Bycatch from Trawlers with special reference to Its Impact on Commercial Fishery, off Mangalore

Trawling, though one of the most efficient methods of fish capture, is also found to be the most important human caused physical disturbance on the world's continental shelves and hence the physical destruction of ecosystems (Jennings and Kaiser, 1998), Trawl fishery is generally a mixed fishery targeting a number of species and sizes simultaneously. Discarding is the practice of returning an unwanted section of the catch back to the sea during fishing operations (Alverson, 1994; Van Beek, 1998; Hall,2000

Spatio-temporal analysis and impact assessment of trawl bycatch of Karnataka to suggest operation based fishery management options

Trawling is one of the most efficient methods of catching fish world over and is also the most important human intervention causing physical disturbance to the world’s continental shelves, and consequently, the physical destruction of ecosystems (Jennings and Kaiser, 1998). Trawling is targeted at specific groups of organisms, and trawl net being a non-selective gear, catches everything available in its towing path

Bivalve resources of Moorad Estuary, north Kerala

A bivalve resource survey of Moorad estuary in Badagara District of north Kerala was carried out during February 2004 to assess the bivalve species, their distribution and potential stock. Sampling sites were fixed within five main zones of the Moorad estuary based on the clam fishery activities and local enquiries. The bivalve distribution in a unit area was taken by demarking the area of clam bed with a quadrant. Observations on the area of clam bed, water clarity, depth and temperature were recorded at each site. Surface and bottom water samples were collected and hydrographic parameters like salinity, temperature, pH and dissolved oxygen content, productivity, nitrate, phosphate and silicate were recorded. Sediment samples were collected to analyse the grain size and organic content of the clam beds. All samples were analysed within 24 h except sediment samples. Average density of bivalve per square metre area was analysed and the potential stock was estimated for each bivalve species in the estuary

Coral fish diversity in Netrani waters off Murudeshwar Karnataka, south India

Fish diversity associated with coral reef patches around Netrani Island, in Karnataka (south India) was investigated by visual census method. Sampling was done in four sites around the Island. A total of 69 species belonging to 39 genera, 19 families and 3 orders were recorded in the transect in four sites. When comparing the abundance, the fishes of Balistidae family dominated in all the four sites (22 %) followed by Pomacentridae (12.5 %), Caesionidae (9.7 %), Labridae (7.8 %), Acanthuridae (7.3 %), Haemulidae (6.7 %) and Scaridae (6.1 %). In line with the abundance and number, Shannon diversity indices (H’) were 2.8 in site 1; 2.6 in site 3; 2.3 in site 4 and 2.2 in site 1. The evenness (J’) of species distribution was more in site 2 (0.9), followed by site 3 (0.8); site 4 (0.7) and site 1 (0.7). The Bray-Curtis similarity was in the range of 69.98 to 79.50. The dendrogram plotted showed that site 2 and 3 form a group with similarity of 79.50, to which site 1 and site 4 got linked. There was no significant difference in the hydrographic parameters of the surface and bottom waters in four sites and also between different sites. The study revealed high coral fish density in the area indicating the need for adopting conservation measures.invertebrates, cnidarians and worms, zooplankton dominated by copepods and nekton dominated by Acetes spp. and clupeid juveniles were the major food items of A. monoceros. The von Bertalanffy growth equation was Lt = 63.53 [1 – e - 0.22 (t + 0.077)]. Natural mortality, fishing mortality and exploitation ratio were 0.53, 0.58 and 0.52 respectivel

Preliminary experiments on application of participatory GIS in trawl fisheries of Karnataka and its prospects in marine fisheries resource conservation and management

Geographic Information System (GIS) has become a part of our day today life in empowering institutions to formulate acceptable solutions in societal issues. More recently, public participatory GIS (PPGIS) and participatory GIS (PGIS) were viewed as more efficient tools in solving social and resource conservation issues, which empower communities those who are often ignored in traditional GIS practices. In fisheries, PGIS concept was first reported from Canada and on these lines pioneering efforts of involving concept of PGIS in fisheries is being attempted in Karnataka, where the geospatial data on fishing, catch and samples of fish caught by commercial fishing vessels were shared with the research organization and the data and samples thus shared were processed by fishery and GIS experts to come out with various tools for fishery management and resource conservation of the region. The study showed that the trawlers from Mangalore carried out trawling operations from sea off Calicut in the south (75 oE, 11 oN) to off Ratnagiri in the north (73.5 oE, 17 oN). Their depth of operation was between 5 m and 167 m, which signify the importance of revalidation of state–wise policies in introduction of mechanized vessels based on the landing in the respective states. The study showed that during the period, 237 species / groups of marine fauna were discarded of which many were juveniles of commercial species and rest were of adult size fishes of low or no market value. Spatio-temportal distribution and abundance of commercially lesser known species, which was not reported earlier from the coast,which have high trophic importance like small crabs, Charybdis hoplites and shrimp species like Metapenaeus andamanensis were brought out as the results of the study. Study also provided information on a unique ecosystem off Karnataka coast and with reef species and there is an immediate need for conserving this ecosystem. Based on the results of distribution and abundance of marine resources, spatial and seasonal restrictions on fishing efforts can be advocated in areas and seasons during which high incidence of bycatch of juveniles and non-commercial biota is being caught. This will help in sustaining marine fisheries from Malabar and Konkan coasts

Shift in diet composition of Indian mackerel Rastrelliger kanagurta - an analysis in relation to climate change

The feeding regime of organisms depend on the plankton community structure which is being studied worldwide to assess the changes in marine ecosystem structure due to climate change or anthropogenic activities. An attempt is made here to study the seasonal and long term variation in feed composition of Indian mackerel over a period of 40 years and its relationship with sea surface temperature to elucidate structural changes in food composition if any over period of time and its relationship to the primary and secondary productivity in eastern Arabian Sea marine ecosystem. The diet study during 2011-2014 reported the domination of phytoplankton consisting of Coscinodiscus sp. consistently and the presence of macroplankton and fish larvae whereas the diet during 1960-1961 showed the dominance of zooplankton and copepods. It could be assumed that increase in sea surface temperature which resulted in dominance of phytoplankton community as reported elsewhere in the world is also observed in eastern Arabian Sea which is reflected in the diet regime of Indian mackerel. The results also indicate its facultative feeding behaviour by compensating the low value phytoplankton with high value macroplankton and hence can be considered as a resilient species with regard to climate change

Fishery and biology of Meretrix casta (Chemnitz) in the Moorad estuary, Kerala

Meretrix casta forms an important fishery in the Moorad estuary. The average annual landing for the period 2000-2004 was 426t, the average catch per effort was 573 kg and total effort was 3182. Clams ranging from 28 to 32 mm size contributed to the fishery. M casta is a continuous breeder with two peaks in March-April and August-September. The precentage edibility ranged between 8 and 16. The standing stock biomass in the Moorad estuary was estimated at 2073 t with an average density of 1096 numbers per sq. m. The present status and management options for this important fishery are discussed

Mapping of fishery resources in trawling grounds along the Malabar-Konkan coast

Two categories of bottom trawl units are in operation along the Malabar-Konkan coast. The first category comprises of small boats (<9.75 m OAL) conducting daily trips operating trawl nets with codend mesh size of 10-20 mm and catch generally prawns, flatfishes and other finfishes

Food and feeding habits of the narrow barred Spanish mackerel Scomberomorus commerson (Lacepede, 1800) off Karnataka, south-west coast of India

Scomberomorus commerson were collected on weekly basis during January 2012 to December 2014 at Mangalore Fishing Harbour. Stomach of 214 narrow barred Spanish mackerel measuring from 48 to 105 cm fork length (FL) for males and 45.5 to 115 cm FL for females were analysed to study their feeding habits. Fish with empty stomach were prevalent in almost all the months. Prey mainly comprised of fishes and crustaceans, with the fish component forming 99.9%. The index of relative importance (IRI) showed that the dominant prey were semi-digested fish remains (44.6%) of Sardinella longiceps (30.1%), Decapterus sp. (18.7%), whitebaits (2.5%), Rastrelliger kanagurta (1.5%) and Epinephelus spp. (1.1%), while Saurida sp. (0.7%), Megalaspis cordyla (0.5%), Scombroides sp. (0.2%) and shrimps (0.1%) were found occasionally in the gut. Index of stomach fullness (SFI) was 0.11 in August and 0.65 in January. Generally, SFI was higher during September to January and lower during February to August. The empty stomach ratio (ESR) ranged from 33.3% (August) to 92.3% (April)

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