Hexbyte Glen Cove To measure is to know: How long is a krill and how heavy is a polar cod?

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Length-weight relationships of the amphipod Themisto libellula caught during several Arctic expeditions on board German icebreaker Polarstern. These expedition took place in various periods of the year. (From the publication of Schaafsma et al. 2020). Information on the size of body parts is helpful. Credit: Wageningen University

A lot is measured and weighed in biological research. Researchers from Wageningen Marine Research and partners published measurements of more than 3000 individuals of 29 species of marine animals from the polar regions in the scientific journal Polar Biology. Relationships between the length and weight of animals, and between different body parts, were also analyzed in this study.

A few thousand sea creatures from the polar regions measured and weighed

In on an organism, size and weight of the examined animals are often determined. This way the measurements can be compared (for example the fat content per gram of fish is easier to compare than the content per individual fish if they are not of the same size) and possible differences between groups can be investigated (for example the diet of large and small fish of the same species). However, the measured sizes and weights of the animals themselves are often not published. During the collaborating ICEFLUX projects of Wageningen Marine Research and the German Alfred Wegener Institute, several thousand animals from both the Southern Ocean around Antarctica and the Arctic Ocean were measured and weighed for various purposes. All these measurements have now been collected and published.

Relationships between length and weight

Publishing lengths and weights is important because such data can be used for different purposes. In particular, the relationships between length and weight, and differences in these relationships between seasons, for example, can say something about the animal’s lifestyle or condition. In addition, other researchers can use these relationships to estimate the weight of their study object in cases where direct weighing is not possible, for example in hydro-acoustic research. For this reason, length-weight relationships of many of the measured Antarctic and Arctic species were investigated and compared. The results of this can also be found in the publication in Polar Biology.

Examples of measurements done on the Arctic amphipods Apherusa glacialis (A) and Themisto libellula (B) and the otoliths of the Antarctic fish species Electrona antarctica (C) and Bathylagus antarcticus (D). Credit: From the publication of Schaafsma et al. 2020

In addition to length and weight, measurements were done on body parts of various animals examined. Relationships between these parts can provide insight into, for example, differences in growth in animals of different ages. In addition, the relationships can be used to estimate the size of the entire animal based on the length of a particular body part. This is often used in dietary research. Information about the size of the prey of the studied animal in question provides insight into its position in the food web. However, due to digestion, eaten prey animals can often no longer be measured directly.



More information:
Fokje L. Schaafsma et al, Allometric relationships of ecologically important Antarctic and Arctic zooplankton and fish species, Polar Biology (2022). DOI: 10.1007/s00300-021-02984-4

Citation:
To measure is to know: How long is a krill and how heavy is a polar cod? (2022, February 4)
retrieved 7 February 2022
from https://phys.org/news/2022-02-krill-heavy-polar-cod.html

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part may be reproduced without the written permission. The content is provided for information purposes only.

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Hexbyte Glen Cove Satellites reveal Ethiopian elephants under threat, study shows

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African Savannah Elephant in the Babile Elephant Sanctuary. Credit: E. Greengrass.

Tens of thousands of illegal human settlements pose a real threat to the continued existence of an endangered elephant population, according to satellite analysis of the Babile Elephant Sanctuary in eastern Ethiopia by University of Oxford researchers and the Born Free Foundation.

Researchers from Oxford’s School of Geography and the Environment and Born Free found, in the 11 years to 2017, that the number of illegal houses in the sanctuary soared from 18,000 to more than 50,000. Of these, some 32,000 houses are in the area in which elephants range.

According to the researchers, unless the integrity of the sanctuary can be restored, and security and resolved, the elephants of the Babile Elephant Sanctuary will be lost within a short time. The sanctuary is home to Africa’s northeasternmost population of African Savannah Elephants—one of only six populations recognized in Ethiopia.

The country’s human population now stands at more than 110 million and there is a chronic shortage of land and a high demand for natural resources.

Previous studies have found that in Ethiopia, the integrity and effectiveness of many protected areas are being compromised by increasing human-related pressures, inadequate government support, and .

Emily Neil, a postgraduate researcher with Oxford’s School of Geography and the Environment, says, “The situation in the Babile Elephant Sanctuary is critical. There are now only around 250 elephants left. Without the rapid resolution of the many human issues putting pressure on the elephants it is difficult to foresee a future in which this population of survives.”

Human pressure on the elephant population comes from different directions. Between 2015 and 2019, the Born Free Foundation ran a field project in the sanctuary, mobilizing Ethiopian Wildlife Conservation Authority rangers to conduct daily monitoring of the elephant population. This helped researchers to understand better the elephant’s range and established that in addition to poaching, human-elephant conflict is a significant cause of elephant mortality.

Within a context of a burgeoning rural human dependent on scarce natural resources, chronic civil instability, poverty and , the team believes that the environmental, poverty, and security challenges in the must be addressed jointly.

The article will be published in Oryx, The International Journal of Conservation.



More information:
Illegal settlement in the Babile Elephant Sanctuary is threatening the resident elephant population, Oryx (2021). DOI: 10.1017/S0030605320001088

Journal information:
Oryx



Citation:
Satellites reveal Ethiopian elephants under threat, study shows (2021, November 29)
retrieved 30 November 2021
from https://phys.org/news/2021-11-satellites-reveal-ethiopian-elephants-threat.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

% %item_read_more_button%% Hexbyte Glen Cove Educational Blog Repost With Backlinks — #metaverse #vr #ar #wordpress