Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 124-136). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Sex-specific nutritional requirements for crude protein and fat were demonstrated in cultured (F1) Penaeus stylirostris brood stock. Female shrimp required diets which had higher protein (32 versus 27%), lower fat (2.5 versus 3.9%), higher protein/calorie ratios (8.5 versus 6.8% protein/kcal/g), and much higher protein/fat ratios (15.4 versus 7.8% protein/% fat) than males. These studies have also demonstrated a nutritional demand corresponding to the onset of ovarian maturation, a phenomenon which was explained as a reduction in growth rates at the attainment of 30 to 35 g in shrimp fed deficient diets. Both the quality and the quantity of dietary fat were shown to affect the growth of P. stylirostris brood stock. Male growth was positively correlated with the quantity of eicosapentaenoic acid (20:5 ω3) in the diets. The females were not affected by the types of fatty acids in the fat; they were influenced more by the quantity of fat, i.e., as the fat level of the diet increased, the growth decreased. Cold extrusion feed (CEF) diets supplemented with squid, and diets which included squid as one of the ingredients in the formulation, were found to stimulate better growth in both male and female brood stock as compared to CEF diets of equal protein and fat content without squid. The protein/fat ratio, as well as the content of polyunsaturated fatty acids (PUFA), were suggested to be responsible for the improved growth. Comparisons were made between the quality of spawns from wild P. stylirostris matured in captivity (P1) and F1 shrimp. Protein levels of the eggs did not correlate with either the number of eggs spawned or the eclosion rate. The number of the eggs spawned was correlated positively with the levels of eicosaenoic acid (20:1 ω9) in both P1 and F1 eggs, and correlated negatively with linoleic acid (18:2 ω6) in P1 eggs only. Spawning times were reported to occur later in the evening as summer approached. A significant, negative correlation was observed between the elapsed time from copulation, i.e., collection of fertilized shrimp, to spawning and eclosion rate. Also, a significant positive correlation was observed between the number of spawns which contained eggs which did not hatch, and the elapsed time from copulation to spawning. The number of eggs spawned and the eclosion rate were found to be higher in P1 shrimp as compared to F1 shrimp. Also, first breeding season spawners (FBS) had better quality spawns than second breeding season (SBS) spawners, i.e., more eggs with higher eclosion rates. A general reduction in the quality of the spawns was therefore implicated as a result of the culture conditions. Multiple spawning behavior was observed and there appeared to be no qualitative or quantitative difference between spawns. Tank size and shape were demonstrated to affect the onset of ovarian development and the transfer of the spermatophore. A minimum of three meters was thought to be required for the development of the ovaries and the successful transfer of the spermatophore.

Black spot development or "melanosis" is a common defect in fresh shrimp which results in product being devalued and rejected by consumers. Currently, sulfiting agents are used to control melanosis in shrimp. However, with increasing regulatory and consumer concerns about the safety of sulphites as a method of melanosis control, the shrimp processing industry is actively seeking alternative methods to control melanosis on, and extend the shelf life of, fresh shrimp. One method which has the potential to fulfill both objectives is glucose oxidase (GOX)/glucose dipping solutions in conjunction with Modified Atmosphere Packaging (MAP). / Preliminary studies have shown that black spot development can be controlled for 14 days at 4$ sp circ$C in white shrimp (Pandalus occidentalis) and pink shrimp (Pandalus borealis) using GOX/glucose or GOX/glucose/ascorbic acid in conjunction with gas packaging (60% CO$ sb2$: 40% N$ sb2$). This dipping/packaging treatment also improves the physical, chemical and microbiological changes in white shrimp compared to samples dipped only in water and air packaged. This study has shown that the combined use of two or more "barriers" can be used to extend the shelf life of, and control melanosis on, fresh shrimp. This novel process of "dipping" shrimp in GOX/glucose solutions in conjunction with MAP will have a significant effect in the area of shrimp hygiene and will have the potential to minimize shrimp spoilage incurred through melanosis.

Graduation date: 1992

Ph.D. (Zoology) / Please refer to full text to view abstract

No description available.

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

published_or_final_version / Zoology / Master / Master of Science