(08-13-2014 10:25 AM)tweedwolfscream Wrote: [ -> ] (08-12-2014 11:53 PM)MuskieBait Wrote: [ -> ]I would tend to use more common sense than trusting the guide fully...but common sense isn't so common these days.
Question is, unless there's been a recent toxic spill or something, how is "common sense" going to tell you the chemical content of a fish fillet better than labratory testing done 3 or 5 years ago? Plenty of people just going on "common sense" would recoil at the thought of eating a pike from the "dirty" lagoons of the Toronto Islands, but can't wait to go to the cottage up Burk's Falls way every weekend of the summer and catch some big Pickerel Lake eyes for dinner with the family. MOE advises the opposite. Gonna prefer the science on this one.
Not that I take the advisories completely literally either, and we've been through this on the forum before, with various opinions... one of the limitations I see is that the actual number of meals/month are kind of arbitrary, 8 is the highest given only because "eat fish twice a week" is a nutritional recommendation from someone or other, and fractions of that number are assigned to fish with various levels of contaminants... and of course these contaminants are cumulative, so what matters is how much you eat in the very long term, not each month. But they still provide a basis of comparison between species and locations that you wouldn't get if you just went by what the water smells like.
I'll continue to use Zebra Mussel/Round Goby as examples...since the original discussion was on Round Goby.
The common sense I mentioned is this:
The environment is not static. It changes base on the activities around it, whether it be natural or man made.
Natural changes can lead to poor quality fish. A rainstorm can flush nutrient into a system causing a natural algal bloom, which can increase blue-green bacteria or E. coli. That leads health risk when eating the fish you catch, especially in the summer. (Yes, in this case, you actually can go by what the water smells like!) A turbulent current can disrupt anoxic layers of bottom to release toxic bacteria into the surrounding area, contaminating the shellfish and fish in the immediate area. Again, storms or high meltwater can do that...so can natural massive landslides that dumps contaminated soil into the water...and the contamination can be natural...such the the naturally mercury-rich substrate surrounding the northern lakes.
Human caused changes can also lead to poor quality fish. Look at the algal bloom in Lake Erie right now. Report suggests that intensive farming could be the cause of the current of blue-green algae.
So just because a lake was tested safe for a given species for a given number of meals, that data may not be current and may not reflect the short term or longer term history. After such algal bloom event, even if the algal bloom has cleared, zebra mussels had still consumed the blue-green algae, round gobies had still consumed the mussels, and smallmouth bass had still consumed the gobies...all of which would then have elevated levels of cyanobacteria toxin than what the test indicate maybe a year back, three years back, or even 10 years back.
Invasion of certain species can take over a lake within a few years. I remember it was in 2005 when the Ministry planned to treat Lake Simcoe's Pefferlaw Brook with rotenone when Round Goby was first found there. Of course, by that time, it was probably too late and indeed, Round Goby had established in Lake Simcoe as we see today. When such event occurs, it leads to disruption of the food chain and a change in diet of predators. While it may be safe to eat Smallmouth Bass at 4 portions a month 2005 (for example) before the goby full established, they are less safe to eat in 2008 when goby are more established and smallmouth bass now prey more significant on gobies. As the goby spread from its initial center outward, it may be less safe to eat smallmouth from Pefferlaw, but may still be safe to eat smallmouth from Kempenfeld. Eventually, when gobies spread to Kempenfeld too, it may be less safe to eat Smallmouth Bass as well.
It's an organic system. Testing and science can only provide a snapshot in time of this organic nature. It's like saying what is the state of this electron at this precise moment. You don't know...you can't know. But you can make an estimate based on the science. However, things will change with the season, and things will change with the years. The guide does not indicate when fish were tested for a particular lake. It could be summer when issues like pesticide use was greater, or it could be winter when issues like algal bloom is less. Yes, you are looking at overall cumulative effect of certain contaminants, but there are fluctuation of these contaminants daily, monthly and annually. The guide does not indicate when the waterbody was last tested. It is especially worrisome if the data is not current (up to 12 months to the publication year).
So going back to your example, Toronto Island pike may be safe to eat and the data may be three years old (TUFA actually knows the testing was recent...but for argument sake...because general fishing public don't attend Great Lake meetings), and Burk's Fall walleye may be less safe to eat and the data is 10 years old. But what is the current state of affairs? What about all the current condo development along the waterfront, washing in more chemicals into Lake Ontario as we speak? What about development of cottages in Burk's Falls and cottages putting in septic tanks and treating their lawns with pesticide in the past 10 years when the fish has not be retested? Is the less safe walleye, which perhaps you may be able to safely eat 4 meals a week based on 10 year old data, still safe to eat currently at the same consumption level? Do you know whether the data was 10 years old, or perhaps 3 years old, or perhaps tested just months before the current publication? With such uncertainty, can you really put that much faith in it?
I know you don't take the guide literally. And I'm not discussing this based on your personal consumption. But it is definitely something to consider and bring out to the member here who may not be aware.
Common sense. If something tells you it's not safe, it probably best to avoid. You "gut" often knows better than you do...call it instinct, call it subconscious...whatever. Instinct tells us smelly water is likely not safe to drink. We don't need science to tell us that it is full of harmful bacteria or toxins or heavy metal...unless you personally knows that current science supports it or refutes it. Seeing cottage development in a previously less developed northern lake should consciously and subconsciously tell you changes to the pristine condition of the lake is underway. Again, you don't need science to tell you that.
Science is good for testing a theory, a hypothesis, our best educated guess based on what we know. The data then supports or refutes what we questions. But the question is often very narrow in scope and full of limitations and assumptions. Those are necessary or else you simply cannot test anything (the world is too complex...but our human brain can actually process this complexity subconsciously...going back to common sense...if you have it). It may or may not be adequate to make our decisions based on the data. This is why, even after millions of dollars spent on preclinical trials, many of the drugs fails at clinical trials in patients. That's why flu vaccines are not 100%. That's why a cure for AIDS has yet to be found. That's why government and agencies cannot predict the current algal bloom. That's why even though Zebra Mussel and Round Goby were supposed to wipe out fisheries across Ontario, fishing (for most part) has never been better for certain species in Lake Erie, Lake Simcoe and Bay of Quinte. Because it is an organic system, because we only know certain results in a given snap shot of time, we are unaware of all the interactions, and we usually do not have all the answers.
