My understanding is that wild-caught fish have more parasites, but they're required to be frozen for sufficiently long to kill the parasites, whereas farmed fish are exempt from this requirement:

From the 2022 FDA Food Code (https://www.fda.gov/media/164194/download):

    3-402.11 Parasite Destruction.
    (A) Except as specified in ¶ (B) of this section, before service or sale in READY-TO-EAT form, raw, raw-marinated, partially cooked, or marinated-partially cooked FISH shall be:
        (1) Frozen and stored at a temperature of -20°C (-4°F) or below for a minimum of 168 hours (7 days) in a freezer;
        [other temperatures/durations elided]
    (B) Paragraph (A) of this section does not apply to:
        [...]
        (4) Aquacultured fish, such as salmon, that:
            (a) If raised in open water, are raised in net-pens, or
            (b) Are raised in land-based operations such as ponds or tanks, and
            (c) Are fed formulated feed, such as pellets, that contains no live parasites infective to the aquacultured FISH.