Results of the Austrian-Ceylonese hydrobiological mission 1970 of the 1st Zoological Institute of the University of Vienna (Austria) and the Department of Zoology of the Vidyalankara University of Ceylon, Kelaniya. Pt. 1. Preliminary report: introduction and description of the stations

The Austrian-Ceylonese hydrobiological mission of 1970 investigated and made collections from 36 flowing water systems (brooks, torrents, rivers); of these, 34 water systems were in the mountains regions of south-west and south-east of Sri Lanka. In the crystalline mountain region, the water systems are extremely poor in electrolytes, very soft and slightly acid; these torrential streams have strong falls, high flow velocities and boulder bottoms. The water temperatures increase from the sources and brooks at 2,000 m altitude to the mouths from 15°C to 28°C. The density of animal population (macro and meso-fauna) increases from the river bank regions (and pools) towards the sections with strong current and reaches on the rocks in the cascades a density of 500 to appr. 750 individuals/1/16m².

Population dynamics of Penaeus indicus at Sofala Bank, Mozambique: a preliminary study

Length-based methods are used to estimate growth and mortalities of Penaeus indicus at Sofala Bank in Mozambique. This Penaeid shrimp is one of the most important species in the fishery as it constitutes 45% of the catches and has a great influence in their trend. First estimates of growth parameters for this species in Mozambique are presented and a comparison of the derived mortalities with the previous estimates is made.

Stock assessment of Haliporoides triarthrus (Fam. Solenoceridae) off Mozambique: a preliminary analysis

The pink shrimp, Haliporoides triarthrus, is an important species in the deep-water shrimp fishery in Mozambique. Total catches are in the range of 1,500 to 2,700 tons, with the pink shrimp accounting for 70-90%. Estimates of growth parameters and of natural mortality are used for a preliminary assessment of the fishery, based on length-structured virtual population analysis and yield-per-recruit analyses. With an arbitrarily chosen terminal fishing mortality F, the results indicate a situation of overfishing, but realistic parameters must be acquired in order to diagnose the state of the stock

Preliminary investigations on the population dynamics of Otolithes ruber (Sciaenidae) on Sofala Bank, Mozambique

Catch length-frequency data of Otolithes ruber (Schneider, 1801) obtained from the "Projecto de Pesca Experimental da RDA" on Sofala Bank, Mozambique, in 1987 were used to estimate growth parameters, mortalities and exploitation rates. The yield-and biomass-per-recruit analyses based thereon suggest that the stock is overfished.

Preliminary estimation of growth in Cheimerius nufar (Sparidae) from southern Mozambique

On the basis of length-frequency data collected in 1987, by the hook-and-line fishery research program, preliminary estimates of the parameters of a seasonally oscillating version of the von Bertalanffy equation for Cheimerius nufar (Ehrenberg, 1830) were obtained, i.e., TL∞=70 cm and K=0.17 yearˉ¹. A discussion of these results is provided.

The history and fishery potential of Kisoro Minor Lakes part two: Preliminary survey of Lakes Mutanda and Mulehe fisheries 

The fisheries of Lakes Mutanda and Mulehe during 1998/9 were mainly at subsistence scale and only few fishers operated at irregular intervals. The commercial catch records between 1963 to 1999 showed that Lake Mulehe was landing more fish than Lake Mutanda despite the fact that Lake Mutanda (26.4 km2) was bigger than Lake Mulehe (4.11 cm2). The constant decline of catches was due to irregular restocking and applying low stocking densities of fry. However, restocking should consider using species that withstand low temperature (15-240C) in the district. These include Oreochromis niloticus (Nile tilapia), Macropterus salmoides (Black bass), and Cyprinus carpio (Common carp). Most of these species have either disappeared or declined to very low levels. Due to lack of commercial fish species for harvest, the fishers by 1998/9 resorted to harvesting the haplochromines, Clarias carsoni and edible frogs (Xenopus kigesiensis) as alternative resources. Experimental studies have shown the need and techniques to enhance fish production on these two lakes.

A preliminary assessment of the shallow water prawn stocks off Mocambique, North of Beira

At present, the trawl fishery for shallow water prawns is the only industrialized national fishery in Mozambique. Most of the catch is exported. Plans are laid for expansion of the fishery, and this report is an attempt to make a preliminary assessment of the potential yields from the stocks occupying the shallow water areas between Beira and Angoche.

A preliminary assessment of the scad and mackerel stocks at Sofala Bank, Mozambique

Scads (Decapterus russellii, D. macrosoma, Selar crumenophthalmus), Indian mackerel (Rastrelliger kanagurta) and horse mackerel (Trachurus trachurus) are the main pelagic species caught in a bottom trawl fishery at Sofala Bank and at Boa Paz. Information on catch and effort is presented together with available data on distribution, spawning, size at first maturity, growth, mortality and biomass of the species. As the present catch and fishing mortality are low compared to the estimates of biomass and total mortality it is concluded that the fishery may be expanded further in the future.

Preliminary report on experimental fishing with purse seine and lampara nets for small pelagic fish varieties around Sri Lanka

Government of Sri Lanka initiated a project for conducting a experimental skipjack fishery using modern pole and line method and an experimental fishery for live bait and small pelagic fish using purse seine and lampara nets, with the, assistance of UNDP and FAO. Accordingly, the survey for small pelagic fish varieties using the purse seine and lampara nets commenced in April, 1972 and will continue until the end of 1975. This paper is a preliminary report on the results of the survey carried out between Septernber 1972 to October 1978.

A preliminary study on the cuttlefish catches from the Wadge Bank trawler fishery

Although much work has been done on the evaluation of the Wadge Bank fishery data, no detailed study has been made in the past on the analysis of cuttlefish catches. In this paper an attempt has been made to analyse this data in order to gather a preliminary knowledge of seasonal and annual variation in the availability, distribution by depth and catches in relation to the time of the day.

A preliminary study on the keeping quality of locally produced marine and freshwater salted dried fish

Experiments were conducted on the storage life of salted dried fish from both freshwater and marine species. It was found that the storage life of salted dried products from the 2 freshwater species tested (Ompok bimaculatus and Labeo dussumieri) is much longer than that of the 2 marine species (Gonialosa manminna and Chorinemus lysan), i.e., 51 days.

A preliminary study for establishing Perna viridis (Mollusca:Bivalvia) as a biological monitor for pollution in Karachi coastal water

Adverse effects of toxic substances on the environmental quality have become a subject of concern in recent years. Toxicity of heavy metals has never been in dispute and therefore their presence in our natural environment is undesirable. This study was undertaken to establish the capability of Perna viridis as a monitor for pollution in the Manora channel. Accumulation of Zinc, Copper, Iron and Manganese by marine mussels, sampled from Manora channel, was determined. Metal load varied markedly between individuals from the same populatin. This variability was partly accounted for systematic relationship between metal load and body weight and age. The distribution of metal between the major organs was considered, but the analysis of separate organs showed no advantage for their use as a biological monitor. comparison between Iron, Manganese, Copper and Zinc concentration in ambient sea water and in the mussel showed no clear correspondence. The results suggest that the mussel is capable of acting as a biological monitor, although may not be a good short term monitor of Iron, Manganese, Zinc and Copper. It may have potential as a long term and site comparison monitor for metals, once inherent variability is taken into account

Rational exploitation of Catla catla (Ham) from Hirakud reservoir: a preliminary account

Frame nets and simple gill nets of identical mesh size were experimented to determine their comparative efficiency for exploiting economic size group of Catla catla. The results indicated that frame nets of 90 mm mesh bar as the most effective.

Preliminary observations of the use of under-water light in fish catch

Experiments with drift gill net with under-water lights were carried out in the sea and estuarine region along with a control net of the same specifications without any light in the same fishing ground for comparison. The experimental net caught more fish in number and weight than the control. Fishes like pomfrets (Pampus chinensis, Parastromafeus niger), seer (Scomberomorus spp), hilsa (Ilisha spp) etc showed positive phototaxis and were gilled encircling the point of illumination. Young skates (Mobula spp) and Polynemus tetradactylus were antiphototactic. The number of fishes caught increased with increase in period of illumination. The catch of larger fishes was maximum at 60 mts of illumination and the total catch increased with increase in intensity of light. Additional cost of operation with under-water light was Rs 1-25 per hr but the catch was 4 to 5 times greater than that of the control net.

Preliminary observations on the lunar and tidal influences on the catches of seer by gill nets

The paper deals with the lunar and tidal influences on the catches of seer by gill nets. The landings during full moon and new moon nights, during low and high tides and during different quarters of the lunar month for three fishing seasons are discussed.