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|Title:||Studies on the effects of salinity and temperature on the commercial shrimp, Penaeus aztecus ives, with special regard to survival limits, growth, oxygen consumption and ionic regulation|
|Authors:||Gulf Coast Research Laboratory (Ocean Springs, Miss.)|
Lakshmi, G. J.
Gunter, Gordon, 1909-
|Publisher:||Hydraulics Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Contract report (U.S. Army Engineer Waterways Experiment Station) ; no. H-74-2.|
Abstract: The distribution and abundance of most commercial and sports marine fisheries species of the Middle Atlantic to Gulf states are dependent upon estuarine areas. Some species such as the oyster Crassostrea virginica and the clam Rangia cuneata spend their whole lives in the estuaries, while several motile species use this habitat as nursery grounds. Species living in low salinities avoid many enemies, the parasites and predators that do not invade low-salinity waters, The low-salinity estuaries are essential to many species and they are certainly conducive to the normal development of the young stages. In the experiments reported here it was observed that low-salinity waters are essential for the faster growth and better survival of young brown shrimp. It was shown that the young brown shrimp survive a direct transfer over a wide salinity range from 8.5 to a maximum of 42.5 ppt, that the salinity tolerance range is size-dependent and that the post-larvae have a higher salinity tolerance than the juveniles. By acclimation the salinity tolerance may be increased either toward low or high concentrations. Sudden temperature fluctuations influence salinity tolerance. In such changes high temperature has an adverse effect compared with normal temperature. Nevertheless, animals acclimated at 31°C rather than 21°C better withstand wide salinity variations with sudden temperature changes. Salinity and temperature together influence certain physiological responses such as growth, metabolic rates and blood ion regulation. Although the young shrimp can survive a wide salinity range, the best growth and survival rates were obtained in salinities of 8.5 and 17.0 ppt. Temperature variations can be advantageous only when combined with optimal salinity concentrations. At high temperature, food consumption increases; but the food was more efficiently utilized in low salinities of 8.5 and 17.0 ppt . The best growth and survival rates were obtained in the low salinity and normal temperature combinations. The basal metabolic rates of the shrimp in these experiments seem to reflect the seasonal cycle of salinity and temperature conditions in estuarine environments. The respiratory rates were minimal in low salinity (8.5 ppt) and warm temperatures (26° and 31°C) and high salinity (34.0 ppt) and low temperature (21°C) combinations similar to the conditions that the young shrimp experience during the summer and winter months. The metabolic rates obtained at low (21°C) temperature showed significant differences from those at 26° and 31°C and a similar trend was observed in the growth rates. At a salinity of 17.0 ppt, the respiratory rates were not affected by the acclimation temperatures and it was in 17.0 ppt that the blood chloride concentration was isosmotic with the outside medium, Blood chloride and sodium ion regulation were impaired by low temperature (21°C). The juvenile shrimp in their estuarine life stage require low salinity and warm waters for normal growth and survival, rather than high salinity and low temperature.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Contract Report|
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