Early Life History of Bighead, Silver, Black, and Grass Carps

Science Center Objects

Grass, bighead, black, and silver carps spawn in turbulent rivers and their eggs develop and hatch while drifting downriver.  The larvae also have a short period of developing in the drift, and then they must swim from the river and find appropriate low- or no-flow nursery areas. Rivers which are not long enough, turbulent enough, or without nursery areas in the correct locations are not likely to support survival of these fishes.  If we can cause these problematic fishes to spawn in locations that will not support survival, or if we can locate spawning and nursery areas to harvest fish or prevent their survival, these would be useful control methods. CERC scientists are studying the behavior of larvae and eggs of these fishes in a flume, to generate data to enhance drift models for early life history stages. These models aid in assessing the suitability of a river for spawning and survival of young, for determining the locations where captured eggs and larvae were spawned, for determining the portion of the river where the larvae are most likely to attempt to laterally disperse from the spawning river, and where larvae might be susceptible to control methods.

Testing set-up to determine olfactory preferences in larval carps

Testing set-up to determine olfactory preferences

in larval carps.

(Public domain.)

The Issue: The early life stages (eggs, larvae, and juveniles) represent a critical period in the lives of fish, one characterized by high mortality rates.  Survival of these stages commonly determines year-class strength and overall population size.  These life stages are not captured using standard fishing gear meant for adults, thus there is a lack of knowledge about survival rates, habitat requirements, and recruitment and dispersal potentials. Understanding the factors during early development is needed for risk analysis of establishment, prediction of transport distances and available nursery habitats, determination of spawning location, and allows development of controls which reduce early life stage survival and year-class strength.

Addressing the Issue: By combining early life biological data with physical and hydraulic data, models such as FluEgg have been developed to predict transport within a specific river system. CERC scientists have learned:

  • Temperature-dependent developmental rates of grass carp, bighead carp, and silver carp.
  • Survival rates of grass carp eggs that settle to the bottom.
  • Physical characteristics of grass carp, bighead carp, and silver carp eggs useful for identification.
  • Swimming behaviors and capabilities of grass carp, bighead carp, and silver carp larvae.

In addition, CERC scientists are currently working on projects to:

  • Determine early life history characteristics of black carp, including developmental rates, stages, physical characteristics of eggs, and swimming behavior.
  • Measure grass carp egg transport and larval swimming behavior in flowing water to improve and expand the FluEgg model for use past the egg stages.
  • Preliminary testing on the effects of turbulence on the survival of eggs and larvae.
  • Test neurosensory development to determine potential environmental cues for dispersal.
  • Train and assist other agencies in the identification of captured larvae.

Next Steps:

  • Enhancement of dispersal models such as FluEgg with relevant biological data for early life history characteristics.
  • Comparison of model predictions with field-collected data.
  • Assist with the development of control mechanisms aimed at early life stages.

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