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Above-Average Fall Water Temperatures May Benefit Some Bay Species

Data from NOAA buoys and satellites and other data sources on conditions in the Chesapeake Bay during fall 2021 give scientists insight into how living resources, including key fish species, may respond.

Fall (September–November) 2021 highlights include:

  • Above-average water temperatures
  • Lower-than-average dissolved oxygen
  • Below-average freshwater flow (punctuated by a few high-flow events)
  • Below-average salinity

The remnants of Hurricane Ida, including strong winds and rainfall, passed through the Chesapeake Bay watershed on September 1, leading to a drop in water temperature and an increase in dissolved oxygen. These effects were temporary, however. 

A steep drop in water temperature kicked off September, but much of the rest of fall featured above-average water temperatures.

Warmer-than-average fall water temperatures can extend the growth season for many species, including blue crabs, oysters, and juvenile striped bass. But it may also mean a later arrival of striped bass that spend some time in the Chesapeake as they migrate down the coast from their summer habitats to warmer waters.

Low dissolved oxygen levels can be particularly harmful when they coincide with high water temperatures. The larger volume and duration of hypoxia—when some Bay waters are starved of oxygen—may have created a stressful environment for some fish including striped bass.

Several heavy rainfalls led to a few high freshwater flow events and resulting below-average salinity. While a large flush of fresh water could result in high local oyster mortality (as oysters require a certain level of salinity to survive, reproduce, and grow), it is not expected that the freshwater flow incidents were enough to significantly affect oyster mortality or growth this fall.

For more information on fall 2021 conditions and how they may have affected living resources in the Chesapeake Bay, see the full scientific seasonal summary.