Environmental criteria for fish farms based on the macrobenthos
H. Yokoyama (Environmental Management Div.)
A quantitative survey of the macrobenthos conducted in fish
farms along the coast of Kumanonada showed that the macrofauna and sediment
parameters based on the macrobenthos will be of practical use as criteria for
assessing fish farm environments.
- In 1999, "the Law to Ensure Sustainable Aquaculture
Production" was established to prevent self-deterioration of aquaculture
grounds. The environmental criteria used in this Law should be revised to the
more appropriate criteria on the basis of the scientific data. In order to
examine the applicability of the adopted criteria to fish farms, and to
specify the new criteria of aquaculture environment, surveys of the bottom
environments and the macrobenthos were conducted in fish farms in Kumano-nada,
- One of criteria used in the new Law is based on the Omori-Takeoka
theory in which the peak of benthic oxygen uptake (BOU) against the loaded
organic matter is regarded as an indicator of the maximum phase in the
process of biological remineralization. In the present study, the peak of
BOU was not found in the observed gradient of acid volatile sulfides
(AVS-S) in the sediment accompanied with increasing loaded organic matter
(Fig. 1). This finding may be explained by
the possible variation of biological BOU in its immediate response to the
change of dissolved oxygen in the overlying, near-sediment-surface water.
A quantitative survey of the macrobenthos was conducted in 22 fish
farms with the collaboration of the Owase Fisheries Laboratory, Fisheries
Research Division, Mie Prefectural Science and Technology Promotion
Center. The biomass in summer peaked in sediments containing 1.2 mg/g of
total nitrogen, where aerobic mineralization of the loaded organic matter
is supposed to occur (Fig. 2). Animals sere
scarcely found in sediments with AVS-S > 1.7mg/g, suggesting this as a
critical condition for the aquaculture environment (Fig.
An index "ED", which shows the topographic
situation of the sampling site, was devised. Six assemblages were
recognized by cluster analysis. These assemblages were classified into
three groups in the gradients of ED and fish production, i.e., a group
with high density and high diversity (A-D), a group characterized by an
impoverished fauna (E), and an azoic site group (F), which respectively
indicate healthy conditions, cautionary conditions, and critical
conditions (Fig. 4). Thus, the macrofauna
and sediment parameters based on the macrobenthos proposed in the present
study will be of practical use as criteria for assessing fish farm
- 1) Yokoyama, H. (2000). Environmental quality criteria for aquaculture
farms in Japanese coastal areas-a new policy and its potential problems. Bull.
Natl. Res. Inst. Aquacult., 29:123-134.
2) Yokoyama, H., A. Nishimura and M. Inoue (2000). Macroinvertebrates as
biological indicators to assess the influence of aquaculture on the
coastal environment. European Aquaculture Society Special Publication
No. 28 (Abstracts of contributions presented at the International
Conference AQUA 2000), p.762.
- 3) Yokoyama, H., Sakami, T. (in press). Examination of the benthic
oxygen uptake rate as an environmental criterion for fish farms in Gokasho
Bay. Nippon Suisan Gakkaishi.
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