Patterns of sex ratio in the oil-sardine, Sardinella longiceps Val., at Calicut

Categorising the fish according to maturity, montti of capture and length groups, the data on the sex distribution of the Indian oil-sardine (5flrrfwW/fl/ong'/fepj) collected at Calicut during 1959-60 to 1965-66 seasons are subjected to statistical tests to find outthe nature and cause of dominance of either sex, if any. For the immature fish the overall inference is that there may not be any significant difierences in the annual recruited population. In the adult fish the possibility of more males in May is suggested as due to the fact that the males may start maturing a little earlier than the females. The dominance of males in 140-150 mm group and that of females in 170-190 mm groups is brought about by differential growth, the females growing faster during June to October period. It is recommended that the size of each sample for sex ratio studies should be at least 50. Based on the earlier and the present studies of this author, It is indicated that 375 million ova can be expected from a tonne of adult biomass of the oil-sardine population

A forecast for the ensuing oil-sardine fishery

The ability to foreca st the course of events likely to be encountered during the approaching fishery season enhances the value of fishery research in the eyes of those in the industry , As Simpson (1956) has put it, "Apart from the value to the industry of forecasting, predicting what is going to happen and checking it against the actual events is to the fishery biologist one form of the universal research tool of formulating a hypothesis and putting it to test

Our pelagic fishery resources Present and potential harvest

The two primary divisions of the oceans are (1) the benthic and (2) the pelagic, the former referring to the ocean floor which supports the demersal resources and the latter, the entire column of water , accomodating the pelagic resources. The pelagic region is a part of the marine biocycle and geographically, it is divisible into Atlantic and Indo-Pacific. Ecologically, the pelagic realm can b e bifurcated as neritic (inshore) and oceanic (opens e a) provinces d epending on the depth to which light penetrates and to the extent and depth of the continental slop

An instance of hermaphroditism in the Indian mackerel Rastrelliger canagurta 'Cuvier'

While instances of hermaphroditism are known to occur in the European mackerel (Scomber scombrus L. no such cases are on record fcr the Indinn mackerel, Rastrelliger canagurta. It is interesting to report, therefore, the occurrence of a single hermaphrodite specimen of R. canagurta in a sample taken from the fish market at Karwar and reported to have been caught at Majali, seven miles north of 'Karwar on 25th March 1958

An instance of hermaphroditism in the Indian oil sardine, Sardinella longiceps (Cuv. & Val.)

Hermaphroditism, as an occasional abnormality, has been observed in some of the marine food fishes but as there is no record of such a condition in the oil sardine, Sardinella longiceps, the present finding will be of interest

On the maturity stages of Indian oil-sardine, Sardinella longiceps Val.,with notes on incidence of atretic follicles in advanced ovaries

Workers engaged in research on the maturity and spawning conditions of fish have prepared different types of maturity scale according to the peculiarities presented by different fishes studied by them. Except for a few remarks about the external appearance of ovaries belonging to stages V to VII by Devanesan (1942), there is no detailed account of the different stages of maturity for Sardinella longiceps. Nair (1959) has adopted the maturity scale prepared by the International Council for the Exploration of the Sea for investigations on oil-sardine. However, when studies on the maturity and spawning habits of oil-sardine were taken up by the author, the absence of a detailed classification was keenly felt and since the International key was found to be not adequate enough to distinguish the different stages, it was considered necessary to prepare a detailed scale for the guidance of workers both in the laboratory and the field so that confusion in the interpretation and assignment of the stages of maturity can be avoided and a uniformity in reporting achieved

Observations on the rate of growth, sexual maturity and breeding of four sedentary organisms from the Madras harbour

The destruction caused to the underwater harbour installations and ships' bottom by the accumulation of sedentary organisms drew the attention of workers in temperate and subtropical regions to a study of the biology and ecology of such animals as a preliminary step in tackling' the antifouling problem. It has been observed under tropical conditions that fouling is more pronounced due to prolonged period of breeding activity, settlement in larger numbers and constant organic growth (Edmondson, 1944 ; Pyefinch, 1947 ; Daniel, 1954). A fact-finding survey to determine the members of the fouling community, their abundance in relation to different environmental conditions, seasonal or ecological succession, if any, their rate of growth and breeding activities will contribute much towards an understanding of the fouling problem. In an earlier paper the author (Antony Raja, 1959) has dealt with the distribution and succession of sedentary organisms of the Madras harbour with a discussion on the influence of environmental factors. Except for a preliminary survey of marine borers of the Cochin harbour (Erlanson, 1936), observations on the growth of a few sedentary organisms of the Madras harbour (Paul, 1942) and brief records from the Vizakhapatnam harbour (Ganapati et al., 1958), information regarding the growth rate of marine sedentary organisms of sheltered waters is not available. Hence an attempt is made here to estimate the rate of growth, size at sexual maturity and breeding of four sedentary organisms, namely, Modiolus striatulus. Bowerbankia sp., Cynthia sp., and Dasychone cingulata as a continuation of Paul's work, which has not dealt with the above forms

Some aspects of spawning biology of Indian oil sardine Sardinella longiceps Valenciennes

Although Homell (1910) made a few observations on the spawning habits and migratory movements of Indian oil sardine. Sardinella longiceps, the first concerted attempt to "understand its maturity and spawning habits and to delimit the spawning season can be said to have been made by Homell and Nayudu (1924). Following this, Devanesan (1943), while confirming some of the earlier findings, also contradicted certain others. Later, Nair (1953 & 1959) giving a detailed review of earlier investigations, did not agree with some of the observations of previous workers in addition to providing more information to our knowledge on the spawning habits of oil-sardine based on his study from 1948 to 1955. Since these authors had to divide their attention not only to administrative problems but also to various other aspects of biology of the fish at the same time, it is but natural that conclusions have been drawn with limited data at their disposal

Indian Oil sardine

In the group-wise composition of the world marine fish production, Clupeoids occupy an unassailable position at the top and India is no exception. This group which contributes on an average about 32% to the annual marine fish production is mainly represented by the sardines of which the Indian oil-sardine, Sardinella longiceps, subscribes to the best part of it. The importance of this fish in the socio-economic life of the fishing community of the Malabar coast is very aptly expressed as Kudumbam pularthi (= provider for the family). The oil-sardine fishery during 1950-1968 period has contributed annually on an average to the extent of 18% to total marine fish landings in India. It is, however, subjected to such wild fluctuations that it has been found to vary between 1% and 33%. It is this undependable and unpredictable nature of the fishery that first drew the concern of Day (1865) and it was left to Hornell (1910b) to emphasise the need for a scientific study which led to the pioneer research report by him and Nayudu (1924). Except for the studies of Devanesan (1943), no important work appeared till almost the beginning of fifties. After the establishment of the Central Marine Fisheries Research Station in 1947, greater attention on various biological aspects was given resulting in the contributions of Nair (1949 et seq.), Chidambaram (1950) and Nair & Chidambaram (1951). The synopsis of information on the biology and fishery presented by Nair (1960) to the ‘World Scientific Meeting on the Biology of Sardines and Related Species’ under the as spices of FAO provided a clear account of the progress made till then. The rapid strides made subsequent to this can be easily evaluated when the history of research contributions of the last 5 decades beginning from the studies of Hornell and Nayudu (loc. cit.) relating chiefly and directly on the oil-sardine of India

Estimation of age and growth of the Indian oil sardine, Sardinella longiceps Val.

Estimates of age and rate of growth of the Indian oil-sardine, Sardinella longiceps Valenciennes, have been made through a study of length frequency distributions obtained during the seasons from l%l-62 to 1965-66 at Calicut. With the availability of very small juveniles, a lifetime growth curve of the fish has been constructed and evidences advanced to prove that the commercial fishery of juveniles belong to O-year class. It is estimated that a growth of about 60-65 mm is attained in one month and about 95-110, 110-125, 125-140, 150-160 and 170-180 mm in 2, 3, 6, 12 and 24 months respectively. Although in rare instances the fish may live up to 3 years, the normal life span is found to be about 2\ years