Changes in the diet of predatory ribbonfish Trichiurus lepturus Linnaeus, 1758 with increasing body size along Chennai coast

In recent years, it has been recognised that predatory fishes are rapidly declining in marine habitats. Hence, gathering information on biological characteristics such as dietary dynamics of predatory fishes has assumed importance. Considering this, the dietary dynamics of the predatory ribbonfish Trichiuruslepturusfrom Chennai coast was assessed by analysing the stomach condition and contents, with reference to body size. Representatives of the Order Clupeiformes (Index of relative importance, IRI 33.7%) comprising oilsardine, lesser sardines and anchovies were the major prey items of T. lepturus.Predation by T. lepturus was aided by morphological adaptations, such as dentition, hard and spinous gill rakers, short stomach, high body depth-total length ratio of 1: 17.1 and large mouth (gape area of 1534 mm2 in adult fish).With increasing body size, the capacity to predate upon relatively larger prey increased. The differences in diet composition between ribbonfish of small, medium and large size were well-represented byIRI, prey specific abundance and cluster analysis. The fish is a top predator (trophic level: 4.17) and a specialist feeder (niche breadth: 2.63). As specialist feeders have a narrow choice of food, they are more vulnerable to fishing. It is important that management of multispecies fisheries should focus more on the sensitive predatory species

Trophic model of the coastal fisheries ecosystem of the southwest coast of India

The Ecopath approach and software were used to construct a trophic model of the coastal fisheries ecosystem of the southwest (SW) coast of India. The model consisted of 11 ecological groups and used estimated landings from all areas along the southwest coast (based on the sample surveys conducted by Coastal Marine Fisheries Research Institute for the years 1994, 1995 and 1996). The trophic model suggests high catch levels, particularly for the large and medium predators, demersal feeders and detritivores. The biomass estimates in the trophic model were comparable to the biomass estimates from trawl surveys based on the swept area method for the southwest coast.Fishery resources, Demersal fisheries, Fishery surveys, Biomass, Population density, Shrimp fisheries, Catch/effort, Trawling, Mathematical models, Coastal fisheries, ISW, India,

Marine fisheries along the southwest coast of India

Marine fisheries production in India has increased from 0.5 million t in 1950 to 2.47 million t in 1997. The gross value of fisheries landings in India was US$2.37 billion in 1997. The contribution of fisheries to the Gross Domestic Product (GDP) has risen from 0.7% in 1980 - 81 to 1.2% in 1994 - 95. The contribution to agricultural GDP has risen from 1.9% to 4%. Fisheries production also plays a critical role in food security and livelihood in rural areas. The southwest (SW) coast, while only 16% of the Indian coastline, is an important area for marine fisheries production, contributing 31.7% (0.74 million t) in 1993 - 98. This production is dominated by pelagic (59% of landings) and demersal species (23%). However, the open access system has resulted in rapid increases in fishing effort, particularly in the coastal areas. The density of fishers inshore has increased from 3.6 to 8.5 fishers per km2 in the past four decades. This excess effort has resulted in overfishing of the stocks and lower economic rent from the fishery. The overall objective of coastal fisheries management along the southwest coast of India is sustainable coastal fisheries development. This requires key ecological, social, economic and administrative issues to be addressed. Ecological sustainability requires the reduction of the excess effort through limited entry and effort reduction schemes, appropriate exploitation patterns through improved gear selectivity and restoration of the degraded coastal environment through integrated coastal zone management initiatives. Key social interventions include: creation of alternative employment to reduce fisher numbers, prevention/management of increasing intra- and inter-sectoral conflicts and empowerment of artisanal fishers through co-management schemes, social legislation and improved support/welfare schemes. The key economic issues include declining earnings, particularly of artisanal fishers, which requires; optimizing fleet composition for economic returns, improvement of the marketing system and cold storage chains, improvement of post-harvest processes to increase product value. The key administrative needs are a strong fisheries policy that balances welfare concerns with sustainability, effective implementation of regulations, and increased government resources for fisheries management. Project briefs covering the key interventions are provided, however these require further review and improvement in collaboration with concerned stakeholders.Fishery resources, Catch/effort, Population characteristics, Coastal fisheries, Marine fisheries, Ecosystems, Economic benefits, Fishery industry, Capture fishery economics, Fish consumption, Fishery policy, Legislation, Fishery management, Flood plains, Demersal fisheries, Pelagic fisheries, Socioeconomic aspects, Surveys, Marketing, Fish storage, Fishing gear, ISW, India,

Service provided by artificial reef off Chennai: a case study

The fisheries service provided by an artificial reef (AR) with a pile size of 450 m3 deployed at 20 m depth off Chinnandikuppam, 20 km south of Chennai was assessed. In 16 months, the fishermen expended 3843.7 hours of hooks & line fishing in the AR ground and landed 6404 kg. The catch index was 14.2 kg/m3 and the total income was Rs. 2,74,000. Compared with the income per hour of operation of gillnet fishing in the non-AR grounds (Rs. 52.5 kg/h), the income was 36% higher from hooks & line fishing in the AR ground (Rs. 71.3 kg/h). This was possible due to aggregation of high quality fish such as the snappers, emperor and carangids in the AR. Biological investigations on three resident species in the AR show that juvenile fish colonise in the initial months after deployment, grow to a larger size and spawn in the AR, indicating the service provided by the AR for enhancement of resident fish stocks

Artificial reef and its impact on artisanal fisheries

Artificial Fish Habitat (AFH) is helpful in increasing fish production.Deployment of artifical reefsAn AFH is an object or a construction, which promotes an ecosystem, provides habitat for fishes by attracting and aggregating them and improve the fisherman welfare

Some recent observations on small-scale fishery In the vicinity of Madras

Madras zone is one of the important fishing centres on the east coast of India. To understand the fish landings from different gears in Madras, three landing centres, viz., Kasimedu, Triplicane and Nochikuppam were selected. Kasimedu is about 8 km north of Triplicane and Nochikuppam is about 2 km south of Triplicane. The major catch components from the demersal trawls of this area arc silver bellies, threadfin breams, sciaenids, lizardfish, prawns, squids and cuttlefish. These groups are landed in a meagre quantity by the traditional gears, thus maintaining compatability between mechanised and non-mechanised gears in the exploitation of fishery resources off Madras

Food utilization in the fish Tilapia mossambica fed on plant and animal foods

Only a few publications are available concerning food utilization in herbivorous fishes (see PANDIAN, 1975). MENZEL (1959) found that angelfish Holacanthus bermudi? nsis, fed on epizoan-free filamentous algae, failed to deposit protein ; he concluded that, though the utilized algae were sufficient to meet the metabolic energy requirements, the animal matter ingested intentionally or accidentally by the angelfish was essential to insure "true growth" (GERKING, 1952)

Food intake, conversion and swimming activity in the air-breathing catfish Heteropneustes fossilis

Pandian & Vivekanandan (1976) and Vivekanandan ([976), who considered feeding rate and conversion efficiency estimates as parameters for assessing metabolic rates and efficiencies. observed that the obligatory airbreathing fish Opiliocepha/us slriatus, reared in aquaria containing different depths of water, swam longer or shorter distance to exhange atmospheric air; such a design of experiment permitted them to measure food intake. growth and sustained active metabolism on a long term basis

Kinetics and mechanism of hallogenative oligomerization of mesityl oxide by Chloramin-T. Evidence for a novel pathway in aqueous sulphuric acid

The kinetics of the reaction between mesityl oxide and chloramine-T (CAT) in aqueous sulphuric acid in the presence of KHSO4 has been studied. The results indicate a radical chain mechanism to be operative which is quite novel in CAT kinetics