Archaeological study shows human activity may have boosted shellfish size

August 31, 2010
Researchers found that the average size of the humped conch increased in conjunction with a growing human population. Credit: Dr. Scott Fitzpatrick, North Carolina State University

In a counter-intuitive finding, new research from North Carolina State University shows that a species of shellfish widely consumed in the Pacific over the past 3,000 years has actually increased in size, despite - and possibly because of - increased human activity in the area.

"What we've found indicates that does not necessarily mean that there is going to be a negative impact on a species - even a species that people relied on as a major ," says Dr. Scott Fitzpatrick, associate professor of sociology and at NC State and co-author of the study. "The trends we see in the in regard to animal remains are not always what one would expect."

At issue is the humped conch, Strombus gibberulus, a small that has been a food source in the Pacific islands for thousands of years. The researchers dated and measured more than 1,400 humped conch shells found at an archaeological site on the island of Palau in the western Pacific. They expected the size of the conchs to decrease over time, based on the conventional wisdom that an expanding human population would result in the conchs being harvested before they could achieve their maximum size.

Instead, the researchers were surprised to find that the average size of the conchs actually increased in conjunction with a growing . Specifically, the length of the average conch increased by approximately 1.5 millimeters (mm) over the past 3,000 years. That may not sound like much, but it is significant when you consider the conchs are only around 30 mm long - which means the conchs are now almost 5 percent larger than they used to be.

Fitzpatrick believes the size increase is likely related to an increase in nutrients in the conch's waters, stemming from increased agriculture and other human activities.

"In the big picture," Fitzpatrick says, "this study tells us to focus on the physical evidence and beware of conventional wisdom. It also tells us that using a large number of samples is important. Previous studies had shown a decline in conch size at Pacific archaeological sites - but they used smaller sample sizes. Maybe that is a factor in their findings."

Explore further: Scientists are first to 'unlock' the mystery of creating cultured pearls from the queen conch

More information: A paper describing the study, "Evidence for size increase in an exploited mollusk: humped conch (Strombus gibberulus) at Chelechol ra Orrak, Palau from ca. 3000-0 BP," will be published in a forthcoming issue of the Journal of Archaeological Science.

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5 / 5 (1) Aug 31, 2010
this article - well to be honest the scientists make the assumption that because an species becomes larger or is recieving more nutrients that this is a totally beneficial gain.

I think that logic has bounds. Such as recieveing more nutrients and variety helps humans grow taller. This is considered true at the moment in science -- but ease of access to food with lower nutritional value and over consuption has created the bigger issue of diabetes. Which is better tall and diabetic or shorter and healthy. I am using an extreme so that whatever is in the middle can be percieved.

The most probably cause is that we are eating one of its predators like squid or octopus -- i do enjoy calimari
not rated yet Aug 31, 2010
You can't conclude any of these answers just by measuring the Conch. Any of these explanations may be true, but it might also be because the conch is just _getting bigger_. Why does human activity have to affect it at all?

You can still get 15 lb lobsters even though we overfish for them.
1 / 5 (1) Aug 31, 2010
Didn't Dr. Fitzpatrick get the memo? Humans are BAD! Or maybe he's taking a cue from current official economic analysis and taking the measured growth the average conch as hard evidence of its eventual shrinkage.

Either way, he'd better get his mind right if he wants the Stimulus to keep paying his bills.

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