Straits Pond Facts in Brief

Size: Straits Pond is a salt pond of approximately 92 acres (1980 survey 91.4 acres).

Location: On the Hull/Cohasset border.

Depth: Approximately 1 –1.5 meters (Depth varies with the tides and seasons and is controlled by a tidal gate at the west end (i.e. by West Corner) of the pond.

Topography: Of the Straits Pond watershed is highly variable and inconsistent.

· Highest point is just west of Tad Lane in Cohasset for an elevation of 102 feet above mean sea level (MSL).

· Lowest elevation is Straits Pond which varies between 3-4 feet above MSL.

· Tide gate is at an elevation of 3.0⁺ MSL.

Water Volume: (1980) Calculated as 98,310,00 gallons or 13,140,000 cubic feet.

Flushing Time: This is defined as the time it takes one pond volume of water to discharge from

the pond. (1980) Because the Pond area is large relative to the watershed area the flushing time was figured as 71 days. Note: During a meeting regarding Straits Pond it was pointed out that it is easier to get water out of the Pond than to refill it. Water drains out of the gate at low tide, but it typically takes several high tides to replace the water.

Environmental Designation:

Area of Critical Environmental Concern (ACEC) with class SB standards.

This designation has been given to both Straits Pond and the Weir River. The SB designation means there are strict standards of protection: “ No degradation of water quality allowed under the law.” Class SB are marine or coastal waters designated for the protection of: fish, other aquatic life, and wildlife; for primarily and secondary contact recreation; and shellfish harvesting without depuration in approved areas (EEOA Office, Final ACEC Guidance Document, 1/92)

Midges:

· There are 5000 recorded species of midges with about 2,500 species of Chiromonidae found in North America.. Most are non-biting and live in water. Some have adapted to a low oxygen environment.

· Of the 40-50 species which may be inhabiting Straits Pond only a small percentage (4-5%) are filter-feeders. The filter feeders are the species that form swarms (in the adult stage) and are a nuisance. The species inhabiting the Pond is a species of Chiromomids, a non-biting aquatic midge.

· The midges have a 4-stage life cycle: egg to larvae to pupae to adult. They inhabit the pond during their larval and pupae stages, primarily existing in the shallow edges of the Pond. The first generation historically emerge from the Pond as adult midges in late April

· During t he 1992 Straits Pond study attempts were being made to positively identify the species of Chironomid midge found in Straits Pond. Past studies have identified the species as C. Decorus (1953 Mass. Dept. of Public Health Study) or C.Riparius (IEP 1980 Study). During the 1992 Study specimens of midge larvae were sent to the Museum of Natural History in Washington DC and reply from there was pending. Communication with Dr.Ashad Ali of the Univ. of Florida and Dr. Joel Margolit of Harvard University tentatively indicate the species may be C. chironomus.

· The 1994 Straits Pond Study refers to the “…species of midge fly known as Chiromonous Riparius”so it appears that final identification of the specific species was made.

· 1994 Straits Pond Study: After 3 years of data collection determined that there are 3 generations of midges during the spring through fall seasons. The first generation is when the over-wintering larvae mature and leave the pond in mid-April as adult flies. Absence of larvae were recorded from mid-April through May. The second generation was recorded by larvae peaks in June followed by a decline in the early part of July. The third generation is recorded by larvae population peaks in August and declines in September when the larvae have matured and emerge from the pond as adult flies.