First published:
Creation
30(2):48–49
March 2008

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Smaller fish to fry

by David Catchpoole

Cooking a freshly caught fish on an open fire at the seaside or riverbank was something many weekend anglers once took for granted. But they’re finding it harder and harder to catch a decent-sized fish for the frying pan. Sometimes even getting one fish of legal size is considered an achievement!

Many have simply blamed ‘overfishing’.¹ But there is now ‘compelling evidence’ that there’s another factor at work, too—namely, that populations of fish such as plaice and cod are undergoing genetic change.² They’re maturing at progressively younger ages, and dramatically smaller sizes.

For example, in the 1940s, commercially-exploited cod in the northeast Arctic had an average size of 95 cm (3 ft, 1½ in), but today the average size is only 65 cm (2 ft, 1½ in).³ Meanwhile, in several populations of cod the age of sexual maturity has diminished by one-quarter. For populations of plaice the time to reach sexual maturity has declined by nearly one-third. In turn, the vigour of fish populations is affected, as small fish produce far fewer eggs than large fish. (A 50-cm-long Baccacio rockfish will produce nearly 200,000 larvae, whereas an individual of that species which is 80 cm long can produce ten times that number—i.e. nearly two million larvae.) Thus fishermen not only have to contend with smaller fish to fry, but fewer as well.

It’s NOT evolution

Perhaps not surprisingly, the genetic shifts undergirding these changes have been described in both the scientific literature and the popular media as ‘evolution’.⁴ However, evolution—the supposedly information-gaining process by which fish are reputed to have evolved into fishermen over millions of years—is nowhere in evidence here.

Rather, fish populations have lost genetic information, not gained it, and this loss is the result of human-imposed selection pressure.

For some years now, many fisheries management authorities around the world have instituted legal minimum size requirements for various fish species. Thus anglers must return ‘undersized’ fish to the water unharmed. Similarly, commercial fishermen use large-meshed nets to spare the smaller fish—with the aim of ensuring the long-term viability of the fishery.

However, the fish that are genetically predisposed to mature at larger sizes are the ones most likely to be caught before they can reproduce. Thus there has been a strong selection pressure favouring scrawny fish that never reach the minimum legal size. Hence the genes for late-maturing larger-sized fish have been progressively lost from many fish populations, leaving early-maturing smaller-sized ones to dominate the gene pool. (So, ironically, by catching only the biggest fish and letting the others go, humans have unintentionally selected against that which they desire most!⁵)

Note that this is not evolution because the selection pressure—which is essentially an artificially-imposed version of ‘natural selection’—simply favours certain genes over others; it cannot generate any new genetic information. Neither such ‘artificial’ nor ‘natural’ selection can turn plaice into people; it can only operate on (i.e. cull out) genetic information that already exists.⁶

Speedy selection

Fisheries scientists David Conover and Stephan Munch, of the State University of New York, observed that size-specific culling of Atlantic silversides rapidly changes the genetic makeup of the population.⁷ After just four generations, fish populations from which the largest 90% of silversides were removed before breeding averaged just half the size of fish in populations from which the smallest 90% had been culled. In other words, removing big fish soon results in a population of little fish (and vice versa).

This is not evolution, as the genes for big or little fish were already present in the population beforehand.⁸ Note that the limits to how big or little the fish can be in the final population are determined by the amount of pre-existing genetic variety. Conover and Munch wrote: ‘Management tools that preserve natural genetic variation [i.e. pre-existing variety] are necessary for long-term sustainable yield.’ In other words, we need to leave at least some of the big fish in the water, so that their desirable genes (from a human perspective) remain in the fish population.

Despite this anti-evolutionary insight, their research paper refers to fish demonstrating ‘evolutionary effects’ and having ‘evolved rapidly’. That last claim took many of their fellow evolutionists by surprise. David Conover reported: ‘Even some fisheries’ scientists have been unwilling to accept that evolution is happening within a few fish generations.’

Given how evolutionists view the world, their surprise is understandable. For example, one writer in New Scientist reported that these genetic changes were ‘not the familiar glacier-slow process found in textbooks, which takes millennia to work its wonders, but a burbling freshet of evolutionary change that can occur in a matter of years or decades’.⁹ Another commentator wrote similarly of these rapid ‘evolutionary changes’, saying, ‘this is not the stuff of geologic time’.³

It is the evolutionists’ standard millions-of-years interpretation of the ‘fossil record’,¹⁰ with its connotations of ‘slow-and-gradual’ processes, that leaves many of them surprised when rapid genetic shifts are observed to be occurring today.¹¹ But, as we’ve seen, such genetic shifts are simply a favouring of genes that were already present in the population, by culling others.

In fact, it seems that in at least one fish population, the genes for large size have gone forever. After the ‘crash’ of the cod fishery on the Grand Banks, off south-east Newfoundland, the Canadian government closed the fishery in 1992, in order to let it recover.¹² But in the 15 years since then, the cod population there has failed to ‘bounce back’.⁹

So that’s bad news for evolutionary theory. It shows that once the genes for large size have been totally lost from the population, little cod cannot even become big cod—let alone cosmologists.

References and notes

1. Cookson, C., Over-fishing produces a Darwinian revenge as only smaller cod survive, Financial Times—FT.com, 28 August 2007, <search.ft.com/nonFtArticle?id=040828001052>, 1 November 2007. Return to text.
2. Hutchings, J.A., The cod that got away, Nature 428(6986):899–900, 29 April 2004. Return to text.
3. Loder, N., Point of no return, Conservation magazine 6(3):28–34, July–September 2005. Return to text.
4. Simpson, S., Survival of the smallest—returning the big ones to keep fisheries healthy, Scientific American 294(4):17, April 2006. Return to text.
5. Similar selection pressures from harvesting of wild game species could also explain their diminished size today compared to historical descriptions and fossil counterparts. Return to text.
6. See also: Wieland, C., Muddy waters—Clarifying the confusion about natural selection, Creation 23(3):26–29, 2001, <creation.com/muddy>. Return to text.
7. Conover, D.O. and Munch, S.B., Sustaining fisheries yields over evolutionary time scales, Science 297(5578):94–96, 5 July 2002. Return to text.
8. Any mutation disabling the gene for growth hormone would also be selected for. Return to text.
9. Holmes, B., In the blink of an eye, New Scientist 187(2507):28–31, 9 July 2005. Return to text.
10. Correctly interpreted, fossil-bearing layers date from the Flood only about 4,500 years ago. Return to text.
11. See: Catchpoole, D. and Wieland, C., Speedy species surprise, Creation 23(2):13–15, 2001, <creation.com/speedy>. Return to text.
12. Olsen, E.M., et al., Maturation trends indicative of rapid evolution preceded the collapse of northern cod, Nature 428(6986):932–935, 29 April 2004. Return to text.