the walls are sufficiently high above the water surface. For example, in the case of juvenile squids, it is preferable to ensure walls that are 10 cm or more high above the water surface, and in the case of adults, it is preferable to ensure walls that are 40 cm or more high above the water surface.

[0026] <Rearing density> The rearing density of cephalopods varies depending on the size and maturity of the squid, but is generally between 200 and 2,000 individuals / m at hatching. ３ , 2-20 individuals / m at maturity ３ The lower limit of the rearing density is not particularly limited, but for example, it is 0.05 individuals / m during the breeding season. ３ The rearing density of cephalopods can vary depending on the growth and death of the cephalopods, but by controlling it to be equal to or less than the upper limit, the survival rate of the cephalopods can be further increased. Note that these upper and lower limits of rearing density can also be applied to juvenile squid immediately after hatching. The rearing density can be adjusted as needed by moving the rearing tanks and changing the tank size as the squid grow.

[0027] <Total Cephalopod Population> The total cephalopod population is preferably 200 or less, more preferably 100 or less. The total cephalopod population refers to the total number of cephalopods present in the breeding tank or fish preserve. The lower limit of the total cephalopod population is not particularly limited, but it can be, for example, 5 or more. Naturally, the total cephalopod population may decrease due to the death of individuals reared in the breeding tank. Therefore, it is preferable that the number of individuals immediately after hatching, i.e., the number of individuals at the start of aquaculture rearing, be within the above range. Furthermore, if a different shoal B1 is added to a breeding tank already rearing a shoal A, the total number of individuals of shoals A and B corresponds to the "total cephalopod population." If the total number of cephalopods in the breeding tank at the start of aquaculture rearing is within the above range, the survival rate of cephalopods in an artificial rearing environment can be further increased.

[0028] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0029] Example 1: Impact of Mixed Populations on Okinawan Bigfin Reef Squid Aquaculture Technology. The cephalopod species selected for cultivation was the Bigfin Reef Squid (Sepioteuthis lessoniana, Ferussac in Lesson, 1830). A free-flowing system was employed for the aquaculture. Seawater was pumped from a depth of 20 m offshore Seragaki Port in Onna Village, Okinawa Prefecture, and then pumped up to the roof of the facility and distributed to each tank. The seawater was filtered through sand to remove organisms and solids. The facility was approximately 300 m from the seawater intake pump room, and the water was routed through a second pump room. After passing through all the aquaculture tanks, the seawater was returned to the ocean via the outlet and a sedimentation pond. The water temperature in Onna Village ranges from approximately 20°C to 30°C, but varies seasonally and annually. This temperature was monitored 24 hours a day using a logger. The free-flowing system did not use any copper, chemicals, or drugs to protect the marine environment and maintain the health of the cephalopods.

[0030] The eggs of the bigfin reef squid were collected from Fuchaku Beach in Onna Village. The eggs were carefully transported to the facility and placed in an aquarium, where they were left to hatch.

[0031] The initial feed after hatching consisted of live isazamemi (live bait) and frozen preserved whitebait (dead bait). As the squid grew, the dead bait was changed from frozen whitebait to frozen silver-stripe round herring used for fishing bait, and once the transition to dead bait was achieved, silver-stripe round herring was fed as the staple food. The size of the breeding tanks was changed as the squid grew, improving the precision of breeding. In this way, by changing the size of the tanks as the squid grew, the breeding density was maintained within an appropriate range and various problems were quickly addressed.

[0032] The effects of mixing 34 groups of 1,239 individuals from a population of captive-raised bigfin reef squid in a breeding experiment were investigated. Mixed groups were assessed by classifying groups that had been mixed at least once immediately after hatching as "mixed groups," while groups that had been reared with only the same individual from hatching were classified as "independent groups." Their survival rates and lengths (number of days they survived) were compared every seven days from 7 to 91 days of age. Mixed groups (16 groups, 500 individuals) were compared, while independent groups (18 groups, 739 individuals) were compared.

[0033] Experimental Results: In the mixed group, the shortest survival time was 9 days, the longest survival time was 139 days, and the average survival time was 48.875 days (SD 43.17 days). In contrast, the independent group had a shortest survival time of 50 days, a longest survival time of 234 days, and an average survival time of 127 days (SD 52.92 days). Figure 1 shows a bar graph in which the 16 mixed groups and the 18 independent groups were assigned identification numbers in order of survival time, and the horizontal axis represents the group identification number and the vertical axis represents survival time. Figure 1 shows that the independent groups had a significantly longer survival time than the mixed group. The average survival rate by age for the mixed group was 59% at 7 days, 38% at 14 days, 25% at 21 days, 21% at 28 days, 17% at 35 days, 14% at 42 days, 13% at 49 days, 12% at 56 days, 10% at 63 days, 9% at 70 days, 8% at 77 days, 8% at 84 days, and 7% at 91 days. In contrast, the survival rates for the independent groups were 80% at 7 days, 64% at 14 days, 55% at 21 days, 47% at 28 days, 41% at 35 days, 38% at 42 days, 32% at 49 days, 29% at 56 days, 27% at 63 days, 23% at 70 days, 22% at 77 days, 20% at 84 days, and 18% at 91 days (see Figure 2). In Figure 2, the solid line represents the average survival rate curve for the independent group, and the dashed line represents the average survival rate curve for the mixed group. Figure 2 shows that the average survival rate of the independent group exceeded that of the mixed group at all ages. Furthermore, over the course of the experiment, it was observed that the average survival rate and average number of days of survival increased with a decrease in the number of times the groups were mixed immediately after hatching (2 times, 1 time, 0 times).

[0034] The results of this experiment demonstrated that the members of a school have an impact on artificial rearing of bigfin reef squid. The survival time and seven-day survival rate of schools with significantly mixed school members were significantly higher in schools reared with the same members from the time of hatching, demonstrating the stability of the school. Maintaining consistent school composition is thought to reduce stress and increase feeding motivation in artificial rearing, making it a crucial factor for sustainable bigfin reef squid aquaculture. Furthermore, this cephalopod rearing method, which significantly improves survival rates, suggests that it may be possible to rear cephalopods for generations.

[0035] According to the present invention, a method for cultivating cephalopods can be provided that can sufficiently increase the survival rate of cephalopods in an artificial rearing environment.

Claims

1. A method for cultivating cephalopods, comprising raising a school of cephalopods in an artificial rearing environment without allowing the school to merge with other schools different from the school of cephalopods for a predetermined period of time immediately after the hatching of the cephalopods, or, if the school of cephalopods is merged, limiting the number of mergers to three or less.

2. A method for cultivating cephalopods as described in claim 1, wherein the cephalopods are not allowed to merge with other shoals different from the shoal for a predetermined period of time immediately after hatching.

3. A method for cultivating cephalopods as described in claim 1 or 2, wherein the cephalopod school is a school containing cephalopod individuals that have been hatched together.

4. A method for cultivating cephalopods according to any one of claims 1 to 3, wherein the cephalopods are raised while being flushed with seawater.

5. A method for cultivating cephalopods as described in claim 4, wherein the temperature of the seawater is 10°C or higher and 30°C or lower.

6. A method for cultivating cephalopods as described in any one of claims 1 to 5, wherein the total number of cephalopods is 200 or less over the predetermined period.

7. A method for cultivating cephalopods according to any one of claims 1 to 6, wherein the cephalopods are squids or cuttlefish which have a habit of forming schools.

8. A method for cultivating cephalopods as described in claim 7, wherein the cephalopods are squids belonging to the family Dolomidae, among the group of squids that tend to form schools.

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