First record of Holothuria (Platyperona) difficilis Semper, 1868 (Echinodermata:Holothuroidea) from the northern Arabian Sea (Pakistan)

During the 1994 winter collections, a small holothurian was collected from the rocky shore of Buleji (24°50'N, 66°53'E). It was attached to the green seaweed, Ulva fasciata and was not immediately noticed due to the same basic colour of the body as that of the seaweed. For identification a microscope slide of the spicules was prepared by placing a small piece of skin on a slide and treating it with (3.5%) sodium hypo-chloride (common household bleach). The specimen was identified as Holothuria (Platyperona) difficilis Semper, 1868.

Note on Nematopalaemon tenuipes (Henderson, 1893) (Crustacea:Palaemonidae) from the Pakistan coast of Arabian Sea

On a few occasions palaemonid shrimps turned up in the collections from the Karachi fish harbour. The specimens resembled Nematopalaemon tenuipes (Henderson, 1893) but for the walking legs which were invariably missing or incomplete, in the latter case the dactyli were broken at or just near the base. The only reference from Pakistan is in context to its distribution (Holthuis and Miguel, 1984). The abbreviation cl. is used in the text for the carapace length measuring from the orbit to the posterior margin of the carapace.

On the results of preliminary fishing trials with shark long lines in Veraval waters

Experimental fishing operations with shark long lines were conducted in the sea off Veraval with a view to studying their efficiency and gathering information on the available resources of sharks to be used for planning the future gear investigations. The trials were undertaken in 1967, employing departmental fishing vessel "Fishtech No. IV" (10.9 m O.L. and 48 H.P. engine). A total of 5525 hooks were employed and 242 sharks weighing 8629 kg were landed. Data on composition of catch, weight of fishes landed, effectiveness of various baits in capture of different species of sharks and effectiveness of gear including its catch efficiency in this area were compiled. Bait preference was also observed in certain species of sharks caught. Chirocentrus dorab proved to be the cheapest and most effective bait in capture of all the three varieties of sharks landed.

Bothid larvae (Pleuronectiformes-pisces) of the Gulf od Thailand and South China Sea

The larvae of bothids were found to be sparsely distributed in the Gulf of Thailand and South China Sea being only 11.9% in the Naga Expedition Collections. They were confined mostly to the coastal waters and were found in near shore stations situated between Bangkok and Saigon. Their density was high in the Gulf of Thailand. The larvae seem to prefer darkness with greater incidence during April 16 to October 15 period, with a peak in the collections taken during April. This report includes the occurrence of 17 species belonging to 6 genera collected from the Gulf of Thailand and South China Sea, along with their regional, seasonal as well as diurnal variations

Studies on the seasonal cycle of sea surface temperatures, salinities and phytoplankton in Puttalam Lagoon, Dutch Bay and Portugal Bay along the west coast of Ceylon.

The monthly average temperatures at Puttalam Lagoon, Dutch Bay, Portugal Bay towards Kovilmunai and Portugal Bay towards Pallugaturai showed a distinct annual cycle. The peak was in April and values gradually fell till September. There was a further gradual fall in temperature from October to January. The highest temperatures in all four stations were in April. The highest salinities in all the stations were from May to October i.e., during the south-west monsoon. The salinities at Dutch Bay and Portugal Bay were high in March and April corresponding to the highest temperatures reached during these months. Two maxima have been observed in phytoplankton production. A primary maximum in May-June and a secondary maximum in October. The primary and secondary maxima are due to the influx of nutrient laden waters from the rivers Kal Aru and Pomparippu Aru. The phytoplankton producing blooms were Rhizosolenia alata. Rhizosolenia imbricata, Chaetoceros lascinosus, Chaetoceros pervianus, Ch,aetoceros diversus, Coscinodiscus gigas, Thallasionema nitzschioides, Thalassiosira subtilis, Thallassiothrix frauenfeldii, Asterionella japonica, Sceletonema costatum, Bacteriastrum varians and Biddulphia sinensis. Sudden outbursts of a single species were common. These diatoms were species of Chaetoceros and Rhizosolenia, and Thallassiothrix frauenfeldii. Wide fluctuations have been observed in the distribution of phytoplankton but no definite conclusions can be drawn as the period of observation was only one year.

Marine bacteria as indicators of upwelling in the Sea

The “oxidase reaction” (using p-amino-dimethyl-aniline oxalate as the reagent) has been used to distinguish oxidase-negative from oxidase-positive bacteria from the sea, when grown on membrane filters. By this means, it has been shown (a) that under conditions of stable stratification of the sea as in the tropics, a relationship exists between the percentage incidence of oxidase negative bacteria in the flora and the depth of the water; (b) that the maximum value for this percentage incidence (100) is reached at or immediately below the upper limit of the oxygen minimum layer; (c) that this percentage value (expressed as Oxⁿvalues) may be used to demonstrate the movements of water masses during upwelling. Such upwelling as indicated by theoretical findings and by temperature determinations along two transects off the west coast of Ceylon during the north east monsoon, has been confirmed by the distribution of Oxⁿvalues at these transects.

A Comparison of the bacterial flora of surface and sub-surface water of the sea off Ceylon

Under stable conditions of stratification of the sea, evidence of generic differences of the associated bacterial flora of the water masses has been obtained, between surface and sub-surface water. Gram negative rods, especially pseudomonads and achromobacters were more frequent at the surface. The fermentative and oxidase negative flora was more frequent in sub-surface water. The surface water in general had a greater variety of bacterial types while the sub-surface water had a flora with a greater range of biochemical activity. These results are discussed in relation to the hydrological condition of the water masses and the bacterial flora of freshly caught fish.

Wadge Bank trawl fishery studies. Pt. 4. An analysis of the length frequency measurements of the sea bream (Lethrinus nebulosus) made in 1949 and 1953 to 1958

Length frequency distributions of the sea bream collected during the period 1953 to 1958 have been analysed. The increase in average sizes of the sea bream with depth suggests a movement to deeper waters with increase in size. By numbers, the sea bream is more abundant between 21 and 30 fathoms than in deeper areas. The recruitment was continuous and regular. There is no sign of entry or progression of a dominant brood throughout the period under study. Length frequency distribution shows three distinct modes. The first mode occurs regularly but does not progress beyond 40cm, recruitment being balanced by natural and fishing mortality. The other two which are not regular are probably the result of fishing outside regular areas. Short sections of “growth” lines which fit into one another when extrapolated, are evident. The larger lines obtained by extrapolation are parallel to one another. These tentative "growth lines" indicate that this species which enters the fishing grounds, when 15 cm or larger in length are exploited by the trawl fishery for a period of three to four years. This species appears to be six months old when it enters the fishing grounds and increases in length by about 37.5 cm in the next 30 months. Later growth slows down. The average size of the specimens sampled continued to get smaller from 1953 till 1957. It is shown that this reduction in size is due to increased fishing effort.

Studies on the seasonal cycle of sea surface temperatures, salinities, oxygen and phytoplankton in Koddiyar Bay, Trincomalee in relation to the shore seine fishery

In Sri Lanka waters, Durairatnam (1963, 1969) had reported on the seasonal variation of plankton at Puttalam lagoon, Dutch Bay, Portugal Bay and in the inshore and off shore waters off Colombo. Similar investigations were carried out at Koddiyar Bay especially in the estuarine waters where the three tributaries of the river Mahaveli empty their waters into the bay. The estuary is perennial. The fishes constituting the estuarine fisheries are mostly shallow water marine species which can tolerate considerable variations of salinities. Prawns and crabs also constitute a very valuable fishery in estuarine waters.

Variance prediction in sea

A method is presented for predicting the variance of the energy levels in a built-up system to accompany the mean values predicted by SEA. Closed form expressions for the variance are obtained in terms of the standard SEA parameters and an additional set of parameters αk that describe the nature of the power input to each subsystem k, and αks that describe the nature of the coupling between subsystems k and s.

A procedure for automatically estimating model parameters in optical motion capture

Model-based optical motion capture systems require knowledge of the position of the markers relative to the underlying skeleton, the lengths of the skeleton's limbs, and which limb each marker is attached to. These model parameters are typically assumed and entered into the system manually, although techniques exist for calculating some of them, such as the position of the markers relative to the skeleton's joints. We present a fully automatic procedure for determining these model parameters. It tracks the 2D positions of the markers on the cameras' image planes and determines which markers lie on each limb before calculating the position of the underlying skeleton. The only assumption is that the skeleton consists of rigid limbs connected with ball joints. The proposed system is demonstrated on a number of real data examples and is shown to calculate good estimates of the model parameters in each. © 2004 Elsevier B.V. All rights reserved.

Development of off-shore and deep-sea fishing in Sri Lanka

Since 1950 onwards, a practice has grown in Sri Lanka of dividing the marine fisheries into three different classes depending on the location of the resource to be exploited viz. coastal fishing, off-shore fishing and deep-sea fishing. The author describes commercial fishing activities, paying attention to changes emerged and future prospectives.

Problems facing the deep-sea fishing industry in Sri Lanka

Fishing in Sri Lanka has been carried on largely with the use of traditional methods and in recent years there has been a marked increase in the use of mechanized craft for fishing. Although some effort has been made in the sphere of deep-sea fishing both by trawlers and long line tuna boats, such efforts have not made a significant contribution towards improving the industry. The progress of deep-sea fishing in Sri Lanka has been hindered due to a number of reasons described by the author.

Demersal fishery resources of Sri Lanka and its present level of exploitation with special reference to off-shore and deep-sea waters

Following a brief review of development of demersal fishing off Sri Lanka, the author reviews the fishing grounds of the Wadge Bank, the Pedro Bank, and the Mannar Bank. He reviews the deepwater trawling fisheries particularly in relation to the 1972 survey conducted by the 'Optimist' and also small boat trawling in coastal waters. Lastly he considers handlining for groundfish, which is principally conducted by fishermen operating traditional craft.