Environmental variables (light irradiance, temperature, salinity, turbidity, and chlorophyll a) in relation to
macroalgal distribution were analyzed bimonthly from April 2001 to February 2002 in Hiroshima Bay. Three
dominant species of brown algae, Sargasstm horneri, S. macrocarpum, and Ecklonia kurome grow at each different
depth 0-1m, 1-3m, 3-9m, respectively.
The environmental gradient from the inner to the outer part of Hiroshima Bay in the vicinity of the seaweed
beds as well as along the center of the bay was surveyed. The suspended matter that originates as effluent from
the Ohta River is suggested to lead to a decrease in the light attenuation. The quantities and the properties of
suspended matter changed seasonally and varied between each seaweed bed. The attenuation coefficient is suggested to be influenced by the suspended matter concentration and the effects were much larger in the imer
part of the bay than in the central and outer parts.
The three dominant brown algae were distributed along the environmental gradient in Hiroshima Bay. The
two sample Hest of environmental variables of temperature and salinity showed significant differences among the
species, except for light irradiance. This means that light conditions might not restrict the distributions of these
algae. This study concludes that other environmental variables might be important to detemine their distribution,
even though macroalgae can acclimate to environmental changes.
On the basis of observation data of water temperature and salinity at Uranouchi Bay during the convection
period, the heat flux of sea surface cooling, the potential energy given to the water column by the heat flux, and
the dissipation energy are estimated. The diameter and the circumference speed of the maximum convection eddy
caused by surface cooling are also evaluated. These results are described as follows :
① The heat flux through sea surface is 130(Jm-2s-1) in December. It's almost the same as the estimation about Mikawa Bay by other methods.
② The potential energy per unit time (deQ/dt) given to the water column by the heat flux is (4-17) × 10-5(Jm-3s-1). More than half of deQ/dt tums to the potential energy of water column, and the remainder turns to dissipation energy (thermal energy) and disappears.
③ The diameter of the maximum convection eddy caused by surface cooling is about 0.4 (m). The circumference
speed of the eddy is about 0.001 (ms-1).
The bottom sediment, benthic community, fish and larvae of commercial shellfish species were investigated
at an artificial tidal flat in Mikawa Bay, Japan. Differences between low and high tidal flat areas were investigated.
The central area of the development was comprised of fine sand, whereas fine sand and coarse sand were present
in the original bottom of the tidal flat. Organic matter content was high in the waterway and the marginal area of
the development. The water purification rate, in terms of macrobenthic biomass, was high in the central and
marginal areas of the development. In contrast, biodiversity in terms of macrobenthos species abundance was low
in the central area of the development. Thus the distributions in the water purification rate and biodiversity were
different. Mactra chinensis, Mactra veneriformis, and Ruditapes philippinarum dominated the commercial
bivalve species at different heights of the tidal flat. Platichthys bicoloratus dominated the fish larvae of commercial
species, and distribution across defferent depths varied according to body length. The marginal area of the
development was important for settling larvae. As distributions of dominant species and functions of the tidal flat
are different, we suggest that it is important to ensure a range of consecutive depths when creating an artificial
Daily catch data of coastal squid jigging boats, their light source output for fishing lamps and monthly mean
wholesale prices of squid were collected from five fishing ports (Hakodate, Sado Island, Noto, Sakaiminato, and
Tsushima) in Japan, for a purpose of evaluating optimum light source output, which created a maximum economic
yield. The daily income were estimated from the relationship between daily catch data and monthly mean wholesale
prices of squid. Then, the optimum light source output was calculated from the relationship between daily
income and daily lighting expenses by each fishing management conditions. The results show that daily income
and daily lighting expenses were significantly increased as light source output for fishing lamps were increased.
The lower light source output which obtained by each fishing management conditions was advantageous when lighting
cost become more expensive or wholesale price become cheaper then ever.
This paper proposes the advanced rudder roll stabilization controI system with hybrid fin controI system
based on multivariate auto-regressive model. To confirm the effectiveness of Fin and Rudder Multivariate Hybrid
System, full scale experiments were conducted by using prototype hybrid control. Research and training vessel
'UMITAKA-MARU' of Tokyo University of Fisheries was used for experiment.
The full scale experiments included measurement of roll angle, roll rate, heading, rudder angle and fin angle.
The rudder roll stabilization system, fin stabilization system and hybrid stabilization.system were carried out for
the experiments to compare the effectiveness of each system. Statistical analysis was used for the time series
data obtained from experiments and the results show that the hybrid controI system with fin and rudder has good
performance for reducing rolling motion and keeping course.
In order to protect the snow crab population a crab sanctuary was established. An Untethered Remotely
operated Vehicle was used to gauge crab population numbers in the protected area and an unprotected area
(reference point) between the years 1996-1999. UROV results conclude higher crab densities in the protected
area each year of the test. Protection efforts were effective.