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Within Loch Ness

How Big Could a Loch Ness Eel Get?

Catch data makes ordinary large eels plausible in Loch Ness, while monster-sized eels become statistically hard to defend.

On this page

  • What eel catch data can estimate
  • The difference between large and monster sized
  • Why probability changes the claim
Preview for How Big Could a Loch Ness Eel Get?

Introduction

The giant eel hypothesis gained attention after the 2019 environmental DNA (eDNA) survey of Loch Ness found eel DNA throughout the loch while failing to find evidence for large reptiles, sharks, sturgeon or catfish. That result left European eels as one of the few ordinary animals that could not be ruled out as an explanation for at least some Nessie reports. However, the debate quickly shifted from biology to statistics. The key question became not whether eels live in Loch Ness—they clearly do—but whether they can plausibly reach the sizes required by monster sightings. Once researchers examined eel catch data and modelled how body sizes are distributed, giant eels stopped being merely a biological possibility and became a problem of probability.[University of Otago]otago.ac.nzfirst edna study of loch ness points to something fishyUniversity of OtagoFirst eDNA Study Of Loch Ness Points To Something FishySep 5, 2019 — University of Otago geneticist, Professor Neil Ge…Eel Odds illustration 1

What Eel Catch Data Can Estimate

Environmental DNA can show that eels are present, but it cannot reveal how large those eels are. To address the size question, researchers turned to measurements from thousands of European eels collected in Loch Ness and other European waters. By analysing real length distributions, they could estimate how likely unusually large individuals would be.[Science Focus]sciencefocus.comloch ness monster dna study reveals plausible explanation for sightingsScience FocusLoch Ness Monster DNA study reveals 'plausible'…Sep 5, 2019 — Professor Gemmell said: “There. Eels are very plentiful in…

A 2023 study by Floe Foxon used eel-length datasets containing more than 20,000 individuals and applied statistical models commonly used to estimate rare extreme values. Rather than asking whether a giant eel is theoretically possible, the study asked how often one should appear if eel growth follows observed patterns.[JMIRx Bio]xbio.jmir.orgx BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…

The results were revealing:<div class="content-enhancement content-enhancement--metric" markdown="1">

  • An eel around 1 metre long appears rare but not impossible.
  • Based on estimated fish stocks in Loch Ness, an eel of that size could plausibly exist somewhere in the loch.
  • The probability falls dramatically as length increases beyond normal biological limits.[JMIRx Bio]xbio.jmir.orgx BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…</div>

This approach transformed the discussion. Instead of debating anecdotes, researchers could compare reported monster sizes with the sizes expected from actual eel populations.

DNA Evidence Reveals The Loch Ness Monster Could Be A Giant Eel | Loch Ness The New Evidence

Channel: Discovery UK

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The Difference Between Large and Monster-Sized

One reason the eel theory initially sounded attractive is that European eels already have an elongated body shape. At a distance, especially in rough water, a large eel surfacing briefly could potentially be misjudged as something much bigger. The statistical analysis does not reject that possibility. In fact, it suggests that unusually large eels may account for some reports of relatively small unidentified animals.[JMIRx Bio]xbio.jmir.orgx BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…

The problem emerges when “large” becomes “monster-sized”.

Foxon’s analysis estimated that a 1-metre eel would be uncommon but plausible, with odds of roughly one in 50,000. Given the estimated number of fish in the loch, that still leaves room for occasional large specimens.[JMIRx Bio]xbio.jmir.orgx BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…

However, many famous Nessie descriptions involve animals several metres long. Some reports describe creatures around 6 metres or more. When researchers extrapolated from observed eel growth patterns, the probability of encountering a European eel of that magnitude collapsed to effectively zero. The study concluded that while large eels could explain some smaller sightings, they do not provide a credible explanation for reports of truly gigantic animals.[ResearchGate+2ResearchGate]researchgate.netResearchGate(PDF) The Loch Ness Monster: If It's Real, Could It Be an Eel?Results The chances of finding a large eel in Loch Ness are aro…

The distinction is crucial. A one-metre eel and a six-metre eel are not separated by a simple factor of six. In statistical terms, they belong to completely different regions of the probability curve. One lies at the extreme end of a known distribution; the other lies beyond what the distribution reasonably predicts.[JMIRx Bio]xbio.jmir.orgx BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…Eel Odds illustration 2

Why Probability Changes the Claim

Before statistical modelling entered the discussion, the giant eel theory often relied on a simple observation: eels are present in Loch Ness, and some animals occasionally grow larger than average. That argument leaves open almost any size.

Neil Gemmell - Environmental DNA for Biodiversity, Biosecurity, Global Health and Monster Hunting

Channel: Genomics Aotearoa

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The Eel Theory After the Numbers

The most evidence-based version of the eel hypothesis today is more modest than early headlines suggested. It does not argue that Nessie is a gigantic eel tens of feet long. Instead, it proposes that some sightings could involve unusually large but still biologically realistic eels, perhaps amplified by distance, poor visibility, wave effects or errors in judging scale.[Phys.org]phys.org2023 07 unraveling loch ness monster eelUnraveling the Loch Ness Monster's eel connection24 Jul 2023 — The study found that giant eels could not account for sightings of larger…

That leaves the theory in an unusual position within Loch Ness debates. The DNA evidence made eels one of the few conventional animals still standing as a candidate explanation. Yet the statistical evidence simultaneously places strict limits on how far that explanation can go. Large eels remain plausible. Monster-sized eels do not.[University of Otago+2Science Focus]otago.ac.nzfirst edna study of loch ness points to something fishyUniversity of OtagoFirst eDNA Study Of Loch Ness Points To Something FishySep 5, 2019 — University of Otago geneticist, Professor Neil Ge…

For cryptozoology, this is a useful lesson in how modern evidence changes old mysteries. The question is no longer simply whether a creature could exist. Increasingly, it is whether the numbers say it should.[JMIRx Bio]xbio.jmir.orgx BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…Eel Odds illustration 3

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Endnotes

1. Source: phys.org
Title: 2023 07 unraveling loch ness monster eel
Link:https://phys.org/news/2023-07-unraveling-loch-ness-monster-eel.html

<summary>Source snippet</summary><p>Unraveling the Loch Ness Monster's eel connection24 Jul 2023 — The study found that giant eels could not account for sightings of larger…</p>

2. Source: researchgate.net
Link:https://www.researchgate.net/publication/390620130_The_Loch_Ness_Monster_If_It%27s_Real_Could_It_Be_an_Eel

<summary>Source snippet</summary><p>ResearchGate(PDF) The Loch Ness Monster: If It's Real, Could It Be an Eel?Results The chances of finding a large eel in Loch Ness are aro…</p>

3. Source: researchgate.net
Title: Research Gate The Loch Ness Monster: If It’s Real, Could It Be an Eel?
Link:https://www.researchgate.net/publication/372563494_The_Loch_Ness_Monster_If_It%27s_Real_Could_It_Be_an_Eel_Preprint

<summary>Source snippet</summary><p>RESULTS The chances of finding a large eel in Loch Ness are around 1 in 50,000 for a 1-meter specimen, which is reasonable given the loch…</p>

4. Source: otago.ac.nz
Title: first edna study of loch ness points to something fishy
Link:https://www.otago.ac.nz/news/newsroom/first-edna-study-of-loch-ness-points-to-something-fishy

<summary>Source snippet</summary><p>University of OtagoFirst eDNA Study Of Loch Ness Points To Something FishySep 5, 2019 — University of Otago geneticist, Professor Neil Ge…</p>

5. Source: sciencefocus.com
Title: loch ness monster dna study reveals plausible explanation for sightings
Link:https://www.sciencefocus.com/news/loch-ness-monster-dna-study-reveals-plausible-explanation-for-sightings

<summary>Source snippet</summary><p>Science FocusLoch Ness Monster DNA study reveals 'plausible'…Sep 5, 2019 — Professor Gemmell said: “There. Eels are very plentiful in…</p>

6. Source: xbio.jmir.org
Link:https://xbio.jmir.org/2023/1/e49063

<summary>Source snippet</summary><p>x BioThe Loch Ness Monster: If It's Real, Could It Be an Eel?by F Foxon · 2023 · Cited by 6 — While the chance of finding a large eel…</p>

7. Source: youtube.com
Title: Neil Gemmell
Link:https://www.youtube.com/watch?v=E4y62Pa4b28

<summary>Source snippet</summary><p>Environmental DNA for Biodiversity…Neil Gemmell will be talking about Environmental DNA for biodiversity, biosecurity, global health a…</p>

8. Source: sciencefocus.com
Title: loch ness monster how edna helps us discover what lurks beneath
Link:https://www.sciencefocus.com/nature/loch-ness-monster-how-edna-helps-us-discover-what-lurks-beneath

<summary>Source snippet</summary><p>Loch Ness Monster: how eDNA helps us discover what…Sep 5, 2019 — In May 2018, geneticist Prof Neil Gemmell of the University of Otago…</p>
Published: May 2018

Additional References

9. Source: illumina.com
Link:https://www.illumina.com/content/illumina-marketing/amr/en_US/company/news-center/feature-articles/loch-ness-edna.html

<summary>Source snippet</summary><p>If there is a monster in Loch Ness, this geneticist will find it10 Jan 2025 — If there is a monster in Loch Ness, this geneticist will fi…</p>

10. Source: theness.com
Link:https://theness.com/neurologicablog/giant-eels-loch-ness-and-probability/

<summary>Source snippet</summary><p>The NESSGiant Eels, Loch Ness, and Probability - NeuroLogica Blog25 Jul 2023 — There is no evidence of anything that can be a giant reptile…</p>

11. Source: theguardian.com
Title: loch ness monster could be a giant eel say scientists
Link:https://www.theguardian.com/science/2019/sep/05/loch-ness-monster-could-be-a-giant-eel-say-scientists

<summary>Source snippet</summary><p>Loch Ness monster could be a giant eel, say scientists5 Sept 2019 — Loch Ness monster could be a giant eel, say scientists · The Loch Nes…</p>

12. Source: oldsaltblog.com
Title: using edna to search for nessie in scotland and angel sharks off corsica
Link:https://oldsaltblog.com/using-edna-to-search-for-nessie-in-scotland-and-angel-sharks-off-corsica/

<summary>Source snippet</summary><p>Using eDNA to Search for Nessie in Scotland and Angel…2 Oct 2023 — Geneticist Neil Gemmell of Otago University, who led the survey, s…</p>

13. Source: reddit.com
Link:https://www.reddit.com/r/Cryptozoology/comments/1qomjhg/the_giant_eel_theory_is_getting_stronger_thanks/

<summary>Source snippet</summary><p>length and many eyewitnesses describe a creature that can be anywhere…</p>

14. Source: youtube.com
Title: DNA Evidence Reveals The Loch Ness Monster Could Be A Giant Eel
Link:https://www.youtube.com/watch?v=6MiiwSuhk8k

<summary>Source snippet</summary><p>The Loch Ness DNA Test Results That Terrified Scientists! - YouTube The Loch Ness DNA Test Results That Terrified Scientists! - YouTube…</p>

15. Source: sci.news
Title: loch ness monster giant european eel 12122
Link:https://www.sci.news/biology/loch-ness-monster-giant-european-eel-12122.html

<summary>Source snippet</summary><p>Breaking Science NewsLoch Ness Monster: If It's Real, Could It Be Giant European…24 Jul 2023 — The chances of encountering a 1-m-long…</p>

16. Source: facebook.com
Link:https://www.facebook.com/groups/1002571683091379/posts/8050728421608968/

<summary>Source snippet</summary><p>in Loch Ness. I never said anything bigger than…Read more…</p>

17. Source: smartwatermagazine.com
Title: could loch ness monster be a giant eel
Link:https://smartwatermagazine.com/news/university-otago/could-loch-ness-monster-be-a-giant-eel

<summary>Source snippet</summary><p>Could the Loch Ness monster be a giant eel?Sep 9, 2019 — The remaining theory that Professor Gemmell cannot refute based on the environme…</p>

18. Source: divernet.com
Title: rise fall of the loch ness monster eel
Link:https://divernet.com/scuba-news/marine-biology/rise-fall-of-the-loch-ness-monster-eel/

<summary>Source snippet</summary><p>Rise & fall of the Loch Ness Monster eel27 Jul 2023 — The maximum length recorded for a European eel was 0.932m, Foxon found, leading him…</p>

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