I have to say something on fish mass death in seawater and it's causes; the new era of life which is our actual era is an era of transition of everything, and this transition could be seen in fish mass death because of soustarction formula which is (-1, +1) (+1, -1); and this means that all existing fish has to go to leave it's place to a new generation of fish adaptable with the new conditions of life on earth.
Fish is one of the first creatures which will be executed by soustraction formula because of it's nature of living in water; and Higgs boson magnetism and it's mechanisms can show 99% efficiency of decaying to particles is in water and that's why up to 72% of matter will be transferred to the water molecule and this is not only on planet earth but in the whole universe.
Oxygen atom is hiding a big secret in particle physics and this is because of it's number of electrons which is (8); and (8) is the perfect number in the building of everything and this is why the oxygen atom instead of decaying it's formation is at increase and this is what allows the increase of the water molecule. Maybe someone asks what about hydrogen atom? Hydrogen atom is the last to decay because of it's light mass.
I should say something strange; the cause of fish mass death is the abundance of the water molecule; the increase of water makes seas and oceans loose salinity and this is what makes fish impossible to survive. I think that rain water and ice melting water are at race with seawater to exceed this last quantity, and this race started (5) years ago. Simply the main cause of fish mass death is milder seawater.
I must say that fish mass death will happen sooner or later and many signs of this mass death are already there and such signs are: seas warming, seas ecosystem deterioration, seawater salinity decreasing, red algae invasion to seas and poisonous gases increase in seawater such as methane.