ANTARCTIC KRILL DECLINE: Industrial fishing or Climate Change?
It is generally reported by ecologists and the climate science camp that there has been a dangerous decline in the species of krill known as Euphausia Superba over the past few decades and the cause is the melting ice of Antarctica by global warming. 
The Krill sometimes feed on the underside of ice. A simple picture, less sea ice from the predicted global warming and there is less Krill.
The story took hold and the media focus on ice loss in West Antarctica on the tip of the Peninsula as evidence of disruption of their habitat. This area has apparently seen some warming but it is only a small percentage of Antarctica.
So is the overall pattern the same? If a decrease in sea ice disturbs their habitat and feeding leading to a decline then it follows that an increase in sea ice will improve their habitat and feeding regime and mitigate any decline, possibly even increasing their biomass.
In a 2006 research paper “Antarctic Temperature and Sea Ice Trends over the past Century: An assessment of Antarctic Climate Data” by George Taylor, the results are that sea ice has been increasing and the temperature falling.
“Conclusion: The data clearly show that Antarctica as a whole is seeing increases in sea ice extent in recent decades, in spite of what climate models suggest should be occurring: steady warming. There are regional differences, with Weddell Sea ice extent decreasing and Ross Sea ice increasing, but overall the pattern is clear: there is more ice, not less, surrounding Antarctica.”
In regards to temperature they state: “Although some regions do show increases, the majority of the continent shows no significant trend or an actual decrease.” http://icecap.us/images/uploads/antarctica_white_paper_final.pdf
The increase in sea ice is backed up by the National Snow and Ice Data Center and NASA whose image is used below: “On Sept. 19, 2014, the five-day average of Antarctic sea ice extent exceeded 20 million square kilometers for the first time since 1979, according to the National Snow and Ice Data Center. The red line shows the average maximum extent from 1979-2014.”—NASA. Image Credit: NASA’s Scientific Visualization Studio/Cindy Starr”
KRILL DECLINE MITIGATED
If a decrease in sea ice disturbs their habitat and feeding leading to a decline then it follows that an increase in sea ice will improve their habitat and feeding regime and mitigate any decline, possibly even increasing their biomass.
It is estimated 25{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} of krill are found in 10{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} of the area they inhabit overall in the waters off the Antarctic Peninsula. This leaves 75{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} of the krill biomass living in 90{154653b9ea5f83bbbf00f55de12e21cba2da5b4b158a426ee0e27ae0c1b44117} of the overall area they inhabit to be experiencing favourable conditions of sea ice to boost their biomass. Statistics indicate sea ice loss is not the main cause of any krill decline. Another explanation is needed.
A quick note on glacial melting
Overall Antarctic is shown to be increasing in ice mass but a small region of the West Antarctica peninsula is not. Climate science also claims the glaciers in west Antarctica are melting faster and this is another dangerous sign of global warming but it has been discovered there is volcanic activity under this area of ice, a more credible explanation.
“The first evidence of a volcanic eruption from beneath Antarctica’s most rapidly changing ice sheet has been reported. The volcano on the West Antarctic Ice Sheet erupted 2000 years ago (325BC) and remains active.”
https://www.sciencedaily.com/releases/2008/01/080120160720.htm
KRILL DECLINE FROM INDUSTRIAL FISHING
Here a graph of krill catch by industrial fishing showing millions of tons of Euphausia Superba have been removed from the open water surrounding Antarctica. This is their main habitat where they generally feed on Phytoplankton.
“During the 1970s, commercial krill fishing in Antarctic waters began expanding rapidly. Initially, the krill were used mostly for pet food and fertilizer, but more recently they’re being used for nutritional products such as omega-3 fatty acid supplements, feed for the rapidly growing aquaculture industry, and even in some new cosmetics.”
Just how much krill is being fished now? “The most recent total notified catch was about 684,000 tons for the year 2007/08,” Miller said, referring to the period from December to November. “That’s all the countries that have notified, about 25 vessels from seven members of the commission and two nonmembers.” http://www.nytimes.com/2008/05/25/business/worldbusiness/25iht-krill.1.13188108.html?_r=0
Krill decline is often put as being first caused by global warming then after industrial fishing is added to the list of causes.
“The decline in the krill population is believed to be a result of global warming. Pack ice is the breeding grounds for the krill, and global warming is affecting the ice (Hayden 1).” https://www.msu.edu/~seremji1/krilldepletion.html
This research indicates that the opposite is happening with industrial fishing being the primary cause of krill decline and the localised sea ice decline being a far smaller contributor which is strongly mitigated/compensated by sea ice gains in other parts of Antarctica.
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By Myles, Principia Scientific International (PSI) researcher.
References:
- Antarctic Temperature and Sea Ice Trends over the past Century: An assessment of Antarctic Climate Data” by George Taylor.
- http://www.nasa.gov/content/goddard/antarctic-sea-ice-reaches-new-record-maximum
- https://www.sciencedaily.com/releases/2008/01/080120160720.htm First evidence of under-ice volcanic activity in Antarctica. British Antarctic Survey. Jan-22-2008.
- http://www.nytimes.com/2008/05/25/business/worldbusiness/25iht-krill.1.13188108.html?_r=0 The New York Times. Overfishing of krill threatens ecosystem. 25-May-2008.
- https://www.msu.edu/~seremji1/krilldepletion.html
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