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Subject: Re: [Fishfolk] : Scripps Oceanography and Sugihara
From: jonas bjarnason <[log in to unmask]>
Reply-To:Scientific forum on fish and fisheries <[log in to unmask]>
Date:Fri, 18 Apr 2008 19:38:59 -0000

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This is a duplicate letter, or a second letter, with different letters than
the previous one as I have been receiving a not understandable letter from
the FISH-list moderators.  I don’t know what was wrong with the first one.


Bill, thanks for your post.  And you refer professor Sugihara and that is
important; I did so myself about a year ago, if I remember correctly.  He is
observing some properties of fish, which others have been describing as
evolutionary changes.  So, what Sugihara is saying is not intrinsically new,
but he uses new terminology, methods and he is, or was, independent and
unbiased ,but an extremely intelligent capacity with all the gear and money
he needed to have fresh look at a multitude of problematics and a world
almost stiff or cemented by wrestlings of biological, statistical,
mathematical, oceanographic, ichtological, genetical or whatever
“Besserwissers” and bigmouths. And coming forward with a picture looking a
bit odd at first glance, but intrinsically containing all the major factor
of the science of evolutionary changes of fish stocks.  If you can look away
from the big fish he is talking about, the swordfishes and so on, and
recreational hook fishing, you ought to be able to see the main picture
about the hopeless idea of single fish management and current fisheries
management as a whole.


Cheers, Jonas


-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] On Behalf
Of William Silvert
Sent: 17. apríl 2008 09:53
Subject: [Fishfolk] UCSD: Scripps Oceanography News Release: Fishing
ThrowsTargeted Species Off Balance


Given the relative quiet on these lists, I feel that a fairly long posting 

will not overload your mailboxes. A colleague sent me this message and while

the view that we should conserve the older fish rather than catching them 

and just letting the younger fish escape has been posted frequently, this is

one of the more interesting arguments that I have seen. It does not address 

the points of larval quality, but introduces the concept of stability 

against environmental fluctuations. It will be interesting to see how these 

ideas affect fisheries management -- not only whether the concept is 

accepted, but how it will be implemented. Mesh size regulations are designed

to let the smaller fish escape, but how do we let the large firsh escape?


Bill Silvert


----- Original Message ----- 

From: Scripps News <[log in to unmask]>

Date: April 16, 2008 12:15:38 PM CDT (CA)

Subject: [Ucomm_sio-l] UCSD: Scripps Oceanography News Release: Fishing 

Throws Targeted Species Off Balance, Scripps Study Shows


The following news release and any accompanying images can be found at:


Scripps Contacts: Mario Aguilera or Annie Reisewitz

858-534-3624; [log in to unmask]


Fishing Throws Targeted Species Off Balance, Scripps Study Shows


Researchers say fishing disrupts age structure, making regulation difficult


Scripps Institution of Oceanography/UC San Diego


Fishing activities can provoke volatile fluctuations in the populations they

target, but it’s not often clear why. A new study published in the journal

Nature by scientists at Scripps Institution of Oceanography at UC San Diego

and colleagues has identified the general underlying mechanism.


Research led at Scripps with a distinguished team of government and

international experts (including two chief scientific advisors to the United

Kingdom) demonstrates that fishing can throw targeted fish populations off

kilter. Fishing can alter the “age pyramid” by lopping off the few large,

older fish that make up the top of the pyramid, leaving a broad base of

faster-growing small younglings. The team found that this rapidly growing

and transitory base is dynamically unstable—a finding having profound

implications for the ecosystem and the fishing industries built upon it.


“The data show that fished species appear to be significantly more nonlinear

and less stable than unfished species,” said Professor George Sugihara of

Scripps. “We think the mechanism involves systematic alteration of the

demographic parameters—and especially increases in growth rates that magnify

destabilization in many ways—which can happen as fishing truncates the age



Imagine a container of water with a 500-pound fish. With food, it grows a

little bigger. Without food it gets a bit smaller. Imagine the same

container with 500 one-pound fish. They eat, reproduce and the resulting

thousands of fish boom, quickly outstripping the resources and the

population crashes. These many smaller fish—with the same initial “biomass”

as the larger fish—can’t average out the environmental fluctuations, and in

fact amplify them through higher turnover rates that promote boom and bust



The study that included academic and government scientists from Alaska, Asia

and Great Britain is based on data from the California Cooperative Oceanic

Fisheries Investigations (CalCOFI), a program based at Scripps that has

monitored fish and oceanographic activities of the California Current for

more than 50 years. To arrive at their results, the researchers compared the

CalCOFI records of larvae, a key indicator of adult populations, of both

fished and non-fished species in the California Current.


Fishing typically extracts the older, larger members of a targeted species

and fishing regulations often impose minimum size limits to protect the

smaller, younger fishes.


“That type of regulation, which we see in many sport fisheries, is exactly

wrong,” said Sugihara. “It’s not the young ones that should be thrown back,

but the larger, older fish that should be spared. Not only do the older fish

provide stability and capacitance to the population, they provide more and

better quality offspring.”


Thus the danger, according to Sugihara, is that current policies that manage

according to current biomass targets (without significant forecast skill)

while ignoring fish size pose risks that can further destabilize the

population. This instability can in principle propagate systemically to the

whole ecosystem, much like a stock market crash or a domino effect, and

magnify risk for the fishing industry itself as well as those of

ecologically related fisheries.


This is especially true when trying to rebuild fish stocks, Sugihara says.


“This may be the most important implication of this work, as we attempt to

rehabilitate fisheries,” said Sugihara. “Regulations based solely on biomass

harvest targets are incomplete. They must also account for age-size

structure in the populations,” he said. “Current policies and industry

pressures that encourage lifting bans on fishing when biomass is

rehabilitated—but where maximum age and size are not—contain risk.”


This is currently the case with Atlantic swordfish, for which industry

pressures to resume fishing are based on the restoration of historic biomass

levels, even though the swordfish are clearly undersized.


“In the extreme case, the danger of such unstable dynamics for certain

populations for management is that harvest targets may lag the population,

potentially making things worse,” said Sugihara. “A high harvest target may

be set after an especially abundant period when the population may be poised

to decline on it’s own. Likewise future abundant periods may represent

missed opportunities, despite current low abundances.  As senior officials

of the Canadian Department of Fisheries and Oceans have said, ‘we are often

a year behind in our stock projections.’”


Sugihara cautioned that nonlinearity is not unique to fished species.

Nonequilibrium overshooting and undershooting occurs in unexploited stocks,

but to a lower extent. Therefore, classical single-species population models

that require equilibrium are unlikely to be very successful in stock

forecasts, except perhaps in the very short term.


"Other methods that do not rely on these assumptions may be more promising,"

suggests Christian Anderson, paper co-author.


In addition to Sugihara and Anderson, the study included Scripps

Oceanography alumnus Chih-hao Hsieh (now a professor at National Taiwan

University); Stuart Sandin of Scripps; Roger Hewitt of the National Marine

Fisheries Service, Southwest Fisheries Science Center; Anne Hollowed of the

National Marine Fisheries Service, Alaska Fisheries Science Center; Sir John

Beddington of Imperial College London (current Chief Science Advisor to the

United Kingdom) and Lord Robert May of Oxford (a former Chief Scientific

Advisor to the UK).


The research was supported by NOAA Fisheries and the Environment program,

The MacQuown Chair of Natural History, The Deutsche Bank – Jameson

Complexity Studies Fund, the Sugihara Family Trust and the Kyoto University

grant for Biodiversity Research of the 21st Century. 



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