1:45 PM - 3:15 PM
[O11-P93] The relationship between fish inhabiting Kikai Island and the coral reefs they use as shelter.
Keywords:How fish hide, Fish and Coral
(Purpose)
Kikaijima Island in the Amami Islands of Kagoshima Prefecture is home to a wide variety of coral species (Fukami et al., 2022). Research in Okinawa has shown that some species of damselfish living in coral reefs tend to inhabit specific coral shapes. Based on this, I became interested in the relationship between the types of fish living in the coral reefs around Kikaijima and the shapes of corals they use as hiding places, and decided to conduct a study.
The purpose of this study is to clarify the relationship between the type and shape of corals, the location and depth of crevices, and the number of fish species that use them as hiding places. Additionally, as I hope to become an aquarium keeper in the future, I aim to understand which types of coral provide a more comfortable environment for fish when they are kept in captivity.
(Method)
Surveys were conducted on August 23, 2024, in a tide pool at Shirami on the eastern coast of the island, and on October 26, 2024, in a tide pool at Sakanmine on the northern coast. I observed the area while snorkeling and approached fish that were near the corals. If a fish hid, I recorded the species on the spot. I also documented the coral species and shape in which the fish hid, as well as the location and depth of the crevice.
(Results)
The observed corals were classified into 11 types.
Since the number of coral colonies recorded varied by species, I calculated the number of fish species hiding per colony. Fish species richness was higher in corals with complex, maze-like structures, while fewer species were found hiding in simpler, massive-shaped corals.
Regarding the location of hiding spots, the greatest number of fish species were found hiding in the spaces between branches.
As for the depth of the crevices and the relationship with fish species, larger fish tended to hide in deeper crevices. Some fish species were observed hiding in multiple coral shapes. Additionally, the depth of the crevices appeared to be influenced by the coral shape.
It was also found that the number of fish species hiding increased with the number of coral colonies present.
(Discussion)
The high number of fish species per coral colony in complexly shaped corals suggests that coral shape significantly influences the number of hiding fish species.
Regarding the location of the crevice, many species were found hiding between branches or plates. These locations allow fish to quickly hide while swimming near the coral and offer a structurally complex refuge, making them more suitable for hiding.
As for the depth of the crevices, fish seemed to prefer spaces just deep enough to fit their bodies—deep enough to enter, but too narrow for larger predators. This suggests that the ideal hiding place is one that fits the fish’s size rather than simply being as deep as possible.
Furthermore, the study revealed a tendency for areas with more coral colonies to harbor more fish species. Therefore, in future research, the number of colonies surveyed for each coral type should be kept consistent to allow more accurate comparisons.
In the summer of 2024, high sea temperatures caused widespread coral bleaching. By conducting the same survey again and comparing the results with the pre-bleaching data, it may be possible to determine whether fish prefer live coral or whether the structure of the coral alone is sufficient as a hiding place.
Kikaijima Island in the Amami Islands of Kagoshima Prefecture is home to a wide variety of coral species (Fukami et al., 2022). Research in Okinawa has shown that some species of damselfish living in coral reefs tend to inhabit specific coral shapes. Based on this, I became interested in the relationship between the types of fish living in the coral reefs around Kikaijima and the shapes of corals they use as hiding places, and decided to conduct a study.
The purpose of this study is to clarify the relationship between the type and shape of corals, the location and depth of crevices, and the number of fish species that use them as hiding places. Additionally, as I hope to become an aquarium keeper in the future, I aim to understand which types of coral provide a more comfortable environment for fish when they are kept in captivity.
(Method)
Surveys were conducted on August 23, 2024, in a tide pool at Shirami on the eastern coast of the island, and on October 26, 2024, in a tide pool at Sakanmine on the northern coast. I observed the area while snorkeling and approached fish that were near the corals. If a fish hid, I recorded the species on the spot. I also documented the coral species and shape in which the fish hid, as well as the location and depth of the crevice.
(Results)
The observed corals were classified into 11 types.
Since the number of coral colonies recorded varied by species, I calculated the number of fish species hiding per colony. Fish species richness was higher in corals with complex, maze-like structures, while fewer species were found hiding in simpler, massive-shaped corals.
Regarding the location of hiding spots, the greatest number of fish species were found hiding in the spaces between branches.
As for the depth of the crevices and the relationship with fish species, larger fish tended to hide in deeper crevices. Some fish species were observed hiding in multiple coral shapes. Additionally, the depth of the crevices appeared to be influenced by the coral shape.
It was also found that the number of fish species hiding increased with the number of coral colonies present.
(Discussion)
The high number of fish species per coral colony in complexly shaped corals suggests that coral shape significantly influences the number of hiding fish species.
Regarding the location of the crevice, many species were found hiding between branches or plates. These locations allow fish to quickly hide while swimming near the coral and offer a structurally complex refuge, making them more suitable for hiding.
As for the depth of the crevices, fish seemed to prefer spaces just deep enough to fit their bodies—deep enough to enter, but too narrow for larger predators. This suggests that the ideal hiding place is one that fits the fish’s size rather than simply being as deep as possible.
Furthermore, the study revealed a tendency for areas with more coral colonies to harbor more fish species. Therefore, in future research, the number of colonies surveyed for each coral type should be kept consistent to allow more accurate comparisons.
In the summer of 2024, high sea temperatures caused widespread coral bleaching. By conducting the same survey again and comparing the results with the pre-bleaching data, it may be possible to determine whether fish prefer live coral or whether the structure of the coral alone is sufficient as a hiding place.