CHAPTER 18 • Management of Tokyo Bay
331
18.2.3
Living Marine Resources
In its natural state, Tokyo Bay was noted for its high productivity and rich biological
diversity. For a long time, the bay provided the highest yield of cultured nori (laver,
Porphyra sp.) in Japan. Native species of the bay included:
• Shellfish: asari (short-neck clam), hamaguri (clam);
• Crustaceans: kurumaebi (prawn), gazami (crab), shako (mantis shrimp);
• Ichthyofauna: kurodai (black sea-bream), suzuki (sea bass), bora (mullet), ishigarei
(flatfish), anago (conger eel), mahaze (common goby); and
• Offshore migrant species: kamasu (pike), inada (yellowtail).
An investigation of fisheries carried out at the beginning of this century showed that
the entire area up to the innermost part of the bay was utilized as fishing grounds. Fishing
activity in Tokyo Bay reached a peak around 1960, when between 16 thousand and 17 thousand households produced total catches of about 140 000 t a-I. The total in 1960 consisted
of. finfish 5 600 t; shellfish 109 000 t; crustaceans and others 2500 t; and seaweed 2500 t.
In addition, about 45 000 t of nori were produced in 1960. The culture of nori was done all
along the shoreline of the bay, except for small areas of the ports of Yokohama and Chiba.
The increasing rate of land reclamation in the '60S, combined with deterioration of the
water quality of the bay, resulted in major declines in the catch of some important fish
species. Nori culture was among the species with the sharpest declines, because of the major
reduction by land reclamation of areas available for nori culture. By around 1980, only three
small areas of nori culture remained, i.e., those adjacent to Ichikawa, Kisarazu, and Futtsu.
With respect to recreational fishing, mahaze angling was long a popular sport for people
in the metropolitan area. Mahaze is quite voracious, and is easy to catch. Until about
1958, about 500 thousand people took part in this type of recreation each year. After
1960 the number of ~glers began to decrease to between 300 thousand and 400 thousand, and the average catch per angler decreased even faster. After the decline of mahaze,
recreational fishers have moved out of Tokyo Bay and turned to alternative species. By
the early '70S, the number of anglers had decreased to between 50000 and 100000.
A summary of fishery activities in Tokyo Bay over the 1965-1980 period is presented
in Table.18.3. Total fish catch in the bay reached bottom in the early '70S, and the catch
has stabilized at a level about half the level in the '50S. The number of fishery households has declined to about one fifth of the number in the '50S. The major decline has
been in shellfish; finfish catch has actually increased slowly since the mid-1960s.
These data, together with data on ambient water quality and rate of land reclamation, suggest qualitatively that a new aquatic ecosystem may have been established. The
new equilibrium is associated with fewer shallow areas for species habitat and somewhat better ambient water quality than in. the early '70S. This new system probably
involves a lower species diversity and lower mean annual yield of fish than in the early
'50S. One might hypothesize that if habitat decreases no further and if ambient water
quality remains at least as good as in the mid '80S, then the new dynamic ecosystem
for the bay could be maintained, or even strengthened to some extent. The recovery in
finfish catch since the late '70S may offer a good prospect for recreational fishing, taking account of steadily and visibly growing demand for such fishing.
331
18.2.3
Living Marine Resources
In its natural state, Tokyo Bay was noted for its high productivity and rich biological
diversity. For a long time, the bay provided the highest yield of cultured nori (laver,
Porphyra sp.) in Japan. Native species of the bay included:
• Shellfish: asari (short-neck clam), hamaguri (clam);
• Crustaceans: kurumaebi (prawn), gazami (crab), shako (mantis shrimp);
• Ichthyofauna: kurodai (black sea-bream), suzuki (sea bass), bora (mullet), ishigarei
(flatfish), anago (conger eel), mahaze (common goby); and
• Offshore migrant species: kamasu (pike), inada (yellowtail).
An investigation of fisheries carried out at the beginning of this century showed that
the entire area up to the innermost part of the bay was utilized as fishing grounds. Fishing
activity in Tokyo Bay reached a peak around 1960, when between 16 thousand and 17 thousand households produced total catches of about 140 000 t a-I. The total in 1960 consisted
of. finfish 5 600 t; shellfish 109 000 t; crustaceans and others 2500 t; and seaweed 2500 t.
In addition, about 45 000 t of nori were produced in 1960. The culture of nori was done all
along the shoreline of the bay, except for small areas of the ports of Yokohama and Chiba.
The increasing rate of land reclamation in the '60S, combined with deterioration of the
water quality of the bay, resulted in major declines in the catch of some important fish
species. Nori culture was among the species with the sharpest declines, because of the major
reduction by land reclamation of areas available for nori culture. By around 1980, only three
small areas of nori culture remained, i.e., those adjacent to Ichikawa, Kisarazu, and Futtsu.
With respect to recreational fishing, mahaze angling was long a popular sport for people
in the metropolitan area. Mahaze is quite voracious, and is easy to catch. Until about
1958, about 500 thousand people took part in this type of recreation each year. After
1960 the number of ~glers began to decrease to between 300 thousand and 400 thousand, and the average catch per angler decreased even faster. After the decline of mahaze,
recreational fishers have moved out of Tokyo Bay and turned to alternative species. By
the early '70S, the number of anglers had decreased to between 50000 and 100000.
A summary of fishery activities in Tokyo Bay over the 1965-1980 period is presented
in Table.18.3. Total fish catch in the bay reached bottom in the early '70S, and the catch
has stabilized at a level about half the level in the '50S. The number of fishery households has declined to about one fifth of the number in the '50S. The major decline has
been in shellfish; finfish catch has actually increased slowly since the mid-1960s.
These data, together with data on ambient water quality and rate of land reclamation, suggest qualitatively that a new aquatic ecosystem may have been established. The
new equilibrium is associated with fewer shallow areas for species habitat and somewhat better ambient water quality than in. the early '70S. This new system probably
involves a lower species diversity and lower mean annual yield of fish than in the early
'50S. One might hypothesize that if habitat decreases no further and if ambient water
quality remains at least as good as in the mid '80S, then the new dynamic ecosystem
for the bay could be maintained, or even strengthened to some extent. The recovery in
finfish catch since the late '70S may offer a good prospect for recreational fishing, taking account of steadily and visibly growing demand for such fishing.