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Subject: Re: Deep Threats for High Seas
From: Tom Pickerell <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Wed, 9 Aug 2006 16:46:20 +0000

text/plain (187 lines)

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Dear All

My tuppence-worth...

With such a difficult to assess ecosystem, shouldn't we be adopting the 
precautionary approach to any fisheries?

The Precautionary Principle has been endorsed internationally on many 
occasions. At the Earth Summit meeting at Rio in 1992, World leaders agreed 
Agenda 21, which advocated the widespread application of the Precautionary 
Principle in the following terms:

'In order to protect the environment, the precautionary approach shall be 
widely applied by States according to their capabilities. Where there are 
threats of serious or irreversible damage, lack of full scientific certainty 
shall not be used as a reason for postponing cost-effective measures to 
prevent environmental degradation.' (Principle 15)

In Fisheries Management this precautionary approach has been defined in two 
international instruments:

the FAO Code of Conduct for Responsible Fisheries (CCRF); and
the Agreement for the Implementation of the Provisions of the United Nations 
Convention on the Law of the Sea of 10 December 1982 relating to the 
Conservation and Management of Straddling Fish Stocks and Highly Migratory 
Fish Stocks (UNIA).

Both of these share common wording and ideas. The wording used in the CCRF 

'States should apply the precautionary approach widely to conservation, 
management and exploitation of living aquatic resources in order to protect 
them and preserve the aquatic environment. The absence of adequate 
scientific information should not be used as a reason for postponing or 
failing to take conservation and management measures.'

Tom Pickerell

>From: "Trevor J. Kenchington" <[log in to unmask]>
>Reply-To: Scientific forum on fish and fisheries <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: Deep Threats for High Seas
>Date: Wed, 9 Aug 2006 13:11:23 -0300
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>>I'm not a professional, and I'm certainly willing to be educated.  But 
>>it generally accepted that a single pass removes an average of  twenty 
>>of benthic life in the track?
>What is "generally accepted" depends on the community whose general  
>acceptance is being evaluated. Over the past five years or so, a  broad 
>swath of public opinion has been shaped by an extremely  effective PR 
>campaign operated by opponents of trawling. I won't  speculate as to the 
>motivations (others have done enough of that) and  I can only tip my hat to 
>the skill and determination with which the  campaign has been carried 
>through, whatever I think of its ends. My  concern is only for the 
>scientific support for the claims being made  in that campaign and, in my 
>judgement, that support is weak.
>If you mean "generally accepted" within the scientific community, you  
>would still not be able to draw much of a judgement as most  scientists 
>have no specialized knowledge of the topic. With some 1200  papers and 
>reports published, there are probably a few dozen or maybe  a few hundred 
>people with that specialized knowledge. Such a small  group is subject to 
>changing opinions, short-lived fads and so forth.  (There was a complete 
>reversal of received wisdom on this topic  around 1990. I think we are 
>seeing another shift now, though such  things can really only be perceived 
>in retrospect.)
>In short, "general acceptance" isn't much of a guide. You need to  look at 
>the hard evidence. In the case of the seabed-impacts  literature, 
>regretfully, that means a paper-by-paper review, not only  of published 
>conclusions but of whether they could be supported by  the data available 
>to the authors. It isn't straightforward.
>As to your 20% figure: I do not think that any one number can be  taken as 
>a useful summary. Removal by a single pass ranges from zero  (deep-living 
>clam passed by an otter trawl) to 95% (coral tree in  path of otter trawl). 
>The number depends on the animal, the gear type  and the bottom on which 
>the animal lives -- if not other factors  besides.
>Personally, I suspect that your 20% figure is way too high, if you  mean to 
>average across numbers of animals or numbers of species. The  small infauna 
>in abundant, speciose and not much impacted. As an  average weighted by 
>biomass, 20% might be closer though I suspect  (without much, if any, 
>evidence) that it is still too high. But that  is me. A recent paper by 
>Hiddink et al. put the removal rate on sand  and gravel bottoms at around 
>50% per pass. I don't think that that is  supportable for the size classes 
>they were dealing with (I would  question whether 5% was supportable) but, 
>since they didn't provide  details of how they arrived at the number, it is 
>a bit hard to refute  it.
>>And that in areas repeatedly being trawled, up to
>>ninety percent is removed?
>90% of what? The only science-based reports that I can immediately  recall 
>of such high losses (and higher: essentially 100%) concern  coral trees, 
>large erect sponges and, in one special case, oyster  reefs. (One case in 
>the sense of only one is supported by scientific  observations. I think I 
>can point to similar losses of reefs in the  19th century but that depends 
>on inference and anecdote.)
>>This would seem to me to be a terrible price to
>>pay in bycatch. After all, such bycatch does provide food for  target 
>Not sure that it is helpful to stretch the meaning of "bycatch" to  cover 
>impacts on the benthos.
>Whether the net effect of the seabed impacts of trawling is to  increase or 
>reduce food supply for exploited species is much argued  and likely depends 
>on where and what exploited species is considered.  Some may gain by having 
>large, old benthic animals broken up, so as  to free production to pass 
>into small, short-lived species which are  available to be eaten by 
>small-mouthed fish.
>The bigger issue is likely to be one of altering the structure of the  
>seabed, to the disadvantage of species that like patch reefs and so  forth. 
>Still, even that only means that the production flows  elsewhere, which may 
>be to the advantage of some fisheries.
>>I may have put the argument too offensively for your taste. But  what I 
>>attempting to convey was that it might be useful to first study these
>>environments before we chew them up.
>In the case of the deep-sea environments, I will guess that a lot of  
>people agree. I certainly do. However, your argument as stated was  not 
>confined to such environments and was equally applicable to areas  long 
>trawled, where if there was ever a stage of chewing up, it is  past and 
>>Why must these fisheries run the risk of collapse first, before  anyone 
>>the issue seriously enough to put a hold on trawling until we know  a bit 
>>about what's going on there? Once we have determined what sort of  methods 
>>sustainable, then we can have the rest of time to farm these unique  
>If by "there" and "unique marine environments" you mean places like  the 
>seamounts, I think that there is no reason not to take the issue  seriously 
>today. However, broadcasting propaganda against mobile-gear  fishing, 
>without focusing the case on those special environments,  just builds the 
>opposition and confuses the issue.
>>Sorry about the "junk" and "garbage". I must have struck a nerve.
>Of course you did. The anti-trawling PR campaign has, as I noted  above, 
>been very effective and it is far beyond the ability of mere  scientists to 
>combat. However, we do have a duty to counter such  propaganda when it is 
>introduced into scientific fora.
>Trevor Kenchington
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