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ThesisItem Open Access Studies on temporal and spatial variations of circulation and hydrographic characteristics of Panangad region of the Vembanad Lake(Department of Fishery Hydrography, College of Fisheries, Panangad, 2003) Vijayakumar, C T; KAU; Varna, K KThe objective of the study was to find the seasonal and spatial variations of different hydrographical factors of the Vcmbanad Lake around Panangad region and compare the situation with that of the other parts of the lake. Salinity, temperature, current velocity and direction, dissolved oxygen, primary production and nutrients like phosphate, nitrite and nitrate were the parameters studied. For this monthly observations of these factors were made from nine stations located in and around Panangad region of Vembanad Lake. Beside this tidal cycle observations were carried out from two stations to study the tidal variation of the factors. S.T.D. meter was used to measure salinity, and temperature and a current meter for the current measurements. Water samples from surface and sub surfaces were collected with a clean bucket and a Van Dorn bottle. The estimation of dissolved oxygen, primary production and nutrients were done by standard methods. Marked seasonal fluctuation was noticed in the temperature of different stations. Annual variation showed two maxima. The temperature was minimum during southwest monsoon and maximum during pre monsoon months. In general, the vertical thermal stratification was small. The salinity exhibited marked seasonal fluctuation and generally the monsoon months recorded very low salinity values. After that there was an increase, reaching the maximum in pre monsoon months. Some vertical stratification was noticed during certain months. The Dissolved oxygen values were low during pre monsoon months and the content was more at surface than at the bottom layers. There was high seasonal fluctuation In the phosphate concentration. It showed high concentration during pre monsoon period. Generally bottom layers showed higher phosphate concentration than the surface layers. In the case of nitrite high values were observed durin 118 the monsoon and low values during dry season. Nitrate concentration also showed seasonal variation and high values were observed during the monsoon and low values during pre monsoon. The nutrient concentration was more in the inner smaller arms of the study area, in general. These inner arms were vertically homogenous also possibly due to higher mixing generated by the friction of the sides. In the tidal cycle observations it is found that salinity showed an increase during flood tide and decrease during ebb tide. At both stations considerable reduction in flood current speed was observed during post monsoon, compared to pre monsoon. During pre-rnonsoon a comparatively well mixed condition was prevailed. Post monsoon observations indicated very clear salinity stratification. This was due to the effect of freshwater discharge, which continued during this season though at reduced rate compared to monsoon season. It is found that the tidal effect on temperature was not well marked. It can be seen that different hydrographic factors of Panangad region of the Vembanad Lake exhibited much seasonal and spatial variations and the trend was in general, same to that shown by other parts of the lake.ThesisItem Open Access Community changes in zooplankton and macrobenthos of a prawn culture field in relation to hydrographical conditions(Department of Fishery Hydrography, College of Fisheries, Panangad, 2003) Shreeram Sudheer, Gubba; KAU; Cherian, C JThe present study was carried out in the prawn filtration field of the College of Fisheries at Panangad adjacent to the Cochin backwater system to find out the faunal variations of zooplankton and macrobenthos and to correlate them with the variations in hydro graphic conditions and compare the results with those obtained from the observations in the adjacent lake. Monthly samples for hydro graphical and biological studies were collected during the period from November 2002 to July 2003 from the culture field and adjacent backwater. Hydrographical features like temperature, salinity, transparency, pH, total alkalinity, dissolved oxygen, nitrate-N, phosphate-P, silicate-Si were observed. Crustacean larvae, copepods, tintinnids, nematodes, rotifers and veliger larvae of molluscs were the zooplankton groups obtained in the present study. Crustacean larvae and copepods were the dominant groups in both places and were found during all the months whereas tintinnids and nematodes were observed during saline period and their number decreased with decreasing salinity. Rotifers were recorded during low saline period only. Veliger larvae were recorded during December and February in the culture field, whereas, they were not present in the samples form the adjacent backwater. Statistical analysis for the influence of hydrographical parameters on the zooplankton showed that none of these had significant influence independently and the variations in the zooplankton abundance may be due to the combined effect of all these factors. Even though the seasonal changes in the total zooplankton were not pronounced the per cent composition of different groups showed fluctuation. Tanaidaceans, gastropods, polychaetes, amphipods, bivalves, isopods and chironomid larvae were the benthic groups obtained. Among these 112250 124 gastropods, tanaidaceans and polychaetes were the dominant forms. In the culture field benthic populations were maximum during the post-monsoon months and a showed a decreasing trend during pre-monsoon. With the onset of the monsoon they showed an increasing trend. In the backwater high benthic abundance was observed during January and February when high salinity prevailed and gradually decreased from March onwards reaching the minimum in July. In the culture field benthic abundance was mainly influenced by substratum characteristics and pH, whereas in the adjacent backwater salinity also played a role. The area of the present study is away from the barmouth and the nutrient levels especially phosphate is low in the culture field. This may be limiting the primary productivity of the area leading to low secondary production in terms of zooplankton and macrobenthos in the culture field. The high pH noticed in the culture field may be another reason for the low productivity.ThesisItem Open Access Development of Malaysian Type Fish Crackers From Nemipterus Japonicus (BLOCH)(Department of Processing Technology,College of Fisheries, Panangad, 2001) Venugopal, Dubakula; KAU; Sajan, GeorgeA study was undertaken for the preparation of fish crackers using a low cost fish, threadfm bream (Nemipterus japonicus, Bloch). A method was standardised for making crackers based on that generally followed in Malaysia. Fish meat was mixed with various food additives such as starch, salt, sugar, monosodium glutamate, colour and water, and stuffed into high-density polyethylene casings as rolls, cooked, cooled, sliced and dried.ThesisItem Open Access Studies on the electrophoretic pattern of Fish/ Shellfish proteins subjected to frozen storage(Department of Processing Technology,College of Fisheries, Panangad, 2000) Bomy, Chummar; KAU; Nambudiri, D DFreezing considered as an excellent process for preserving the quality of fish for longer periods. But freezing may affect various flesh components, especially the proteins. Sarcoplasmic proteins play a major role in species identification of fish and fishery products. While myofibrillar proteins play a major role in the jellying properties of surimi and surimi based products. The changes to these groups of proteins due to freezing and frozen storage have received much attention. Four species Megalaspis cordyla, Labeo rohita, Penaeus indicus and Parapenaeopsis styli/era were used for the frozen storage study. Samples were stored for 90 days at -18°C and samples were collected at 15 day. intervals and Salt Soluble Nitrogen (SSN), Water Soluble Nitrogen (WSN) and Non-Protein Nitrogen (NPN) content were determined. Electrophoretic pattern of both Salt Soluble Proteins (SSP) and Water Soluble Proteins (WSP) of frozen stored sample were compared with that of the fresh sample.ThesisItem Open Access Individual and combined lethal toxicity of pesticide combination on the juveniles of Rohu Labeo Rohita (HAM)(Department of Fishery Biology, College of Fisheries, Panangad, 2003) Vinita P, Nair; KAU; Rajasekharan Nair, JIn the natural aquatic ecosystems, fishes are exposed to more than one biocide or contaminant at a given time. In the present study an attempt is made to understand the individual and combined toxicity of the common biocides- malathion, methyl parathion, endosulfan and 2,4- D on the juveniles of rohu (Labeo rohita) under laboratory conditions. The 48-h LCso values were computed based on the probit analysis method of Finney (1971). The 48-h LCso value of malathion was 7.89 mg.l" (7.28 to 8.61); methyl parathion was 7.34 mg.l" (7.25 to 7.43); endosulfan was 0.0036 mg.l" (0.0025 to 0.0047) and 2,4-D was 962.43 rng.l" (954.02 to 970.81). The 'additive index' values and 'magnification factors' for the combined toxicity were calculated for the different pesticide pairs based on the method of Marking (1977). For 2,4-D-malathion it was -0.018 (-0.09 to 0.50) and xO.98 (0.91 to 1.05) respectively; for 2,4-D-methyl parathion it was 0.218 (-0.02 to 0.40) and x1.22 (0.98 to 1.40) respectively; for 2,4-D-endosulfan it was -0.073 (- 0.40 to 0.16) and xO.93 (0.60 to 1.16) respectively; for malathion-methyl parathion it was 0.24 (0.021 to 0.53) and x1.24 (1.0214 to 1.53) respectively and [or malathion-endosulfan it was 1.648 (0.74 to 2.93) and x2.65 (1.74 to 3.98) respectively. Individually it is found that 2,4-D (chlorophenoxy herbicide) is 'moderately toxic', malathion and methyl parathion (organophosphate insecticides) are 'toxic' and endosulfan (organochlorine insecticide) is 'very toxic' to juveniles of rohu under t ' stc£c with renewal 48-h LCso test. But the 'strictly additive' nature of the insecticide-weedicide combinations and the 'more than additive' nature of the insecticide pairs coupled with the sequential or even simultaneous application of these chemicals in the paddy fields and plantations increase the potential [or pollution of these pesticides in the freshwater and coastal ecosystem of the State. Chronic combined sublethal toxicity 81 studies under tropical condition would throw more light on these aspects.ThesisItem Open Access Role of putative male pheromoneiIn the ovarin maturation of the fresh water prawn Macrobrachium Idella (Hilgendorf)(Department of Fishery Biology, College of Fisheries, Panangad, 2001) Patil Chandrakant, Sitaram; KAU; Jose, T MSex pheromones are reported to be present in many crustaceans which mostly have releaser effect on sexual behaviour. The discovery of a male (primer) pheromone with stimulatory effect on ovarian maturation and ovulation has added an important external factor to the basic mechanisms regulating reproduction in fresh water prawns. But studies in these lines are very few in the economically important species of Macrobrachium. Knowledge about this male pheromone will be useful to help or potentiate reproduction and/or extend the breeding period of freshwater prawns, which are of great aquacuItural importance. The present study was carried out in the slender nver prawn, Macrobrachium idella. Seven ovarian maturity stages have been distinguished here. Histological studies of the maturing oocytes helped to understand the changes taking place during oocyte growth and maturation through the progressive maturity stages. Yolk vesicles start appearing in the cytoplasm of oocyte in maturity stage II which is the beginning of vitellogeneis (vitellogenesis I). In stage IV, yolk platelet synthesis starts and 'a peripheral layer of yolk platelets appear in this stage. Later these yolk platelets completely fill the ooplasm through stages V and VI when the ova increase in size enormously. Gonado- somatic index (ovarian index) of different maturity stages was determined and was found useful to differentiate especially the late maturity stages. Ova diameter studies along with the other observations showed a clear picture of protracted multiple spawning in this species with batches of ova undergoing maturation and ovulation in successive maturation cycles. When the females were reared in isolated condition, their ovarian growth was found to be arrested at early stage IV. This restriction of ovarian maturation was found mostly in the second maturation (gonadal) cycle after isolation. But those isolated females which had a common water circulation with males showed normal ovarian maturation and ovulation. Therefore, it can be concluded that a male pheromone exists in this species which is essential for normal ovarian growth and maturation. Another experiment was conducted to find out the tissue source of this putative male pheromone. When these isolated females were exposed to extracts of testis, vas deferens or muscle, both testis and vas deferens extracts were found to stimulate the ovarian maturation and ovulation in isolated females, while the muscle extract (control) was ineffective. This shows that in M idella, the male pheromone is produced by testis and vas deferens or it is produced by testis and transported to vas deferens. Further experiment showed that charcoal extraction destroys the pheromonal activity in testis and vas deferens extract while boiling has no such effect which indicates that the ovary stimulating pehromone in M idella may be a steroidal molecule as reported in some fishes.ThesisItem Open Access Effect of cryoprotectants during frozen storage jon quality of leached minced meat from tilapia Oreochromis mossambicus (Peters)(Department of Processing Technology, College of Fisheries, Panangad, 2003) Ritu, Agrawal; KAU; Nambudiri, D DA study was conducted to develop the combination of cryoprotectants for preventing quality changes in minced meat of tilapia (Oreochromis mossambicus Peters), during frozen storage. A Japanese paste product called Kamaboko was also prepared to study the effect of cryoprotectants on quality of minced meat based product. The cryoprotectants used for study were sucrose (8% w/w), sorbitol (8%w/w), sucrose: sorbitol (8%w/w, 1:1 mixture) and sorbitol: sucrose: polyphosphate (8%w/w, 3:4:1). A reference sample as control (without cryoprotectants) was also maintained. Minced meat treated with different cryoprotectants was wrapped in 150 gauge polythene sheets and then was packed in waxed cartons. These waxed cartons were then frozen in deep freezer at -40° C followed by storage in cold storage at _200 C for 4 months. Quality changes during storage were' monitored at fortnightly interval based on various tests viz., cooking yield, free drip, centrifugal drip, myofibrillar protein content, Sarcoplasmic protein content, folding test and sensory evaluation based on whiteness, muddy taste, sweet taste and texture of cooked meat. Minced meat treated with sorbitol: sucrose: polyphosphate and sucrose: sorbitol remained acceptable with no significant difference in sensory quality, for all four months of study: However minced meat treated with sucrose and sorbitol separately and control (without cryoprotectant) showed significant lowering in quality parameters during storage and were acceptable only for 45 days.ThesisItem Open Access Evaluation of protein requirement of angel fish [Pterophyllum scalare (Lichtenstein)] larvae using defatted clam meat as the chief protein source(Department of Aquaculture, College of Fisheries, Panangad, 2001) Deepa Viswanath, K; KAU; Mohan, M VThe effect of artificial diets with varying protein levels on the growth and survival of Angel fish, Pterophyllum scalare (Lichtenstein) larvae using defatted clam meat powder as the chief protein source was studied. One-day-old free-swimming hatchlings were used in the investigations done for a period of 21 days. The different diets used were with 24.91 %, 29.83%, 34.72%, 39.86%, 44.79%,49.85% and 54.63% protein levels with 3 replicates for each treatment. The results showed that the growth of larvae in terms of gain in length, gain in weight and specific growth rate was maximum for the diet with 44.79% protein level. From the relationship established between protein level and SGR, the optimum level of protein attaining maximum SGR (21.163) was found to be 53.099%. No significant difference was found in the survival rate of larvae fed with different diets. Thus artificial diet with 44.79% protein level can be used efficiently for rearing Angel fish larvae.ThesisItem Open Access Cause of yellow discolouration in iced and frozen cuttlefish fillets and its control(Department of Processing Technology, College of Fisheries, Panangad, 2001) Sophia Margaret Joseph; KAU; Sherief, P MThe cause of yellow discolouration in ice stored and subsequently frozen cuttlefish fillets of Sepia aculeata was investigated in this study. The fillets were subjected to the following treatments (l) control (2) dip in 2% salt + 0.2% citric acid solution for 10 min. and (3) dip in 0.01% BHA solution for 10 min., prior to ice storage for a duration of six days. The iced fillets were frozen on the zero day, second day and fourth day of iced storage. Both the iced and frozen samples were periodically subjected to various biochemical and sensory evaluations. The NPN and alpha amino nitrogen contents of the salt + citric acid samples, both in the iced and the frozen samples, were found to be higher than those of the other two. This suggests that salt + citric acid are capable of retaining moisture and preventing the leaching of NPN compounds. This is supported by the sensory evaluation results, which gave higher scores~lt + citric acid treatment. The increase A in TVBN and TMA contents were found to be less pronounced in the salt + citric acid treated samples suggesting the microbial and enzyme inhibitory action of the salt and citric acid. The increase in the PV and TBARS were also less in this treatment when compared to the control, showing antioxidant property of citric acid. The BHA treated samples showed the least rise in PV and TBARS both in iced and frozen material, indicating its effectiveness as an antioxidant. . Sensory evaluation of the iced samples showed no discolouration during the period of six days, but the fourth day frozen untreated samples showed yellow discolouration after the eight weeks of storage. Since the salt + citric treatment and BHA treatment are effective in retarding the yellow discolouration, a Maillard or an 149 aldehyde amine type reaction is postulated as the possible cause of yellow discolouration in frozen stored cuttlefish. As the proteolytic activity at the site of appearance of yellow discolouration was high, the amino compounds formed by the enzyme action may be taking part in the aldehyde - amine reaction, the aldehyde being produced by autoxidation of the unsaturated phospholipids of the meat.