Jasmine Smalls and Steven G. Hughes
Aquaculture Research and Education Laboratory
Cheyney University of Pennsylvania
Cheyney, PA 19319
The cost for feed can represent from 50-60% of the total rearing cost for salmonids reared in aquaculture facilities. The size of the fish, the temperature in the rearing environment, and the amount of energy in the feed can all be significant variables when calculating growth and feeding rates. Historically, however, the rates at which fish are fed have been determined using subjective criteria that can lead to either underfeeding (resulting in reduced growth) or overfeeding (resulting in low feed efficiencies and increased effluent pollution). The first study described here was designed to determine a mathematical formula to accurately determine the amount of feed to be fed daily to juvenile rainbow trout which will take into account the three important factors listed above and will maximize growth while minimizing waste. In Addition, a second study was conducted which evaluated the comparative feeding efficiency and weight gains obtained with this new formula and several other published feeding formulas for trout. The data from this second study, though variable, indicates that feeding formulas which take into account all three of the parameters above outperform those which only take into account one or two.
Steven Hughes
Aquaculture Research and Education Laboratory
Cheyney University of Pennsylvania
Cheyney, PA 19319
It has long been recognized that fish are capable of absorbing calcium directly from the water by way of the gills and recent studies have indicated that the addition of calcium to soft waters may relieve some of the stresses of handling and transportation for striped bass. The staff of the Aquaculture Research and Demonstration Project at the University of Maryland Eastern Shore along with staff from the Horn Point Laboratory of the University of Maryland has been conducting research to quantify the amount of calcium required and the physiological impacts of the absence and presence of adequate levels of calcium. Research to date indicates that there was a significant positive impact on survival, blood calcium levels and the levels of other blood ions when the fish were transported into water with calcium levels above 250 mg/L. Fish placed into receiving waters containing either 30 or 100 mg/L calcium experienced very high mortality rates and showed greatly depressed levels of blood calcium and other ions. This research indicates that the previous striped bass guidelines for aqueous calcium may in fact be too low
and that higher levels are required for optimum survival rates. Additional research has also indicated that the physiological stress induced by low aqueous calcium levels could not be relieved by increasing the intake of dietary calcium and that aqueous calcium levels had a direct positive relationship with blood clotting times. All of these findings when applied to hauling systems should lead to striped bass being transported with fewer transport related mortalities and with better survival after delivery.
Kathleen T. Rajkowski (1) and Steven G. Hughes (2)
(1) Eastern Regional Research Center, Agricultural Research Service U.S. Department of Agriculture 600 Mermaid Lane Wyndmoor, PA 19038
(2) Aquaculture Research and Education Laboratory Cheyney University of Pennsylvania Cheyney, PA 19319
Aquaponic systems combine aquaculture and hydroponics to raise both fish and produce using recirculating water. There is limited microbial data on the aquaponic system. In this study an aquaponic basil farm used good agricultural practices (GAP). The fresh basil plants and water, collected in bottles and gauze, were analyzed for their microbial quality. No Salmonella, Escherichia coli, Listeria monocytogenes or Staph. aureus were recovered from any of the samples. Using GAP reduced the risk of pathogen contamination. The aerobic plate count (APC) on the retail basil and water samples ranged from 4.0 to 6.3 and 2.5 – 5.4 log cfu/g, respectively. There was not statistical difference (P > 0.05) for the APC water results collected in bottles or the gauze method. These results indicate that when an aquaponic farm uses GAP, pathogen contamination is reduced providing the consumer a safe food product.
Steven Hughes and Amelia Potter
Aquaculture Research and Education Laboratory
Cheyney University of Pennsylvania
Cheyney, PA 19319
Preliminary profiles of lactate dehydrogenase (LDH) activity in four Chesapeake Bay sport fish species were determined to identify possible relationships between fish muscle LDH activity and their ability to cope with metabolic acidosis. The species used in this study were striped bass (Morone saxatilis), summer flounder (Paralichthys dentatus), Atlantic croaker (Micropogonias undulatus) and bluefish (Pomatomus saltatrix). Their selection was based on their physiological differences and their relative importance to the Maryland sport fishing industry. The results of this study indicated a trend for decreasing LDH activity in white muscle when comparing muscle composition (percent red muscle) and relative activity levels (active swimmers, bottom swimmers, and sit and wait predators). The rank, in order of decreasing LDH activity (KM) was bluefish (0.013 + 0.009 mM/min/mg protein), striped bass (0.012 + 0.080 mM/min/mg protein), Atlantic croaker (0.008 + 0.005 mM/min/mg protein), and summer flounder (0.005 + 0.050 mM/min/mg protein). From the data collected in this study (data not shown), I concluded that LDH activity for pyruvate to lactate conversion observed in muscles or tissues varies with the amounts of lactate produced. There was lower LDH activity for pyruvate to lactate conversion in the white muscle of each species compared to other tissues. These findings agree with literature reports that lactate is removed at its site of origin (i.e. white muscle). LDH activity for lactate to pyruvate conversion could not be determined at the substrate concentrations used in this study.