OK, here's what I found out. The Yantic has a Trout Management Area further upstream that has special regulations. The area you are referring to is closed. Here is the regulation that permits certain streams (which includes rivers) to remain open year round. If the stream (river) is not included in this list then the statewide season applies.

26-112-44. Closed seasons
(a) Streams. The closed season for fishing in streams shall be from midnight on the last day in February through 6:00 a.m. on the third Saturday in April, except as provided below:
(1) Streams open to fishing throughout the year. There shall be no closed season for fishing in the following streams, or portions thereof, as specified:
(A) Coginchaug River, Middletown – downstream from Route 3 bridge to its junction with the Mattabassett River (Sebethe River).
(B) Connecticut River and its coves.
(C) Farmington River – downstream from the outlet of the Rainbow Dam Tailrace Canal to its confluence with the Connecticut River (all fishing is prohibited in the Rainbow Dam Tailrace Canal and in the Farmington River from the Tailrace Canal upstream to Rainbow Dam).
(D) Housatonic River – downstream from the dam on Lake Housatonic (the Derby Dam).
(E) Mattabasset River (Sebethe River), Middletown – downstream from the Route 372 bridge to its junction with the Connecticut River.
(F) Mystic River, Groton and Stonington – downstream from the confluence of Whitfords Brook and Haleys Brook.
(G) Naugatuck River – downstream from the Kinneytown Dam (Seymour) to its confluence with the Housatonic River.
(H) Niantic River, East Lyme and Waterford
(I) Quinnipiac River – downstream from the highway bridge on Route 5 in North Haven to its junction with New Haven Harbor.
(J) Salmon River, Haddam and East Haddam – downstream from the bridge on Route 151 to its junction with the Connecticut River.
(K) Thames River and its coves – downstream from Greenville Dam.


The Yantic River is not included in this list. The Thames River and its coves is open below the Greenville Dam, but Indian Leap is part of the Yantic River and is not a cove of the Thames, it is a separate river (stream) so the closed season applies.