Dynamics of Dissolved Oxygen in Relation to pH and Survival of Fish Culture in Fiber Glass Tank

The study aims at determining the dynamics of dissolved oxygen in relation to pH and survival of fish culture in fibre glass tank. Three feeds were used. They are dried chicken manure only (Treatment I), mixture of dried chicken manure with commercial diet (coppens) (Treatment II) and commercial diet only (coppens only) (Treatment III). The physicochemical characteristics of water for the treatments (T1, TII and TIII) in fibre glass tank were determined twice a month using standard methods. ANOVA was used to analyze the effects of the rate of changes between dissolved oxygen, pH and the fish survival. The result from this study showed that the fish in treatment III had the highest weight gain of 272.10g followed by treatment II (172.07g) and 3 (143.47g) (P<0.05). There was no significance difference at probability level 0f (P<0.05) in survival rate. Variation exists in the water quality parameters examined, dissolved oxygen and pH falls within the range for fish survival. pH was correlated with dissolved oxygen. The findings also provide the useful information about the conditions of the three treatment which will ultimately help to manage the water body for sustainable production. The model showed that dissolved oxygen depends on pH. Keywords— Dissolved Oxygen, dried chicken, commercial diet, Fiber Glass Tank.


INTRODUCTION
Water quality is the totality of physical, biological and chemical parameters that affect the growth and welfare of cultured organisms. Water quality affects the general condition of cultured organism as it determines the health and growth conditions of cultured organism. Water quality parameters vary with feeding frequency and have wider impacts on primary productivity and fish production. Good water quality refers to that with adequate oxygen, proper temperature, transparency, limited levels of metabolites, and optimum levels of other environmental factors affecting fish culture.
Water quality in tanks change continuously and are affected by each other along with the physical and biological characteristics.
The term pH refers to the hydrogen ion (H + ) concentration in water, pH refers to how acidic or basic a water is. pH is interdependent with a number of other water quality constituents, including carbon dioxide, alkalinity and hardness. It is known to influence the toxicity of hydrogen sulphide, cyanides and heavy metals, as well as having an indirect effect on ammonia levels; un-ionized NH3 increases with pH (Klontz 1993). Meade (1989) recommended that pH be maintained at between 6.5 and 8 for all aquaculture species. In fresh water, pH can change quickly due to the amount of carbon dioxide added or removed during plant growth.
Most estuarine and freshwater species are tolerant of a relatively wide range of environmental pH (Tomasso 1993). Swingle (1969) claims that the desirable range for warm-water pond fish is 6.5 to 9. A range of 5 to 9 was It should be noted that pH can change by the hour as a function of photosynthesis which removes carbon dioxide.
Dissolved oxygen (DO) is considered as one of the most important water quality parameters in aquaculture. It is needed by fish to respire and perform metabolic activities. Thus, low levels of dissolved oxygen in fish culture cause stress to cultivated fish (Boyd, 1982) resulting in reduced feed intake, poor feed conversion and growth, and are often linked to fish kill incidents. Dissolved oxygen refers to the level of free, noncompound oxygen present in water or other liquids. It is an important parameter in assessing water quality because of its influence on the organisms living within a body of water (Wetzel, 2001). A dissolved oxygen level that is too high or too low can harm aquatic life and affect water quality (Kemker, 2013). UNEP (2007) pointed out that dissolved oxygen level was a good indicator for water pollution.
Dissolved oxygen is also produced as by product of photosynthesis from phytoplankton, algae, seaweed and other aquatic plants (Kemker, . 2013).
Dissolved oxygen and pH affects directly or indirectly other limnological parameters such as transparency, viscosity, total dissolved solids and conductivity (Whitney, 1942); all of which constitute the very important physical and chemical parameters that form the basis for an enlightened fisheries and water resources management (Araoye et al., 2007). DO is measured by the azide modification of the Winkler method. The DO level in natural and wastewater depends on the physical, chemical and biochemical activities in the water bodies. Oygen is considered as poorly soluble in water. Its solubility is related to pressure and temperature. In fresh water, DO reaches 14.6mg/l at 0 o C and approximately 9.1, 8.3 and 7.0mg/l at 20, 25 and 35 o C, the level of saturated DO is 9.0 -7.0mg/l. for living organism, about 4mg/l of minimum DO should be in water.
Dissolved oxygen is critical for fish and other water inhabitants. Generally, waters with dissolved oxygen concentrations of 5.0 milligrams per liter (mg/L) (equivalent to 5 parts per million (ppm))1 or higher can support a well balanced, healthy biological community. As dissolved oxygen drops below 5.0 mg/L, aquatic life is put under stress. (Hach Company 2001).

II. MATERIALS AND METHODS
The study was conducted at the Nigerian Institute for Oceanography and Marine Research Sapele out station Sapele Local Government Area of Delta State, Nigeria (N50 54´.5´´E005 o 39´56.4´´). six circular fibre glass tanks were used in the experiment. All experimental tanks were identical in shape and size. Tanks capacities were 3.08m 3 and depth of 60.5cm each and diameter 176.78cm. Sex reversed Nile tilapia (Oreochromis niloticus) of 0.80g average size was stocked.
The tanks were divided into three culture systems that is intensive, semi intensive culture and extensive culture in triplicates for each culture system. The treatments were dried chicken manure only, dried chicken manure plus commercial diet (coppens) and commercial diet (coppoens) only These treatments was used to determine the dissolved oxygen dynamics in each culture system and to predict the effect of pH and survival of fish culture in fibre glass tank. Three hundred (300) fish were stocked in each tank.
The fish used for this experiment were fingerlings of all male Nile tilapia (O. niloticus). Fish were fed at 800hr and 1600hr with dried chicken manure, chicken manure plus commercial feed (coppens) and commercial feed (coppens) only. The feeding rate was 5% of the total fish biomass presented in each tank and the feed amount was adjusted every two weeks for each tank separately according to the biomass available which was determined during sampling. Random samples of 75 fish were taken biweekly from each treated tank during the experimental period. Fish samples were obtained in the early morning (between 7.00hr to 9.00hr) From the measurements, the following parameters were determined: Initial weight of Fish in gram (g): Final weight of fish harvested (g) The water quality was monitored using the following water testing meters: At the end of the hand picking. Total weight of the fish was taken Random fish samples 50 from each treatment were taken to determine the final mean weight. Harvested fish were kept in plastic containers for marketing.
From the foregoing the primary data collected where used for modeling the dissolved oxygen in the fibre glass tanks with respect to the treatments administered to them vis-à-vis Chicken manure, Chicken manure plus coppens and Coppens only . The average (mean) for each parameter per two weeks was computed, considering the values from three treatments. their interrelations of twenty four weeks were determined by the analysis of variance (ANOVA) using the MiniTab 17 software. All test were carried out at 5% probability level (P <0.05).   The model intended to be developed is of the form Y = bo + b1y1 + b2y2 (1)

Treatment I
The       The results presented in Tables 7, 8 and 9 shows that for the models representing all three treatments, the model p-value was less than 0.05. This suggests that the response models were significant and can be used for predictive purpose.     Table 14 gives the values and this was estimated using eq. 5.

IV. CONCLUSION
The water quality parameter table show suitable environmental conditions for rearing All Male Tilapia during the experimental period.
It was observed that dissolved oxygen interact with pH, the yield increase as the dissolved oxygen increase, also the lower the pH the better the dissolved oxygen for the survival of the fish.
It was observed that the response model is significant (p < 0.05).