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Subject: Re: Deep Threats for High Seas
From: "Trevor J. Kenchington" <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Wed, 9 Aug 2006 10:15:29 -0300
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Michael Elvin wrote:

> I think you're missing something. Dragnet trawling is just too  
> efficient at
> scooping up everything in its path. There are photos on the web of  
> before and
> after scenes, and trawling does indeed transform areas rich in  
> benthic life
> into barren deserts.
>
> By way of analogy, it would be like fencing a forest and then  
> burning it
> down. Sure, you could very efficiently capture every animal living  
> there. But no
> one would think it was a sustainable method.

It is garbage like that which discredits the drive to ban high-seas  
bottom trawling.

As of last night, the bibliography I maintain on seabed impacts of  
fishing gears topped 1200 listed items. Nothing in that corpus of  
literature supports the notion that trawling "scoops up everything in  
its path" while many studies have shown that most of the benthos  
(most of the benthos being composed of small animals) in most  
habitats suffers only a low rate of loss per pass of a trawl.

Yes, there are "before and after" photos going the rounds but very  
few of them (if any) show the same location before and after a trawl  
passes. It is just too difficult, to the point of being impossible,  
to put a trawl across a chosen spot that has just been photographed.  
More to the point, study after study has been able to describe the  
immediate effects of the passage of a trawl (or a dredge) in the  
track of that gear but detecting the consequences of even commercial- 
scale trawling over larger scales of time and space is a whole lot  
tougher -- partly because of swift recovery from the immediate  
impacts but mostly (I suspect) because the longer-lasting effects  
easily get lost in natural spatial and temporal variability of the  
seabed.

Transformation of "areas rich in benthic life into barren deserts"  
might, arguably, be a reasonable description of the consequences of  
trawling and/or dredging in some very special environments (e.g. the  
former oyster reefs of Foveaux Strait, the coral forests on seamounts  
south of Tasmania) but it is the grossest of distortions of the  
consequences of using mobile gear on typical trawling grounds.

I will not even dignify Michael's latest twist on the forestry  
clearcutting analogy with a response. That stuff has no place in a  
mailing list intended as a scientific forum.


Les Kaufman has stated the case for banning high-seas bottom trawling:

> The habitats that Dr. Earle was speaking of in her editorial "Deep  
> Threats for High Seas" are constructed and inhabited by, for the  
> most part, extremely slow-growing organisms about which very little  
> is known.  They can not be exploited in a sustainable manner on any  
> time scale of interest to human industry.   They can certainly be  
> exploited, but for all intents and purposes, only once.

Michael was right to add:

> The worst practise is seamount trawling. The tops of remote  
> seamounts are
> island biospheres, containing many species not found anywhere else.  
> Despite the
> fact that they have not been extensively studied, we can readily  
> understand
> there is zero justification for allowing trawlers to clearcut  
> there, decimating
> endemic species before we even know what they were. It's a one time  
> plundering
> of the earth's bounty. Once the money is spent, everything's gone.

I would only add that, should some deep-sea demersal resource support  
sustainable fishing or should a policy decision be made that some  
such resource be "mined" as a one-time operation, existing  
international regimes entirely lack the capability to manage high- 
seas bottom fisheries so as to achieve anything resembling optimal  
outcomes. Until that changes, a blanket ban is the sensible solution  
[though perhaps with an exemption for those few areas where  
continental shelves project into high-seas areas].

Unfortunately, opposition to such a ban is not coming solely from  
nations engaged in high-seas bottom trawling but also from some with  
a vested interest in trawling their own continental shelves -- Canada  
being a case in point. The kind of junk propaganda offered to this  
list by Michael only makes it that much more difficult to separate,  
in the minds of politicians, the very different issues of  
unregulated, deep-water, high-seas bottom trawling for long-lived,  
low-productivity species (often in areas of exceptional biodiversity  
and vulnerability, like seamounts) versus trawling at continental- 
shelf depths for high-productivity resources under management regimes  
that at least offer some hope of sustainability and on seabeds that  
are relatively robust to the impacts of towed gear. Failing to  
distinguish those issues only makes it less likely that we will see  
the required effective ban on the former style of fishing.


Trevor Kenchington

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