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Subject: Re: Deep Threats for High Seas
From: "Johnston, Justin C" <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Wed, 9 Aug 2006 09:39:25 -0400

text/plain (149 lines)

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I don't want to get caught in the argument, but I am curious about your
comment that you have literature that shows that, "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."  What exactly is a "low rate of loss"?  How is that
quantified and what was it compared with?  If that is on a per trawl
pass basis, what happens when multiple passes occur in the same area?
Would multiple trawl passes have a linear, logistic, or synergistic
effect on benthos/habitat loss? 


Justin C Johnston

Wexford Prof. Bldg. III
11676 Perry Hwy, suite 3101
Wexford, PA 15090
Phone: (724) 940-4200x229
Cell: (231) 282-2192
Fax: (724) 940-4205

-----Original Message-----
From: Scientific forum on fish and fisheries
[mailto:[log in to unmask]] On Behalf Of Trevor J. Kenchington
Sent: Wednesday, August 09, 2006 9:15 AM
To: [log in to unmask]
Subject: Re: Deep Threats for High Seas

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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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