Tolerance to, and avoidance of, hypoxia by the penaeid shrimp (Metapenaeus ensis)

Aquatic hypoxia caused by eutrophication may lead to mass mortality of valuable living resources such as fish and shrimp. However, there is little information on the hypoxic tolerance of penacid shrimp, and whether they are able to avoid hypoxia. In laboratory experiments, LC50, LT50, and heart beats per minute were determined for juvenile Metapenaeus ensis at 0.5, 1.0, 2.0 and 6,0 mg O-2 l(-1). The 8-h LC50 for DO was 0.77 mg O-2 l(-1), while the LT50 at 0.5 mg O-2 l(-1) was 399 min. Heart beat rate significantly declined when DO fell below 1.0 mg O-2 l(-1). When confronted with a gradient of dissolved oxygen, M. ensis were able to avoid hypoxic areas and move to oxygenated water. M, ensis appeared to be sensitive to hypoxia, and their ability to detect and avoid hypoxia may enhance their survival in habitats where hypoxia may occur. (C) 2002 Elsevier Science Ltd. All rights reserved.