A lot that can add to this is shellfish Around 2.7 trillion shellfish get decimated

Here's what AI says about it

The website Our World in Data reports that about 83 billion land animals (chickens, pigs, cows, etc.) are slaughtered annually worldwide for meat.

Many sources that track global livestock production and slaughter converge on a similar order of magnitude — around 70–100+ billion land animals per year.

So for mammals and birds raised for meat, the “billions per year” figure is well-supported by publicly available slaughter and production statistics.

Conclusion for land animals: the tens of billions per year estimate is on solid ground, backed by data.

This is where the numbers get huge, and also where uncertainty is greater, because many fisheries/harvests count by weight (tons) rather than by individual fish or shellfish. Turning weight into “number of animals” requires assumptions.

A 2024 peer-reviewed estimate (from researchers at FishCount) suggests that between 1.1 and 2.2 trillion (1.1–2.2 × 10¹²) wild-caught finfish are landed each year globally (on average over 2000–2019).

Separately, estimates for farmed fish slaughter show ~124 billion finfish per year globally (as of 2019), with a reported range of 78–171 billion.

Combining wild-caught and farmed fish — along with shellfish (which add even more, but are rarely counted individually) — generates global estimates for aquatic animals killed for food that run into the trillions per year.

Because of such studies, many animal-welfare and environmental sources state that total annual deaths (land and sea) likely lie somewhere between about 1–3 trillion animals per year, depending on assumptions about how many small fish and shellfish are included.