Life history of South African snoek, Thyrsites atun (Pisces: Gempylidae): a pelagic predator of the Benguela ecosystem

Snoek (Thyrsites atun) is a valuable commercial species and an important predator of small pelagic fishes in the Benguela ecosystem. The South African population attains 50% sexual maturity at a fork length of ca.73.0 cm (3 years). Spawning occurs offshore during winter−spring, along the shelf break (150–400 m) of the western Agulhas Bank and the South African west coast. Prevailing currents transport eggs and larvae to a primary nursery ground north of Cape Columbine and to a secondary nursery area to the east of Danger Point; both shallower than 150 m. Juveniles remain on the nursery grounds until maturity, growing to between 33 and 44 cm in the first year (3.25 cm/month). Onshore– offshore distribution (between 5- and 150-m isobaths) of juveniles is deter-mined largely by prey availability and includes a seasonal inshore migration in autumn in response to clupeoid recruitment. Adults are found through-out the distribution range of the species, and although they move offshore to spawn—there is some southward dispersion as the spawning season progresses—longshore movement is apparently random and without a seasonal basis. Relative condition of both sexes declined dramatically with the onset of spawning. Mesenteric fat loss was, however, higher in females, despite a greater rate of prey consumption. Spatial differences in sex ratios and indices of prey consumption suggest that females on the west coast move inshore to feed between spawning events, but that those found farther south along the western Agulhas Bank remain on the spawning ground throughout the spawning season. This regional difference in female behavior is attributed to higher offshore abundance of clupeid prey on the western Agulhas Bank, as determined from both diet and rates of prey consumption.

Recent advances in the hatchery production of seed of some commercial bivalves in India

The Central Marine Fisheries Research Institute has established a shellfish hatchery laboratory at its Tuticorin Research Centre with the objective of developing appropriate technology for the production of seed of commercial bivalves. A viable technology was developed for the mass production of the seed of Pinctada fucata, P. margaretifera, Crassostrea madrasensis, Perna indica, P. viridis, Anadara granosa and Meretrix meretrix. The hatchery facility and the technology, comprising brood stock conditioning, induced spawning, larval rearing and seed production are described. In the light of these developments the future outlook is appraised.

Importance of live feed organisms in prawn hatcheries: a review

Live food organisms play a vital role in the artificial propagation of penaeid prawn seeds. The methods practiced for the culture of phyto and zooplankton for rearing prawn larvae through their various developmental stages are reviewed. Selection of a suitable species depends mainly on the culture characteristics, local environmental factors and the food requirements of the species of prawns cultured. Suitability of a few species isolated from Karwar waters is discussed.

A survey of the microbiological quality of commercial frozen prawn products

The paper presents the results of a bacteriological survey carried out on 2,917 samples of frozen prawn, 55 samples of raw material, 35 samples of water, 4 samples of ice and 42 samples of various equipment used for processing. The survey covered a period of three years (1960-63) and comprised of samples collected from five of the leading processing factories in Cochin. Frozen products tested consisted of headless (marine and fresh water), peeled and deveined and cooked frozen samples. Statistical analysis of the data shows that there is no significant variation between samples and between factories with respect to product quality. The standard plate count varied between 1.0x10(4 superscript) and 1.0x10(6 superscript) per gram for headless and between 1.0x10(4 superscript) and 1.0x10(7 superscript) for peeled and deveined and cooked frozen samples. Majority of the samples had bacterial load well within the limits prescribed for such products.

Commercial utilization of dolphins (porpoises) in Ceylon

Two species of mammal dolphin are found in waters adjacent to Ceylon, namely the common dolphin (Delphinus delphis) and the bottled-nosed dolphin (Tursiops truricatus). Both these species are predators and cause damage to finishing nets by attacking fish trapped in them. This menace to nets is particularly pronounced when fish populations in a particular area become somewhat depleted. Dolphin can be successfully captured from a motor boat by use of a simple hand harpoon with a detachable dart and bladder buoy. Fresh dolphin meat when placed on the market sold readily despite some local prejudice against the naturally dark colored meat. The flesh of the dolphin is nutritious and can be used successfully in both western and eastern types of cookery.

Studies on the storage behaviour of laminated and commercial Bombay duck

A modified method for the preparation of laminated Bombay duck is presented. Investigation was carried out to find out an effective chemical to control the discoloration of dried laminated Bombay duck. Among various chemicals tried, NDGA and BHT were found to have considerably retarded the discoloration and extended the storage life of the product. Attempt was also made to suggest the optimum humidity level for the proper storage of the commercially dried fish. It was found that a level of about 65% R. H. provided maximum storage life to commercial product.

Effect of supplementary feed on the growth of shinghi (Heteropneustes fossilis Bloch)

Effect of two supplementary feed (food A and food B) on the growth of shinghi, Heteropneustes fossilis was observed for 3 months period during winter and summer. Food B containing rice bran 2 g, wheat bran 2 g and blood 10 ml, showed better growth. The net gain in length was 70.04 mm and in weight was 13.82 g. Total net production was observed as 254.00 g/m² with feed A and 345.50 g/m² with feed B.