Physiological and behavioral effects of hypoxia on Atlantic

croaker in the Chesapeake and Coastal Bays

Andrea K. Johnson University of Maryland Eastern Shore

Collaborators:Dr. Mary Fabrizio (VIMS)Dr. Richard Brill (NOAA/VIMS)

World Hypoxic and Eutrophic Coastal Areas

415 eutrophic and hypoxic coastal systems worldwide

• 169 hypoxic areas

• 233 areas of concern

• 13 systems in recovery

HYPOXIA

• Result– changes in species

composition– population decline– mass mortalities – production of extensive

“dead zones” such as that in the Gulf of Mexico

Massive Fish Kill in Gulf Caused by "Dead Zone,” Oil?

Photograph courtesy P.J. Hahn, Plaquemines Parish

Environmental degradation has been increasing the occurrence of hypoxia.

Spawning(Fall-Winter)

Larvae

OffshoreEstuary Juveniles

STUDY OBJECTIVEWe proposed to use Atlantic croaker, an economically and ecologically important demersal species, as a model species to assess the sublethal effects of seasonal hypoxia on fish physiology, movement and distribution.

ATLANTIC CROAKER• Good indicator species in which to study

the effects of environmental degradation– Well researched– Hardy – Matures quickly– Found in hypoxic waters• 1.6-3.7 mg/L DO in the Gulf of Mexico (Craig and

Crowder, 2005; Thomas et al., 2007)• < 2 mg/L DO Chesapeake Bay (Fabrizio pers. obs.)

SPECIFIC OBJECTIVES

1. Laboratory Study (Year 1-2)

Determine the effects of hypoxia exposure on

immunological, reproductive and endocrine

functions of croaker under controlled laboratory

conditions.

 

2. Field Study (Year 1)

Determine the persistence (presence/absence over

time) of croaker in areas that develop hypoxia in

Chesapeake Bay using active acoustic telemetry.

SPECIFIC OBJECTIVES

3. Field Study (Years 3-5)

Compare immunological, reproductive and endocrine

functions in croaker collected from hypoxic and reference

sites in the Chesapeake and Coastal Bays.

4. Field Study (Years 1-5)

Integrate observed physiological responses determined in

laboratory and field studies to behavioral responses of

croaker, and to changes in water quality and other

environmental variables (tested under subprojects 1 and 2)

in the field.

HEALTH INDICATORS

GENERAL HEALTH STATUS

BIOCHEMICAL STATUS

ENDOCRINE AND IMMUNE FUNCTION

EXTERNAL STRESSORS (e.g. hypoxia, toxicants)

Gonadotropins

Testes Ovaries

T, 11-KT T, E2

GnRH

Plasma vitellogenin

Liver vitellogenesis

Adrenocorticotropic Hormone (ACTH)

Interrenal tissueCortisol

Muscle proteinGrowth

ReproductionImmune functions

SurvivalDisease

Corticotropic Releasing Hormone (CRH)

HPI AXIS HPG AXIS

PROJECT TIMELINE

EDUCATION AND OUTREACH

THANK YOU