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The study of the food and feeding of the mackerel,Rastrelliger canagurta was based on the periodical examination of stomach contents of the mackerel and the plankton of the coastal waters near Calicut during the years 1949 and 1950. The relative importance of various food elements have been determined by thenumber and thepoints methods. The mackerel has been observed to feed almost exclusively on plankton organisms. The main food constituents were copepods, cladocerans, larval and adult decapods, peridinians and diatoms. Post-larval bivalves, fish eggs and larvae, polychaete larvae, cirripede nauplii, appendicularians and pteropods were minor elements in the food. There was no appreciable difference between the food of the young and that of the adult mackerels. The composition of the food varied from season to season depending upon the fluctuations in the occurrence of various planktonic elements. There was a close correlation between the food constituents and the planktonic organisms of the inshore area. Non-edible forms like salps, medusae, ctenophores, stomatopod larvae, chaetognaths and noctilucae were avoided and to that extent there was selective feeding. There was feeding throughout the year although the feeding intensity varied from season to season. There was no marked period of fasting. The feeding intensity was low during the prespawning and spawning periods and comparatively high in the 16 to 20 cm. size group. It was maximum during the period from September to December when edible plankton was abundant.

Herbs and spices, having antimicrobial effect, can be incorporated into edible films, to extend product shelf life and the reduce the risk of microbial growth on food. The aim of this study is to develop chitosan film incorporated with Garcinia atroviridis, also known as ‘asam gelugur’, ‘asam gelugo’, or ‘asam keping’. The film with different concentrations of Garcinia atroviridis (1 to 5% v/v) with chitosan (1.5% w/v) were investigated for its physical, mechanical and antibacterial properties. With the increase of Garcinia atroviridis extract incorporated, water solubility of the films increases (from 21.17 to 53.61%). Increase of Garcinia atroviridis incorporated into chitosan film also increase the total color difference. Film with higher concentration of Garcinia atroviridis extract produced thicker film compared to the film without extract (from 0.048 to 0.143 mm). The film with 5% (v/v) Garcinia atroviridis possessed low tensile strength (3.28 MPa) and elongation at break (13.90%). Young’s modulus was decreased in value (from 0.72 to 0.24 MPa) as the higher concentration of Garcinia atroviridis extract was added. High Garcinia atroviridis extract (5% v/v) in the chitosan films demonstrated greater inhibitory activity against the bacteria strains (Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus). With the edible film of 5% (v/v) Garcinia atroviridis applied, the Indian mackerel was found to have a longer shelf life (3.5 days) as compared to the control (2.5 days).

The storage stability of eviscerated Indian mackerel (Rastrelliger kanagurta) irradiated at a dose of 1.5 kGy and held under melting ice was examined. Packaging in polyethylene pouches prior to irradiation gave a shelf-life of 25 days, while, nonpackaged, irradiated fish remained in acceptable condition up to 20 days. The nonpackaged irradiated fish has less irradiation odor and better appearance as compared with packaged irradiated fish during the course of ice storage. Uni-radiated and nonpackaged mackerel kept in ice were acceptable only for 14 days. The results suggest that pre-irradiation packaging was not essential for commercially adequate extension in shelf-life of the iced fish.

THE problem of the food of fishes with its varied bearings on their shoaling habits and migrations has engaged the attention of fishery biologists since the beginning of the present century. The mackerel is an important food fish in both hemispheres. Several contributions1–5 have been made to our knowledge of the food of the Indian mackerel, Rastrelliger kanagurta, which contributes to one of the largest fisheries of India. All these observations, except those of Chacko3, which are from the Gulf of Manaar, are confined to the west coast of India. According to these workers, mackerel is a noted plankton feeder, securing its food by filtration. Chidambaram2, while observing the adult mackerel as plankton feeder, suggested the carnivorous habits of the young mackerel. Later, in a detailed account on the food of this fish, Bhimachar and George4 observe that “the food of the young mackerel does not radically differ from that of the adult”. Pradhan5 has arrived at a similar conclusion regarding the food of mackerel; but one will not fail to note from his observations that young mackerel less than 89 mm. in total length are not represented in his material.