Relationships between growth and hydrological parameters for fed Atlantic croaker and unfed striped mullet.
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Atlantic croaker (Micropogon undulatus) and striped mullet (Mugil cephalus) were cultured in cages in the intake area, at the head of the discharge canal, and at three locations in the cooling lake of a power plant near upper Galveston Bay, Texas, from 1 February 1976 to 20 August 1976 to assess the suitability of each location for mariculture. Interpretations were based on daily measurements of six hydrological parameters and survival and growth of the fish. Primary sources of mortality included high effluent temperatures, abrupt changes in conductivity, and lymphocystis. Growth rates of fed Atlantic croaker were strongly related to water temperature. Regression procedures were used to develop a polynomial function to describe the parabolic relationship between growth rate of croaker and mean monthly water temperature. The curve described by this model indicated no growth at temperatures below about 13.5 C or above about 33.5 C and maximum growth near 27 C. This information might be valuable in selecting optimum locations for culture of Atlantic croaker or related fishes within thermally heterogeneous environments. Growth rates of unfed striped mullet were not related to water temperature but were linearly related to pH and dissolved oxygen, which were probably indicators of primary production. However, the growth of mullet was poor even at the most productive location; consequently, the use of unfed caged mullet to harvest phytoplankton does not seem feasible unless the primary study area.