BITMAX I and BITMAX II: Bio-Physical Interactions in the Maximum Turbidity Zone

Reproductive success (referred to as recruitment) of anadramous fishes is tightly coupled to the physics and biology of the highly turbid, salt-fresh transition zone in the upper regions of estuaries. The Estuarine Turbidity Maximum (ETM) is a physical feature located at the heads of coastal plain esturaries. ETMs trap and retain sediment, detritus, zooplankton and early-life stages of fish. Our BITMAX projects, funded by the National Science Foundation, are multidiciplinary programs advancing fundamental knowledge of ETM structure and dynamics. The ETM enhances trophic transfer from microbes to plankton to fish. The multidisciplinary research addressed two hypotheses of direct importance to recruitment of anadromous striped bass and white perch: 1) abundant food and stable stratification in the ETM enhance feeding conditions and production of zooplankton and fish larvae, and 2) life-history strategies of fishes are adapted to respond to pulses in ETM circulation patterns. The research was conducted through coordinated field, laboratory, and numerical modeling experiments in the ETM region of Chesapeake Bay.
      In this research, the nutritional wellbeing of larval-stage striped bass was found to be strongly related to the timing and amounts of freshwater flow entering the upper Chesapeake Bay and to the associated production of suitable zooplankton prey, especially the copepod Eurytemora affinis, near the salt front and ETM. Coarse control over recruitment strength of striped bass was exercised in the larval stage and related to nutritional sources and amounts, and to the physics of the salt-front, ETM region. Strong density dependence in growth and mortality was observed in the small juveniles of striped bass in which the more than 30-fold variability in abundance of age-0 juveniles was regulated to result in only 3-5-fold variability at age 3 when striped bass are recruited to the fishery.

Locations of sampling stations, 2007 and 2008, in the channel of upper Chesapeake Bay, USA. Locations of the salt front and ETM usually fall within the bounds of the Blue oval.

Representative Publications