Estimation of ploidy and hybridization status by erythrocyte and nucleus size analysis in carps

The present experiment was designed to observe whether the nuclear volume and area are affected by the ploidy and hybrid status of the individual. Polyploidy was induced by heat shock treatment given at 44 ± 0.5°C for 30 seconds and 45 seconds which was found to be most effective (64.7%) for induction of triploidy in Cyprinus carpio. Cell and nuclear volume and cell and nuclear area varied significantly in triploid fishes as compared to those of controls. Triploid fishes showed significantly higher growth compared to diploid counterparts. It was also observed that catla x rohu hybrid and its parents showed significant difference in the nuclear volume and area of their erythrocytes. Except nuclear volume, all the parameters were significantly different between catla and catla x rohu hybrid. The hybrids showed a closer relationship with catla as compared to rohu.

Biology, stock size and catch of small pelagic fish along the coast of Mozambique

A compilation of all the available information on the main small pelagic fish resources of Mozambican waters is presented. Resource data on distribution areas, reproduction, age, growth and stock size are described. Actual catch and catch per unit of effort of the commercially exploited stocks are also given. Results of the preliminary assessment of the stocks of scad and mackerel and the problems involving the assessment of Kelee shad stock at Maputo Bay are discussed.

Scale characteristics in relation to size in cichlid fish, Oreochromis mossambicus

Teleostean scale characteristics like length, width, number of circuli, primary radii, secondary radii and ctenii were studied to delineate its relationship with total length in a euryhaline fish, Oreochromis mossambicus (perciformes: cichlidae). Statistical analysis proved a positive correlation between the scale characteristics and fish size. The characteristics of midlateral scales indicated that these scales appeared first during squamation chronology. Further observations also indicated that differences in salinity could modify the morphometries of scales.

Size related feeding patterns and electivity indices of silver barb (Barbodes gonionotus Bleeker) from a pond, Bangladesh

The feeding patterns with respect to quality and quantity of food of silver barb, Barbodes gonionotus varied with their size and development. The results indicated that the fish in the size group I (7-25 mm TL) were fairly omnivore with particular liking for rotifera, green and blue-green algae while the size group II (25.1-44 mm TL) and III (44.1-55 mm TL) were omnivore with higher tendency of feeding on debris, aquatic plants, green algae, blue-green algae and rotifera. However, the fish of the size group IV (55.1-80 mm TL) were found to be herbivore with feeding preference for aquatic plants, green and blue-green algae. In all the size groups, debris was the most dominant food item. Feeding preference of the fish showed clear ontogenetic shift. The electivity indices revealed that the fish were selective feeder.

Size frequency distribution and carapace length-total length relationship of Acetes chinensis in the Kutubdia channel of Bangladesh coast

The seasonal mean size distribution of A. chinensis were estimated as 29.229mm ±4.77, 25.125mm ±2.55, 25.165mm ±2.29 and 32.44mm ±3.63 for annual, monsoon, postmonsoon and pre-monsoon period, respectively. Seasonal mean carapace length distribution were estimated as 9.37mm ±1.457, 8.063mm ±0.63,8.258mm ±0.59 and 10.37mm ±l.ll3 for annual, monsoon, post-monsoon and the pre-monsoon season. The carapace length and total length relationships was found to be TL= - 1.39±3.23 CL. Linear relation was found in arithmetic and as well as logarithmic scale.

An observation of performances in carp-prawn polyculture in respect of fingerlings size and water area

Performances of fingerling size and water area was studied. Seven species of fish included 25% of Hypophthalmichthys molitrix, 15% of Gada catla, 20% of Labeo rohita, 10% of Cirrhinus mrigala, 10% of Ctenophyringodon idella and 20% of Macrobrachium rosenbergii were stocked at the rate of 8,000 individual/ha along Barbodes gonionoms at 6.0g weight size with a stocking density of 2,000 indl./ ha. Survival of all species was in the range of 39.9 to 96.3% except M. rosenbergii The highest survival was obtained from L. rohita (96.3%) followed by C mrigala (96.0 %)., B. gonionotus (92.3%), C idella (90.6%), H. molitrix (84.0%), C cada (81.7%) respectively. While the survival of M. rosenbergiiwas 13.1%. The highest production of 4912 kg/ha/yr was obtained from the bigger ponds (0.4 ha) stocked with 20-32g size of fingerlings, while lowest production (3123 kg/ha/yr) from small pond (0.1 ha) stocked with 3-10 g fingerlings. Economic analysis shows the highest net profit in bigger ponds stocked with bigger fish seed.

Food of two size-groups of the catfish Mystus giulio (Hamilton-Buchanan) in Vemblai canal, Vypeen Island

The stomach contents of two length-groups of the catfish Mystus gulio collected from Vemblai Canal in Vypeen Island (Kochi) were examined by frequency of occurrence and points methods. Analyses using standard indices proved difference in diet composition between the two size-groups.

Evolution of suitable trawl nets for medium size trawlers - 1: Comparative fishing efficiency between 32 m bulged belly, long wing and four panel trawls

Comparative studies of the efficiency of 32 m bulged belly, long wing and four panel trawls have shown that the bulged belly trawl to be superior to the other nets in catching bottom fishes and column fishes. 40% of the bottom fishes and 48% of the column fishes were caught by the bulged belly trawl. However, for prawn catch, the long wing trawl appears to be better as it landed 52% of the total prawn catch of the three nets. Bulged belly trawl was found to be next only to long wing trawl in this respect.

Evolution of suitable type of bottom trawls for the medium size steel trawlers of Orissa Fisheries Department

This paper deals with the results of fishing operations conducted with conventional trawls of size 22.3 - 25.6 m and gear of 32 m long wing and bulged belly designed and developed at the Central Institute of Fishery Technology, from four medium size trawlers of Orissa Fisheries Department during 1970-71 and 1971-72 fishing seasons. By employing suitable and standard size gear there was proper utilisation of the engine power with resultant increase in the total landings of shrimps and bottom and off bottom fishes.

Shore seines for reservoirs - Part 2 - Studies on optimum mesh size

Fish landings by shore seines operated in the Hirakud reservoir were analysed species wise and their morphometrical details were recorded. Based on the above investigation proportionality coefficients in respect of important species of fish were worked out in order to detetmine the optimum mesh size as this was important from the conservation point of view. This communication discusses the significance of mesh regulation for shore seines.

Effect of variation in mesh size on trawl efficiency

Result of comparative fishing trials with a bulged belly design with three different mesh ranges in the body and wing to study the effect of mesh size difference on the performance of gear is discussed. While there is no significant difference in catch rate, predictably the 40 mm mesh size trawl fared wen when small sized fish like anchovies formed the major catch. The trawls with 60 and 80 mm mesh size gave better horizontal spread at a lower resistance showing savings in fuel.

Preliminary study on the internal genital organ of the giant tiger prawn, Penaeus monodon

This report gives information on the anatomy of the internal genital organs of male and female Penaeus monodon.

Growth and survival rates of hatchery-produced and wild milkfish fry grown to fingerling size in earthen nursery ponds

Growth and survival rates of hatchery-produced and wild milkfish (Chanos chanos ) fry grown to fingerling size were compared. Data show no significant difference between the 2 fry. At a recommended stocking density of 30 fry/m super(2), hatchery-produced milkfish fry could attain fingerling size of almost 2g with a survival of 68%. The study indicates that hatchery-produced fry/fingerlings can equal the culture performance of the wild fry. Comparative performance of hatchery-bred and wild fry should encourage intensified research on milkfish broodstock development and refinement of induced spawning methods.

On the optimum mesh size for the capture of Barbus tor (Hamilton)

Results of mesh selectivity experiments on B. tor are presented in this paper. Selectivity curve on the basis of maximum girth of fish in relation to perimeter of mesh was worked out. The optimum girth/mesh perimeter ratio was found to be 1.31. A linear regression of G+0.445L=12.8 was fitted for conversion of length to girth.

Size distribution of heavy mineral grains in some modern Nile Delta coastal sands, Egypt

This study includes determination and discussion of the texture and heavy mineral compositions of some modem Nile Delta coastal sands (river, coastal dune, beach-face, and nearshore marine) in order to delineate the process and factors that regulate the size distribution of heavy mineral grains comprising these coastal sands. Textural analysis of unseparated bulk samples indicate that the examined four types of sands differ in their mean grain sizes and degree of sorting. However, analysis of size distribution curves of 10 heavy mineral species or group of species in the four environments having the same general shape and nearly similar in that general order of arrangement. However, these curves vary both in median sizes and sorting. The size distribution of a heavy mineral in the Nile Delta coastal sands appear to depend on: (1) range of grain size fractions in each sample, (2) relative availability of heavy mineral in each size grade of the sample, (3) specific gravity of minerals comprising these sands, and (4) some other unknown factor or factors. Results of size measurement of heavy minerals indicated that increasing specific gravity is accompanied by increasing fineness of the heavy minerals. This study may be useful in search for marine placers and understanding the processes of grain-sorting on the sea beaches.