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Fishing industry says Setonai Sea too clean for the fish

23 Comments
By Karen Masuda

Efforts to clean up the sea have caused an adverse reaction giving the fishing industries in Hyogo, Okayama and Oita prefectures along the Setonai inland seaboard a major headache. The irony being that the sea is too clean for the fish to thrive.

An analysis of the seawater by researchers found the natural levels of nitrogen and phosphorous in the salt content of the water needed for the nutritional growth of healthy plankton have diminished to the point that it has affected the natural ecosystem of the sea. Without enough plankton, the major nutrition for many small sea animals, the whole food chain is disrupted to the point of great loss to the fishing industry.

A reporter at Yomiuri Shimbun spoke with a 38-year-old fisherman in the fishing town of Izumisano near Kansai International Airport after he returned from eight hours of trawl net fishing in the Setonai sea. His face reflected the critical state of his current situation. That day he fished for the usual flatfish and prawns but the numbers in both fish and profit were too low.

Ten years ago he got 70,000-80,000 yen per catch. Today his profit won’t exceed 20,000. With gasoline prices so high, this barely covers the running cost of the boat and there is hardly no profit left over.

The Ministry of Agriculture, Forestry and Fisheries' statistics show that fishery catches after peaking to 460,000 tons in 1982, dropped consistently on a yearly basis until in 2010, when they only reached 175,000 tons. Compared to the 1980s, flatfish catches have decreased by half, small fish catches are 1/6th of what they were, while clam type catches dropped drastically to 1/190th of what they were.

Most fishermen put off repairing boat parts and replacing engine parts, and have to go out to work extra hours at night on part-time jobs to make ends meet. Noboru Matsubayashi, the chairman of one of the major unions of the fishing industry for Osaka, laments that the fishing industry cannot survive at this rate.

Decrease of natural nitrogen by 60%

Fishermen say the reason for this decline in their catch is that the seawater has become too clean for the fish to survive due to lack of sustenance. A spokesman for the Agricultural and Fisheries Technological center said that the depletion of the nutritive value of the salt water is due to the lack of natural nitrogen in the seawater salt.

During the industrial boom era of Japan, laws had to be passed to avoid water contamination from pollution. Still, there was damage from the red tides caused by contaminated seawater in the 1970s. Industrial waste water was strictly regulated as well as the building and maintenance of new water pipe systems. This remedy set the stage for the disappearance of fish in the Setonai sea by 2001. The seawater's natural source of nitrogen and phosphorous started to be depleted.

As a result, a liter of Setonai seawater from 1983 had a nitrogen level of 0.34 mils per gram compared to a liter of water last year with only a 0.14 mils per gram nitrogen level. The visibility of the water in Osaka Bay has increased from an average of 3 meters visibility to 6 meters visibility.

One thing can be said for sure: the diminishing catches of the fishing industry are in direct correlation with waste water regulation.

The seaweed industry has also been affected – especially the seaweed cultivation farms as seaweed absorbs nitrogen from the salt water. Discoloration of seaweed harvests turn the harvests into a sickly yellow color. Another victim of this unsettling phenomenon.

Source: Yomiuri Eco News

© RocketNews24

©2019 GPlusMedia Inc.


23 Comments
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Another way to make the fish disappear is... fishing 460.000 tons of it every year!!!!

7 ( +7 / -0 )

The article seems to want us to believe that the natural source of nitrogen and phosphorus was industrial pollution.

Not buying it.

11 ( +10 / -0 )

and there is hardly no profit left over

Brain. Hurts.

2 ( +2 / -0 )

What is this nonsense? It seems that they are suggesting that more pollution is good for fish. Are they saying that there were fewer fish before they started polluting the sea? I very much doubt it. The reason catches have declined is very simple: overfishing.

One thing can be said for sure: the diminishing catches of the fishing industry are in direct correlation with waste water regulation.

This is demonstrably false. I suggest that catches increased from the Meiji period as Japan industrialised, peaked at some point, then decreased as resources were depleted. Over the same period waste water regulation has gradually increased from zero to whatever it is now. There is no correlation between catches and waste water regulation.

6 ( +6 / -0 )

This article is hogwash....

De-nitrification occurs in water where oxygen, a more energetically favourable electron acceptor, is depleted, and bacteria respire nitrate as a substitute terminal electron acceptor.

Oxygen depletion or hypoxia occurs due to fossil fuel emissions and water pollution from fertilizers and sewage. This in turn kills the bacteria and organisms which make nitrogen available to plankton and other forms of plant / sea life.

Most likely the culprits are, over-fishing, sea temperature rising, and over pollution.

6 ( +6 / -0 )

and there is hardly no profit left over.

You missed the "dawg" off at the end.

and there is hardly no profit left over, dawg.

There you are, I've fixed it for you.

2 ( +3 / -1 )

the diminishing catches of the fishing industry are in direct correlation with waste water regulation

Just bad science. Correlation does not necessarily equal causation.

3 ( +3 / -0 )

So is the author, Ms. Masuda, suggesting we ease restrictions on industrial pollution, as though the 'remedy' were actually the cause for the loss of fish? Should we be dumping toxic chemicals, which the fish would absorb, so that there can be bigger profit for the fishing industries??

4 ( +5 / -1 )

I am willing to believe that certain kinds of pollution could help drive a food chain. After all, poop in the water would also be pollution, but the catfish would love it.

But to suggest it was natural or good or should be continued or renewed? Forget it. If they need to feed the ecosystem clean nutrients to get more fish, okay. We do that on farm land every day. But just have industry dump their waste again? No.

7 ( +7 / -0 )

it's called over fishing...................

6 ( +7 / -1 )

AlternateUniverseAug. 29, 2012 - 07:50AM JST

The article seems to want us to believe that the natural source of nitrogen and phosphorus was industrial pollution.

Hardly. This is actually a topic that has been studied by professors I studied under. The regulations in Japan are actually so stringent that most streams are too "dirty" even before the plants have their way with them. As such, the plants end up diluting the "pollutants" to have downstream water fit government requirements. This is especially true of sulphates and heavy metals, but can also impact other elements due to the fact that factories are usually downstream of farms and natural phosphate sources. It drives down the bottom line for factories as well as damage ecosystems (lack of phosphates in Fukushima soil may be attributable to this as well), and so the law should be changed to ensure that the waste water is equal to the natural water by site, not by nation wide averages.

-2 ( +4 / -6 )

So before rampant industrialization there weren't enough fish? The mind boggles at the excuses this industry comes up with to excuse over fishing. Up here (Tohoku) they are blaming Antartic whales and local sharks for upsetting the natural balance.

1 ( +2 / -1 )

peanut666Aug. 29, 2012 - 09:52AM JST

De-nitrification occurs in water where oxygen, a more energetically favourable electron acceptor, is depleted, and bacteria respire nitrate as a substitute terminal electron acceptor.

Oxygen depletion or hypoxia occurs due to fossil fuel emissions and water pollution from fertilizers and sewage. This in turn kills the bacteria and organisms which make nitrogen available to plankton and other forms of plant / sea life.

This is actually incorrect in most cases, as you are trying to describe the events of a "red tide" backwards of the generally accepted order. The bacteria and plankton actually thrive because of nitrogen and phosphorous rich water, and thus consume both the fuel sources and massive quantities of oxygen. After a "red tide" event there is the possibility of denitrification, but that is generally short lived and not nearly long enough to remove all the nitrogen added.

This article talks about a very different event, which is practically the reverse of an algae bloom, in which levels fall enough so that an area cannot sustain significant numbers of larger organisms by a lack of nitrogen and phosphorous.

Very likely this region had only slightly higher levels before the factories, and after the factories but before the clean water laws it actually was providing just below the limit for an algae bloom, hence acting like a sea wide version of farm fertilizer. If they were to check records from before the 1960s, they would likely find that just a bit more fish were present than there are now, and that fish populations swelled as nitrogen/phosphorous levels increased.

0 ( +4 / -4 )

Early Western visitors to Japan describe the crystal clear waters of the Seto-nai-kai.

These waters may be described as too 'clean' today, but full of 'clean' sediment, they look filthy.

0 ( +0 / -0 )

This is the first article I have ever heard that is complaining there is not enough pollution and its hurting the environment

1 ( +1 / -0 )

avengerAug. 29, 2012 - 06:32PM JST

This is the first article I have ever heard that is complaining there is not enough pollution and its hurting the environment

As with most articles sourced from rocketnews, it is simply poor journalistic style that makes people believe that. "Clean" should actually be reworked to "nitrogen and phosphorous deficient", as the article never mentions levels of other impurities in the water, including the salt levels. Note that impurities is simply stating anything but pure H2O, and sea water usually includes large amounts of natural and necessary impurities including salts and non-metal elements necessary for life.

-1 ( +4 / -5 )

Smells fishy to me!

The whole world over fish are disappearing from over-fishing, but the Inland sea, which the last time I checked was one of the most industrial, used (by boats and effluent), and stuffy (like a room w/closed windows, being inland amongst so many isles, the flow of new water from outside is less) and also well-fished oceans,

is experiencing sudden fish decreases because it suddenly got clean? and TOO clean at that?

0 ( +0 / -0 )

Clear water doesnt necessarily mean clean water & cloudy water doesnt necessarily mean dirty water!

My vote goes to over fishing, its a concept that just isnt understood in this country

3 ( +3 / -0 )

Agree with GW, checks self for fever. That fisherman will someday be complaining about no fish. He will pull the last fish out just to make money. He can not think of anyone but himself.

0 ( +0 / -0 )

wondering why people keep on insisting on overfishing...algea and plankton are food for the fish. There are no algea and planktons now because their much needed phosphates and nitrogen has diminished to the point that they dont survive. No food for the fish means no fish.

0 ( +0 / -0 )

miki,

to be sure nutrients in oceans are very important, but this blurb & many others on fishing almost NEVER seem to consider over fishing to play into things when often they do & a lot of the fishing techniques for bottom dwelling species are very destructive/disruptive to ocean floor habitats!

0 ( +0 / -0 )

to be sure nutrients in oceans are very important, but this blurb & many others on fishing almost NEVER seem to consider over fishing to play into things when often they do & a lot of the fishing techniques for bottom dwelling species are very destructive/disruptive to ocean floor habitats!

You can't just dismiss the impact these changes in nitrogen and phosphorus levels have had, though. Is overfishing a problem? Yes. But that doesn't mean it's the only problem.

-1 ( +0 / -1 )

This is actually incorrect in most cases, as you are trying to describe the events of a "red tide" backwards of the generally accepted order. The bacteria and plankton actually thrive because of nitrogen and phosphorous rich water, and thus consume both the fuel sources and massive quantities of oxygen. After a "red tide" event there is the possibility of denitrification, but that is generally short lived and not nearly long enough to remove all the nitrogen added.

This article talks about a very different event, which is practically the reverse of an algae bloom, in which levels fall enough so that an area cannot sustain significant numbers of larger organisms by a lack of nitrogen and phosphorous.

Very likely this region had only slightly higher levels before the factories, and after the factories but before the clean water laws it actually was providing just below the limit for an algae bloom, hence acting like a sea wide version of farm fertilizer. If they were to check records from before the 1960s, they would likely find that just a bit more fish were present than there are now, and that fish populations swelled as nitrogen/phosphorous levels increased.

The most simple test is to measure the amount of free oxygen in the water. It is very, very low. Thus the lack of fish. The hypoxia is caused by pollution - which is in most cases absolutely correct.

0 ( +0 / -0 )

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