This would be helpful to know. If the incidence of deformity in unexposed bluefin cod is generally the same, then it would seem the chemicals made no difference. If the incidence was lower, then the chemicals would explain the 3% rate in Cod Bay.

If the incidence of deformity in bluefin cod didn't change, then it would seem the chemicals made no difference. If the incidence was lower before dumping, then that would establish a temporal correlation. This would help to evaluate the hypothesis.

Whether or not the cod deformity impacts human health isn't relevant to what caused the deformity in the first place. This information wouldn't weaken or strengthen either way, so it's not useful.

If the answer is yes, then these diseases rather than the chemical may have been responsible for the deformities. If the answer is no, then that eliminates an alternative cause to the chemicals. This is useful information.

Like (D), this points to an alternate cause, so it's useful. If other pollutants can cause deformities, then chemical waste might not be to blame. If other pollutants can’t cause deformities, chemical waste remains a highly viable explanation.