I think a whole fish farm is a "deleterious substance" according to that article.
...."14. The Submitters state that
[c]onfined salmon [in aquaculture operations] are fed concentrated fish feed,
commonly soaked in chemical treatments and antibiotics designed to remedy
parasite infestations (such as sea lice) and bacterial infections. Any unconsumed
feed, excrement, pesticides and antibiotics pass through the pens and enter the
surrounding environment. Decapod crustaceans such as crabs, lobsters, prawns
and shrimp, which are important scavengers in wild salmon habitat, tend to be
drawn to accumulate[d] discharge on the seabed beneath finfish aquaculture
operations.23"
sounds delicious....."Submission cites a scientific article reporting that “some
sources of fish feed have been found to contain high levels of mercury.”24 The same scientific
article explains that fish farms produce “zones of anoxic sediment, a condition that promotes
conversion of inorganic mercury into the biaccumulative organometallic form
methylmercury,”25 and goes on to describe additional environmental effects. The same article
also states that “Elevated mercury concentrations in rockfish prey near net-pen salmon farms
likely result from a combination of mercury loading (in waste feed and fish feces26) and
mobilization of native and added mercury in sediment due to farm-induced anoxia.”27