Question 1

What is dark pool trading activity for MMSI?

Accepted Answer

Dark pool activity for MMSI represents trades executed on Alternative Trading Systems (ATS) — private exchanges where institutional investors trade large blocks of shares away from public exchanges. StonkWhisper tracks this off-exchange volume using FINRA ATS data.

Question 2

How do I interpret dark pool data for MMSI?

Accepted Answer

Key metrics to watch for MMSI include total dark pool volume as a percentage of overall trading volume, which ATS venues are handling the most shares, and week-over-week volume trends. A rising share of dark pool volume can indicate growing institutional interest, while shifts between venues may signal changes in execution strategy.

Question 3

What are ATS venues and which ones trade MMSI?

Accepted Answer

ATS (Alternative Trading Systems) venues are SEC-registered private exchanges operated by broker-dealers. Common venues include Citadel Connect, Virtu Americas, and UBS ATS. StonkWhisper shows which venues handle the most MMSI volume and how that distribution changes over time.

Question 4

How often is dark pool data updated for MMSI?

Accepted Answer

FINRA publishes ATS volume data on a two-week delayed basis. StonkWhisper ingests and processes this data as soon as it becomes available, updating MMSI's dark pool page with the latest weekly volume figures and venue breakdowns.

Week	Shares	DP %	WoW
2026-06-01	1.1M	—	+16.0%
2026-05-25	952.9K	—	+19.1%
2026-05-18	800.4K	—	-46.3%
2026-05-11	1.5M	—	-6.8%
2026-05-04	1.6M	—	-23.0%
2026-04-27	2.1M	—	—
2026-03-23	1.1M	—	-14.3%
2026-03-16	1.3M	—	-26.5%
2026-03-09	1.8M	—	—
2026-02-02	828.9K	—	+2.7%
2026-01-26	807.2K	—	+16.2%
2026-01-19	694.7K	—	-51.4%

MMSI

Weekly History

ATS Venue Breakdown (latest week)