Featured Research

from universities, journals, and other organizations

Ancient Fish Bones Reveal Impacts Of Global Warming Beneath The Sea

Date:
December 18, 2007
Source:
Census of Marine Life
Summary:
Through the study of archaeological material, tax accounts, church registers and account books of monasteries, an international group of fisheries ecologists and fisheries/maritime historians have drawn a picture of marine life in the northern European seas as it looked in the past.

Vertebrae of anchovy caught by the Stone Age people at Krabbesholm. Two connected vertebrae from a recent anchovy are shown for comparison. Scale 10 mm.
Credit: G. Brovad

Scientists studying ancient fish bones in Scandinavia have discovered that warm-water species like anchovies and black sea bream that once thrived in Danish waters during a prehistoric warm period are now returning. Some cold-water species, such as cod, were also abundant during this period, having benefited from a lower fishing effort.

Through the study of archaeological material, tax accounts, church registers and account books of monasteries, an international group of fisheries ecologists and fisheries/maritime historians have drawn a picture of marine life in the northern European seas (North Sea, Wadden Sea, Baltic Sea, and White Sea) as it looked in the past.

New historical documentation is increasingly becoming available. Its interpretation is providing a broader basis for understanding processes and mechanisms that lead to variations in marine populations and ecosystems. The studies in this special issue are important contributions to the establishment of new baselines for management of marine ecosystems including conservation strategies for overexploited living resources. They were conducted under the auspices (or as part of) the History of Marine Animal Populations, a project of the international collaboration, the Census of Marine Life.

108,000 fish bones from 7000 BC predict the future

Global and regional climate models predict that air and sea temperatures will rise by approximately 3C during the next 70--100 years. In order to understand some of the processes by which global warming might affect marine fish species near Denmark, researchers have investigated the fish fauna during one of the warmest prehistoric periods (the warm Atlantic period: ca. 7000--3900 BC).

A total of 108,000 fish bones were identified, and amongst them were bones of many species, for example, anchovy and black sea bream, which we usually consider to be typical of waters much farther south and warmer like the Bay of Biscay and the Mediterranean Sea. When temperatures cooled after the warm period ended, most of these species disappeared from the archaeological record, suggesting that local abundances declined. However, many of those same warm-water species have recently reappeared in waters around Denmark as temperatures have risen in the last 10--15 years. The archaeological information can be an indicator of which species may become common as climate change progresses and warms.

There were also thousands of cod bones present together with the warm-water species. That result was surprising because investigators knew that the increase in sea temperatures since the late 1980s to the early 1990s has reduced the survival of young cod in the North Sea. How can these two findings be reconciled? The researchers believe that the difference is due to the much lower fishing pressure in the archaeological period. The message from their work is that sustainable cod populations can be maintained in the North Sea even during the climate change expected in the 21st century, but the fish mortality needs to be lowered.

The climate influence the Gulf of Riga fisheries in during the 17th century

The exploited fish population in the Gulf of Riga was very different in the beginning of the 17th century from what is seen today. Archival evidence reveal that the timing of the fishing season, and species composition and, to an extent, the amounts of fish catches in the Gulf of Riga are strongly linked to climate dynamics.

The time-period 1675-1696 belongs to the coldest period of the Little Ice Age. During that time, fishing in the Gulf of Riga took place at more than 20 localities along the whole coast of the basin and was therefore an important livelihood at these times. Herring, flounder and eelpout (considered to be cold-tolerant species) formed the majority of the catch while the importance of species such as perch, pikeperch and various cyprinids, which prefer warm-water and are nowadays relatively widespread, was less than 1% of the catches.

Herring were in the coastal areas from the end of March to November. The highest catch was in today's terms taken during the warm season - June and July. This should be considered as a direct effect of severe winters, due to which the ice-cover melted relatively late and therefore, massive herring migration to spawning areas near the coast was shifted later in the season.

During the period studied, two sub-periods were identified: 1675-1683 and 1685-1696. Winters were more severe during the second period, and as a result, herring fishing seasons started later due to a shift in the timing of herring spawning in the summer months. As a result, the window where fish were available for fisheries was a shorter period of time. This led to substantially lower herring catches, and this is direct evidence of a climatic impact.

Why did the fishery collapse in the Limfjord in 1830?

The Limfjord in northern Denmark is a shallow sound which has supported commercial fisheries for centuries. In the beginning of the 19th century, the fishery declined by 90%, and fishermen went bankrupt when all the fish disappeared. What happened to all the fish?

By reconstruction of historical data series for herring, eel and whitefish the question has now been answered. We now know that both nature and humans played a significant role in the collapse.

In 1825 a winter storm broke the narrow Agger Tange isthmus, which used to separate the Limfjord from the North Sea. That led to an increase of salinity in the western part of the Limfjord. The eel population declined due to the salt water intrusion, and resulted in a 15-year long crisis for the eel fisheries before it had fully recovered. The whitefish did not survive the salinity obstacle and has never returned to the area.

The commercially most important fishery was for herring. The collapse of the herring fishery was most likely due to unsustainable fishing practices, such as fishing on top of spawning areas, eventually destroying the production rate of new young herring. Today the herring have returned to the area, but not nearly in the same numbers as they were in the early 19th century.

The study of the Limfjord fisheries provides an example of how historical ecology may help 'shift the baseline' by revealing the previous existence of a marine ecosystem very different from that which is known from contemporary ecological research.

These findings are presented in a special issue of Fisheries Research "History of Marine Animal Populations and their Exploitation in Northern Europe," 14 papers starting from ca. 7000 BC to present. The volume is edited by Henn Ojaveer and Brian R. MacKenzie.

Reference: Fisheries Research "History of Marine Animal Populations and their Exploitation in Northern Europe Volume 87, Issues 2-3, Pages 101-262 (November 2007)


Story Source:

The above story is based on materials provided by Census of Marine Life. Note: Materials may be edited for content and length.


Cite This Page:

Census of Marine Life. "Ancient Fish Bones Reveal Impacts Of Global Warming Beneath The Sea." ScienceDaily. ScienceDaily, 18 December 2007. <www.sciencedaily.com/releases/2007/12/071212201437.htm>.
Census of Marine Life. (2007, December 18). Ancient Fish Bones Reveal Impacts Of Global Warming Beneath The Sea. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2007/12/071212201437.htm
Census of Marine Life. "Ancient Fish Bones Reveal Impacts Of Global Warming Beneath The Sea." ScienceDaily. www.sciencedaily.com/releases/2007/12/071212201437.htm (accessed July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Dogs Appear To Become Jealous Of Owners' Attention

Dogs Appear To Become Jealous Of Owners' Attention

Newsy (July 23, 2014) A U.C. San Diego researcher says jealousy isn't just a human trait, and dogs aren't the best at sharing the attention of humans with other dogs. Video provided by Newsy
Powered by NewsLook.com
Professor Creates Site Revealing Where People's Cats Live

Professor Creates Site Revealing Where People's Cats Live

Newsy (July 23, 2014) ​It's called I Know Where Your Cat Lives, and you can keep hitting the "Random Cat" button to find more real cats all over the world. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins