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

Pelagic resources around Sri Lanka may be categorized into three major groups: (1) the small pelagic varieties such as the sprats, halmessa, sardines (salaya, soodaya), and herrings (hurulla). (2) the medium size pelagic species such as the mackerel (kumbala and bolla), barracuda (jeela), seer Spanish mackerel (thora), frigate mackeral (alagoduwa), mackerel tuna (atawalla) and the skipjack (balaya). (3) the large size fishes such as yellow fin tuna (kelawalla), big eye tuna, marlins (koppora and gappara), sail fish (thalapath), sharks (mora) and rays (maduwa). Production levels of exploited resources are noted, and seasonal patterns and annual in their abundance are considered. On the basis of observations and estimations of the existing fisheries, and the results of experimental fishing, figures are presented of the potential yield of those species already exploited. The development of that potential depends on the development of modern techniques of pole and line fishing, application of tuna longline and shark longline, increasing the number of units of drift nets and the introduction of a bait fishery for the longline and pole line fishery. Some features upon which the successes of any venture to exploit such resources are noted, particularly those which relate to the nature of the fishing vessels used.

Fishing gear and methods for off-shore fishing in Sri Lanka

The author describes the commercial viable off-shore fishing methods for catching known commercial resources available around Sri Lanka. He also describes the in-shore fishing methods such as bait fishery which are related and of prime importance for carrying out certain off-shore methods. The paper is intended as a background for the description of fishing methods. The methods discussed are: (1) Longlining for large pelagic species such as large tuna (yellow fin, big eye), shark, spearfish and others; (2) Drift-netting for small and large tuna species (skipjack, yellow fin and others), shark, spearfish, etc.; (3) Pole and line for all deep-sea pelagic species such as skipjack, yellow fin, frigate mackerel, etc.; and (4) Purse seining (small scale) for small pelagic species suitable as bait fish for pole and line and longline fisheries.

Operatives for off-shore and deep-sea fishing vessels

The need for operatives for the offshore and deep-sea fishing vessels is currently very great, and the importance of fisheries training has long been recognized by the Department of Fisheries. In 1974 the Sri Lanka Fisheries Training Institute was established with Japanese aid. The author discusses the purpose and functions of the institute, the first batch of trainees from which finished their training in June 1977. Annexes describe the courses offered, diplomas and certificates, admission requirements, and the conditions required for candidates sitting second-hand fishing vessel examination of the Mercantile Marine Department, Bombay District.

Infrastructure facilities for deep-sea and off-shore fishing

The author presents a brief account of the infrastructure facilities required for the fishing industry. He describes those facilities presently available in Sri Lanka, and those that are under construction, and gives a few suggestions indicating the nature of infrastructure facilities that are vital to the local situation at its present stage of development. The principal facilities discussed are (1) fish landing places; (2) unloading handling facilities; (3) vessel servicing facilities; and (4) navigation aids.

Private sector to invest in off-shore fishing and to encourage the financial incentives to be introduced for deep-sea fishing in Sri Lanka

The author discusses the financial aspects of private sector investment in off-shore fishing, with particular attention to tax incentives, such as those offered to tourist hotels, which are considered applicable to the current case of fishing vessel purchase, and the operation of the vessels themselves, hiring, publicity and profitability. Tax incentives which were introduced to encourage investment in the tourist industry should be introduced to encourage investment in the fishing industry on the lines presented. It is essential that wide publicity be given for the incentives introduced so as to achieve the desired results.

Population dynamics of killifish Aphanius dispar (Ruppel) in Sandspit area off Karachi

Growth and mortality parameters of Aphanius dispar a cyprinoides generally observed in the catches of near shore area were estimated from the length frequency data collected from Sandspit area of Karachi, using LFSA. The von Bertalanffy growth parameters were estimated as Loo=71.73 mm & K=L35/yr for Male Aphanius dispar and Loo=70.66 & K=l.41 for female. Total Mortality coefficient (Z) was estimated using Length converted catch curve which is equal to 2.12/yr, for male and for female 2.19/yr. Natural mortality (M) was estimated by Pauly's empirical formula: M=l.64/yr (male) and 1.70/yr (female). The species also displayed two cohorts a year.

Heavy metals in certain commercially important finfish off Mahim in Mumbai coastal waters

The coastal water of the metropolitan city of Mumbai has deteriorated due to the indiscriminate discharge of untreated sewage and industrial waste in huge quantities. Mahim creek is one such locality surrounded by a large number of industrial units discharging heavy metals. The accumulation of the heavy metals Cu, Cd, Zn and Pb in finfishes (Coilia dussumeri, Lepturacanthus savala, Harpodon nehereus and Johnieops elongates) from this locality along with that in the sediment was studied. The rate of accumulation of Cu was high compared to Cd, Zn and Pb. A gradual increase in the bioaccumulation of heavy metals was noticed in fishes with increase in average body weight and length, perhaps due to biomagnification. A declining trend in concentration of heavy metals horizontally from inshore to offshore was observed in these fishes.

On the trend of prawn catch off Paradeep

The distribution and landings of important varieties of prawns off Paradeep coast, Orissa, in relation to the climatic and hydrographic conditions from 1970-1976 are presented. The prawn fishery as a whole, showed a quadrennial cycle along the coast. The post-monsoon migration of all varieties of prawns along the coast directly depends on the annual precipitation. Temperature gradient, fluctuations in salinity and southerly wind in the Bay of Bengal influence the migration of the different species of prawns.

Food and feeding habits of Saurida Tumbil (Block, 1795) off Mumbai waters

The present investigation suggests that Saurida tumbil (Bloch, 1795) is carnivorous and predacious feeding mainly on fishes followed by crustaceans and molluscs. Cannibalism has been observed in the species. Young ones of this species were observed to feed on small fish and Acetes spp., while adults feed on a variety of food. However, fish seems to be the preferred food item. Monthly gastro-somatic index in males indicates poor feeding in the month of february and maximum during august and september. In females, monthly gastro-somatic index indicate poor feeding in december and maximum during january and march. Sex wise study of feeding intensity did not reveal significant difference in males and females.

Inshore demersal fisheries off Orissa coast

Results of bottom trawling in inshore areas off Paradeep with reference to total catch composition and catch per unit effort during 1962-1978 are reported. With increase in fishing effort, benthic species recorded the highest catch in 1969-'70 and thereafter it fluctuated. Fluctuations till 1968-'69 may be due to seasonal migration of fishes. The decline after 1971-'72 can be attributed to overfishing. Off Mahanadi, Devi and Rushikulya river mouths, showed a north-south migration of fishes from october. Presently off Devi river mouth is a rich ground for demersal fishes.

Hydrography of fishing grounds of Arabian sea off Mangalore

Hydrographical parameters, namely temperature, salinity, dissolved oxygen and density of the fishing grounds off Mangalore extending over an area of ca 850 km² have been studied during March 1976 - March 1977. Twelve stations along three transects up to 50 m isobaths were located for sampling. The vertical distribution of temperature show three distinct phases, namely, a period of conspicuous variation, a short intermediary phase and a period of thermal stability. The dissolved oxygen of the bottom waters was drastically low during September. Salinity fluctuations were not considerable between months and depths. Dense waters existed over the shelf region, especially along the bottom during september and to a certain extent in october also. The distribution patterns of temperature, dissolved oxygen and density clearly indicate the movement of cold, dense, oxygen-poor- bottom waters from greater depths to the upper reaches of the shelf during September.

A review of experimental trawling from small and medium sized mechanized vessels off Kanikada

The most suitable otter trawl for small boats was found to be a 10.9 to 15m 2-seam trawl with 100cm x 50cm x 35kg horizontally curved otter boards together with long single sweep line. For operation from medium sized trawls, 18.26m 2-seam 18.3m 4-seam and 29.26m long wing trawl were found suitable. An 18.3m 4-seam trawl was netting a considerable quantity of off-bottom fishes. Shrimps predominated in the catches of the 29.26m trawl. Productive grounds for Cynagris species, Psenus species and Decapterus species within 50 to 100m depth ranges off Kakinada were available for profitable exploitation.

On the results of bottom-drift-long-lines operated off Veraval with particular reference to selective action of baits and hooks used

Hither to comprehensive data on the various types of baits used for capture of predatory fish and selective action of different hooks for bottom-drift-long lines is conspicuous by its absence. In the present studies attempts were made to evaluate the effectiveness of three types of baits and four sizes of hooks. Significant results obtained during the course of these investigations are presented in this communication.

On the resources of demersal fishes for bottom trawling in inshore waters off Kakinada by small mechanised boats

An attempt is made to assess the available resources of demersal fishes for bottom trawling off Kakinada, in inshore waters. From the experimental fishing operation during 1964-66, the average catch per hour was 52.79 kg for 9.13 m (30') OAL mechanised boat. The catch composition was dominated by prawns and sciaenids forming 45% of the total catch. The average catch per trawling hour was more during the quarter April - June. An assessment on productive depth range has indicated that catch rate is increasing with increase in the depth of fishing.

Purse-seines off Goa

The design, construction and operational details of the purse-seines operated from Goa, for sardines and mackerel are reported briefly. The deck equipment and details of vessel along with the fishing season, fishing grounds and catches are briefly accounted. The design has been compared with Japanese purse-seines operated for the same species of fishes. Based on the findings an improved design of purse-seine has been presented.