Striped bass scales and

life history tales:

fish and physics in the St. John’s

River

Appearance

Striped bass are quick powerful fish with silvery sides and white belly. They have seven or eight black stripes along the sides. Stripes are absent on young fish of less than six inches

Habitat

In Florida, striped bass are found primarily in the St. Johns River and its tributaries, and a few panhandle rivers. Striped bass need long stretches of flowing water to reproduce successfully. These conditions are rare in Florida.

Behavior

Stripers do not tolerate water temperatures over 75˚F for long. During Florida summers, striped bass become less active and must find cool water to survive. Striped bass populations depend on annual stockings from FWC and federal hatcheries.

State Record

42.25 lbs.

Big Catch: 30 inches or 12 lbs.

Striped bass scales

http://www.mdsg.umd.edu/MarineNotes/Sep-Oct98/

EggsSize: 1.8 – 3.7 mmDuration: 2 days

AdultsSize: 0.5-2.0 m

Duration: 35 years

http://www.dnr.state.md.us/fisheries/education/rockfish/rockfish.html

Note: Source for images is listed the first time the image is used.

Life history tales

Fish photographs by D. Flescher, downloaded from www.fishbase.org

Fish illustrations from: Lippson, A. J. and R. L. Moran. 1974. Manual for identification of early developmental stages of fishes of the Potomac River Estuary. Prepared for MD DNR Power Plant Siting Program. PPSP-MP-13. 282 pp.

Larvae

http://www.dnr.state.md.us/fisheries/juvindex/index.html

Juveniles

Adults

Eggs

http://www.mdsg.umd.edu/MarineNotes/Sep-Oct98/

Striped bassdistribution

http://seawifs.gsfc.nasa.gov/SEAWIFS/

St. John’s River

Jacksonville

http://seawifs.gsfc.nasa.gov/SEAWIFS/

The Lower St. John’s River

To understand how physical conditions affect striped bass in the St. John’s River, we need to:

determine how physical conditions change in the St. John’s River

identify how striped bass respond to physical conditions

Physical conditions affect all life stages

Water temperature, salinity, dissolved oxygen concentrations, and currents influence:

survival (heat shock, winter mortality)

growth rates

location, movement, migration

Outline

1. Water temperature2. Salinity 3. Dissolved oxygen

Water Temperature

Chesapeake Bay Program Monitoring Data

http://tidesandcurrents.noaa.gov/ofs/sjofs/fore_temp.shtml

Striped bass and water temperature: lethal limits and optimal ranges

Juveniles Adults

Stress/Mortality

Optimal

oCoC

Optimal

Stress/Mortality

Setzler-Hamilton and Hall 1991

http://tidesandcurrents.noaa.gov/ofs/sjofs/sjofs.html

The St. John’s River is in the optimal temperature range, so Striped Bass move throughout thesystem during fall and winter.

http://tidesandcurrents.noaa.gov/ofs/sjofs/sjofs.html

Striped Bass congregate in large cold water springs, such as Croaker Hole during the summer.

Croaker Hole

Outline

1. Water temperature2. Salinity 3. Dissolved oxygen

Find current salinity at http://tidesandcurrents.noaa.gov/ofs/sjofs/now_sal.shtml

Salinity measures the amount of salts dissolved in water. An estuary can exhibit a change in salinity throughout its length as fresh water entering from the tributaries mixes with seawater from the ocean.

Striped bass are migratory fish which spend most of their life in bays and the ocean, but travel up tidal freshwater rivers in the spring to spawn. 

Outline

1. Water temperature2. Salinity3. Dissolved oxygen

Dissolved Oxygen (DO) is one of the most important indicators of water quality. It is essential for the survival of fish and other aquatic organisms.

The DO test tells how much oxygen is dissolved in the water.

Factors that effect the amount of dissolved oxygen in the water

Water Temperature: Colder water holds more oxygen.Warmer water holds less oxygen.

Salinity:Fresher water holds more oxygen.Saltier water holds less oxygen,

too many bacteria or algae in the water may reduce oxygen levels.

The DO test tells how much oxygen is dissolved in the water.

Striped bass and dissolved oxygen concentrations: lethal limits

Juveniles Adults

Stress

Mortality

Preferred

Setzler-Hamilton and Hall 1991

Dissolved Oxygen

Helpful LinksWater Quality St. John’s Riverhttp://www.lake.wateratlas.usf.edu/river/waterquality.asp?wbodyid=1025&wbodyatlas=river

St. John’s River Operational Forecast System: Get current data at specific parts of the St.John’s using Nowcasthttp://tidesandcurrents.noaa.gov/ofs/sjofs/sjofs.html

SummaryPhysical conditions affect all life stages of striped bass

Understanding changes to striped bass habitat is important for fisheries management

Habitat quality is determined by a suite of physical conditions