Sea Lice and Fish Farms

[Dave]

Or, that is a staged photograph. Any proof it isn't?

 

[bones]

So that's your bar of acceptability. Protecting wild salmon smolts by making sure they leave your sphere of influence with just one sealice each.

Great question.... I dont have a bar of acceptability or better word maybe how many lice can load a subject before death occurs. So with the hundreds of peer reviewed papers what is it? The paper you just commented on says 7.5. What number do you have?

 

[bones]

I

Or, that is a staged photograph. Any proof it isn't?

It doesn't matter Dave. The picture shows only 3 lice which isn't enough to kill a smolt.... If 7.5 is the limits and even with a 50% fudge factor its still within limits of survivability.

 

[fogged in]

Or, that is a staged photograph. Any proof it isn't?

Is it proof you want, try this site
No...these Sea Lice did not all come from Fish Farms, but it is a fact Fish Farms have a Sea Lice problem worldwide and they are attempting to control it.
https://www.google.ca/search?q=sea+...AhVKymMKHZP9DcwQ9QEIOTAH#imgrc=mxvGactMWG7PUM:

 

[agentaqua]

The real metric to estimate lice mortality is number of MOTILE lice per gram of host weight - that ranges dependent upon species and life history stage - so there is some debate about what that exact number is. However, it is in the range of+1.6 lice per gram (Bjorn and Finstad 1997) of MOTILE lice per gram of host weight to cause mortality - and something greater than 0.04 lice/gram host weight (Nolan et al. 1999) to cause morbidity (i.e. sub-lethal effects). Although they grow rapidly - keep in mind that pink fry are only something like 0.3 gram when they 1st outmigrate from the creeks.

The reason why the stage is important is that when sea lice are motile (verses attached) - is that they do the most damage on the host. You can actually see the holes on the sides of that pink fry from the motile (and also gravid) lice in the picture Terrin posted.

It takes ~107 days at 4°C, ~38 days @ 10°C, and ~28 days at 20°C for them to complete their lifecycle (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088465#s3) - so one can approximate when a louse got onto a fish working backwards from what stage - using water temperature as a guide.

 

[agentaqua]

BBC One Show on Scottish salmon farming: "The Dead Salmon Run" (11 December 2017)

 

[bigdogeh]

I
It doesn't matter Dave. The picture shows only 3 lice which isn't enough to kill a smolt.... If 7.5 is the limits and even with a 50% fudge factor its still within limits of survivability.

Wow, comments like that are really going to get your industry a lot of sympathy. Shows just how much you care about wild salmon. Think that smolt is going to be able to swim away from a predator for very long carrying around those sealice sucking the lifeblood out of it, and possibly infecting it with other diseases and virus'es?

 

[bigdogeh]

Here, I'll save you your post bones... "oh, that's a video from somewhere in a different ocean. Couldn't possibly be any similarity's with what's happening here. "
Sorry, I beg to differ. I see many similarity's.

 

[agentaqua]

It doesn't matter Dave. The picture shows only 3 lice which isn't enough to kill a smolt.... If 7.5 is the limits and even with a 50% fudge factor its still within limits of survivability.

Wow, comments like that are really going to get your industry a lot of sympathy. Shows just how much you care about wild salmon. Think that smolt is going to be able to swim away from a predator for very long carrying around those sealice sucking the lifeblood out of it, and possibly infecting it with other diseases and virus'es?

Sometimes bigdogeh - I am still occasionally surprised at the lack of math skills from FF pundits - even though they often claim to be focused on business and finances. The mortality depends on the weight of the host. Not sure what the heck is the 7.5 limit bones, claims.

 

[bones]

Bones posted those exact same studies last January in the "Sea Lice and Fish Farms" thread. I responded back then: http://www.sportfishingbc.com/forum...-lice-and-fish-farms.64546/page-2#post-814772


I guess you cant read then.....
So what are the numbers then AA?

 

[bigdogeh]

http://alexandramorton.typepad.com/alexandra_morton/2012/10/when-is-truth-a-tactic.html
Not sure if this was posted in the past but found it an interesting read. Really make me want to try some of that yummy open net penned farmed atlantic fish... (sarcasm)

 

[agentaqua]

Bones posted those exact same studies last January in the "Sea Lice and Fish Farms" thread. I responded back then: http://www.sportfishingbc.com/forum...-lice-and-fish-farms.64546/page-2#post-814772
I guess you cant read then.....
So what are the numbers then AA?

You need to know the weight of the fish, bones.

 

[bones]

So

You need to know the weight of the fish, bones.

why not all of them? Or the average or C1, C2,C3, C4?.........

 

[agentaqua]

C1, C2,C3, C4? - sorry - you lost me, bones

 

[agentaqua]

Call for closure of fish farms after 'catastrophic' drop in salmon numbers
Nan Spowart Journalist
10th December
http://www.thenational.scot/news/15...tastrophic__drop_in_salmon_numbers/?ref=fbshr

 

[Dave]

Nothing closer to home today, aa?

 

[agentaqua]

I think this one is close enough, Dave:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0188793

 

[bones]

Abstract
A threshold of lethal infection was estimated from previous controlled laboratory exposures to be 7.5 Lepeophtheirus salmonis g(-1) for pink salmon Oncorhynchus gorbuscha averaging < 0.7 g. This threshold was used to assess the risk of mortality caused by L. salmonis among pink salmon of the same size class in the Broughton Archipelago, Canada from 2005 to 2008. Virtually all (> or = 98.9%) pink salmon collected in late March belonged to this size class, and this proportion declined to < or = 1% by early July. The proportion of these small pink salmon with infections equal to or exceeding the threshold declined from 4.5 in 2005 to 0% in 2008, coincident with an overall decline in parasite prevalence and intensity during this period. In 2005 and 2006, this proportion was greatest in March (7.8 and 1.1%, respectively) whereas in 2007, the proportion exceeding the threshold was greatest in May (2.9%). In 2008, no infections exceeded the threshold. Parasite development coincided with fish migration through the study area. The declining risk between 2005 and 2008 was possibly related to changes in ocean conditions such as temperature, to changing treatment practices for this parasite on salmon farms, or to changes in the abundance or distribution of non-farmed hosts. The concept of a threshold of L. salmonis infection density may be used to assist in the management and conservation of juvenile pink salmon in the Broughton Archipelago region.

Infection threshold to estimate Lepeophtheirus salmonis-associated mortality among juvenile pink salmon (PDF Download Available). Available from: https://www.researchgate.net/public...sociated_mortality_among_juvenile_pink_salmon [accessed Dec 13 2017].



could you just give me any kind of numbers showing death by sealice? c1 c2 any stage..... avg weight by sampling

 

[agentaqua]

I am unsure that you actually read that paper, bones: Why do you think Simon Jones stopped his study before most of the lice on his fish got big enough to harm the salmon?

p.136: "...most parasites on fish that died following laboratory exposures had not developed beyond the chalimusIV stage."

 

[terrin]

I think this one is close enough, Dave:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0188793

Just went over a linked report by Marty. Seems he was a bit off in the bullets.http://marineharvest.ca/globalasset...rus-prv-information-sheet_gary-marty_2013.pdf