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Justin: overfishing is a common term of course derived from informal language
but the technical definition is easily found in every fishery science book,
you may also distinguish between growth overfishing and recruitment
overfishing (e.g.Sparre, 1987 and many others). For years the importance or
the exitence of r.o. was neglected, till the sad history of the Canadian cod
(I was in Canada in 1990, the first signals of decay were still on) when the
SEALS (!!!) were found guilty, regardless the population structure, that was
neglected ( Cushing and many others from 1996, before, academic silence!!!)and
the presence of only immatures in 1992 (3 cohorts, the species may support 20)
was determinant in the crash. Of course the climate may not help, but if you
say that is more important, i think this may be misleading, as the assuption
of indipendence of recruitment from parental biomass.Last but not least we
must distinguish among species.best regards. D.Del Piero
Scrive Justin Johnston <[log in to unmask]>:
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> My thought is that overfishing is neither legal nor scientific, but a
> 'common' term. I don't know how far back one would need to look to cite
> the
> first paper that defined overfishing. I think that it has been used in
> common language for quite some time; probably since the first commercial
> fisherman started to experience reduced yields. It was probably used in
> everyday language before ever being used in a scientific paper. It is
> important to keep in mind that overfishing is only one factor of many that
> can cause reduced yields in a fishery. Extrapolating from the theory that
> stocks are heavily influenced by year class strength (I think it is a fair
> assumption that the fish must first recruit to fishable sizes before
> overfishing can occur), and that year class strength is determined during
> early life stages (Hjort 1914, Sissenwine 1984, Kendall and Duker 1998),
> overfishing is probably not the primary factor controlling the health of a
> fishery. However, overfishing reproductive size classes combined with
> heavy
> predation by other organisms on younger size classes may have an influence
> on the overall health of the fishery. My thought would be that pollution
> or
> natural variation would likely have a greater influence on stocks of fish
> or
> scallops. The most insidious form of pollution that has probably been
> influencing the stocks of many great lakes fishes would be biological
> pollution or invasive species near the base of the food web like Dreissena
> sp., Bythotrephes sp., and Cercopagis pengoi. In any case I would say that
> simply throwing out the blanket statement that just because a stock is down
> overfishing must be the culprit is not a good idea. It may be part of the
> answer, however the fishery should be studied first to determine the cause
> of decline. It will be interesting to see what others think about this
> topic.
>
> Cheers!
>
> Justin C Johnston
> Biologist
> AMEC Earth and Environmental
> Professional Building III
> 11676 Perry Highway, suite 3101
> Wexford, PA 15090
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> -----Original Message-----
> From: Scientific forum on fish and fisheries
> [mailto:[log in to unmask] <mailto:[log in to unmask]> ] On
> Behalf Of Mike Flaherty
> Sent: Thursday, May 26, 2005 9:05 AM
> To: [log in to unmask]
> Subject: Is overfishing a scientific or legal term?
>
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> An article titled, "Scallops overfished for past 2 years, official says",
> appeared on the front page of today's New Bedford Standard Times.
>
> http://www.southcoasttoday.com/daily/05-05/05-26-05/a01lo102.htm
> <http://www.southcoasttoday.com/daily/05-05/05-26-05/a01lo102.htm>
>
> There was one excerpt in it which gave me pause...
>
> ===============================
> "Overfishing is a legal term, not a scientific term, and is therefore not
> an
> accurate way to evaluate the health of the scallop fishery, Dr. Kenchington
> said."
> ===============================
>
> As I roughly understand things, "overfishing" is defined as a point beyond
> which harvest/mortality levels exceed sustainable levels in a fishery. It
> is further my understanding that the thresholds for sustainability are
> arrived at scientifically. If this is true, then isn't overfishing truly a
> scientific term? More importantly, is it a reasonably accurate way to
> evaluate the health of a fishery?
>
> Thanks,
> Mike Flaherty
> Wareham, MA
>
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