Swimbladder inflation study
Absence of swimbladder development is a major problem in larval rearing of many species including striped bass. There is a narrow window when inflation can occur between four and eight days post hatch at 17 to 20oC. Larvae that do not inflate swimbladders during that time period will not do so later and develop a deformity know as lordosis (second photo). Studies on factors influencing swimbladder inflation in various species indicate that problems occur primarily in intensive culture, and that physical factors in culture systems including access to surface air, surface cleanliness, turbidity, turbulence, aeration, and lighting are important factors influencing swimbladder inflation. In our studies of swimbladder inflation we have found that keeping the water surface clean, keeping the tanks in constant darkness for days 4 through 7 post-hatch and maintaining water hardness above 100 ppm are the most important factors to produce larvae with a high percentage of inflated swimbladders.
Pfiesteria related research
As participants in the ECOHAB project we are investigating physiological responses of fish subjected to stressors associated with harmful algal blooms (HABs). Our primary goal is to determine fish responses to HABs by measuring physiological changes in their blood chemistry. Parameters that we are interested in measuring are ammonia and urea nitrogen concentrations in fish blood serum. A second goal is to determine if nutrient loading, from ammonia and urea excretion have a significant effect at the ecosystem level. Nitrogen loading from large schools of fish has the potential to contribute to the persistence and/or intensity of HABs.
Fish Health Studies
HPL is working with the Maryland Department of Natural Resources on joint projects to address concerns surrounding the overall health of fish in the Chesapeake Bay. Areas of concern include the deep ulcerative lesions found in juvenile menhaden, ulcerative dermatitis in striped bass and the relation of malnutrition to disease. Menhaden have been grown in tanks at HPL for over 9 months. The healthy juvenile menhaden have been successfully deployed in cages as sentinels in the field in areas where wild menhaden have appeared with deep ulcerative lesions and we hope to be able to use them in challenge studies to determine if measures of stress can be developed.
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Current Research
Selective breeding study
In a current study we are using superior performing males from the strain evaluation study to determine if there is a paternal contribution to growth and aquaculture performance. We divided the eggs from a wild female and fertilized them with sperm from males known to have superior growth characteristics. We used males from a Maryland and Canada strain and a wild caught male. In addition, we fertilized a portion of the eggs with sperm from a white bass to produce the hybrid known a Palmetto bass. We also used sperm from the superior Maryland male to fertilize eggs of a white bass to produce the other hybrid known as a Sunshine bass. All five groups of fish produced were grown to market size under identical conditions. The study is still in progress, but early indications are that males with known superior growth characteristics pass on those traits to their offspring.
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