Plankton stories, or How to raise live display specimens
Being one of the most species-diverse habitats at the Primorsky Aquarium, the Sea of Japan/East Sea exhibit is also interesting in relation to “biographies” of its inhabitants: many of them have been raised right at the Aquarium. Biologists of the scientific and educational center grow future residents of the exhibit from ichthyoplankton collected in Peter the Great Bay.
“Some of the local fish species live at considerable depths or hide between rocks and in shells, and it is much easier to capture their larvae for rearing at the Aquarium,” said Yuri Nekotinev, Lead Specialist at the Department of Russian Far East Marine Species. “We collect ichthyoplankton in Zhitkov Bay, jointly with staff scientists of the National Scientific Center of Marine Biology FEB RAS. One part of the catch is sent to the Laboratory of Ichthyology for research, and the rest of it goes to the Aquarium to be grown out. But our collaboration with the NSCMB does not stop here: to describe all developmental stages, the scientists require fish specimens of various sizes, which we provide for them.”
The species whose larvae have been captured in ichthyoplankton samples include Jordan’s sculpin (Triglops jordani), haired warbonnet (Chirolophis saitone), green cockscomb (Alectrias benjamini), brightbelly sculpin (Microcottus sellaris) and blackedge sculpin (Gymnocanthus herzensteini). The growing fish are kept in tanks of the Science and Acclimation Building where each species is given optimal conditions for its development. Right after being caught, the larvae are fed with brine shrimp, and as they get older, daphnids and mysids are added to their diet.
Some fish get to the scientific and educational center even at a younger age – as eggs collected along with algae by scuba divers. The antlered sculpin (Enophrys diceraus) and Japanese sandfish (Arctoscopus japonicus) are among those Aquarium residents that are reared from eggs.
“The Japanese sandfish typically deposits small spherical egg masses, each of 200-300 eggs, on seaweeds, tending to select particular species of Sargassum but last year the bay nearly lacked them due to a storm, and sandfish had to spawn on other plants: for instance, their eggs have come to us with Codium seaweeds,” said Yuri Nekotinev. “We incubated the eggs found on the algae, then in the spring hatchlings emerged, and now the fish are several centimeters in length. Japanese sandfish are plankton eaters; they bury themselves in sand and attack small crustaceans from there. We feed sandfish on brine shrimp; this species has a slightly upturned mouth and does not eat from the bottom but waits for food to fall from above. When our Japanese sandfish grow longer than 5 centimeters, they will be relocated to the Main Building.”