The Fish Farm ProblemFish that are added to open water pens are initially sea lice free, but quickly become infected. What is the source of the infection? Adult salmon. As stated earlier, the adults carry sea lice back to the coastal waters. Normally there is no significant mass of fish in the coastal environment to carry-on the sea lice infection. However, a fish farm with millions of adult salmon is the perfect host.
Given the close proximity of fish in farms and the sheer numbers of fish, it's no surprise that sea lice infections quickly become a major problem. Around 50 adult lice can be found on an average farmed salmon. Multiply that by 100,000 fish, then multiply that by thousands of eggs released per lice. The number of sea lice eggs produced by a single farm is in the billions.
In addition, the sea lice are able to over winter on the farms. Juvenile salmon that would normally migrate out through clean coastal waters are now swimming through billions of sea lice eggs. The juveniles quickly become infected. Those lice develop into adults.
Sea Lice and Juvenile SalmonA typical juvenile pink or chum salmon is only 1 to 3 grams and roughly 30-60 millimeters long. They have yet to even develop scales. They are tiny.
An adult female sea lice, with developing eggs and a voracious appetite, is completely devastating to a juvenile salmon. I have seen juveniles literally chewed to the bone by the lice. It may take only 1 or 2 lice to kill a juvenile salmon. When a salmon farm is producing billions of eggs, the likelihood of a juvenile becoming infected is incredibly high. Once infected, there is little chance for a baby salmon.
Furthermore, the juveniles rarely only have to pass one fish farm. In the Broughton Archipelago they often have to pass 5 or 10 farms before reaching Johnstone Straight. Then there are even more farms along the north-east coast of the island.
MisinformationLet's return to the editorial letter written above and examine some of the statements.
When researchers exposed pink and chum salmon to either 243 or 735 lice per fish, they didn't measure any mortality at all.
There are two key questions to ask here. 1) What stage of sea lice? and 2) What size of fish?
1) What stage of sea lice?
243 and 735 lice is a lot of lice per fish. The lice however, were the just-developed attached stage. This is also 'exposure' NOT 'infection.' Infecting a salmon of any size with 243 or 735 lice would be impossible. Although it is hard to discern, I believe the study states that just 7 days after exposure to 243 lice, the number of lice on a total of 160 pink or chum salmon (320 fish total) was 34 and 50 sea lice, respectively. Only 1/3 of the pinks were infected and of those pinks, the average number of lice per fish was just 0.9! The numbers for chum are just slightly higher.
By the time the sea lice had developed into adults (21 days) the number of sea lice had dropped to just 2 on all the pinks. That's an average of 0.1 lice per fish, +/- 0.1 lice per fish. That effectively means none of the fish were infected! These are all numbers from the study by the way.
Is anyone surprised that with just 2 sea lice on 160 pink salmon that none of them died? Of course not! No mortality is almost expected.
2) What size of fish?
I said before that the typical size of an out-migrating juvenile salmon that is found to be infected with sea lice is just 1-3 g. Well in this study the average size of the exposed pink and chum salmon were 19.0 g and 17.2 g, respectively. So 160, 19 gram pink salmon had a total of 2 adult sea lice on them and none of them died.
Onto part two...
DFO-led research has also shown native sticklebacks appear to be a significant source of sea lice.
Getting into the stickleback issue requires a whole separate level of explanation I am not going to get into. There's a lot of debate going on right now as to whether sticklebacks are a source of sea lice infection to juvenile salmon, or in fact, a sink for sea lice (e.g. the sticklebacks absorb sea lice away from the salmon).
I will state these facts from a study that was published by the same author that did the pink/chum infection experiment analyzed above (DFO scientist).
The author sampled a HUGE number of sticklebacks from the coastal waters of the Broughton Archipelago. In total, over 1,300 sticklebacks were examined and from those sticklebacks came 19,960 of one sea lice species, and 2,340 of another. The more abundant sea lice species is the one most commonly found on juvenile salmon, so let's focus on that.
Of those 19,960 sea lice over 97% were in the development stage. That's the 'attached, not going anywhere, and definitely not infecting juvenile salmon' stage. In fact, out of the 19,960 sea lice only 5 were adults. Put in percentage terms, thats 0.025%. It was not stated if those adults were male or female.
With only 0.025% of the population at the reproductive stage, how exactly are the sea lice maintaining an infection on sticklebacks? And since the developmental sea lice can't jump onto juvenile salmon from sticklebacks, how are lice from sticklebacks infecting salmon? Both are very important questions. Regardless, the author of the paper concluded that sticklebacks appeared to be a significant source of infection to juvenile salmon. Don't ask me how.
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If you managed to get through all that, you'll have come to realize that there is a HUGE amount going on with this issue. I've completely omitted any references to modeling because that data is currently beyond my off-hand knowledge level. But let me tell you the most important thing of all this.
Europe has had fish farms for ages. They have been through all this research we are doing now and unequivocally concluding that fish farms are the source of sea lice infection to juvenile salmon. They have made laws to avoid the issues we are having right now with our juvenile salmon. The data collected here by researchers other than DFO, matches the data from Europe. It is only DFO data and DFO models that work together. Nothing else fits with what DFO is saying.