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The present dissertation is a study of juvenile shrimps collected from Sandspit backwaters during the period from June 1987 to May 1989. The study was initiated in view of the significance of shrimp fishery to the economy of the country., Sandspit backwater act as nursery area for juvenile shrimp, hence of significance for both commercial and artisanal or subsistence fisheries. The study provides a comprehensive account of penaeid juveniles from the backwaters of the Karachi coast, chemical and physical parameters of their habitat, identification, and various aspects of population structure and bionomics Salinity, seawater temperature, dissolved oxygen, and pH were recorded fortnightly both from backwater and water from open sea during the entire study period. The salinity of the backwater ranged between 16.99 ppt to 45.00 ppt with an average value of 37.98 ± 4.32 ppt (S.D.) (n=48). The open sea salinity varied from 34.30 ppt to 39.48 ppt, with an average salinity value of 36.91 ± 0.97 ppt (S.D.) (n=48). The average temperature of the backwater was found to be 28.9 ± 3.9 ºC (S.D.) (n=48) with a range of 19.5 ºC to 34.5 ºC. The average temperature of the open sea was found to be 27.2 ± 2.5 ºC, whereas the highest temperature was 33.0ºC. The monthly mean of daily maximum temperature ranged between 25.6 ºC to 36.4 ºC, while the monthly mean of daily minimum temperature ranged between 10.5ºC to 28.4 ºC. Mean monthly temperature ranged between 18.1 ºC to 32.3ºC. The maximum rainfall was 85 mm, while the minimum rainfall recorded was 0.5 mm. The mean value of dissolved oxygen in the backwater was found to be 5.01 ± 0.97 ml/L (S.D.) (n=48). The lowest value was 3.00 ml/L, whereas the highest value was 6.55 ml/L. The average value of dissolved oxygen for the oprn sea was found to be 5.25 ± 0.85 ml/L (S.D.) (n=48). The average pH of the backwater was found to be 7.61 ± 0.46 (S.D.) (n=48), and ranged from 6.34 to 8.05. For grain size analysis and organic content, sediment samples were collected to represent both the post-monsoon (southwest) and the pre-monsoon (southwest) periods and from two sub-stations (sub-station 1-A, inter-tidal pond; sub-station 1-B, mud flat). The samples collected from sub-station 1-A had agreater percentage of sand fraction (79.70-89.84 %) as compared to those collected from sub-station 1-B, which had 63.33 to 79.86% of sand fraction. The organic content was found from 3.19 % to 8.32 %. The sample collected from sub-station 1-A had low organic carbon as compared to those collected from sub-station 1-B Juveniles of a total species have been identified, with particular reference to genus Penaeus spp. Among Penaeus spp. Emphasis has been given mainly to the morpho-species complex for which electrophoresis has been also performed. Morphological characters of adults are described and their usefulness in case of juveniles is discussed. Where adult characters are not useful for the determination of juvenile shrimps into species, other characters are described A total of 18242 juvenile shrimps were collected and examined to study the various population parameters, such as species composition, seasonal abundance, size distribution, sex ratios, and length frequency distribution. Sex ratios, and length frequency distribution. In all, juveniles of ten species were found inhabiting the Sandspit backwater. The genus Penaeus was represented by six species namely, P. penicillatus, P. merguiensis, P. indicus, P. monodon, P. semisucatus, and P. japonicus. The genus Metapenaeus was represented by only three species: M. monoceros, M. stebbingi and M. affinis, whereas, genus Parapenaeopsis was represented by only one species, P. stylifera. Of these ten, three species viz, P. semisulcatus, P. japonicus and Parapenaeopsis stylifera were found only once. The population parameters described above were therefore, studied for remaining seven species. The juvenile population in the Sandspit backwater was predominantly composed of two species namely, M. monoceros (40.97%) and P. penicillatus (32.64%). They together constituted 73.6% of the population. Next to these, in the abundance were M. stebbingi and P. merguiensis, which were 10.73 % and 9.29%, respectively. The three less abundant species were P. indicus (3.27 %), M. affinis (2.14%) and P. monodon (0.87%). P. penicillatus predominates in one season (July to October). M. stebbingi predominates only in the months of December and January. The average total length of P. penicilltus juveniles was found to be 57.1±8.4 mm (S.E) with a range from 11 mm to 119 mm. In P. merguiensis the total length varied from 11 mm to 123 mm with an average length of 54.3 mm ±9.9 mm (S.E.). The total length of P. indicus varied from 12 mm to 117 mm, with an average length of 60 ±14 mm (S.E.). The total length in P. monodon juveniles ranged from 49 mm to 163 mm. The average size was found to be 105 mm± 20mm (S.E.). M. monoceros ranged from 11mm to 93mm in total length with an average size of 46 mm ±9mm (S.E.). The size of the juvenile M. stebbingi varied from 10 mm to 90 mm in total length. The average size was found to be 31 mm ± 5mm (S.E.). In M. affinis, the range of total length was found to be 18 mm to 95 mm with an average 55 mm ± 8 mm (S.E.). The overall sex ratios in juveniles of all the species were not found significantly different from the natural 1:1 ratio. However, in certain size classes, the sex ratios deviated significantly from 1:1 The analysis of stomach content revealed the presence of both animal and plant matter in the diet of juvenile shrimps. Crustaceans and polychaetes were found to be the major food eaten by Penaeus penicillatus and P. merguiensis. The food of P. monodon was mainly comprised of seaweeds (plant matter). Moulting and growth were observed in captivity. Growth factor, intermoult period and increase in weight were studied in Penaeus penicillatus and P. monodon. The regression equation for the correlation between the permute carapace length (CLn) and postmoult carapace length (CLn+1) was found to be CLn+1 = 0.952 CLn + 2.92 for P. penicillatus and CLn+1 = 0.9844 CLn + 3.2311 for P. monodon. Sediment preference experiments showed that the juveniles prefer fine and very fine sand

Item Type:Thesis (PhD)
Uncontrolled Keywords:shrimp, genus penaeus, juvenile shrimps, p. penicillatus, p. merguiensis, p. indicus, p. monodon, p. semisucatus, p. japonicus, genus metapenaeus, m. monoceros, m. stebbingi, m. affinis, genus parapenaeopsis, p. stylifera
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Biology (c13)
ID Code:1140
Deposited By:Mr. Muhammad Asif
Deposited On:03 Jan 2007
Last Modified:04 Oct 2007 21:04

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