Abstract.A reproducible, experimental model of columnaris disease was developed to study the pathogenesis of cutaneous disease associated with Flavobacterium columnare infection in koi (Cyprinus carpio). In experimental infections, lesions were usually restricted to skin and fins; gill necrosis was not a consistent finding. Cytologic and histopathologic examinations provided a presumptive diagnosis of columnaris disease. Specific detection of F. columnare was done using the polymerase chain reaction and DNA in situ hybridization (ISH). Polymerase chain reaction allowed the detection of F. columnare in fresh biological material and in formalinfixed, paraffin-embedded tissues. The DNA ISH technique allowed the identification and localization of F. columnare in formalin-fixed, paraffin-embedded tissues. Using these molecular techniques, F. columnare was readily detected in skin specimens from infected fish; however, the bacterium was infrequently detected in specimens of liver, kidney, and spleen. These observations suggest that columnaris disease generally presents as a cutaneous disease that is unassociated with systemic infection in koi. Hematologic studies indicated that most infected koi developed microcytic, normochromic, nonregenerative anemia and leukopenia characterized by lymphopenia, mild neutrophilia, and monocytosis. Biochemical changes in diseased fish included significant hyperglycemia, hyponatremia, and hypochloridemia.
The black sea bass Centropristis striata has recently gained popularity in the live seafood markets of the northeastern United States. Fish farmers need instruction on optimizing environmental parameters for the growth of black sea bass. In this study, optimal temperature and salinity were determined experimentally for the growth of juvenile black sea bass (initial mean weight, ∼9.2 g). The temperature experiment compared growth at temperatures of 15, 20, 25, and 30°C; the salinity experiment compared growth at 10, 20, and 30‰ salinities. Both of these experiments were performed in closed aquaria. At the end of the temperature experiment (6 weeks), Tukey's Studentized range test (α = 0.05) showed that fish reared at 25°C were significantly larger than those reared at 20°C and 30°C. All of these temperatures produced significantly larger fish than did the 15°C treatment. At the end of the salinity experiment (12 weeks), Tukey's Studentized range test (α = 0.05) showed that salinities of 20‰ and 30‰ did not produce significantly different weights in fish. However, both of these salinities produced significantly larger fish than did a salinity of 10‰. Given the results of these experiments, fish farmers can manipulate the environmental parameters of their aquacultural systems to optimize growth of juvenile black sea bass, thereby reducing the time required to produce a marketable product.
The bivalve Mulinia lateralis is a dominant member of estuarine benthos, but its presence and abundance in Georgia estuarine waters is sporadic over time. Recruitment and production was monitored fuom 1977 through 1981 at three inner and one outer more saline ( ) 18 ppt) areas of Wassaw Sound. Until the winter of 1981, Mulinia lateralis was absent or at very low densities. Significant settlement occurred in January 1981 when densities in the outer sound reached as high as 63,000 individuals . m-2 , The clam was more abundant in sandy mud (x = 10,161 ' m-2 ) than mud (i=271 .m-2) orsand (T=263.m-2).Cohortproductionvariedfrom0.3gdrywt.m-2.4 months-l intheinner sound to 325 e dry wt . m-2 .7 months-l in the outer Sound, with the mean biomass ranging from 0.6 to 513 g dry wt . m -2, respectively. When present, Mulinia lateralis contributes significantly to benthic production available to commercially valuable fish and crabs. That this food resource is annually and seasonally episodic could contribute to year-toyear fluctuations in production of species preying on benthos.
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