Gonad Index the concept Technique Outre Mer rue Bayard special refer - PDF document

Gonad Index the concept Technique Outre Mer; rue Bayard, special reference to P.Cayré and value: application Concept of for skipjack pelagic migrators, short period week: Kaya this facilitates favourable environ- reproduction mode done without the strict sense of terms (Sharp, from which average be ensured are at point it maximum of four groups modes) of oocytes has reached is clearly the others; They have then calculated the females which show advanced mode value” (which then been defined females show value determined Purpose of respect to of skipjack comparing it indicates the size of group of oocytes maturity stage determined the mathematical these oocytes, thus the maturity understand the The gonads caught in East Tropical Fork length Long. 30%’) were sampled and put in free the The measurements per sample micrometer mounted on a binocular oocytes of greater than were ob- in a sample do not include non advancing constitute the stock of oocyte cells. The GIs to the previously mentioned. were taken from oocyte group Instead of preferred, like determine

the diameter for the totality a sample; advanced group of oocytes in fact is 5% group in a it is that there due to sizes given in this from here on do this fact having been placed d in the oocytes before being placed in the and diameter the largest chose model a detailed diverse aspects of the advanced group of oocytes men- tioned previously (i.e. two different relation- diameter corresponding the linear equations; a, the linear equations; Gonad Index critical value; for the its critical value: application skipjack tuna 100 125 150 Relationship between Gonad Index most advanced oocytes the function: of model estimated by 1 computer. This method modified Newthon After studying of the out another the sum: raising factor. GI-d,, was evaluated using to the varying from The index k designates each the mean each given average of the same The shape GI-diameter of a range maximal oocyte between values (Fig. 1); close to Station, Harpenden Hertfordshire, was studying comparisons between oocytes sampled the central Pacific Gonad Index its critical the contrary, it that the

GI and linear relationship (for will give later) for smaller than section). It should, be pointed that there strong variability for a (or a to these small sized oocytes. It can particular that the separation value of The statistics described that the normal indepen- be seen can accordingly be noted the residuals fish (whose is only should approximatively follow Fisher’s that, for fishes whose strong variability in the oocyte size any value or Dgs if IGS a minimization residual sum squares without application a weighting factor Parameters Estimated Correlation factor 0.49 0.74 the model after minimization squares (see Parameters Estimated Correlation factor BI 0.890 1.23 0.55 the squares: has been The fact parameters obtained from A and similar points out to test to reflect correctly analysis of square obtained from is superior to that here, therefore represents the between GI choice of models of describe the have chosen since it the ability point for largest oocytes analysis of that the In any breaking point species involved here; this does not that other mode

ls would as satisfactorily, they would define very poorly. the GI, corresponds to for the set points in different parts, objective criteria undoubtedly more is in principle; these authors have reference the close to stage; these females were of a group of oocytes clearly separated from the others in appears that point value the critical its critical value: application “weighted” least as a function of of x IO )“ I A 80 120 160 200 G.I. NORMALI SED RESIDUALS B Fig.2A. Repartition of the the model the least squares application of a as a these authors, same meaning; has been a more is similar this simi- the biological reality the reliability have chosen to express could very have been expressed current use, and the practical aspect the GI value have motivated advanced group be noted GI and straight line with a the actually observed modal value the diameter advanced oocytes least partially, can be when random measure- F.Laloë: Gonad Index critical value: application to skipjack tuna ments of made, the oocytes which correspond to the the total all sizes

; enough to have oocytes (with the last mode of included in the calculation of that do not really belong this case systematically underestimate the modal last group the lower limit of the percent of the largest this case the model would be: this case =2.36; b‘,=0.91 not different and do not modify the of the relationship GI-diameter of the largest The fact value of seems to without any could also oocytes, which are more during the (stirring in Gilson However, this does not seem have been proved as exclude the hypothesis of the destruction biggest oocytes, of the does not modify conclusions obtained much beyond certain value growth in of the Without being response to this question since supplementary research has been carried try to “only” express the increase of the phenomena which to sexual could provoke increase in relationship to the would explain increase noted in histological studies of gonad tissue itself oocytes that precise biological explanation of the changes observed GI and could therefore prove of the numerous phenomena their materializati

on trying to evaluate by only although precise (for example the oocytes) could lead to curate caricature. can thus question the ability of the oocyte size translate the sexual sense of term) reliably. The observation of the relationship between diameter of the largest oocytes certain maturity stage particular for becomes unrealistic to to distinguish several maturity stages the diameter of the largest The process is very concept of the relationship between whose complexity to comprehend the measurement of factors (for example: oocytes); the gonad index could in fact a true the multiple together constitute what mean by the general term can therefore not be expected an index stages defined function of one parameter, expression, of the strong variability of the values within each stage, the overlapping of their stage to prove the aspect of the imposed limits for each of these its value are interesting present the same (maturity index, parameter) as the skipjack. The “critical value” of the distinguish the individuals which for reproduction those in resting st

age of tion, beginning of maturation post-spawning stage. Sexual maturity, fecundity and North Carolina waters. Some aspects biology of Hawaiian Islands. Spawning habits some Philippine based on diameter measurements sex-ratio du listao côtes d’Afrique partir des débarquements thoniers 83/12, présenté réunion de clôture sue le listao Atlantique, Teneriffe D. Hendrix, Queenth: Rapid and spontaneous its critical to skipjack tuna by newly 393-396 (1982) (Parathunnus mebachi, near the southern Mar- skipjack tuna. Fisheries synopsis the oceanic skipjack, Minicoy waters. of the Symp. Ser. Ross, R. efficient use of function minimization linear maximum likelihood estimation. Appl. Schaefer, M. Studies of of yellowfin tuna Neothunnus niacropterus three areas of Pacific ocean, of gonads. Inter-Am. Trop. modes of opportunism Sup. Doc. the Workshop survival of larval pelagic Lima. Pérou (Ed. by D. Sharp) Workshop. Ser. pp. Paris: Millier: La régression: regards sur une technique ancienne. Ed. spawning in the Marquesas Fish. Wildl. fecundity of bigeye in the Wildl.