Sublethal Effects of Hypoxia on Atlantic croaker (Micropogonias undulatus) in the Chesapeake Bay

Low dissolved oxygen (DO) in water column

Both natural and anthropogenic causes Increasing global problem

Largest US estuary Long history of

hypoxia Large human

impact Croaker

commercially important

Found in hypoxic areas

Kemp et al. 2005

Wicks et al. 2007

Chesapeake used for industrial, commercial, and recreational purposes

Hypoxia can negatively affect water quality and aquatic organisms (ex. croaker)

Croaker !

Acoustic Telemetry Study: Summer 2011

Lab Hypoxia Study: Summer 2011 & 2012

Field Hypoxia Study: Summer 2012-13

Telemetry: Determine behavioral responses between normoxic and hypoxic sites

Lab/Field: Determine physiological effects under hypoxia Quantify immune, general health, and

reproductive effects

Spring and Summer 2011

Stratified and reference sites

56 fish total

Day and day/night sessions

Vemco VR-100 Receiver

Directional & 360º hydrophones

V91P-L transmitter (depth sensor)

Benzocaine anesthetic

Surgical implantation External T-bar tag Recovery Release

Tangier Sound (Reference)

Point No Point (Stratified)

Croaker utilize deep channels Some indication of shallow water use in

hypoxic site Prefer benthic structures (holes, oyster

sanctuaries, lighthouses) Less overall movement in later session Greater mobility at night

STRATIFIED

REFERENCE

Determine physiological effects under hypoxia

Quantify immune, endocrine, and reproductive effects Phagocytosis – immune function response Organosomatic Indices –overall health, immune &

reproductive response Hematology – general health; stress; homeostatic &

osmotic balance Lab trials will determine indicators for use in field

study

24, 48, and 72h trials 1.5 mg/L DO Hematology

Plasma chemistry Electrolytes

Complete Blood Count Differential

leukocyte count Organosomatic Indices

Hepatosomatic (HSI) Splenosomatic (SSI) Gonadosomatic (GSI)

Decreased HSI & SSI in hypoxic fish (48 & 72h) Indication of stress Recruitment of blood

into circulation Neutrophilia and

lymphocytopenia in 24h hypoxic fish Innate immune

response Increased glucose

*

FIELD SAMPLING

LAB TRIALS

Anesthetized fish are bled

Blood Drawn Blood put in

centrifuge

Blood smears

Extract plasma

Hematocrit

WORKSHOP: HEMATOLOGY

Plasma chemistry

Electrolytes

Plasma protein

EYE

GILLSPECTORAL FIN PELVI

C FIN

ANAL

FIN

CAUDAL FIN

FIRST DORSAL SECOND

DORSALLATERAL LINE

Liver Gonads

Kidney

Spleen

Swim Bladder

Brain & Otoliths

Hepatosomatic (HSI)

•Environmental stress

•Nutritional status

Splenosomatic (SSI)

•Immune response

•Blood capacity and transfer

Gonadalsomatic (GSI)

•Gonadal growth•Reproductive

response

Studies of Chesapeake Bay and At. Croaker important to understanding human impact on environment

Hypoxia is a growing problem that causes serious behavioral and physiological effects

If we don’t understand more about hypoxia and its effects, this is the result:

FISH KILL

Capt. Daniels & El Diablo

Luis López-Cruz

Eshaddai Ephrem

SEEL

Ria Mandan

Nivette Perez-Perez