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Articles by O.A. Oyelese
Total Records ( 18 ) for O.A. Oyelese
  O.A. Oyelese
  Feeding trials was conducted for 12 weeks to evaluate the utilization of processed soyabeans meal on the growth and nutrient utilization of Clarias gariepinus fingerlings. A control diet with no soyabeans inclusion (Diet 1) and 4 others with differently processed soyabean seeds supplements were formulated i.e. (Diets 2-5). Five isonitrogenous diets (control inclusive) with 35% crude protein were compounded, in all, The diets are: (1) The control, no soyabean inclusion and no processing (2) Autoclaving and Oven Drying (AOD) (3) Autoclaving and Sun Drying (ASD) (4) Oven Drying (OD) and (5) Sundrying (SD). Ten (10) fingerlings of Clarias gariepinus were stocked with average mean weight range of 2.80 gm-3.60 gm in each of the experimental plastic bowls, stocked in 26.9 litres of water. Fish fed on AOD and OD diets gave the best growth performance. Processing significantly affected mean weight gain at p<0.05. The fourth processing method (Sundrying i.e., the fifth diet) gave the least growth performance with poor growth and nutrient utilization which thus confirms sundrying as an unacceptable form of processing soyabeans. The choice of AOD as the best diet is confirmed, since it has the highest specific growth rate SGR (0.61), Protein efficiency ratio PER (0.392), Productive protein value (PPV (0.787) and least Food Conversion ratio FCR (7.31). The OD diet (which is the second best diet) is not significantly different from AOD p>0.05 with SGR (0.59), PER (0.378), PPV (0.657), FCR (7.70). The third ranking diet is the control. This suggest that utilization of soyabeans for fish diets in Clarias gariepinus is best if the processing method involves oven- drying.
  O.A. Oyelese
  The relative abundance of Bonga, Ethmalosa fimbriata, a clupeid schooling pelagic trash fish in the Nigerian Coastal waters coupled with the low price because of its numerous tiny bones promotes its use for fish meal as an alternative to the expensive conventional fish meal. This study aims to test the suitability of using processed Bonga (fish meal) and determining its level of supplementation with conventional fish meal in promoting Clarias gariepinus fingerlings growth. Twentyfive (25 kg) kilograms fresh weight Ethmalosa fimbriata was ovendried for 45 h at 80-90°, ground, sieved into fine powder and supplemented into 6 isonitrogenous diets each of 38% crude protein level (0, 20, 40, 60, 80 and 100%) diets. The Crude Protein (C.P) level of the processed Bonga fish meal was 57.79%. A twelve week nutritional experiment was carried out in which Ethmalosa fimbriata fish meal based diets were fed to (90) ninety fingerlings of Clarias gariepinus distributed in 6 graduated plastic bowls at the rate of 15 fingerlings per bowl with a weight range of 2.40 gm-2.51 gm/fingerling. The 6 isonitrogenous diets (0, 20, 40, 60, 80 and 100%) were fed ad libitum twice daily at 09.30 and 16 h, respectively after daily changing of water in the plastic bowls. Analysis of variance (ANOVA) for the growth and nutrient utilization parameters showed significant (p<0.05) variations for specific growth rate, protein efficiency ratio, food conversion ratio, productive protein value, feed intake and gross food conversion efficiency. The highest Specific Growth Rate (SGR) of 1.95 least Food Conversion Ratio (FCR) of 2.02 and the highest average daily growth rate (DGR) 0.120 gm/day showed the 40% diet as the best. This was closely followed by the 20% diet with SGR (1.90), FCR (2.02) and DRG (0.115). While the least grow out of Clarias gariepinus fingerlings was recorded for the 100% diet with SGR (1.37), FCR (2.97) and average DRG (0.067). This study shows that supplementation of Bonga (Ethmalosa fimbriata) fish meal of C.P 57.79% with the conventional Danish fish meal (of C.P 72.00%) is best at the 40% level of supplementation while 100% supplementation of Ethmalosa fimbriata fish meal will not give the best growout result for Clarias gariepinus.
  O.A. Oyelese
  The utilization of cheap, abundant, highly prolific whole Tilapia (Oreochromis nilotica) for fish meal in Clarias gariepinus fingerlings diets as an alternative to conventional Danish fishmeal is tested in this study. The fish meal was produced and kept for 3 months and the quality was found to be intact,in terms of its proximate composition (crude protein, fat,moisture, crude fibre and nitrogen free extract were the same at the end of the third month). Part of the fish meal was used in compounding six tilapia fishmeal based isonitrogenous diets (0, 20 40, 60, 80 and 100%) of 40% Crude Protein (C.P) to feed Clarias gariepinus fry (0.517-0.733 gm), stocked at 30 fry/250 litre bowl for six weeks, with daily changing of water before feeding. The tilapia fish meal (C.P-65.69%) qualities were intact at 3 months and compare favorably with the 72.00% Danish fish meal with which it was supplemented. Significant variations in terms of growth performance and nutrient utilization p<0.05 occurred at all levels of diet treatments. The Tilapia fish meal (TFD)-80% (SGR-3.68) was the best having the lowest fish mortality rate of 17.48%, lowest food conversion ratio (F.C.R) of 1.4269% and highest specific growth rate (S.G.R) of 3.68% coupled with highest protein efficiency ratio of 0.2365%. While the TFDB0% (with no tilapia fish meal inclusion ) had the least growth performance; with the lowest S.G.R of 1.61% and highest mortality rate of 28.01% along with the TFD -20% diet which also recorded mortality of 28.85%
  O.A. Oyelese
  The utilization of cheap, abundant, highly prolific whole Tilapia nilotica (Oreochromis niloticus) processed for fish paste, cake and especially fish meal in fish diets as an alternative to conventional fishmeal is tested in this study. Eight differently processed whole Tilapia nilotica fish paste preparations were set up for 7 days. Also well processed dried fish cake and fish meal were produced and kept for 3 months. The unfermented, cooked, salted and frozen (at-25°) fish paste (super grade 1) of crude protein (c.p) 52.13% was the best. The fish cake (c.p-38.59%) and fish meal (c.p-65.69%) qualities were intact at 3 months.
  O.A. Oyelese and M.O. Opatokun
  This study is aimed at investigating the exposure time on bacteria flora/count and shelflife of conned sardine (Sardinella pilchardus) under ambient and cold storage conditions. Twenty five cans with an average weight of 165.05 g of the Titus (with an expiry date of 4 years(30/9/2004-30/9/2008 pf batch no 1432) were purchased and stored under the ambient at an average temperature of 27° and cold (-4°) storage conditions as samples for 12 weeks. Proximate analysis of the samples were taken at the beginning of the experiment and at the end for both the ambient stored and cold stored (after an exposure time of 24 h). Initial base line and biweekly studies were carried out for 12 weeks for (a) Ogranoleptic (odour, taste, texture, appearance, rigidity of fillet, colour and reaction of fish with can (b) Chemical (Trimethylamine (TMA), Peroxide Values (PV) and Thiobarbituric Acid (TBA) and lastly 8 Microbiological analysis for bacteria count and identification of the bacteria on the samples from each storage environment after an exposure time of 24 h in each cases. All the chemical parameters (TMA, TBA and PV) were significantly (p<0.05) correlated with exposure/storage time. Correlation coefficients r = 0.60, r = 0.66 and r = 0.54 were recorded respectively with all indicating spoilage rate increases progressively with exposure time/storage period. Highest PV ranges of (0.023-0.715), TBA (0.057-1.056) and TMA (1.01 x103-3.63 x 103) were recorded for canned sardines stored at ambient temperatures of 27°. However these are still within acceptable tolerance limit. Organoleptic assessment with average scores of 5.5 and 6.0 recorded for cold and ambient stored samples. No viable bacteria count was recorded for cold stored samples throughout the experiment. However the range initial 0.1 x 104 and final 5.0 x 104 cfug B1 total viable count recorded for ambient storage were still below the minimum bacteria count for spoilage, that could cause significant or deleterious effect that could result in food poisoning. Traces of the following bacteria sp. were recorded at ambient temperatures (a) Bacillus subtilis (1.2 x 104cfng-1) (b) Streptococcusfaecium (0.9 x 104 cfng-1), 8 Proteus vulgaricus (0.7 x 104 cfng-1) (d) Pediococcus halophilus (0.6 x 104 cfng-1) (e) Micrococcus acidiphilus (0.4 x 104 cfug-1) (f) Streptococcus lactis (0.4 x 104 cfng-1) and (g) Aerobacter aerogenes (0.4 x 104 cfng-1) w hile fungi sp. Aspergillus terrens (0.1 x 104 cfng-1) Aspergillus niger (0.3 x 104 cfng-1) were recorded also for samples stored at ambient temperature of 27°. Hence in view of this the four years recommended expiry data may be upheld for canned sardine (Sardinella pilchardus fish products in oil sources provided the HACCP (Hazard Analysis and Critical control points) and closely monitored. It is therefore recommended that exposure of c anned sardine in oil should not exceed 12-24 h under whatever food storage temperatures to avoid food poisoning.
  O.A. Oyelese and A.F. Fatunmbi
  Canned mackerel (Scomberomerus sp.) a widely accepted food product in the tropic, with shelflife of 3 years after production (Dec 2004-Dec. 2007) is being assessed after a 24 h exposure period under both cold (-4°) and ambient temperatures (27°). A total of 13 cans (Geisha brand of mackerel in tomato sauce) were analysed. The base line data was obtained at (0 day) with the first can. The remaining 12 cans were grouped into 2 samples in relation to the storage media adopted. After an opening the cans were kept at their respective storage media for 24 h exposure period before analysis. The readings were taken biweekly for 12 weeks. The assessment made were: organoleptic, biochemical Trimethyamine (TMA) Thiobarbituric acid (TBA) and period value (PV), microbial assay (count and identification) and proximate analysis (initial and final).The organoleptic parameters assessed were (texture, colour, rigidity of fillets and reaction of can with the product) which showed no significant variation (p>0.05) while odour, taste and appearance showed significant difference (p<0.05). The biochemical tests revealed that all parameters increased in their values in both media with increasing exposure/storage time. The ambient (PV = 4.380 meq kg-1), TBA = 1.849 mg kg-1 and TMA = 2.531 mgN/100 fish) were greater than the cold medium (PV = 4.300 meq kg-1, TBA = 1.638 md kg-1 and TMA = 2.20 gm N 100 g-1). significant (p<0.05) increase were recorded for TMA and TBA with strong positive correlations (r = 0.61 and 0.63 respectively) with exposure storage time, while PV had a slower rate of increase with r = 0.40. The ambient medium showed fourteen bacteria sp. and four fungi sp. with a higher total viable count range of (2.8-40.7 x 104 cfug-1) as against the cold medium which had eight bacteria sp. and no fungi sp. represented with a range of (2.8-7.8 x 104 cfug-1). The bacteria growth in both media were significant (p<0.05) and present progressive increase in growth pattern with storage time. However cold storage at -4° suppress the rate of multiplication of the identified bacteria. However, the most prominent bacteria spp at ambient temperature were (a) Staphylococcus aureus (27.4 x 104 cfug-1) (b) Pseudomonas aureginosa (26.5 x 104 cfug-1) and (c) Bacillus cereus (21.5 x 104 cfug-1) whole for the cold (a) Klebisella aerogenes (6.6 x 104 cfug-1) (b) Micrococcus acidiophilus (5.7 x 104 cfug-1) and (c) Bacillus cereus (4.0 x 104 cfug-1). All viable counts recorded were still below maximum microbial count limit of (1.0 x 106 cfug-1). Canned mackerel in tomato sauce is advisably consumed before the 3 years expiry date and also immediately it is opened to prevent food poisoning. Since increase in bacteria count and biochemical values in both media with exposure/storage time were evident in this study.
  O.A. Oyelese
  Sixteen samples of Skip Jack Tuna (Katswonus pelamis) with a size range of 9.58-1.62 gm werecollected at the Lagos Jetty of the Nigerian Institute for Oceanography and Marine research, Victoria Island, Lagos and stored at a cold storage temperature of-21 for a period of 13 weeks. Samples were kept in the cold room for 6 weeks before the commencement of the experiment using one piece of fish per week for both organoleptic and chemical studies (Trimethy lamine (TMA), Total Volatile Bases (TVB) and Free Fatty Acids (FFA). This is in a bid to determining the level of spoilage and limit of acceptability (Shelf life) of the fish. Organoleptic assessments of a five-man panel, showed the general conditions (appearance, taste and odour) of the fish was unsatisfactory at the end of the 12th week of storage, with an average score of 3.9`0.30. However the uncooked fish was still acceptable (4.5`0.33) up till the 11th week of storage. Also for the cooked specimen the general conditions (texture, odour and taste) of the fish were unsatisfactory at the and of 12th week, with an average score of (4.6`0.38). The chemical assessment results were significant (p<0.05) and there was a strong positive linear correlation (TMA = 0.9823, TVB = 0.9855 and FFA = 0.9847) between the chemical indices and the length of storage. For the TMA and TVB, the limit of acceptability was the 8th week of storage with values of 4.0 mg 100 g-1 fish and 3.75 mg 100 g-1 fish, respectively. With FFA as a chemical index of spoilage, (a less sensitive index) acceptability limit of 1.07% was recorded at the 11th week of cold storage. The limit of acceptability (shelf life) for the cold storage of Tuna (Katsuwonus pelamis) as shown in this study is between the 8th and 11th week of storage at-21C using the chemical assessment (as the lower limit) and organoleptic assessment results (as the upper limit) as indicators. However using Least Significant Difference (LSD) to test, the shelf life of Tuna under cold storage of-21C is 2 months.
  O.A. Oyelese
  The implications of carcass quality and condition factor to the consumers, preservators and processors was studied using the following common representative members of five selected fresh water fish families. They are family. Clariidae-Clarias gariepinus, Mochkidae-Synodontis clarias, Cichlidae-Tilapia nigrodigitatus, Bagridae-Chrysichthys nigrodigitatus, Channidae-Channa obscura.Four fish replicates (2 females and 2 males) were used for each fish family. Each fish specimen were dissected after taking the standard /Total length and weight readings. The visceral organs were removed and the wet carcass weight were recorded. Samples of each family representative were taken and subjected to initial proximate analysis. The dry carcass weight of the fish specimen were also taken after oven drying at 105° for 24 h in order to determine the moisture content. All length and weight reading were replicated four times in each case, the condition factor (k) and carcass quality factor (productive potential carcass quality factor (PPCQF) was also calculated. The condition factor (K) and carcass quality factor (PPCQF) of the fresh water fish families were significantly different (p<0.05) from each other with highest condition factor (K) of 2.32 and lowest carcass quality factor (PPCQF) of 1.2855 recorded in Tilapia niloticus while the lowest condition factor (k) 0.71 and highest carcass quality factor 2.1764 was recorded in Clarias gariepinus. Also in terms of carcass quality Synodontis clarias with PPCQF of 1.8381 is second, followed by Chrysichthys nigrodigitatus, 1.5133 and fourth Channa obscura with PPCQF of 1.4429 and also with lower values of 1.19, 0.87 and 0.80 condition factor recorded respectively. The carcass quality of a fish is not determined by the Astate of well being >= or condition factor but it is a function of its protein and fat content as shown in this study with higher values of protein (62.00%) and fat (5.80%) recorded for Clarias gariepinus compared to lower crude protein (39.61%) value and fat(4.58%) recorded for Tilapia niloticus. However the latter is better adopted for culture in the wild with its high condition factor (2.32) value. While the culture of Clarias gariepinus with a low condition factor (0.71) is highly favoured under aquaculture practices. The culture of other fresh water fishes also with low condition factor like Synodontis (k = 1.19), Chryschthys (k = 0.87) and Channa (k = 0.80) should also be promoted under well monitored culture condition.
  O.A. Oyelese
  The implications of organ weight to body (tissue) weight to the consumers preservations and processors was studied using the following representative members of five selected fresh water fish families. They are family. Clariidae example used is Clarias gariepinus, Mochokidae example used is Synodontis clarias, Cichlidae example used is Tilapia niloticus, Bagridae example used is Chrysicthys nigrodigitatus, Channidae example used is Channa obscure, Four replicates (including 2 females and 2 males of fish were used in each case) were dissected after taking their initial total body weights. Each internal organ (the gonad, liver, heart, gall bladder, spleen, kidney and gut) were weighed using a sensitive accoulab weighing scale. The percentage organ weight of the total body weight was calculated for each representative member of the five families. Also the total organ weight was deducted from the total body weight to five the actual fleshy edible tissue weight for each family. From this the productive potential fish yield factor (PPFYF) was calculated. The productive potential fish yield factor was not significantly (p>0.05) different among the 5 fish families with the highest value of 0.9695 recorded for Chrysichthys (Bagndae), second is Tilapia (Chichlidae) with 0.9692, this is followed by Channa (channidae) 0.9639 fourth is Synodontis (Mochokidae) 0.9543, while the least PPFYF of 0.9422 was recorded in Clarias (Clariidae). The least total organ weight of 3.05% was recorded in Chrysichthys, while the highest total organ weight of 5.78% was recorded in Clarias also with the second highest values of 4.57% recorded in Synodontis. The lowest PPFYF (0.9422) recorded for Clarias gariepinus is as a result of the gonad weight (1.95%) and heart weight (0.11%) while the PPFYF value (0.9543) recorded for Synodontis clarias was as a result of the liver weight (1.09%), kidney weight (0.67%) and gut weight (2.33%) of total body weight. This implied total overall body weight does not determine fish yield (PPFYF) as in this study Clarias gariepinus had the highest total mean weight of 402.50 gm but the highest total organ weight of 23.28 gm (i.e., 5.78% of total body weight). Also a high proximate Crude Protein (C.P) composition of a fish does not necessarily imply a proportional or corresponding laying of fish flesh as shown in this study with Clarias gariepinus having the highest crude protein of 62.00% followed by Syodontis clarias with 53.38%.
  O.A. Oyelese
  A study of time series behavioural effects and post mortem changes of Clarias gariepinus under varying gear handling conditions was carried out using forty live samples of Clarias gariepinus of average body weight 165 gm bought from Aleshinloye market in Ibadan, Oyo State, Nigeria. The samples were grouped into 4 treatments A, B, C and D with 10 pieces in each treatment. Treatment A fish were fixed to Hook and line, fish species in treatment B were fixed to the gill net, treatment C fish were dragged from the pond with a dragnet and fish in treatment D (which served as the control) were washed with clean water and left to die naturally in a clean bowl of water. All treatments were left in the different gears to struggle and die at ambient temperature. They were also left in their various conditions after death for rigor mortis to occur and the time taken for rigor to resolve was noted and at the temperature they occurred. After fish from each treatment were packed in polythene bags with labels and then stored in the freezer at a temperature of-20°C. Organoleptic and chemical assessment test were carried out on samples of each treatment every fortnight for 10 weeks. The death time/rigor time and temperatures at which they occur were as follows:-Treatment A (Hook and line) 158.5 mm death time/181.00 rigor time at 26°C. Treatment B gilled fish) death time 241.50 min/169.00 min rigor time at 28°C. Treatment C (Dragged fish) death time 667.00 min/269.50 min. rigor time at 25°C. Treatment D (control left to die naturally) death time was 827.00 min/289.50 min. rigor time at 26.50°C. Rigor mortis does not last longer in struggling and exhausted fish as it is the case with treatments B and A coupled with their earlier death than in treatments C and D, although rigor mortis started earlier in C. Hence treatment A and B showed earlier signs of spoilage than C and D. Significant differences exist p<0.05 between the Total Volatile Base (TVB) and the weeks of storage with the gilled fish (Treatment B) having the highest overall TVB accumulation of 93.00 mg 100 gm-1 fish indicating the fastest rate of spoilage, followed by Hook and line (Treatment A) 88.20 mg 100 gm-1 fish, ranking third is the Dragged fish (Treatment C) with 84.50 mg-1 100 gm fish, while the least value of 79.20 mg-1 100 gm fish was recorded (in the control) indicating least spoilage. The organoleptic assessment followed a similar pattern. This is further confirmed by the positive correlation coefficients (A-r = 0.99, B-r = 0.99, C-r = 0.60 and D-r = 0.98) in all cases indicating increase rate of spoilage with storage length (weeks). The best gear to use for catching Clarias gariepinus (apart from allowing the fish to die naturally) as shown in the study is the DRAGNET, since this exerted far much less stress on the fish.
  O.A. Oyelese
  The determination of the hypoxanthine levels chemical studies and bacteria flora/ count of alternate frozen/thawed market simulated croaker (Psendotholithus senegalensis) was carried out weekly for 12weeks under cold storage conditions at -4C. Twenty two pieces of Croaker (Psendotholithus senegalensis) caught within the Nigerian Coastal waters with an average weight of 270 g were removed fortnightly allowed to thaw and exposed for 12 h before taken them for analysis. While organoleptic assessment and biochemical parameters (Hypoxanthine levels (Hx), Trimethylamine (TMA) Peroxide Value (PV) and Free Fatty Acid (FFA) were carried out fortnightly, however microbial assessment (bacteria count and identification) were assessed every 4weeks (monthly). Also initial and final proximate analysis were carried out. The cold storage medium does not totally halt spoilage, this is because hypoxanthine levels increased with storage length just as the bitter taste becomes more pronounced by the end of the 12weeks, this is further confirmed by the organoleptic results which also showed a progressive increase in their values. The biochemical test revealed that all parameters had a consistence increase in their values as the length of storage period increase, significant increase (p< 0.05) was recorded for (PV, TMA, FFA and Hx) with strong positive correlation (R=0.98, 0.99, 0.96 and 0.96, respectively) with length of storage period. The microbial count and identification results shows that 7 bacteria species have invaded the samples, in which Micrococcus acidophilus is the only bacteria with the lowest count of 1.60104 cfu g 1 (and also showed it presence in the 12th week) and also out of the 7 bacteria identified 4 were prominent which include Lactococcus acidophilus (occurred from 0-12th week) Clostridium welchii (4-12th week) Bacillus substilis (8-12th week) and Proteus morganii ( 8-12th weeks) had the highest number of occurrence with (5.58, 4.29, 3.37and 3.18104 cfu g 1). Microbial build up rises with increase in the length of storage period, this is because the Total Viable Count (TVC) increase from 0 week (1.64104 cfu g 1) to(10.5104 cfu g 1) in the 12 week. However the limit of acceptability for Croaker (Pseudotolithus species) under cold storage at -4C is 8 weeks (2months) since values of all measured parameters increased drastically and sharply at the end of the 8th week.
  O.A. Oyelese
  This study intends to promote the rearing (production) and marketing of the African giant snail (Archatina marginata) especially for the production of processed snail meal to supplement the conventional fish meal in the diets of Clarias gariepinus as used in this study. The visceral mass (entire flesh) of about 150 pieces of snail (Archatina marginata) were washed with alum and water. They were cut into pieces and dried in an oven at a temperature range of 60-70C in an oven for about 72 h. The dried snail meat was used in compounding 6 isonitrogenous diets each with Crude Protein (C.P) of 38.25%; labeled 0% (no snail meal) (Control) 20, 40, 60, 80 and 100% snail meal diets (i.e. Treatments 1, 2, 3, 4, 5 and 6). The processed snail meal (with C.P 55.16%) was gradually being supplemented with fishmeal (C.P 65.00%) in each of the diets. The diets were fed to 90 juvenile Clarias gariepinus of average weight range from 4.35-4.63 g randomly distributed in 6 plastic bowl (15 fish per bowl). The fish were fed this 6 diets twice daily (10.00 a.m. and 5.00 p.m.) for an experimental period of 12 weeks (84 days). Proximate analysis of the feed, initial and final proximate composition of the experimental fish were also determined. Fish were weighed weekly and feed fed daily were recorded to determine growth and nutrient utilization pattern of the experimental fish. The best grow out of fish and best nutrient utilization pattern was recorded in Diet 4 (60% snail meal inclusion) with the highest Mean Weight Gain (MWG) (7.33 g), Specific Growth Rate (SGR) (1.154), Protein Efficiency Ratio (PER) (0.620) and Gross Efficiency of Food Conversion (GEFC) (0.240) but with the least Food Conversion Ratio (FCR) (0.34). The second best diet is Diet 3 (40% snail meal inclusion). While the poorest diet (Diet 6) (100% snail meal inclusion) recorded the lowest Mean Weight Gain (MWG) (2.22 g), SGR (0.500), PER (0.250), GEFC (0.017) and highest FCR of 0.84. This implies snail mean is best when used in supplementation with conventional fishmeal at a ratio of 60% snail meal to 40% fish meal. The present cost of production of 1kg of processed snail meal is put at N250.00 kg 1 compared to N300.00 kg 1 of fishmeal (i.e., just with a profit margin of 16.67%) could still further be reduced by promoting the active rearing and marketing of the African Giant snail (Archatina marginata) especially for fishmeal production, snail meat protein supply to the populace coupled with its medicinal value and liming properties of the snail shell in improving the quality of acidic (fish pond) soils.
  O.A. Oyelese
  The effect of brining on the keeping quality of gutted, ungutted, gutted common Carp (Cyprinus carpio) were monitored under low storage (deep frozen) conditions of-21Oc for 8 weeks. Three treatments were used for the study viz: Treatment 1- Normal brined Carp (saturated) Treatment 2-superbrined Carp (super saturated) and treatment 3- control- (carp with no brine treatment). These were monitored through organoleptic (cooked and uncooked) and chemical tests (TVB) to indicate extent of spoilage. Weekly variations in mean weights and initial and final proximate composition of fish in each treatment were also monitored. A concurrent loss in weight was recorded form 1st- 3rd week in all the brining treatments employed and equally affects the fillets, gutted and ungutted samples. This suggests displacement of locked up water which could have accelerated spoilage in the tissue of the fish (Cypriuns corpio) by salt crystals, hence the corresponding loss in weight of the fish, weight loss was negligible in Treatment 3, the control fish without brining. The correlation efficient (r) for TVB values with length of storage were positive in all cases for gutted, ungutted, and fillttetted samples (super brine -0.80, 0.84 and 0.87), (Normal brining -0.86, 0.90 and 0.44) and (control -0.98, 0.94 and 0.62 respectively) which implies TVB values increases with the spoilage rate/ length of experimental period. However delayed production of TVB were experienced in Treatments 1 and 2 (Normal and superbrined fish) up to the end of the 5th week which suggests that brining in whatever form causes delayed responses to spoilage in deep frozer Cypriuns carpio. The much lower crude protein (6.59-15.42% (Super brine) and 9.62-13.22% (Normal brine) and higher ash content 16.85-18.78% ash (super brining) and 12.08-16.77% ash (normal brine) on proximate analysis of the final fish products for normal and supper brined fish suggests salt protein denaturation coupled with cell (tissue) damage by the frozen salt crystals. The larger surface of exposure of the fillets in Treatments 1 and 2 and there thinness compared to gulled and ungutted samples makes it a better preserved product and it is also responsible for the higher degree of saltiness. All measured parameters the organoleptic assessment (cooked and uncooked), weight loss and TVB values followed a similar pattern of variation. However, there was no delayed response in the TVB production for the control fish which commenced at the 2nd week for fillet control (4.89-24.49 mg 100 gm 1 fish), ungutted control (9.79-26.93 mg 100 gm 1 fish) compared to much lower values recorded for normal and superbrined products from the 6th-8th week. Normal brining should be done to deep frozen Cyprinus carpio to reduce the degree of saltiness to taste. However, if a more permanent product form/preparation) is desired, like it is the case if further processing to Carpfish meal, cake or paste superbrining is recommended in the fillet form to enhance a better keeping (shelflife) quality. If superbrined fish is desired for cooking immediately it should be soaked in water for at least 3 h to desalt it or if used directly little or no salt should be added.
  O.A. Oyelese
  Hypoxanthine levels, chemical studies, organoleptic assessment and bacteria flora/count were studied for a 12 week period on market simulated fresh samples of the Chub Mackerel (Scomber japonicus) in order to assess its keeping quality and shelflife under cold storage conditions of 40C. Twenty-two (22) fresh samples of average weight of 260gm were used for the study. Two pieces were exposed for 12 hours to thaw and defroze biweekly to simulate market conditions before taken them for further chemical analysis and microbiological assessment. Initial proximate analysis were carried out on the fresh fish and also final proximate analysis at the end of the 12 week experiment. The chemical parameters analysed are Hypoxanthine levels, trimethylamine (TMA), peroxide value (PV), free fatty acid (FFA) (fortnightly) and bacteria identification and count (monthly). Organoleptic assessment was also carried out on the fresh and cooked fish samples forthnightly. The final proximate analysis showed increase (74.36%) in the moisture content compared to (69.25%) the initial. There were decreases observed in crude fibre (2.42% as against 2.78%), ether extract (fat) (16.89% as against 17.38%) and ash (2.86% as against 3.18%), but increase in crude protein content from 19.65% to 21.34%. The other chemical parameters assessed increased e.g peroxide value (PV from 26.40 to 34.60 Meq/kg), trimethylamine (TMA from 29.62 to 39.20mg/100gm fish), free fatty acid (% FFA from 1.74 to 2.32%) over the assessment period. The hypoxanthine level also increased considerably from 28.24mg/100gm fish to 37.54mg/100gm fish at the end of the experiment (hence the increasing bitter taste with length of study). The organoleptic assessment also ranged from very good (2.0) to just fair (6.0) quality at the end of the 12 week study. The number of bacteria identified also increased with storage time. The overall bacteria total viable count varied from 0 week (1.82 Cfu/gm) 14.70 Cfu/gm) in the 12th week with 29.36 Cfu/gm overall count recorded for the 12 weeks. A total of 10 bacteria specie were detected in the study with Lactoccocus acidophilus showing the highest prevalence of 6.14 Cfu/gm fish) also showing its presence from the 0 week (1.82 Cfu/gm fish) to 1.60cfu/gm fish recorded in the 12th week. Second to it is Pseudomonas aureginosa (3.50cfu/gm) detected from (8th 12th week), while the third bacteria prevalent was Clostridium welchii with 2.72 Cfu/gm detected at the end of the 4th week and 12th week of study. The other bacteria species detected (arranging them in their order of prevalence) include Bacillus substilis (2.40 cfu/gm), Proteus morganii (2.40 Cfu/gm); Eschericha coli (2.36 Cfu/gm fish); Bacillus cereus (2.10 cfu/gm), Micrococcus acidiophilus (1.50 Cfu/gm), Staphylococcus aureus (1.30 Cfu/gm) and lastly Streptococcus faecium (1.10 Cfu/gm). All parameters measured showed drastic rises in their values as from the 8th week to the 12th week. Hence the limit of acceptability and shelflife of the market simulated Chub Mackerel (Scomber japonicus) under cold storage conditions of 40C is 8 weeks (2 months).
  O.A. Oyelese
  The study intends to promote the use and marketing of agricultural, animal waste products with special emphasis on the production of maggot from faecal poultry droppings. This study therefore aims to determine the best level of supplementation of maggot with compounded ration, the rate of growth and nutrient utilization by Clarias gariepinus and the economic viability of feeding Clarias with the combination of maggot and compounded ration.Forty juvenile Clarias gariepinus of weight ranges between 100-120 gm were randomly allocated to four treatments (each of 10 juvenile Clarias gariepinus per hapa of 111 m) in a nursery pond with over flow supplied with bottom springing clean water. They are treatment 1 (100%) compounded ration of 35% crude protein), Treatment 2 (50% compounded ration+ 50% maggot), Treatment 3 (25% compounded ration+75% maggot), Treatment 4 (100% maggot) were set up for 7week experimental period. Growth performance was significantly (p<0.05) different among the 4 diet treatments with Treatment 2 (50% compounded ration+50% maggot) recording the highest Mean Weight Gain (MWG) (119.65 gm). Specific Growth Rate, (SGR) (1.303), Protein Eufficiency Ratio (PER) (0.3860), Daily Rate of Growth (DRG) (0.2442) but lowest Food Conversion Ratio (FCR) (5.9410). Ranking second is Treatment 1, third is Treatment 3, while the least growth performance of MWG (58.15 g) SGR (0.416). PER (0.2890), DRG (0.1187)and highest FCR (16.54) was recorded for Treatment 4, as the poorest diet. However the Crude Protein (CP) from proximate composition shows Treatment 4 with the highest CP of (63.31%) > Treatment 3 (54.65)> Treatment 2 (48.36%) > Treatment 1 (34.75%). This implies feeding maggot alone with fish (Treatment 4) will not supply the required protein quality (balance diet) that will supply at least 10 essential indispensable amino acids that is required for optimum growth. Hence a combination of compounded ration and maggot (Treatment 2) will meet this requirement and this will also yield the highest economic gain by reducing the cost of feed by 40% of the proposed total cost when compared with Treatment 1 and 2. High yield in terms of weight of fish, over 200% yield (double profit) on harvesting (Treatment 2) when compared with treatment 4 (100% maggot diet).
  O.A. Oyelese
  This study is aimed at determining the effect of water temperatures on fertilization and hatchability rates of artificially induced Clarias gariepinus. Sixty six (665 broad-stock 132 females and 34 males) were purchased from Agodi fish farm, Ibadan of average weight 398 g and conditioned for two weeks after which some were sacrificed for fresh pituitary hormone and milt. Four trials were carried out. Injection of females was done at different periods of the day (8.00 am, 4.30, 8.00 and 12.00 pm) that is 0800, 1630, 2000 and 2400 h at an average temperature of 26.00, 24.30, 27.66 and 25.00°C, respectively and stripped after 10 h for eggs. Significant variations exist (p<0.05) between water temperature at the time of injection and hatchability/fertilization rates, this is further confirmed by the strong positive correlation of r = 0.95 in both cases. The highest hatchability rate of 77.84% and highest fertilization rate of 66.65% was recorded at 8.00 p.m with water temperature of 27.66°C this is followed by 75.51% at 26.00°C hatchability rate/51.23% fertilization rate for fish infected at 8.00 a.m and stripped 6.00 p.m (10 h later).
  O.A. Oyelese
  This study was conducted to determine the best dissolved oxygen level and culture medium for the survival of the African catfish Clarias gariepinus fry.The experiment was carried out for a period of 8 weeks, out of which the brood stock used to produce the fry were maintained for 4 weeks on a diet of 40% crude protein. The study was carried out in four plastic bowls subjected to different treatments in the departmental laboratory. The plastic bowls were designated I, II, 8.III, IV respectively each representing a treatment with bowl I containing deionised spring water unaerated kept in the laboratory, bowl II contain sprung water without aeration kept in the laboratory, bowl III contain constantly aerated spring water also kept in the laboratory and bowl IV contain spring water without aeration kept outside the laboratory under ambient conditions to serve as the control. The acclimatized Clarias broodstock were semi-induced under hatchery management conditions to produce Clarias gariepinus fry on a weekly basis for 4 weeks (as when required for experiment). Each experimental treatment bowl contain 100 Clarias gariepinus fry. The experimental treatment replicates was carried out for four weeks. The mean dissolved oxygen levels and survival rates of swim up fry values obtained for the 4 weeks are:- Oxygen levels 6.57, 7.04, 7.29 and 7.06 mg L-1 for treatments I, II, III and IV, respectively, survival rates were 84.80, 95.30, 100.00 and 96.80%, respectively for each experimental treatment. Analysis of variance shows that there is significant difference in the mean survival rate values of p<0.05 level of significance. Despite the anoxic conditions r was shown to be positively correlated (r = 0.99) for survival rate implying generally that the survival rate for Clarias gariepinus fry increases with increase in oxygen level in the water. Treatment III gave the highest percentage survival rate of 100% which coincided with a 7.29 mg L -1 oxygen level and ranking second to it is the survival rate/oxygen level of treatment IV with the values 96.80%/7.06 mg L-1.
  O.A. Oyelese
  This study was carried out to monitor the suitability of Clarias gariepinus as a predator on Tilapia (Oreochromis niloticus) populations. In order to (a) recommend a stocking ratio for Tilapia-clarias prey-predation relationship, (b) determine the size/level at which the prey is most vulnerable to predation and (c) to determine whether sudden cohabitation with or without feeding/sparing feeding will trigger predation. Four different treatments of (1) 10 Clarias juveniles/100 Tilapia fingerlings fed to satiation (2) 10 Clarias juveniles/100 Tilapia fingerlings fed sparingly (3) 50 Clarias fingerlings/50 Tilapia fingerlings fed sparingly (4) 15 Clarias fingerlings/90 Tilapia fingerlings fed to satiation and (5) 15 Clarias fingerlings/90 Tilapia fingerlings fed sparingly were monitored over a period of 12 weeks. Predation occurred only in Treatments 1 and 2 where the predator was bigger than the prey and the highest level of predation of 71% Tilapia fingerlings occurred in Treatment 2 compared to 26% in Treatment 1. The predation level was highest during the first 6 weeks of the study due to increasing size of the prey. Hence growth performance from 7th-12th week depended solely on the feed fed for Treatments 1 and 2. However, since virtually no predation was recorded for Treatments 3 (0%), 4 (0%) and 5 (2.22%) growth performance for these 3 treatments from weeks 1-12 was dependent solely on the feed fed whether fed to satiation or not. The Analysis of Variance test (ANOVA) to test significance in the predation level showed significant differences (p<0.05) among the treatments (at least for treatments 1 and 2) and Duncan`s Multiple range tests puts the order of predation as Treatment 2 (71a)>1(26b)>3(0c)>4 (0cd) and > 5 (0cde), but there were no significant differences (p>0.05) among 3, 4 and 5 where the prey and predator were of similar sizes. Treatment 1 recorded the best growth performance in both species of fish with respect to mean weight gain, food conversion ratio and increase in total length. The order of growth performance is Treatment 1>2>4>3>5. The food conversion ratio among treatments 2 and 1 (where predation occurred) showed that it is higher in Treatment 1 where the level of predation was lowest. Analysis of Variance (ANOVA) shows growth rate of prey and predator were significant at (p<0.05), respectively. The correlation coefficients `r` between the size of the prey and predator in all the treatments were all positive viz: Treatment 1 (1.00), 2(0.96), 3(0.88), 4(0.95) and 5(0.81), this implying the size of the predator increased as the pray size increases. The sudden cohabitation of Clarias gariepinus and Tilapia (Oreochromis niloticus) with or without feeding did not trigger predation because the initial number stocked in Treatments 4 and 5 (each specie of fish raised separately and the two brought together at the end of 2 weeks) were recovered at the end of the 12 weeks experiment. The best level of growth performance and fairly balanced survival/predation level is achievable with Treatment 1 which gave the highest overall weekly mean weight gain and 90/74% Clarias/tilapia survival rate closely followed by Treatment 2 with 100/29% Clarias/tilapia survival rate. However if the intention of Clarias/tilapia polyculture is not to embrace predation, but to maintain at least about 100% survival of both species solely dependent on the feed fed Treatments 4>3>5 is recommended in that order.
 
 
 
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