Research

1 Ecological studies on the life history characteristics and production mechanisms of fishes 

The Seto Inland Sea is known as a highly productive water. However, a lot of ecological characteristics of fishes or aquatic organisms inhabiting the area are still unclear. Our goal is to reveal production mechanisms of commercially important fishes in and around the Seto Inland Sea, to contribute to sustainable fisheries in relation to SDG_14. We investigate life history traits such as growth, feeding habits, and reproduction of fishes through field surveys and laboratory experiments. The growth rate or other parameters of fishes in the study area are compared with those in other areas to elucidate the intraspecific variations. We have also tried to clarify the mechanisms causing recent decline of some stocks of fish species.

The target fishes are as follows.

<Sand lance and anchovy>

Anchovy and sand lance are fishes that mainly support the high fisheries productivity in the Seto Inland Sea, because they are forage fishes for piscivorous predators.

(Western sand lance Ammodytes japonicus)

(Larval Japanese anchovy Engraulis japonicus)

(Collecting larval sand lance in the Seto Inland Sea, using Training Vessel Toyoshio-maru of Hiroshima University)

<Cutlassfish>

Cutlassfish (hairtail) is a piscivorous fish and is an important target species for fisheries in the Seto Inland Sea, accounting for about half of the national catch of this species. However, the stock has reduced drastically in and around the Seto Inland Sea, resulting in a major problem.

(Trichiurus japonicus)

<Flatfishes>

Four pleuronectid flatfishes inhabit the Seto Inland Sea: stone flounder (Ishigarei), marbled flounder (makogarei), ridged-eye flounder (meitagarei), and spotted halibut (hoshigarei). In particular, because the stock of marbled flounder has declined drastically, we are investigating the factors behind the decrease. We have also studied growth characteristics of juveniles under various temperatures or salinities through laboratory experiments.

(Juveniles of stone flounder (left) and marbled flounder (right))

(Juveniles of spotted halibut)

(Feeding experiment in the laboratory)

<Others>

We have investigated life history traits, such as distribution, feeding, and growth at various life stages, of several fish species. The research interests are on the thermal responses of fishes in relation to climate change, the importance of species-specific habitats in early life stages, and mechanisms underlying the population dynamics. Field surveys and laboratory experiments have been conducted.  

(Juvenile Japanese Spanish mackerel)

(Chub mackerel)

(Japanese jack mackerel)

(Rockfishes Sebastes spp.)

2 Secondary production of benthic ecosystem in tidal flats

In the Seto Inland Sea, the catch of asari clam (Manila clam) has greatly decreased from 1980s to 2010s. Tidal flat ecosystems have also changed. To evaluate the importance of tidal flat ecosystems and contribute to the conservation, we have investigated interspecific relationships between clams and their predators or ecological characteristics of dwelling organisms. 

<Moon snail>

Laguncula pulchella is a moon snail that feeds mainly on bivalves. It had been an endangered species in western Japan, but this species has been an alien species by being mixed with clam seedlings imported from foreign countries and released to the tidal flats in many areas. We have studied biological characteristics of this species to contribute to the effective management of the non-indigenous population.

(Laguncula pulchella) 

<Sea spider>

Nymphonella tapetis is an endoparasitic sea spider and is a harmful parasite for clams inhabiting tidal flats. We have studied host-parasite relationships between the sea spider and host clams, to contribute to reduce the impact of parasitism.

<Asari clam>

The asari clam Ruditapes philippinarum is the most important clam at tidal flats in Japan. We have studied their growth and other biological traits such as shell morphology, aiming an increase in their production.

<Fishes>

We are studying ecological traits of some fish species including flatfishes around tidal flats.

(Sharp-nosed sand goby Favonigobius gymnauchen) 

3 Biological characteristics of demersal fishes in the Joban water

The Joban water is a highly productive area where the Oyashio (cold current) and Kuroshio (warm current) collide. We have continued studies on ecological traits of demersal fishes including flatfishes in this area. 

(Trawl survey in Sendai Bay)

(Snailfish Liparis tanakae, a predator for flatfish juveniles)

(Snow crab caught in the Joban water)

4 Others

I am involved in various projects.

(Cutlassfish landed at a fish market in Myanmar)