As in not limited to humans. It is seen in many mammals.
I was only able to find "Sperm counts in semen of farm animals 1932-1995" https://pubmed.ncbi.nlm.nih.gov/9401823/
Which states that farm animal sperm count has unchanged or has increased over time.
https://www.astralcodexten.com/p/declining-sperm-count-much-...
"This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50–60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand. "
If the "data are very noisy" argument were a sound argument it would have dismissed most of the science that we have today.
[0] https://academic.oup.com/humupd/article/29/2/157/6824414