Growth Experiment and White Sturgeon Feeding

No one died as a result of each of the feeding experiments. In row 1 tank 1, all of the growth efficiency values were positive. The body weight of the white sturgeons rose exponentially from 42g to 62g at a feeding rate of 2.5 percent body weight/day. When compared to tank1 row 2, which had the same feeding rate of 2.5 percent, growth increased from 48g to 65g, and in tank2 row 3 with the same 2.5 percent growth rate, growth increased from 59g to 76g. Therefore, by providing a feeding rate of 2.5% in the four weeks period, the body weights of white sturgeons increased by 20g, 17g, and 17g respectively, for three tanks. In addition, it is important to note that in 2.5% feeding rate, there was no values that showed growth performance to be negative.

Feed rate of 2% also showed continued increases of body weights in the four weeks in all the three tanks that used it. In row 1 tank 5 for example, the average body weights for white sturgeons increased from 50g to the final weight of 76g in the fourth week, which depicts that there was an increase by 26g. In row 2 tank2, which was similarly treated by 2% feed rate, the average initial body weight was recorded as 60g, which increased exponentially to 69g by the fourth week to record a total body weight increase of 9g. In row 3 tank 3, the average initial weight was 51g, which did not change in the first one week, but went on increasing to 61 by the end of the fourth week, thereby recording a total increment of 10g.

The treatment with 1.5% feed rate showed increases of average body weight from an initial of 63g to 76g at the end, which was a total raise by 13g in row 1 tank 3. The same treatment was applied in row2 tank3, which showed an initial average body weight of 63 and a final body weight of 78g to record a total of 15g increase. In row 3 tank 1, the final average body weight of white sturgeons was recorded as 58g from an initial average body weight of 59g, which showed negative values of growth performance.

At a feed rate of 1%, increases in body weights in four weeks period, in the three tanks that received the treatment showed 1g in row 1 tank 2, 8g in row 1 tank 6, and -4g in row2 tank 6. It was also evident that there are times when the average body weights of the fish remained stagnant between weeks and instances when there were decreases in body weights despite the treatments.

Treatment using 0.5% feed rate shows an increase in average body weight in one tank, but not in the other two tanks that received the same treatment. While in row tank 4 the average final body weight had increased by 5g to 56g from the initial average body weight of 52g, in row 2 tank 4, the total body weight increase was recorded as -9g and in row2 tank 5 there was also a negative growth performance as indicated by a decrease in average body weight by 5g from the initial average body weight of 61g to a final of 56g.

Based on the statistical analysis software (SAS), a feed rate of 2.5% and 2% showed a specific growth rate (SGR) of 1 at standard deviation of 0 and 1 respectively, while all other treatments, 1.5%, 1% and 0.5% showed a SGR of 0 at standard deviation of 0. In addition, feed efficiency (FE) was shown to be 57 at feed rate of 2.5%, 55 at feed rate of 2%, 38 at feed rate of 1.5%, 12 at feed rate of 1% and -51 at feed rate of 0.5%.

Discussion

How the Present Results Compare With Those of Previous Studies

From the current experiment, feeding rate is a very important factor on the growth progress of fish. White sturgeons reared at18.6 °C portrayed a notable increase in body weight when feeding rate was increased from 0.5% to 2.5% body weight per day. The absence of mortality in this experiment could have resulted from the fact that the lowest rates of feeding that were utilized were greater than the levels of maintenance.

As reported by Hung et al. (1993), feed intake information is very significant to fish’s excellent nutrition and feeding. It is very hard to approximate the intake of feed of white sturgeon since they feed slowly as they normally take between 1 and 2 hours to finish a meal in the settings of a laboratory. As such, extreme feed intake as well as the required extent of feed intake for maintenance of the fish at varying temperatures is hard to determine which is why the current study standardized the temperature at18.6 °C for all treatments in all the tanks.

Hung et al. (1993), define optimum feeding rate as the rate of feeding that gives the maximum growth ratio to ration, which was determined through passage of tangent through the growth-ration curve origin. According to Cui & Hung (1996), other than defining the optimum feeding rate as a rate at which there is maximal ration of growth to feed intake, they based the definition to their earlier works and defined it as the rate above which there is no increase in growth even when the feed rate is increased. Tangent probe of the body weight increase-curve of the feeding rate through the origin put forward that the peak feeding rate, which is the ratio of body weight increase to rate of feeding of the sampled white sturgeon was at 2.0 to 2.5% body weight/ day at 18.6°C. In the study by Hung et al. (1993) that determined the effect of rate of feeding and temperature of water on the growth of young white sturgeon on 30g, the authors found out that the optimum feeding rate was similarly 2.0 to 2.5% body weight/ day.

As shown earlier by Hung & Lutes (1987) that body weight increase percentage, the ratio of feed gain and final body weight were notably affected by the rate of feeding, the current experiment conformed to these finding by showing that as the feeding rate increased, final body weight and percentage increase in body weight were affected. However, as it regards the minimum feed gain ratio as a determinant of the optimum feeding rate, the current study showed clear difference to that of Hung & Lutes (1987). While previously the authors reported that the feed gain ratios were increased when the rates of feeding were below or above the optimum range, but reduced when the rates of feeding were close to the optimum feeding rate, the current study has shown directly the opposite. The feed gain ratio that based on the SAS shows that it was low when the feed rate was low and increased as the feed rate increased.

At 0.5% feed rate, the specific growth rate was low, which suggests that the feed rate was very close to the needed nutrient for maintenance as there was no death reported. Therefore, much of the nutrient that was contained in the given diet was utilized in the maintenance of life, thereby leaving only a small fraction available to support any growth. In the four week period, the fish that received the low feed rate of 0.5% showed the least increase in body weight compared to others. By increasing the feed rate, and especially between 2 and 2.5%, increased fraction of the nutrients in the diet was utilized for growth, which is the reason why there was recorded better growth as well as feed efficiency. Hung et al. (1989) say that the notable increase in body weight increase percentage as the feed rate is increased is importantly a direct outcome of a raised fraction of nutrients in the diet that is going to support growth and not to maintenance. Unlike in the previous study by Hung & Lutes (1987) that showed that feeding above 2% body weight per day led to wastage of feed, which resulted to a plateau in the body weight increase percentage, the current study shows that feeding above 2% led to optimum growth. Moreover, unlike Lee et al. (2016) who reported that there was weight gain increase with increased feeding rate until 1.2%, the current study exhibited a significant increase in weight gain with increased feeding rate even at 2.5%. The optimum feeding rate from 2.0% to 2.5% that was suggested in this study falls within the values that were reported by Hung et al. (1989) at 18 °C.

According to Hung et al. (1989), optimum rates of feeding, which are expressed as body weight percentage, decrease as the fish size increase, and as the water temperature decrease. In the current experiment, the fish size was below 100g, but it can be argued that the differences in results recorded in different studies compared to the current experiment can be explained as resulting from the variation in rations calculations, which complicate how fish size and effects of temperature on the optimum feed rates can be directly compared.

How White Sturgeon Compare with other fish Species

Zheng et al. (2015) conducted a similar study to determine how the growth performance was affected by feeding rate but used the green sturgeons and not the white sturgeons. The same parameters as those in this experiment were used including setting the temperature of the water at 18 °C and feeding on salmonid. In addition, just like in the current study, Zheng et al. (2015) reported that the final body weight, specific growth rate and efficiency of feed were notable influenced by the feeding rates. However, unlike in the current study, Zheng et al. (2015) reported that the optimum feeding rates between 5.3% and 7.1%, which were decreasing as the green sturgeon grew older following exogenous feeding initiation. Deng et al. (2003) used white sturgeon larvae to determine the manner in which growth performance was affected by feeding rate, and reported that as the larvae grow older, the feed rate decrease. During the first week, Deng et al. (2003) found out that 26% feed rate was optimal, but decreased to 13% in the second week, 11% in the fourth week and 6% in the fourth week. De Riu et al. (2011) used the white sturgeon fries under the same conditions as those used in the current study, and even though the authors reported mortality, they say that it was not related to feeding rate, but like in this experiment, increases in body weight, specific growth rates and efficiency of feed were notably affected by feed rate. The authors also reported optimum feeding rates that decreased with increase in number of weeks.

The Limitation of the Present study

According to Hung, Conte & Lutes (1995), the temperature of the water as well as the concentration of dissolved oxygen are very important environmental factors that affect growth and efficiency of feed in the production of fish. While this study aimed to test whether offering different amounts of feed would cause a difference in the growth and development of the white sturgeons, it did not subject the experiment to different temperatures and dissolved oxygen to guarantee that the gotten results were comprehensive and inclusive of all factors necessary for fish production. The lower feed efficiency that was observed in feed rates between 0.5% and 1.5% could have resulted from conditions that were less than optimum in this experiment. The current study utilized one-way analysis of variance to obtain the optimum feeding ratio. However, Lee et al. (2014) showed that the best model that can be used in the estimation of optimum feeding ratio is the bi-exponential models, which should be used with white sturgeon below 1kg.  

Moreover, the maximum weight of fish in this experiment was 78g, which means that the reported optimum feeding rate should not directly applied to larger fish. For this reason, there is need for data regarding the association of growth and feeding rate to ascertain the best feeding rate at particular size of fish. In addition, the optimum feeding rates were based only on 0 samples, which could not be sufficient to generalize the findings. It should also be noted that additional data concerning optimum feeding tares of white sturgeon under different parameters such as size of fish, type of diet and temperature of water are required as they were lacking in this experiment.

Future Recommended Studies

The results from this experiment demonstrate that under a feed rate between 2 and 2.5%, there can be rapid growth and favorable feed efficiency of young white sturgeons that are below 100g. Based on the current findings, future researchers should go on and research the optimum feed rate for older fish under the same conditions, to enable production of up to 1kg size. In addition, there is a possibility that different temperatures have an impact on feed rates as well as growth rate and feed efficiency, which is why it would be important to conduct researches that incorporate different temperatures and different feed rates as variables to determine the optimum temperature and the optimum feed rate that can support growth and development. Lastly, there is a need to conduct a similar research using more samples to be able to validate the findings and generalize them well.

References

Cui, Y., & Hung, S. S. (1996). A prototype feeding-growth table for white sturgeon. Journal of applied Aquaculture, 5(4), 25-34.

De Riu, N., Zheng, K. K., Lee, J. W., Lee, S. H., Bai, S. C., Moniello, G., & Hung, S. S. (2011). Effects of feeding rates on growth performances of white sturgeon (Acipenser transmontanus) fries. Aquaculture Nutrition, 18(3), 290-296.

Deng, D. F., Koshio, S., Yokoyama, S., Bai, S. C., Shao, Q., Cui, Y., & Hung, S. S. (2003). Effects of feeding rate on growth performance of white sturgeon (Acipenser transmontanus) larvae. Aquaculture, 217(1), 589-598.

Hung, S. S., & Lutes, P. B. (1987). Optimum feeding rate of hatchery-produced juvenile white sturgeon (Acipenser transmontanus): at 20 C. Aquaculture, 65(3-4), 307-317.

Hung, S. S., Conte, F. S., & Lutes, P. B. (1995). Optimum feeding rate of white sturgeon, Acipenser transmontanus, yearlings under commercial production conditions. Journal of Applied Aquaculture, 5(1), 45-51.

Hung, S. S., Lutes, P. B., Conte, F. S., & Storebakken, T. (1989). Growth and feed efficiency of white sturgeon (Acipenser transmontanus) sub-yearlings at different feeding rates. Aquaculture, 80(1-2), 147-153.

Hung, S. S., Lutes, P. B., Shqueir, A. A., & Conte, F. S. (1993). Effect of feeding rate and water temperature on growth of juvenile white sturgeon (Acipenser transmontanus). Aquaculture, 115(3-4), 297-303.

Lee, S., Haller, L. Y., Fangue, N. A., Fadel, J. G., & Hung, S. S. O. (2016). Effects of feeding rate on growth performance and nutrient partitioning of young‐of‐the‐year white sturgeon (Acipenser transmontanus). Aquaculture Nutrition, 22(2), 400-409.

Lee, S., Wang, Y., Hung, S. S., Strathe, A. B., Fangue, N. A., & Fadel, J. G. (2014). Development of optimum feeding rate model for white sturgeon (Acipenser transmontanus). Aquaculture, 433, 411-420.

Zheng, K. K., Deng, D. F., De Riu, N., Moniello, G., & Hung, S. S. (2015). The effect of feeding rate on the growth performance of green sturgeon (Acipenser medirostris) fry. Aquaculture nutrition, 21(4), 489-495.