lab16 USE THIS!!!! - J . F ishBiol. (1980)16,613-619 The...

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FishBiol. (1980)16,613-619 The influence of salinity on oxygen consumption and plasma electrolytes in grass carp, Ctenopharyngodon idella Val. M. J. MACEINA*, F. G. NORDLIE~ AND J. V. SHIREMAN" *Aquatic Weeds Research Center, ?Department of' Zoology, University of' Florida, Gainesville, Florida 3261 I, U.S.A. (Received 31 July 1979, Accepted 18 September 1979) Fingerling grass carp, Ctenopharyngodon idella, 90-160 mm T.L., were acclimated to experi- mental salinities of < I (fresh water), 9 1, 195 and 3 I7 mOsm/kg. Oxygen consumption rates of fish declined, as salinity increased, from 0 16 mg O,/g-h in fresh water to 0.1 1 mg O,/g-h at an ambient concentration of 3 17 mOsm/kg. Plasma electrolytes (Na+ and Cl-I) and total plasma ionic concentrations increased slightly following I0 days of exposure to ambient salinities greater than 195 mOsm/kg. At 317 mOsm/kg fish appeared to lose control of plasma electrolyte concentrations. As the osmotic gradient was reduced between the fish and the external medium it might have become advantageous to the maintenance of the osmotic equilibrium to reduce blood circulation to the gills, thus imposing a reduction in metabolic rate. I. INTRODUCTION Grass carp, Ctenopharyngodon idella Val., are being investigated as a biological control of excessive submerged macrophytes. Concern has been raised on the possible adverse impact grass carp might have on the coastal regions of south- eastern United States. Invasion by these fish into brackish water ecosystems is possible as evidenced by data presented by Cross (1970), Chervinski (1977), Maceina & Shireman (1 979). Aquatic macrophytes are integral components of brackish water marshes and contribute to high animal productivity. These areas also serve as nursery grounds for a wide variety of marine invertebrates and fish, and provide valuable habitat for wintering waterfowl. Maceina & Shireman (1980) found survival, feeding and growth of grass carp fingerlings are possible in salinities to 9%0. Although grass carp consumption rates during exposure to 3 and 6%0 salinity did not vary from rates in fresh water, dietary conversion rates were less, causing slight reductions in growth. Two physiological mechanisms may explain this phenomenon: (1) a short acclimation period to hypotonic salinities might have caused an increase in the energetic cost of osmo- and ionic regulation (Styczynska-Jurewicz, 1970; Paloheimo & Dickie, 19666); (2) a change in the ion and nutritional absorption process in the intestinal tract (Ellory et al., 1972) and/or alteration of digestive enzyme properties might have caused a decrease in food assimilation. The influences of salinity on oxygen consumption and metabolic rate in grass carp were investigated to explain decreases in dietary efficiencies observed in Journal Series No. 188 1 ofthe Florida Agricultural Experiment Station 0022-1 1 l2/80/0606 I347 $02.00/0 613 0
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This note was uploaded on 09/12/2010 for the course BIOLOGY 225 taught by Professor Pavgi during the Winter '10 term at University of Michigan.

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lab16 USE THIS!!!! - J . F ishBiol. (1980)16,613-619 The...

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