For Kentaro Amemiya of Tokyo Sea Life Park, perspective is everything when dealing with a creature as unusual as the finespotted jawfish.
“Here we arrange our exhibitions so that visitors can enjoy observing the fish from four perspectives: swimming, eating, self-defense and breeding,” Amemiya, who is in charge of rearing the fish, said. “The fine- spotted jawfish is a species good for observing the latter two aspects.”
As paternal mouthbreeders, adult male finespotted jawfish incubate fertilized eggs in their mouths for about 10 days until they hatch. At the aquarium, visitors can clearly see the grayish mass of eggs inside its mouth.
The species is typically found in the eastern Pacific Ocean, stretching from the Gulf of California to the shores of Panama, and can grow as long as 40 cm.
From catching the fish to transporting them to Tokyo, Amemiya had to overcome hurdles every step of the way.
For example, on the flight from Mexico to Japan, the fish had to be transported in a plastic bag filled with seawater and oxygen because the airline wouldn’t allow him to bring on a fish tank as carry-on luggage.
Amemiya, 39, also had to minimize fluctuations in the water temperature of the bag during the 40-hour journey to Tokyo by placing it inside a cooler box.
He also reduced the amount of food they had before departing to limit the feces they would produce, since he couldn’t change the water in midflight, he said.
The challenges continued even after they got to the aquarium.
“We had a hard time trying to get the fish to dig their burrows where they can be easily observed by visitors,” Amemiya said.
At the beginning, the jawfish kept digging burrows in the hidden corners of the tank, areas that are difficult for visitors to see clearly. This prompted Amemiya to install large rocks in the corners of the tank and make the fish dig elsewhere. It worked.
At first, the burrows collapsed easily. When Amemiya mixed bits and pieces of coral and clamshell into the sand, however, the fish surprised him by automatically using the material to build much stronger burrows.
“They did it by instinct, without being taught by anyone,” he said. “Nature is really amazing. I never get bored watching them making burrows, carrying the sand here and there or fighting over it with each other.”
When the fish finally began laying eggs, however, yet another problem surfaced. Perhaps sensitive to movement outside the tank, the male fish gave up brooding or even swallowed the eggs. It was not until Amemiya applied a special film to the inside of the tank to make the outside world invisible that the fish finally settled down and began breeding.
Amemiya also remodeled a tank for rearing fry hatched from the eggs so that a slow current would flow up from its bottom.
“Fry that have just hatched are weak swimmers, but I came up with the idea that if they circulate inside the tank along with the feed, there would be a bigger chance for them to stumble upon the food and thus eat more,” he said.
When switching to new feed as the fry grow bigger, Amemiya said he takes care to do it gradually so the fish can get used to the new food; otherwise, they might starve to death.
His strenuous efforts are paying off. The six fish born in 2010 have already grown to about 30 cm in length, and about 40 others born since then are also doing well. Amemiya’s next goal is to breed a “grandchildren” generation from the fish born at the aquarium, he said.
A native of Yokohama, Amemiya has been an ocean lover since childhood. During his elementary school days, he used to bike to the seashore with his friends to fish or just have fun.
“The ocean is simply gigantic,” he said. “I also loved the smell of the sea and would be excited just by getting near it.”
Through his work at the aquarium, Amemiya said he hopes to convey to visitors what is happening in the oceans right now.
“I will be happy if what I do can help inspire people to make a trip to the seashore or to learn about marine pollution and global warming, or to trigger an interest in natural sciences among children,” he said.
“I want to do something in return for the many things and experiences I have received from the sea.”