310
1
Importance of the Protection
and Management
of Offshore Sea-Hill Fishing
Grounds
Sea-hills, which we propose in this paper to be
included in the areas for the protection and management of fi shing grounds, are the hills on the
seafl oor 500 m high or less and large-scale natural
reefs interspersed on the continental shelves. With
regard to the mountains on the seabed 1,000 m
high or more found in the ocean, i.e., seamounts,
a number of studies have been conducted on the
management of their resources (Menard 1964 ;
IHO-IOC 2001 ). Because seamounts are supplied
with nutrients from the depths of the sea by the
upwelling generated by the seabed topography
and fl ows, primary production is very active
around the seamounts; thus, many fi sh, the consumers of these nutrients, live there (Rogers
1994 ). Seamounts are mostly distributed in the
open sea out of the exclusive economic zone
(EEZ), and thus there have been fears about the
depletion of resources as a result of, among others, unplanned fi shing activities; therefore, international surveys, including those by the UNEP,
have been carried out on these seamounts (e.g.,
IUCN 2013 ). On the other hand, the areas around
sea-hills interspersed on the continental shelves,
which are the subject of this paper, have been used
as fi shing spots more familiar to local fi shers,
such as those of pole and line and gill net fi shing
(Hamano et al. 2001 ). However, it has begun to be
feared that due to the global-scale depletion of
marine resources in recent years, as well as the
increases in the price of crude oil, large-scale fi shing fl eets using trawl nets and purse seine, whose
main fi shing areas have been in the open sea, may
turn their eyes to sea-hills situated nearer to their
ports, and thus surveys on the management of
resources around sea-hills were started.
2
An Example of Surveys
on the Fishing Ground
Environment at “Hachiriga- se” in the Southwestern
Part of the Japan Sea
(East Sea)
The continental shelf off the San’in Coast in the
southwestern region of the Japan Sea (East Sea)
is used as the bases of various fi shing methods,
such as large- and medium-type purse seine fi shery, offshore trawl fi shery, angling, long-line fi shery, and stake net fi shery (e.g., Ogawa et al.
1977 ). In 1999, the survey of the fi shing ground
environment of the Hachiri-ga-se area, one of the
natural offshore hills existing on the continental
shelves, was mainly started by the National
Fisheries University, universities in the district,
and the fi sheries experiment station of Yamaguchi
Prefecture (Hamano and Nomura 2002 ) (Fig. 1 ).
Hachiri-ga-se is an important fi shing area used
daily by local fi shers and is also famous as a
place for recreational fi shing, such as the pole
and line fi shing of bluefi n tuna ( Thunnus orientalis ). As for the area north of Hachiri-ga-se, partly
because the area is close to the borders of Korea
and China, it has often been reported that overseas fi shing fl eets operate there without permission (e.g., Hamano and Uchida 2000 ).
In the above-mentioned survey, in an effort to
obtain information necessary for “responsible
fi shing” by Japanese fi shers, such devices as
acoustic survey equipment, ROVs, and larva and
Therefore, how we should protect the fi shing grounds and effectively
manage the coastal fi sheries for sustainable harvest is a very important and
urgent issue. In this study, we proposed an acoustic monitoring method to
assess the distribution of marine algae vegetation and fi sh schools. These
results show that the acoustic monitoring method would be effective to
provide an example of solution for protection and management of these
offshore sea-hill fi shing grounds.
A. Hamano et al.
1
Importance of the Protection
and Management
of Offshore Sea-Hill Fishing
Grounds
Sea-hills, which we propose in this paper to be
included in the areas for the protection and management of fi shing grounds, are the hills on the
seafl oor 500 m high or less and large-scale natural
reefs interspersed on the continental shelves. With
regard to the mountains on the seabed 1,000 m
high or more found in the ocean, i.e., seamounts,
a number of studies have been conducted on the
management of their resources (Menard 1964 ;
IHO-IOC 2001 ). Because seamounts are supplied
with nutrients from the depths of the sea by the
upwelling generated by the seabed topography
and fl ows, primary production is very active
around the seamounts; thus, many fi sh, the consumers of these nutrients, live there (Rogers
1994 ). Seamounts are mostly distributed in the
open sea out of the exclusive economic zone
(EEZ), and thus there have been fears about the
depletion of resources as a result of, among others, unplanned fi shing activities; therefore, international surveys, including those by the UNEP,
have been carried out on these seamounts (e.g.,
IUCN 2013 ). On the other hand, the areas around
sea-hills interspersed on the continental shelves,
which are the subject of this paper, have been used
as fi shing spots more familiar to local fi shers,
such as those of pole and line and gill net fi shing
(Hamano et al. 2001 ). However, it has begun to be
feared that due to the global-scale depletion of
marine resources in recent years, as well as the
increases in the price of crude oil, large-scale fi shing fl eets using trawl nets and purse seine, whose
main fi shing areas have been in the open sea, may
turn their eyes to sea-hills situated nearer to their
ports, and thus surveys on the management of
resources around sea-hills were started.
2
An Example of Surveys
on the Fishing Ground
Environment at “Hachiriga- se” in the Southwestern
Part of the Japan Sea
(East Sea)
The continental shelf off the San’in Coast in the
southwestern region of the Japan Sea (East Sea)
is used as the bases of various fi shing methods,
such as large- and medium-type purse seine fi shery, offshore trawl fi shery, angling, long-line fi shery, and stake net fi shery (e.g., Ogawa et al.
1977 ). In 1999, the survey of the fi shing ground
environment of the Hachiri-ga-se area, one of the
natural offshore hills existing on the continental
shelves, was mainly started by the National
Fisheries University, universities in the district,
and the fi sheries experiment station of Yamaguchi
Prefecture (Hamano and Nomura 2002 ) (Fig. 1 ).
Hachiri-ga-se is an important fi shing area used
daily by local fi shers and is also famous as a
place for recreational fi shing, such as the pole
and line fi shing of bluefi n tuna ( Thunnus orientalis ). As for the area north of Hachiri-ga-se, partly
because the area is close to the borders of Korea
and China, it has often been reported that overseas fi shing fl eets operate there without permission (e.g., Hamano and Uchida 2000 ).
In the above-mentioned survey, in an effort to
obtain information necessary for “responsible
fi shing” by Japanese fi shers, such devices as
acoustic survey equipment, ROVs, and larva and
Therefore, how we should protect the fi shing grounds and effectively
manage the coastal fi sheries for sustainable harvest is a very important and
urgent issue. In this study, we proposed an acoustic monitoring method to
assess the distribution of marine algae vegetation and fi sh schools. These
results show that the acoustic monitoring method would be effective to
provide an example of solution for protection and management of these
offshore sea-hill fi shing grounds.
A. Hamano et al.