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Retention and Transport of White Perch and Bay Anchovy Eggs and Larvae in Chesapeake Bay: Mechanisms and Implications for RecruitmentEPA Grant Number: U915366
Title: Retention and Transport of White Perch and Bay Anchovy Eggs and Larvae in Chesapeake Bay: Mechanisms and Implications for Recruitment
Investigators: North, Elizabeth W.
Institution: University of Maryland - College Park
EPA Project Officer: Boddie, Georgette
Project Period: August 1, 1998 through August 1, 2001
Project Amount: $71,846
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Fellowship - Oceanography , Aquatic Ecosystems , Academic Fellowships
The objectives of this research project are to: (1) evaluate potential impacts of physical conditions on early life histories of two estuarine fish, bay anchovy (Anchoa mitchilli), and white perch (Morone americana) in the Chesapeake Bay; and (2) describe mechanisms of dispersal or retention of eggs and larvae that result from small-scale interactions of physics and biology, and explore their implications for survival to adulthood (i.e., recruitment).
The factors that control the transport and retention of white perch and bay anchovy larvae were studied in two field-sampling efforts. Data on bay anchovy eggs and larvae were collected on a 10-day cruise in June 1996, in the mainstem of the Chesapeake Bay. After a survey of larval abundance along the Bay axis, repeated depth-stratified sampling was conducted at a fixed station. On every tide, both day and night, depth-stratified collections of ichthyoplankton, microzooplankton, and gelatinous zooplankton were made. Water column measurements of salinity, temperature, dissolved oxygen, fluorescence, and current velocity also were collected. Multivariate statistics will be used to identify the biological (prey, predators, and ontogeny) and physical (tides, dissolved oxygen, temperature, and salinity) factors that most influence bay anchovy egg and larval distributions. A numerical model of larval flux will incorporate diel migrations and current velocities to provide estimates of speed and directions of larval transport. Data on white perch larvae were collected during three cruises to the upper Bay in May 1998, and two cruises in May 1999. On each cruise, a series of conductivity, temperature, and depth (CTD) casts along the Bay’s axis located the Estuarine Turbidity Maximum (ETM). Gradients in depth-specific abundance of ichthyoplankton, zooplankton prey, and potential predators were mapped above, within, and below the ETM in conjunction with measurements of turbidity, salinity, temperature, oxygen, and pH. In addition, a time series of depth-stratified ichthyoplankton and microzooplankton collections and physical measurements was conducted within the ETM. Physical and biological characteristics of the ETM that are important for larval survival will be identified, and potential mechanisms (physical and behavioral) for larval retention within the ETM will be determined. Retention mechanisms revealed in the field sampling program will be combined with young-of-the-year indices, historical data, and numerical modeling of larval behavior to link physical and biological conditions to larval survival and juvenile recruitment.