Some aspects of the biology of Otolithes cuvieri (Trewavas) and Johnius glaucus (Day) from Veraval

The length-weight relationship in O. cuvieri and J. glaucus can be described by the equations log W=-5.27997+3.13225 log L and log W=-4.93431+3.02556 log L respectively. The length at first maturity in O. cuvieri is estimated as 256 mm and in J. glaucus as 180 mm. Empty stomachs occurred in high percentage in both the species. A study on composition of food items revealed that O. cuvieri feeds on a variety of organisms while J. glaucus a selective feeder.

Length-weight relationship of intertidal molluscs from Mumbai, India

A study on the length-weight relationship of common intertidal molluscs from Mumbai showed a high degree of correlation between their length and weight. Most of the molluscs exhibited isometric growth pattern but in some species, allometric growth was found, which is attributed to maturity, nonlinear growth of shell and the ecological conditions. The variations in the growth rate of Gafriarium divaricatum sampled from two geographically separate sites, Bandstand and NCPA, is a result of variation in ecological conditions.

Reproductive biology of the blue spot mullet Valamugil seheli (Forskal) from Mangalore Region, southwest coast of India

The blue spot mullet Valamugil seheli spawns once a year between August and February with peak spawning during October - November. Males attain maturity at 250.5 mm and females at 256.5 mm total length. Males outnumbered females in the commercial catches, although the sex-ratio (M:F=1:0.90) in the population showed no significant deviation. The fecundity of this species varied from 108378 to 910350 eggs with an average of 327944. Linear relationships were found between fish length, gonad weight and fecundity; and between fish length, fish weight and ovary weight.

Growth of Tilapia mossambica Peters in different salinities

Tilapia mossambica was found to grow better in saline media than in freshwater. The fish not only grew to maturity but were able to reproduce viable fry in 100% sea water.

Escala macroscópica de maturaçāo e ciclo sexual das espécies Penaeus indicus H. Milne Edward e Metapenaeus monoceros (Fabricius)

The macroscopic scale used for determination of sexual maturity in shrimps was tested against objective parameters namely the gonad-somatic index and the size of oocytes. The two main species caught in Mozambique, Penaeus indicus and Metapenaeus monoceros, were the object of the work. In order to reduce the subjectivity in the macroscopic exam, a table with the colours representative of each stage is presented. Since this study was conducted over a period of 13 consecutive months and there were observations from previous years, the sexual cycle of the two species is also presented, as well as an estimate of the size at first maturity.

Reproduction, age and growth of the kelee shad, Hilsa kelee (Cuvier, 1829) (pisces: fam. Clupeidae) with informations on its fishery in Maputo Bay, Mozambique

Age, growth and reproduction of H. kelee were studied, and a brief description of its fishery in Maputo Bay (Mozambique) is given. Most material was collected from gill net fisheries during 1977-1980, but some was taken from shrimp trawlers operating in the same area during 1980-1981. Main spawning takes place during October-January with a peak in December. There is also some evidence that spawning takes place during June-July. The size at first maturity was approximately equals 14-15 cm. Ageing was carried out using primary growth rings in the otoliths and length-frequency analysis of fish caught by shrimp trawlers. Von Bertalanffy's growth equation parameters were determined. Males and females grew in similar fashion. There are seasonal trends in the catch composition of the gill net fishery, showing high values during April to September and low during October to December.

Camparaçāo entre os cruzeiros de investigaçāo realizados no Banco de Sofala pelo navio SRTM "Sebastopolsky rybak" em Setembro-Outubro e Novembro-Dezembro de 1982: camarao de [águas pouco profundas]

During the last 4 months of 1982, two research cruises had been carried out at the Sofala Bank by the SRTM "Sevastopolsky Rybak". The authors analyze and compare data on biological characteristics, sexual maturity and localization of Penaeus indicus and Metapenaeus monoceros.

Relatório do cruzeiro realizado no Banco de Sofala pelo navio SRTM "Sebastopolsky rybak" de Novembro a Dezembro de 1982: camarāo de águas pouco profundas

From November 18th to December 17th 1982, the SRTM "Sebastopolsky Rybak" carried out research cruises on the Sofala Bank in the area between 16°20'S and parallel 19°40'S. The authors analyze data collected on biological characteristics, sexual maturity and localization of Penaeus indicus, Metapenaeus monoceros, Penaeus japonicus, Penaeus monodon and Penaeus latisulcatus.

A preliminary assessment of the scad and mackerel stocks at Sofala Bank, Mozambique

Scads (Decapterus russellii, D. macrosoma, Selar crumenophthalmus), Indian mackerel (Rastrelliger kanagurta) and horse mackerel (Trachurus trachurus) are the main pelagic species caught in a bottom trawl fishery at Sofala Bank and at Boa Paz. Information on catch and effort is presented together with available data on distribution, spawning, size at first maturity, growth, mortality and biomass of the species. As the present catch and fishing mortality are low compared to the estimates of biomass and total mortality it is concluded that the fishery may be expanded further in the future.

Fishery and biology of Penaeid prawns at Harnaii, Mahatashtra

Penaeid prawn fishery at Harnaii in Ratnagiri District of Maharashtra was investigated during fishing seasons of 2002-03 and 2003-04 from mechanized (MLD) and hand operated trawlers (HT). During the two years, MLD contributed 86% and HT 14% to the average annual penaeid prawn catch of 2,242 t. The catch showed two peaks, a major during October-December and a minor during April-May in both the gears but abundance of the individual species differed. P. stylifera, Metapenaeopsis affinis, Solenocera crassicornis, Metapenaeopsis brevicornis, P. merguiensis and Metapenaeopsis dobsoni mainly constituted the fishery and their species composition, seasonal abundance, annual size distribution and monthly mean size were investigated. Biological studies on food, size at maturity, spawning period, sex-ratio and juvenile abundance were carried out to explain temporal abundance of the species in the fishery. Among the species P. stylifera, M. affinis and S. crassicornis exhibited distinct seasonality with two spawning peaks, one in pre-monsoon and the other in post monsoon period to produce two discrete broods while P. merguiensis despite two spawning peaks exhibited a single dominant brood. M. brevicornis showed monsoon and post-monsoon spawning while M. dobsoni showed only post-monsoon spawning. Migrations between nearshore and offshore waters resulted in mixing of the broods and they remained inseparable in the catch.

Reproductive biology of Otolithes cuvieri (Trewavas, 1974) from Mumbai waters

The reproductive biology of Otolithes cuvieri (Trewavas, 1974) is reported in the present communication. The size at first maturity for the females was estimated to be 275 mm. The spawning activity was observed throughout the year with two peaks occurring in April and June. Two prominent peaks of gonadosomatic index (April and June) also support the view of two major spawning. Relative fecundity ranged from 71,574 to 79,680 eggs per 100g of body weight. Relationship of fecundity with fish length, fish weight and ovary weight of the species has been established as F = -132971 + 1447.441 x L, F = 124195 + 468.798 x W and F = 250517.5 + 3369.029 x OW, respectively. Study of sex ratio by random sampling of the catches indicated the dominance of females in commercial catches of Mumbai coast.

Cephalopod fishery at Kakinada along the east coast of India: Resource characteristics and stock assessment of Loligo duvauceli ·

At Kakinada along the east coast of India, cephalopods were exploited by trawls. Fishery occurred round the year with peak during August-October. Peak abundance and fishery of cuttlefishes coincides with this period, whereas for squids it is during March-May. Cephalopod production continued to increase initially with fishing effort, until 1995, but declined thereafter despite increased fishing effort and expansion of fishing to deeper waters. Fishery, growth, mortality, recruitment pattern and exploitation rates of Loligo duvauceli were studied. Nearly 97% of their catch was by zero year groups. They attain sexual maturity and spawn during the first year itself. Spawning occurred round the year with peak during December-February. Exploitation rate of the species is large, 0.741 compared to Emax (0.44). This indicated that their stock is under heavy fishing pressure and subjected to over-exploitation. Stock also exhibited declining trend over the years during 1995-'99. These necessitate immediate attention to avoid coHapse of the stock and fishery.

Fishery, population characteristics and stock assessment of cuttlefishes, Sepia aculeata and Sepia pharaonis at Kakinada along the east coast of India

Cuttlefishes were exploited exclusively by trawls along the coast. Growth, recruitment, mortality and exploitation rates of Sepia aculeata and Sepia pharaonis were studied. Fishery of the former was supported mainly by zero year and the latter by zero and one + age groups. Both attain sexual maturity during the first year itself and spawn during August-March with peak during November-December. Natural mortality of S.aculeata was 2.22, fishing mortality 2.34 and total mortality 4.56. It was 1.69, 1.97 and 3.66 respectively for S.pharaonis. Exploitation rate was 0.52 and Emax 0.72 for S.aculeata and it was 0.54 and 0.76 respectively for S.pharaonis. Their mortality and exploitation rates indicated that stock remains under-exploited and have considerable scope for improving the production. However, both stock and catch exhibited wide annual fluctuation with declining trend during the period. These necessitated immediate attention including measures to minimise juvenile exploitation for improving stock and fishery.

Some aspects of the biology of Johnieops sina (Cuvier, 1830) from Mumbai waters

Investigations on food and feeding of Johnieops sina indicated that it feeds mainly on penaeid prawns, Acetes spp. and fishes. Penaeid prawns were found to be its preferred food item. The spawning activity was observed throughout the year with two peaks in February and August, supported by prominent peaks of gonadosomatic index in the same months. The minimum size at first maturity for females was 153 mm. The absolute fecundity ranged from 28,495 to 135,346 eggs for the ovaries weighing 1.30 to 9.49 g.

Natural diet of penaeid prawns in the coastal waters of Mumbai

Foregut contents of eight commercially important species of penaied prawns namely Penaeus merguiensis, Metapenaeus affinis, M. monoceros, M. brevicornis, Parapenaeopsis stylifera, P. hardwickii, P. sculptilis and Solenocera crassicornis were investigated from inshore, nearshore and offshore fishing grounds of Mumbai. Feeding intensity and index of preponderance (IP) of the dietary items were compared statistically for the species, sexes, fishing areas and maturity condition of females. All the species except M. monoceros and P. sculptilis showed that females were better fed than males. The feeding intensity in the three depth-zones was different for M. affinis, M. brevicornis, M. monoceros, P. hardwickii and S. crassicornis, and uniform for P. merguiensis, P. stylifera and P. sculptilis. Acetes spp., prawn remains, polychaetes, benthic crustaceans, foraminifers and fish remains were the important food items of the prawns. Dietary comparison between the two sexes of the species did not show any difference, but mature females of M. monoceros and P. sculptilis had different diets. Comparison of food items for all the species together showed significant difference between the three areas. Crustacean diet was the favorite in the inshore and nearshore, and polychaetes in the offshore waters. All the species except P. hardwickii showed difference in their dietary composition in the three depth-zones. It is concluded that these coexisting species are primarily carnivorous and exhibit diverse food preferences in different depth-zones by browsing on interstitial organisms, chasing epipelagic prey, raptorial predation, scavenging on dead organisms or adopting different temporal abundance to avoid inter-specific competition for food.