Report on Herring-Investigations Until January 1910

Hjort, Johan

doi:10.1093/icesjms/s1.53.1

Cited by 22 publications

(19 citation statements)

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“…Generally five (Qasim 1957, Qayyum & Qasim 1964 to eight (Hjort 1910) stages of maturation of gonads have been defined. However, in fish species which continuously spawn all year round and do not become spent once attained maturity, the arbitrary classification of gonads in five or eight stages of maturation becomes difficult.…”

Section: Breedingmentioning

confidence: 99%

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha, Kenya

Siddiqui

1979

Environ Biol Fish

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SynopsisTilapia zillii breeds all year round in the equatorial Lake Naivasha with slightly high breeding intensity during wet months (March, May and July-August). A sex ratio of 1 : 1.28 was found between males and females. The smallest mature male and female were 9.0 and 11.0 cm respectively. The fecundity ranged from 2990 to 12344 eggs, with a mean of 6606 eggs. Fecundity showed a curvilinear relationship with total length (log F = 1.7034 + 1.6370 log L) and a linear relationship with body weight (F = 2197 + 28.76 W).

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Section: Breedingmentioning

confidence: 99%

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha, Kenya

Siddiqui

1979

Environ Biol Fish

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“…Equally, reference to other indices (e.g. The International (Hjort) Scale for the Herring (Hjort, 1910) in which an attempt has been made to relate histological examination with macroscopic appearance (Bowers & Holliday, 1961)) has been found impracticable owing to the differences in body form and gonad morphology between istiophorids and other species (e.g. the herring).…”

Section: Stages In Gonad Maturitymentioning

confidence: 99%

Aspects of the biology of billfish (lstiophoridae) from the equatorial western Indian Ocean*

Merrett

1971

Journal of Zoology

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With 17 figures in the text)A tuna longline survey of billfish was carried out in the equatorial western Indian Ocean during 1964-67, in which 265 specimens of five species (Zstiophorus platypferus, Tetrapferus audax, T. angustirostris, Makaira indica and M. nigricans) were caught. The comparative morphometric evidence obtained is used in confirming the conspecificity of these istiophorids with Pacific Ocean forms. However, the insufficient depth and detail of the data allow only preliminary observations on populational differences. The distribution and seasonal abundance of the species are discussed in terms of percentage catch rate. The weight-length relations of the species are examined. The size composition of the catches is shown by the analysis of length and weight frequencies, and tentative estimates of the year classes present in the catches of T. audax are given. An examination of the sex ratio of the species is made. Gonad maturation indices for males and females are established, based on both macroscopic and histological evidence. The indices are used to study breeding in the species caught in the survey area. Relative gonad weight is also considered as a means of assessing the stage of gonad development. The results of the gonad examination indicate that little spawning occurs in the area, and it is suggested that seasonal abundance of certain species is related to feeding. Preliminary observations on the size at first maturity are made, and the fecundity of female I. platypferus, T. audax, and T. angustirosfris is examined.

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“…I n earlier studies of seasonal changes in gonad condition, various arbitrary classifications of maturity have been used. These classifications have generally been based on such features as colour (Graham, 1924)) shape and size of gonads in relation to those of body cavity (Hjort, 1910 ;Bowers, 1954), weight of gonads or ratio between gonad weight and body weight (Hickling, 1930;Chrzan, 1949) or diameters of oocytes (Clark, 1934).…”

Section: Classification Of Gonad Conditionmentioning

confidence: 99%

THE BIOLOGY OF BLENNIUS PHOLIS L. (TELEOSTEI).

Qasim

1957

Proceedings of the Zoological Society of London

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Summary. The growth rate in B. pholis has been studied mainly from the zones on the otolith. One wide opaque zone and one narrower transparent zone are laid down during the course of a year. The transparent zones are formed in spring, from March to May, following a period of minimum sea temperatures, reduced food intake, maximum gonad development and no observed growth in length of the fish. The opaque zones are formed during the rest of the year, mainly during the summer period, to which the whole of the growth in length is confined. Seasonal size frequency distribution curves show distinct peaks which evidently correspond to two or three year classes, because they fall in close agreement with the lengths of these classes determined from direct otolith readings and from back calculations. Otoliths show slight negative heterogonic growth, which was allowed for in the back calculations. Both sexes show a similar growth rate and attain a similar longevity. Growth in length seems to occur mainly during summer in older age groups, but in the first year group it seems to continue at a reduced rate during autumn and winter. Growth is rapid during the first two years. It gradually decreases in subsequent years. This causes the older age groups to overlap considerably in size. A study of the seasonal changes in the gonads of B. pholis, based on an arbitrary classification of maturity, showed that both sexes mature when nearly two years old and begin to spawn when about 8 cm. in length. The males ripen earlier and remain ripe for a longer period than the females. Each individual spawns successively during the breeding season, which lasts from April to August. There is a quick recovery of the gonads in both sexes after spawning is over. Ripe fish occur throughout spring and summer but no spent females were seen until July. Eggs were found in abundance on the shore from mid‐April to mid‐August, with a maximum in June. Seasonal changes in gonad weight are less marked in males than in females. The ovaries reach their maximum weight during May, in preparation for maximum spawning, which occurs in June. In both sexes there is a regular seasonal cycle in the “condition factor” which cannot be explained as being due to seasonal changes in the gonad weight alone. Alternating periods of growth in weight and growth in length seem to account for most of the seasonal rise and fall in the condition factor. There is a temporary fall in February and March, which is probably due to net loss of reserves on account of reduced feeding at the coldest season. The mean K values obtained for each length group, from the pooled data of all seasons, gave no indication of the size at first maturity, but some evidence of this was obtained by separate treatment of the samples from the months when spent fish were abundant. The size frequency distributions of oocytes in ripening and ripe ovaries show multiple groups, which are successively ripened and shed during the breeding season. The food of Blennius pholis was investigated by the examination of the...

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Report on Herring-Investigations Until January 1910

Cited by 22 publications

References 0 publications

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha, Kenya

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha, Kenya

Aspects of the biology of billfish (lstiophoridae) from the equatorial western Indian Ocean*

THE BIOLOGY OF BLENNIUS PHOLIS L. (TELEOSTEI).

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