Local herring used for dog food

[agentaqua]

Nor do I, but I'm pretty sure removing 15-20% of the biomass of forage fish right before they spawn is not a great thing for the ecosystem, particularly for those organisms that depend on the eggs and larvae to grow and survive. They do not remove them uniformly, they are hit hard in certain areas, and since herring are local populations they can be wiped out in one area but still be abundant in others. Howe sound populations are only now beginning to rebound after being wiped out decades ago.

You accurately restate the 2 main issues - as I mentioned above, California.

The 15-20% removal comment gets into the debate about precautionary triggers on TAC as benchmarked by DFO using Limit Reference Points. The suitability of using Limit Reference Points is entirely related to the accuracy of the biomass estimates - which is under debate also for 2 reasons: 1/ methodology (field AND office), and 2/ assumptions (esp. Q and priors) when extrapolating those field data into a biomass estimate. Both have issues, also.

The comments around areas and impacts gets into the discussion around subpopulations (metapopulations) and management actions being detailed and specific and fine enough to conserve local populations verses broad-scale population dynamics. Again - much debate here wrt the ability of DFO to be able to discriminate and manage metapopulations.

I certainly wouldn't disagree w your comments - as there is an unfortunate history of DFO going through a learning curve wrt herring management.

 

[Fishmyster]

What you need for the first stage of degradation of ammonia (actually mostly ammonium) are oxic conditions for nitrosomonas and then you need anoxic conditions for the second stage for the nitrobacter. I venture to say that anoxic conditions are naturally rare to find in our rivers and therefore the denitrification will remain incomplete with nitrite instead if nitrate. Eventually other oxidization processes will still break the nitrite down back to N2.

You are also not getting the water chemistry just right, you blame acidification for the occurance of fish toxic ammonia when in fact under acidic conditions ammonia does not exist but all in form of harmless ammonium. If the ph goes well above 7 then ammonia takes over and cause issues for fish. At ph 9.5 you would virtually have 100% toxic ammonia and no ammonium. Just to get the facts straight. Back to the herring discussion.

Thank you chris73. Most of our streams are not acidic. It is episodes of acidification during heavy rains that are concerning. From what I have read it takes 7ppm of alkalinity for nitrobacters to convert ammonia to eventually nitrate. Acidification events do seem to lower base flow alkalinity as indicated from historic water quality reports. Possibly this is having a negative effect on the denitrification process?
The private fish hatchery at GCL has to increase alkalinity of the natural water they draw from GCL because the nitrobacters cannot perform correctly and the fish will be polluted by ammonia from the fish waist and unused food. So the process is not working correctly in the natural water of Great Central lake. Historic water quality reports also indicate high levels of ammonia in many VI streams tested during the mid 1990's.

 

[chris73]

Thank you chris73. Most of our streams are not acidic. It is episodes of acidification during heavy rains that are concerning. From what I have read it takes 7ppm of alkalinity for nitrobacters to convert ammonia to eventually nitrate. Acidification events do seem to lower base flow alkalinity as indicated from historic water quality reports. Possibly this is having a negative effect on the denitrification process?
The private fish hatchery at GCL has to increase alkalinity of the natural water they draw from GCL because the nitrobacters cannot perform correctly and the fish will be polluted by ammonia from the fish waist and unused food. So the process is not working correctly in the natural water of Great Central lake. Historic water quality reports also indicate high levels of ammonia in many VI streams tested during the mid 1990's.

Nitrification process spits out H+ and therefore lowers the ph or uses up about 7mg/l alkalinity in CaCO3. Since our coastal rivers are usually very low in alkalinity (5-20 mg/l) nitrification will lower the ph. A lower ph will inhibit further nitrification and denitrification (bacti comfort zone ~ ph 8) and therefore prevent this from spiralling out of control in nature. Our coastal rivers are often slightly acidic, always have been, very soft with low alkalinity, due to little limestone here and coniferous forests producing acidic runoff. I have not seen any data showing a significant change in the ph spectrum in our coastal rivers. Possible that this is a localized issue due to industrial or communal wastewater effluent or agricultural impacts but not on a coastal scale.

 

[Fishmyster]

Nitrification process spits out H+ and therefore lowers the ph or uses up about 7mg/l alkalinity in CaCO3. Since our coastal rivers are usually very low in alkalinity (5-20 mg/l) nitrification will lower the ph. A lower ph will inhibit further nitrification and denitrification (bacti comfort zone ~ ph 8) and therefore prevent this from spiralling out of control in nature. Our coastal rivers are often slightly acidic, always have been, very soft with low alkalinity, due to little limestone here and coniferous forests producing acidic runoff. I have not seen any data showing a significant change in the ph spectrum in our coastal rivers. Possible that this is a localized issue due to industrial or communal wastewater effluent or agricultural impacts but not on a coastal scale.

Your explanation of how nitrifying functions is consistent what I have been reading. Do you test stream and lake water yourself? I am eager to learn more!
Check out the EMS database. You will be able to view decades of water quality samples that have been uploaded by many different agencies. There you will find many test results where water quality parameters like pH, alkalinity, aluminum and ammonia have exceeded thresholds deemed safe for aquatic ecology in salmon streams. There you will be able to view significant changes in pH in provincial salmon streams.
In the early i990's I personally witnessed a major change with how salmon carcasses decompose. This happened in most V.I. streams. Dead salmon originally decomposed to nothing within a couple weeks. After 1990, [timing was varied in different streams], the fish decomp changed where even in February there was piles of fuzzy salmon laying in the stream beds. Then again in 2015 my local streams decomp sped up to decomposition within two weeks and no fuzz on the carcasses. This phenomena was accompanied with algae change and invertebrate die off. What are your thoughts as to what would cause this?

Please respond on the ph and salmon productivity thread. ty.