Posted: 19 Nov 2010 03:30 PM PST
By digging up and poring over old books and records of Mediterranean marine life, scientists have filled a 200-year gap in fish population data.
The data, generated from from naturalists' accounts and fish market records published between 1818 and 2000, shows the clear decline of fishes in the Adriatic Sea (east of Italy) and provides a crucial baseline comparison for the ongoing collapse of today's fisheries.
"The understanding of fish communities' changes over the past centuries has important implications for conservation policy and marine resource management," the authors wrote in a study published Nov. 17 in the journal PLoS ONE. Ignoring old records, they added, has led to a "historical myopia" in fishery science that underestimates the loss of natural resources.
It's no puzzle why. Prior to the mid-20th century, large-scale surveys of marine life didn't happen and, for that matter, there wasn't the modern-day level of concern about natural resources or the impetus to conserve them. Back then, there were only fish catch records and naturalists' qualitative descriptions of life beneath the waves.
To gather the information, an Italian team of ecologists and marine scientists scoured the libraries, museums and archives of six European cities. In total, the search turned up 36 books by naturalists and dozens of detailed catch records from fish markets spanning almost two centuries.
Using statistical methods to combine and integrate the descriptive naturalist records with fish catch tallies, the scientists partially reconstructed the rise and fall of 255 fish species in the region.
In 1800, sharks in the Adriatic Sea made up about 17 percent of the total fish population while bottom-dwellers (such as hake, flounder and anglers) made up 27 percent of all fish. By 1950, the populations had dipped to 11 percent and 20 percent, respectively. Meanwhile, the proportion of smaller and faster-breeding fish rose from about 12 percent of the population to more than 28 percent.
"Chondrichthyes are highly vulnerable to [human] disturbances, and especially to fishery," the authors wrote, thanks to their large size, slow growth and breeding behavior. As fishermen nabbed such large fish, the smaller and more nimble species thrived because they weren't being eaten as readily (by sharks or humans).
Fish population declines due to human activity since the mid-20th century are established and substantial, with encroachment by non-native fish species, habitat alteration and pollution all contributing to shrinking and more fragile populations of fish. While it's not entirely clear how large of a role fishing pressure played prior to 1950, the authors say their "results indicate that pre-industrial fisheries had already had significant impacts" on fish populations in the Adriatic region.
The study can't offer a worldwide assessment of fishery health in the past. But turning old records of marine life into useful data sets may prove promising for assessing past fish populations in other regions.
"Naturalists' eyewitness accounts of fish species, which have long been disregarded by fishery biologists as being 'anecdotal' and not 'science,' proved to be a useful tool for extending the analysis into the past, well before the onset of field-based monitoring programs," the authors wrote.
Image: A naturalist's catalogue of species used to reconstruct past fish populations. PLoS ONE/Cori C.I.
Citation: "Coding Early Naturalists' Accounts into Long-Term Fish Community Changes in the Adriatic Sea (1800–2000)." By Tomaso Fortibuoni, Simone Libralato, Saša Raicevich, Otello Giovanardi2 and Cosimo Solidoro. Nov. 17 PLoS ONE.
Posted: 19 Nov 2010 09:40 AM PST
Now you can hear a marine-inspired melody from before the time of the Little Mermaid's hot crustacean band. Acoustic scientists put their lips to ancient conch shells to figure out how humans used these trumpets 3,000 years ago. The well-preserved, ornately decorated shells found at a pre-Inca religious site in Peru offered researchers a rare opportunity to jam on primeval instruments.
The music, powerfully haunting and droning, could have been used in religious ceremonies, the scientists say. The team reported their analysis November 17 at the Second Pan-American/Iberian Meeting on Acoustics in Cancun, Mexico.
"You can really feel it in your chest," says Jonathan Abel, an acoustician at Stanford University's Center for Computer Research in Music and Acoustics. "It has a rough texture like a tonal animal roar."
" width="200" height="20"> " />Archaeologists had unearthed 20 complete Strombus galeatus marine shell trumpets in 2001 at Chavín de Huántar, an ancient ceremonial center in the Andes. Polished, painted and etched with symbols, the shells had well-formed mouthpieces and distinct V-shaped cuts. The cuts may have been used as a rest for the player's thumb, says study coauthor Perry Cook, a computer scientist at Princeton University and avid shell musician, or to allow the player to see over the instrument while walking.
A group of conch-shell instruments made by a pre-Inca civilization sound similar to a kid learning to play the trumpet.
" width="200" height="20"> " />To record the tunes and understand the acoustic context in which the instruments, called pututus, were played, the researchers traveled to Chavín.
A musician plays the fundamental frequency and the first overtone of a 3,000-year-old shell trumpet unearthed in Peru.
As an expert shell musician blew into the horn, researchers recorded the sound's path via four tiny microphones placed inside the player's mouth, the shell's mouthpiece, the shell's main body and at the shell's large opening, or bell. Similar to a bugle, the instruments only sound one or two tones, but like a French horn, the pitch changes when the player plunges his hand into the bell.
The team used signal-processing software to characterize the acoustic properties of each trumpet. Following the sound's path made it possible to reconstruct the ancient shell's interior, a feat that normally involves sawing the shell apart or zapping it with X-rays.
The researchers also wanted to know how the site's ceremonial chamber, a stone labyrinth with sharply twisting corridors and ventilation shafts, changed the trumpet's sound. To find out, the team arranged six microphones around the musician and reconstructed the sound patterns on a computer.
If the trumpets were played inside the stone chamber in which they were found, the drone would have sounded like it was coming from several different directions at once. In the dimly lit religious center, that could have created a sense of confusion, Abel says.
"Were they used to scare people while they were there?" asks Abel. "There are still a lot of things left open."
Turns out, such questions about how sounds affect people and their behavior, an area called psychoacoustics, can be tested. It's a field of active research, and not just for ancient civilizations: Another group at Stanford is now studying how a room's acoustics affects human behavior. In one recent experiment, researchers separated test subjects into different acoustic environments to do a simple task — ladling water from one bucket to another in a dimly lit room.
"What your ear can actually hear plays into how you would behave, or the psychological experience in the situation," says Abel.
Images: 1) Ancient civilizations in Peru might have played this 3,000-year-old shell trumpet as part of a religious ceremony. New research has reconstructed what the instrument would have sounded like inside the religious site's ceremonial chamber. Jyri Huopaniemi 2) Computer scientist and musician Perry Cook plays a tune on a 3,000-year-old conch-shell instrument discovered in Peru. José Luis Cruzado, Chavin de Huantar Investigation and Conservation Project
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