I'ill happy to have it. thanks
Donatella Del Piero
Dip. Biologia
via Weiss 2
I-34141 Trieste

 ++39 040 676 2016
Murphy law: few months in  laboratory may save three hours in the library
----- Original Message -----
From: Mark Tupper <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 11, 2002 5:35 AM
Subject: Re: Fishing of large vs. small fish


> Dear Fish-Sci,
>
> Regarding the Conover and Munch study, there were some excellent
discussions
> posted on FishFolk over the last couple of days. If anyone not subscribing
> to FishFolk would like to read this material, I will happily compile it
and
> send it to you.
>
> Cheers,
> Mark Tupper
>
>
>
> Dr. Mark H. Tupper, Assistant Professor
> University of Guam Marine Laboratory
> UOG Station, Mangilao, GU 96915, USA
> tel 671-735-2185; fax 671-734-6767
> www.uog.edu/marinelab/tupper/index.html
>
> Coordinator, Marine Protected Areas Research Group
> www.uog.edu/marinelab/mpa/index.html
>
>
> ----- Original Message -----
> From: "William Silvert" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, July 10, 2002 4:14 AM
> Subject: Fishing of large vs. small fish
>
>
> > The AFS mailing list recently reported the following item. I don't find
it
> > surprising, a number of my colleagues are concerned about
> over-exploitation
> > of large mature fish, but I thought that the item was worth reposting.
> >
> > Some of you may have seen a posting on the sci.bio.ecology newsgroup
about
> > the FISH-ECOLOGY mailing list being located at SEARN. I don't know how
the
> > item got posted, but it is several years out of date. FISH-ECOLOGY is
> > located in the Canary Islands, and FISH-SCI continues to be the list
> located
> > at SEARN.
> >
> > William Silvert, co-owner, FISH-SCI list
> >
> > July 09, 2002
> > Study Questions Wisdom of Harvesting Only the Largest Fish
> >
> > SCIENCE
> >
> > Fisheries managers frequently set minimum size limits for captured
> animals,
> > mandating that the smallest--and thus youngest--be freed to allow for
full
> > maturation. But findings detailed in the current issue of the journal
> > Science suggest that these regulations may actually be shrinking the
> average
> > size of wild fish over time. Plucking the largest fish from the gene
pool,
> > the authors report, leaves only hereditary information from the smallest
> > fish for the next generation.
> >
> > To examine the potential evolutionary effects of selective extraction ,
> > David Conover and Stephan Munch of the State University of New York at
> Stony
> > Brook studied a common marine fish called Menidia menidia. Allowing
groups
> > of the fish to grow in separate tanks, the scientists removed and
weighed
> > the largest 90 percent of individuals from some tanks, the smallest 90
> > percent from others, and a random 90 percent assortment from the rest.
> After
> > the remaining fish matured and spawned, the team repeated the process.
> > Initially, the large fish-harvested tanks produced the highest yields.
> After
> > four generations of such "fishing," however, the total weight of all the
> > fish extracted from the small fish-harvested tanks, as well as the
average
> > weight of each creature, amounted to twice that of the large
> fish-harvested
> > tanks. Additionally, since the reproductive capability of large fish is
> much
> > greater than that of small ones, small fish-harvesting resulted in more
> > fertile animals. Juvenile survival rates were about the same for all
> groups,
> > indicating that evolved changes in growth, not viability, caused these
> > results. The findings suggest that in the real world, taking only the
> > largest fish may in the long run result in a calamitous decrease in
yield,
> > and thus income, for the entire industry.
> >
> > Fishing is big business for many coastal communities. "In New York State
> > alone, the commercial fishing, recreational fishing, and the seafood
> > industries make a $11.5 billion contribution to the state's economy and
> > employ over 100,000 people," remarks Jack Mattice of New York Sea Grant,
> one
> > of the funders of this project. A successful industry is based on a
> healthy
> > fishery, however. "Our study illustrates how well-intentioned management
> > plans that appear to maximize yield on ecological time scales may have
the
> > opposite effect after accounting for evolutionary dynamics," Conover
> notes.
> > The researchers thus propose both creating no-fish areas to prevent an
> > irreversible loss of important genetic diversity, and setting a maximum
> size
> > limit in addition to the minimum. --Rachael Moeller
> >
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