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DOES OVERFISHING PRODUCE SMALLER FISH?

 

 

 

By Jon Christian Ryter

September 2, 2004

NewsWithViews.com

Addressing the EuroScience Forum in Stockholm on Friday, August 27, 2004, respected Sweden marine biologist Ulf Dieckmann of the Institute of Applied Systems Analysis warned that undesirable genetic changes are currently taking place in fish stocks around the world that is leading to smaller fish. The genetic changes, Dieckmann said, are caused by commercial exploitation from overfishing. Dieckmann insists that evolutionary pressure has resulted in a slower growth rate of fish that is producing, overall, smaller fish which in turn reproduce less successfully than their predecessors did under similar conditions. If Dieckmann is correct, his doom and gloom prediction will not bode well for the world fishing industry—and an increasing world population that consumes hundreds of tons of fresh fish daily.

"The evolutionary changes have been largely overlooked until now in the debate about the management of marine resources," he told the Forum. "The changes are a cause of grave concern because [it is a trend] that will be hard to reverse."

In his address, Dieckmann cited as research statistical evidence which had been accumulated from several overexploited cod fisheries as evidence that his theory was fact. The statistics, Dieckmann maintains, showed a decline in the size of mature cod that begins to occur after four "cod" generations. Dieckmann argued that the cod caught in the North Arctic Ocean which were an average of 95 centimeters in length in the 1940s are about 65 centimeters in length today.

While Dieckmann has advanced some interesting theories based on statistical observations in fish farms where cod are raised in a controlled environment, his findings do not necessarily translate to wild cod populations that are harvested in the world's oceans. There is no evidence that nonfarm-raised cod are undergoing a genetic change. What Dieckmann has likely stumbled on is an anomaly that science discovered about the mammal population decades ago.

One of Dieckmann's peers, David Conover of the University of New York at Stony Brook, argued that many "...fisheries scientists have been unwilling to accept that evolution is happening with a few fish generations." Conover has been doing his own experiments, again, in controlled environments, with Atlantic silversides (a fast-maturing cod). In the lab, Conover observed what Dieckmann observed—selective harvesting of the largest fish appeared to have a genetic impact on the fish population after four generations. The mature fish became physically smaller. Not only were the fish smaller, but they were also less fertile and they produced less meat.

When "fishing" (i.e., harvesting) stopped, Conover and Dieckmann both observed that there was no "selective pressure" to force change in the opposite direction, so the generational cod populations regained their previous physical characteristics only very slowly—much longer than four generations. Dieckmann observed that "...this is a Darwinian debt that will have to be paid by future generations."

The suggestion advanced by Dieckmann and seemingly confirmed by Conover is that in the darwinian world of "survival of the fittest," when the largest predators are removed, size no longer becomes a necessary ingredient for survival and, thus, the species devolve. In reality, animals (and this includes fish) in captivity live in a confined world in which they have limited mobility. It is this limited mobility and not some Darwinian clock ticking backwards that causes regressive growth. When the species cannot fully use its skeletal-muscular system, that skeletal-muscular system slowly retards. (In the orient, small feet on women is viewed as a sign of beauty. For that reason, for centuries, women bound the feet of their female children to retard the growth. Without room to grow, the feet stop growing. Under Dieckmann's logic, after several generations it would no longer be necessary to bind the feet to retard growth since theoretically, Darwin's rules apply equally to all species. However, if the bindery is not used on the child, or if the binds are removed before full mature growth is achieved, the foot continues to grow.)

In other words, the Darwinian theory of "survival of the fittest" is simply a matter of basic biology and has nothing to do with one species evolving into another. To a degree, we are all prisoners of our environment, and over generations the limitations of that environment will affect our muscular and possibly skeletal development either in a positive or negative manner. The same is true of cod in the farm environment.

Dieckmann, you will recall, also reflected that North Arctic cod have lost a third of their average mature size—from 95 cm to 65 cm—over er a period of sixty years. Since the EuroScience Forum of the European Union is one of those scientific forums which believes in global warming, they don't realize that over the past 100 years the world has been cooling, not heating up. Over the past 50 years there has been a global temperature departure of -.5 degrees—oor a half of one degree over the entire Earth. What that means is that while there are some land surface areas around the equator and sub-equator where the temperatures are hotter due to sunspot activity, the winters in the far northern regions are much, much colder, and thus the waters in our oceans are colder as well. (If you are an avid brook fisherman, you know that fish—in every cycle of life—which spawn in cold water streams are smaller than fish that spawn in warm water streams.) It stands to reason that ocean cod that live and breed in Arctic waters that are anywhere from one-or-two to five-or-six degrees colder than they were in 1940 might not grow to the same mature length as cod sixty to a hundred years ago. Further, since scientists do not have an accurate yardstick to measure the "average" size of wild cod in the frigid Arctic ocean, Dieckmann 's claims about North Arctic cod appear to be more speculation than fact.

When you are comparing apples to oranges, you should not be surprised when the conclusions come in the form of lemons. The evolutionary-minded scientists at the EuroScience Forum concluded that the solution to Dieckmann's dilemma was a simple one. They concluded that "evolutionary pressure" could be reversed by simply mandating both "minimum" and "maximum" lengths of fish harvested in fisheries, Thus, they theorized, if the largest fish are allowed to escape the butcher's block, they will reverse the trend and the captive cod will retain their size.

The Chicken Little darwinianism of the scientific community defies logic. Since the gradual reduction in size has nothing to do with there being no gargantuan fish in the fisheries, keeping first generation giants from being harvested will not maintain the size of the fish in ensuing generations since it is the habitat in which the fish exist and not the size of their parents that will determine the growth rate of future generations. If the marine biologists in charge of the cod fisheries want to increase the physical size of the "catch," then they need to double the size of their fisheries without doubling the fish populations.

© 2004 Jon C. Ryter - All Rights Reserved

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Jon Christian Ryter is the pseudonym of a former newspaper reporter with the Parkersburg, WV Sentinel. He authored a syndicated newspaper column, Answers From The Bible, from the mid-1970s until 1985. Answers From The Bible was read weekly in many suburban markets in the United States.

Today, Jon is an advertising executive with the Washington Times. His website, www.jonchristianryter.com has helped him establish a network of mid-to senior-level Washington insiders who now provide him with a steady stream of material for use both in his books and in the investigative reports that are found on his website. E-Mail: BAFFauthor@aol.com


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The suggestion advanced by Dieckmann and seemingly confirmed by Conover is that in the darwinian world of "survival of the fittest," when the largest predators are removed, size no longer becomes a necessary ingredient for survival and, thus, the species devolve.