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Theses

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1988 - 19894
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Subject: Aquaculture × Author: KAU × End date: 1989 × Start date: 1988 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Effect of low salinities on the growth and survival of Penaeus mondon Fabricus
    (Department of Aquaculture, College of Fisheries, Panangad, 1988) Navas, K A; KAU; Sebastian, M J
    Growth and survival of P.monodon are influenced by a number of ecological factors (Chakraborti et al. 1986) salinity, being one of the most important of them. Knowledge on the tolerance of this species to low salinity conditions has great implications in its culture especially in extending its culture to low saline fields. In the present study, the postlarvae were subjected to wide fluctuations in salinity ranging from 1 to 20ppt. The influence of gradual acclimation in improving ranges of tolerance of postlarvae was studied. The lowest lethal salinity (LC 50) was determined by step-wise reduction of salinity. Salinity in which more than 50% mortality occurred at the end of 120h was considered lethal. Growth of juvenile in different test salinities ranging from 1 to 20 ppt for a period of 56 days was undertaken. Preliminary tolerance studies indicated that fluctuations in salinity ranging from 4 to 20ppt did not influence the survival of postlarvae significantly (P>0.05). Gradual acclimation extended the range of tolerance. A probit regression line for the relation between the logarithmic salinity level (dose =X) and mortality (Probit response =Y) was found to be Y=5.982023 + 1.332194X. The lowest lethal salinity (LC 50) was 0.5479 ppt with its upper and lower limits being 0.377 and 0.790 ppt respectively. Post larvae exhibited abnormal behaviour and higher rate of cannibalism at suboptimal salinities. Low salinities had a highly significant influence on the growth of juvenile (P<0.001). However, mean values of growth rate between 4 and 15 ppt did not differ significantly (P>0.05) from the control (19.5 + 0.5 ppt). Shrimps reared in different test salinities were subjected to sensory evaluation. Flavour of cooked meat of shrimps differed significantly with variation in salinities (P<0.05). The overall taste panel score was highest at 9.5 + 0.5ppt. The possibility of the influence of salinity on flavor of cultured shrimps is suggested.
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    ThesisItemOpen Access
    Effect of salinity on survival, growth and breeding of the shrimp
    (Department of Aquaculture, College of Fisheries, Panangad., 1989) Ignatius, C A; KAU; Thampy, D M
    The present study has been undertaken with the major objective of elucidating the effect of salinity on survival, growth, ovarian development, fecundity, incubation period and batch hatching of the freshwater prawn Macrobrachium idella. Mortality of juveniles of M. idella which were acclimated at 0 and 20 ppt and treanferred abruptly to varying salinities, was found to start at 27.5 and 32.5 ppt respectively, whereas in those which were gradually acclimated from 0 to 45 ppt, it was found to start only at a higher salinity level of 37.5 ppt. The 120 Hr LC50 values were 30.90 + 0.7107, 35.89 + 0.7842 and 40.74 + 0.7402 ppt for the prawns acclimated at 0 and 20 ppt and for those gradually acclimated respectively. Thus it could be seen that this prawn is a highly euryhaline one and that acclimation at a higher salinity level and gradual acclimation have got advantage in extending the upper tolerance level. Growth was found to be significantly influenced by salinity, being highest at 0 – 10 ppt, lower at 15 ppt and almost nil at 20 ppt and beyond. Sporozoan infection was noticed in the prawns reared at 15, 20 and 25 ppt. Salinity was found to have no significant influence on fecundity, while ovarian development is being influenced by it. The rate of ovarian development was high at 6 and 12 ppt and low at 0 ppt. Incubation period, which takes about 13 – 15 days was not found to be influenced by salinity, while there was some effect on batch hatching, the rate of which was more at 0 ppt and less at 6 ppt. During incubation, mortality of eggs due to infection was observed only at 0 ppt. Thus, it could be seen that a salinity level of around 6 ppt is ideal for ovarian development, maximum fecundity and synchronous hatching.
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    ThesisItemOpen Access
    Effect of salinity on survival and growth of Macrobrachium rosenbergii (De Man)
    (Department of Aquaculture, College of Fisheries, Panangad, 1988) Venugopalan I K; KAU; Thampy D M
    The effect of salinity on survival and growth of macrobrachium rosenbergii (De Man) was studied with a view to establish the optimum salinity conditions under which it can be cultured. The effect of salinity on survival was assessed by conducting short-term tolerance studies wherein the effect of abrupt transfer and gradual acclimation to the test salinity levels of 5,10,15,20,25,26.5,28.5,30 and 35 ppt was separately studied. In both abrupt transfer and gradual acclimation, no mortality was observed upto 25 ppt within a period of 120 hrs. The LC50 values for 72 hr and 120 hr were 33.3 ppt and 31.6 ppt for gradual acclimation and 29.85 ppt and 28.18 ppt for abrupt transfer respectively. Acclimation prolonged the survival time of the juvenile in the test salinity levels. The study on the effect of salinity on growth was conducted in cement cisterns, wherein salinity levels from 0-10 ppt with regular increments of 2ppt from treatment to treatment were used. There was no significant difference between treatments upto 6 ppt, but all the levels upto 6ppt differed from 8 and 10 ppt with respect to growth. A field trial to verify the growth pattern in different salinity levels was conducted in one fresh water pond and two brackish water ponds having different salinity levels. The growth rate of the prawns was almost equal in both the fresh water pond (0.119 g/day) and the pond with lower salinity levels (0.126 g/day), whereas it was much lower in the high saline pond (0.063 g/day). The survival rate obtained in the high saline pond (58%) was comparable to fresh water (59%) showing that prawns could survive upto a salinity of 20ppt , although the growth rate is lower in higher salinity levels. Studies were conducted to evaluate the effect of salinity on oxygen consumption, ammonia excretion and O:N ratios of M.rosenbergii within the test salinity levels of 0-10 ppt. Oxygen consumption and ammonia excretion were found to be strongly influenced by the wet weight of the juveniles, but the influence of salinity on these physiological indices were not significant within the test levels used in this study. However, a trend of an increase in oxygen consumption and decrease in ammonia excretion towards the lower salinity levels was observed. Oxygen to nitrogen ratios were found to be lower in the higher salinity levels indicating an increase in protein catabolism in such salinity levels.
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    ThesisItemOpen Access
    Food selectivity of pond reared and wild Etroplus suratensis (Bloch) and effect of supplementary feeding on its growth
    (Department of Aquaculture, College of Fisheries, Panangad, 1989) Sathiavathy, C R; KAU; Susheela, Jose
    Food and feeding habits of E.suratenis during fry (30-49 mm), fingerlings (50-69) mm, subadult (70-89 mm) and adult (90-120mm) stages in the captive environment of a culture pond and wild environment viz. Cochin backwater were studied. The study was conducted from October 1986 to March 1987. A culture pond in the College of Fisheries, Panangad was stocked with E. suratensis of the above four length groups in 1:1:1:1 ratio, at a stocking density of 5600 Nos/ha, after preliminary preparations. Samples were collected from both these environments form the end of first month onwards. Each month, the numbers that were removed from the culture pond were restocked with same numbers of specimens of various length groups. Salient ecological parameters viz, temperature, PH, salinity, alkalinity,dissolved oxygen,phytoplankton primary productivity, zooplankton and zoobenthos of the culture pond and the backwaters were analysed at monthly intervals . The feeding intensity of the specimens in the captive and wild environment, relative lengths of gut during different stages, food items consumed in the culture pond and in the backwaters and selectivity index of various food items were studied. A feeding experiment was also conducted with fingerlings of E. suratensis where five feeds were used in duplicate. The feeds used were (I) conventional feed made of groundnut oil cake and rice bran (1:1) having 31.50% crude protein (II) 50% conventional feed + 50% fresh hydrilla verticillata having 24.55% crude protein (III) Fresh Hydrilla verticillata alone having 17.60% crude protein (IV) 50% conventional feed + 50% fresh Enteromorpha intestinalis having 23.30% crude protein (V) fresh Enteromorpha Intestinalis alone having 15.1% crude protein. Analyses of the physio-chemical parameters of the captive and wild environments show that their range was tolerable for the normal life activities of fishes and did not affect the food intake of the species. The feeding intensity of E.suratensis was found to increase from the first length group to the fourth length group in both the environments. The feeding indices of the four different length groups in the brackish water culture pond were 13.89, 19.45, 33.33 and 44.44 while the corresponding values in the backwaters were 55.56, 66.67, 72.72 and 77.78. Feeding intensity of E.suratensis was higher in the backwaters than in the culture pond. The RLG of E.suratensis from first to fourth length groups in the culture pond were 2.911, 3.111, 3.850 and 4.420 while the corresponding values for the fishes form the backwaters were 3.011,3.331, 4.010 and 4.535. The food items in general of the four length groups in culture pond were detritus, diatoms, filamentous algae, rotifers, copepods, other crustaceans, insect larvae and gastropods, with some variations in their order of preference among different length groups. In the backwaters the major food items in general were diatoms, higher aquatic plants, detritus , rotifers, copepods, other crustaceans and insect larvae. Selectivity index of the important food items in the culture pond and backwaters during October 1986 and March 1987 were studied for all the length groups. Selectivity index values were obtained for diatoms, filamentous algae, rotifers, copepods, other crustaceans and insect larvae for all the for length groups in pond and backwater. The selectivity index of detritus was +1 for all the four length groups in culture pond and backwaters, during both the months under study. For the higher aquatic plants, the selectivity index was +1 for the length groups II, III and IV in the backwater. But for the length group I in the backwaters and for all the four length groups in culture pond, no selectivity index exist for higher aquatic plants. In the feeding experiment, maximum values for average specific growth rate expressed as percentage wet body weight d-1 (0.455), average monthly increment (39), percentage gain in the body weight (14.634%) and best food conversion factor (18) were obtained for feed V, viz; fresh Enteromorpha intestinalis alone. Statistical analysis using analysis of variance technique showed that there was significant variation due to the effect of feeds. Analysis of least square method indicate that these five feeds can be grouped into two. In the first group, with feeds I and II, there was no significant difference between the feeds. In the second group with feeds III, IV and V , no significant difference were seen among themselves, but all these feeds show significant difference with the feeds I and II. The growth performance obtained by these feeds in the second group were superior that the feeds I and II.