Research outline

An approach to improving the bioproductivity of Northern waters

Figure 1 Directly controlled fishery
development project sites
(click to enlarge)

 Figure 2 Migratory route of
Alaska pollock in the northern
group on the Sea of Japan.
(click to enlarge)

 Figure 3 Mechanism of upwelling
(Fisheries Agency)
(click to enlarge)

 Figure 4 The food chain,
with Alaska pollockat the top
(click to enlarge)

  National fishing ground development project (Frontier Fishing ground Development Project) started in 2007 with the aim of enhancing the productivity of fishery resources in our exclusive economic zones to ensure stable supply of fishery products. As shown in Figure 1, several activities have been implemented in the western part of the Sea of Japan, such as the installation of protective rearing reefs for flathead flounder and snow crab, and the preparation of artificial upwelling mound reefs for the sardine. Also, west offshore of the Goto Islands in Nagasaki Prefecture, the preparation of artificial upwelling mound reefs for Japanese horse mackerel, chub mackerel and sardine has been implemented.

  Alaska pollack is a major fisheries resource of Hokkaido. However, it's catch has significantly declined. Therefore, Alaska pollack was designated as a species covered by the Total Allowable Catch (TAC) system, which based on The 1997 Act on the Preservation and Control of Living Marine Resources. Now the Alaska pollock catch is being monitored. Figure 2 shows the migratory route of Alaska pollack in the northern area of the Sea of Japan. The Musashi Bank and its environs, which are offshore of Rumoi in Hokkaido (Figure 2) and are a nursery for Alaska pollock, are known as excellent fishing grounds for this fish. The Musashi bank has also potential to be the National fishing ground development project site for fish species such as the Alaska pollock.

  Possible methods for developing the fishing ground in this area are the following: 1) the installation of an artificial upwelling mound reef, 2) the installation of a reef for food production and 3) the installation of a reef for protective rearing.

  1) The installation of an artificial upwelling mound reef is a measure against the depletion of nutrient salts in the surface layer, a depletion that restrains the basic production of phytoplankton. The artificial upwelling mound reef serves to enhance phytoplankton activity in the whole sea area by creating upwelling currents that circulate abundant nutrient salts from the bottom layer to surface layer (Figure 3). With this method, phytoplankton at the bottom of the food chain (Figure 4) are increased; therefore, the body thickness of Alaska pollock increases and the decline in their population is slowed. Additionally, a condition necessary for this method to be implemented is the existence of a current in the bottom layer, which creates the upwelling current. 2) A reef for food production aims to improve the feeding environment and to provide effective feeding by increasing the availability of small organisms, such as zooplankton, which are feed for Alaska pollock. 3) A protective rearing reef is a habitat for Alaska pollock, and the purpose of this facility is to provide fish with a hiding place from predators and to protect juvenile fish from being fished.

  To determine the basic policy of the project, we will select appropriate methods and sites. We will be working on developing research on the resource conditions of targeted fishes, and we will be researching the physical environment of the currents around fishing grounds, the living conditions of organisms and the conditions of their feeding environment, the annual trends in basic production and surveys of suboceanic microtopography.

(Contact: Fisheries Engineering Research Team, Civil Engineering Research Institute for Cold Region (CERI))