Methods of stomach content analysis of fishes- Winter School on Towards Ecosystem Based Management of Marine Fisheries – Building Mass Balance Trophic and Simulation Models

The study of the feeding habits of fish and other animals based upon analysis of stomach content has become a standard practice (Hyslop 1980). Stomach content analysis provides important insight into fish feeding patterns and quantitative assessment of food habits is an important aspect of fisheries management. Lagler (1949) pointed out that the gut contents only indicate what the fish would feed on. Accurate description of fish diets and feeding habits also provides the basis for understanding trophic interactions in aquatic food webs. Diets of fishes represent an integration of many important ecological components that included behavior, condition, habitat use, energy intake and inter/intra specific interactions. A food habit study might be conducted to determine the most frequently consumed prey or to determine the relative importance of different food types to fish nutrition and to quantify the consumption rate of individual prey types. Each of these questions requires information on fish diets and necessitates different approaches in how one collects and analyzes data. Here, we outline qualitative and quantitative techniques used to describe food habits and feeding patterns of fishes

Studies on food and feeding of marine Demersal finfishes with special Reference to trophic interactions

Food and feeding habits of fourteen demersal finfishes exploited off the Karnataka coast were studied to investigate trophic interactions within the marine food web. The demersal finfi shes selected for the present study are Epinephelus diacanthus (rockcod), Grammopli/es suppasitus (spotfin flathead), Priacan/hus hamrur (bulls eye), Johnieops sina (drab jew fish), O/oli/hes cuvieri (lesser tigertooth croaker), Nempilerus japanicus (threadfin bream), Nemipterus mesoprion (thread fin bream), Leiognathus bindlls (si lvcrbclly), CYlloglosslIS macros/om liS (tongue sole), PUII/PIIS argenteus (silver pomfret), Lactarill.v lactarill.r (bigjawed jumper), Pseudorhombus arsius (Iargetooth flounder), Carcharhinus Iimba/us (blacktip shark) and Rhync'loba/us djiddensis (guitar fish). • For understanding the importance of various diet components, the widely accepted diet index, the Index of Relative Importance (IRI), which integrates large data on three diet indices such as number, volume or weight and frequency of occurrence, was used to quantify diet components of each predator. Ontogenetic, seasonal (pre-monsoon, monsoon and post-monsoon) variation in feeding and prey-predator relationship studies were conducted. Prey-spece fi c abundance plots (Amundson plot) and Electivity index were drawn to interpret each predators feeding strategy and prey se lectivity respectively. • The resu lts showed that the rockcod, E. diacanthus is a demersal carnivore and preferred to feed largely on benthic crustaceans. Crustaceans followed by fishes and molluscs were the most important food components of E. diacanti1l1s. Of all the stomachs analysed, 73% were empty and 27% contained food items. The most important crustaceans were benthic crabs (69.4%) followed by Acetes indicus (15.9%) and Oratosquilla nepa (6. 1%). Dietary breadth had great seasonal variations. The mean trophic level was 4.11 ± 0.26. There was a significant ontogenetic shift toward larger benthic crabs in larger rock cods (P<0.05). Electivity study showed strong positive selection to all crustaceans in all the seasons

Length-weight relationship of commercially important marine fishes and shellfishes of the southern coast of Karnataka, India

The parameters of the length-weight relationship of the form W = aLb are presented for 51 species of commercially important marine fishes and shellfishes caught along the southern coast of Karnataka, India. Samples from commercial (trawl, purse seines, gill nets) and artisanal gears were taken during August 1999 to May 2001.The 'b' value ranged between 1.942 and 3.616 with a mean of 2.80, standard deviation of 0.32, and mode of 3

Trophic organization and predator prey interactions among commercially exploited demersal finfishes in the coastal waters of the Southeastern Arabian Sea

Trophic interactions in commercially exploited demersal finfishes in the Southeastern Arabian Sea of India were studied to understand trophic organization with emphasis on ontogenic diet shifts within the marine food web

Trophodynamics of the Spotfin Flathead Grammoplites suppositus (Troschel 1840) from the Southeast Arabian Sea

The dietary habits of the spotfin flathead, Grammoplites suppositus which inhabits the southeast Arabian Sea was studied. The stomach contents of 581 specimens were analysed between September 2001 and May 2002. G. suppositus preyed primarily on crustaceans. The most important preys were benthic crabs and penaeid prawns, and fishes were next in rank. During premonsoon, fishes and crustaceans were equally important, whereas in monsoon and postmonsoon benthic crabs and penaeid prawns were the predominant prey. There were significant (p<0.001) ontogenetic changes in the diet. Smaller length groups (<165 mm) ate mostly the flatfish Cynoglossus macrostomus and other fishes, whereas individuals of larger length groups (>165 mm) ate crustaceans such as the benthic crabs, penaeid prawns, the paste shrimp, Acetes indicus and the mantis shrimp, Oratosquilla nepa

Depleted and Collapsed Marine Fish Stocks along Southwest Coast of India – A Simple Criterion to Assess the Status

India’s marine fishery has grown from a subsistence level to an industrial one. From a meagre 0.6 million tonnes in 1950s it has crossed 3.0 million tonnes in 2008. Kerala, and to a lesser extent, Karnataka have been the major contributors to the marine fish production of the country (having 12% of the total coastline and contributing 30-35% of the production). Mechanization of the fishing fleets has focussed increased effort on the fish stocks in the region (southwest coast), and consequently, many stocks are not as abundant as they were before. The intense exploitation of commercial marine species along these coasts has reportedly led to threats of species loss. So far no comprehensive study has been made to assess the health of Indian marine fish stocks with respect to depletion and collapse, and therefore, no restoration or stock rebuilding plans are available. Most of the world’s most valuable fish stocks are either fully exploited or overexploited (FAO, 2007). The 25% of the stocks that remain underexploited tend to comprise of low-value species

भारत के दक्षिण-पशिचम तट में 1926-2005 के दौरान तारली और बँगडा मात्स्यिकी में हुए उतार-चढाव पर पर्यावरणीय प्राचलों क प्रभाव

कृपया पूरा लेखा पढ

How environmental parameters influenced fluctuations in oil sardine and mackerel fishery during 1926-2005 along the south-west coast of India?

The south-west coast of India is one of the major upwelling systems of the world (Malabar upwelling zone) and contributes to nearly 30-50% of the total marine fish catch from India. Generally, the coastal upwelling ecosystems are colonized by planktivorous small pelagic fishes such as anchovies, sardines and these fish populations are characterized by significant inter-annual fluctuations in their abundance

Alpha, beta and gamma diversity of fished marine taxa along the southwest coast of India during 1970-2005

The data on species-wise marine fish landings at Kerala and Karnataka during 1970-2005 were used to examine diversities of fished taxa through alpha, beta, and gamma diversities which are the fundamental descriptive variables of ecology and conservation biology. In Kerala, fishing zone K5 (Kochi) and K3 (Kollam-Neendakara) and in Karnataka, fishing zone KN4 (Gangolli-Coondapur - northern Udupi district) followed by KN11 (Mangalore) had high alpha diversity values. These zones are major trawling zones. The beta diversity values and the species turnover rates were also high for these zones. The high beta values indicate uniqueness in species diversity when compared to other zones. The gamma diversity was 818 for Kerala and 524 for Karnataka. Beta diversity index showed a positive relationship with alpha index, indicating dependence of beta on alpha values. While the arthropod diversity was similar in Kerala and Karnataka, the chordate and mollusc diversity was higher in Kerala. The results from the present study indicate that similar studies have to be carried out from other ecosystems along the Indian coast, so that it becomes benchmark information for studying the anthropogenic impacts on biodiversity

Diet and trophic ecology of silver pomfret, Pampus argenteus (Euphrasen, 1788) exploited from the Southeast Arabian Sea

Stomach content analysis of the silver pomfret, Parnpus argenteus using the Index of Relative Importance (IRI) revealed that crustaceans (IRI= 48.2%) and semi-digested pulp (IRI= 47.6%) formed the important diet. Copepods formed the largest propartion among crustaceans. Proportion of empty stomachs was higher in large fishes and the diet changed with body size as well as with season. Fishes in smaller length group (<I40 mm) had semi-digested pulp as the dominant component, whereas fishes above 140 mm had copepods and fish. The relationship between the mean weight of semi-digested pulp and mean number-of copepods with that of predator length suggested probable diet shift from omnivory to carnivorous feeding habits. The mean weight of semi-digested pulp gradually decreased with increasing length of the fish. The highest similarity in diet was observed between the monsoon and post-monsoon seasons, and by length groups, between the fishes of 191-240 and 241-290 mm. Diet breadth is narrow as revealed by Levin's index. The trophic level was estimated as 2.4 + 0.1. The Amundsen plot showed that P. argenteus is a specialized feeder on semidigested pulp and copepods