Research

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

The Seto Inland Sea is recognized as a highly productive marine environment. However, many ecological characteristics of fishes and other aquatic organisms inhabiting this region remain poorly understood. Our primary goal is to elucidate the production mechanisms of commercially important fish species in and around the Seto Inland Sea, thereby contributing to sustainable fisheries in line with SDG 14. To achieve this, we investigate life history traits such as growth, feeding habits, and reproduction through field surveys and laboratory experiments. Growth rates and other biological parameters of fishes in the study area are compared with those in other regions to clarify intraspecific variations. In addition, we aim to identify the mechanisms underlying the recent decline in some fish stocks in line with SDG 13.

Target species include the following:

<Sand lance and anchovy>

Anchovy and sand lance are key forage fishes that sustain the high fisheries productivity in the Seto Inland Sea, serving as prey for piscivorous predators.

(Western sand lance Ammodytes japonicus)

(Larval Japanese anchovy Engraulis japonicus)

(Collection of larval sand lance in the Seto Inland Sea using the training vessel Toyoshio-maru of Hiroshima University)

<Cutlassfish>

The cutlassfish (hairtail) is a piscivorous species and an important fishery resource in the Seto Inland Sea, accounting for approximately half of Japan's total catch of this species around 2010. However, its stock has declined drastically afterwards, posing a serious problem.

(Trichiurus japonicus)

<Flatfishes>

Four pleuronectid flatfish species inhabit the Seto Inland Sea: stone flounder (Platichthys bicoloratus), marbled flounder (Pseudopleuronectes yokohamae), ridged-eye flounder (Pleuronichthys lighti), and spotted halibut (Verasper variegatus). In particular, the stock of marbled flounder has decreased significantly, prompting investigations into the factors driving this decline. We also examine juvenile growth characteristics under various temperature and salinity conditions through controlled laboratory experiments.

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

(Juveniles of spotted halibut)

(Feeding experiment in the laboratory)

<Others>

We study life history traits, including distribution, feeding, and growth at various life stages, of several fish species. Our research focuses on thermal responses to climate change, the significance of species-specific habitats during early life stages, and mechanisms governing population dynamics. Both field surveys and laboratory experiments are employed.  

(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 Ruditapes philippinarum) has declined sharply from the 1980s to the 2010s, accompanied by changes in tidal flat ecosystems. To assess the ecological importance of these habitats and support conservation efforts, we investigate interspecific relationships between clams and their predators, as well as ecological characteristics of associated organisms. 

<Moon snail>

Laguncula pulchella is a moon snail that feeds primarily on bivalves. Once considered endangered in western Japan, this species has become invasive after being introduced via imported clam seedlings released into tidal flats. We study it's biological characteristics to inform effective management of this non-indigenous population.

(Laguncula pulchella) 

<Sea spider>

Nymphonella tapetis is an endoparasitic sea spider and that poses a significant threats to clams inhabiting tidal flats. We exmine host-parasite interactions to mitigate the impact of parasitism.

<Asari clam>

The asari clam Ruditapes philippinarum is the most important bivalve species in Japanese tidal flats. We investigate its growth and other biological traits, including shell morphology, with the aim of enhancing production.

<Fishes>

We also study ecological traits of fish species associated with tidal flats,  including flatfishes.

(Sharp-nosed sand goby Favonigobius gymnauchen) 

3 Biological characteristics of demersal fishes in the Joban water

The Joban water is a highly productive region where the Oyashio (cold current) and Kuroshio (warm current) converge. We conduct ongoing studies on ecological traits of demersal fishes, including flatfishes, in this area. 

(Trawl survey in Sendai Bay)

(Snailfish Liparis tanakae, a predator of flatfish juveniles)

(Snow crab caught in the Joban water)

4 Other projects

We are also involved in various collaborative projects.

(Cutlassfish landed at a fish market in Myanmar)