BEHAVIOUR AND BREEDING BIOLOGY OF THE FISH TOR PUTITORA MAHASEER

Abstract

Breeding biology and behaviour of the putitora mahaseer (To~ putitoha) inhabiting Rawal lake and its tributaries in Islamabad were studied with focus on (1) gonadal maturation, seasonal rhythm and spawning, size and age at first maturity, (2) fecundity, (3) breeding behaviour, (4) schooling behaviour of juveniles, and (5) food and feeding behaviour. Morphological details of ovaries and testes and gonadosomatic index determined over a 2-year period reveal that the breeding season of the putitora mahaseer lasts from late July to early October with peaks in August-September . The maturation of the gonads coincides with the onset of monsoon season when the water temperature also declines from a peak value of 2S oC in the summer . There is evidence that spermatozoa occur in the testes of some males as early as May. The above observations have been supported by details of histocytological changes in the ovaries and testes as well as compartmentation of the seasonal ovarian and testicular rhythm into distinct stages . It is not~worthy that oocyte development in the ovaries is asynchronous and presence of more than one advanced stage of oocytes x iv indicates that the ma haseer spawns mor e t h an once i n the breeding season . The mean GSlvalues for the two se x e ~~ hbw peaks in August and September. The female putitora mahaseer become mature first at a size of 326 mm tot al length and ~5l g body weight when they are in the 3rd year of life or have completed 3 years of age . The males become mature first at a size of 170 mm total length and 104 g body weight when they are in the 2nd year of life . The f e cundity of the s pecies determined g r avime t r ically r anges from 7,570 to 30,295 ova for fish measuring 470 - 667 mm total length and 757 - 2997 g body weight . The relationship of fecundity with total body length, body w~ight, ovarian weight and age has been described on the basis of Least Squares estimates and analysis of regression : The equations yielding the best fit to the data reveal a strong correlation of fecundity with the above parameters . The breeding behaviour of the mahaseer involves upstream migration . The fish breeds in shallow pebbly xv and rocky sites in the Ramli and the Kurang streams between sunset and dawn. The behaviour comprises courtship and spawning act. During courtship several males follow a single female with display of nudging and tail- flapping. The spawning act occurs in currents of swift water where the female is joine'd by a male (rarely more than one), the bodies of the individuals arch as they make jerky quivering movements apparently signifying release of eggs and milt. This tehaviour is repeated periodically involving the same female and other males . Schooling behaviour is shown here to emerge only gradually in the juvenile stage. During November when the fry have a mean size of 9 . 5 mm, they generally occur as solitary individuals . with increase in size during December and January there is a tendency toward formation of loose groups (non - polarized) as well as polarized schools comprising' 2 - 5 individuals. In February (70 mm mean size) a polarized state becomes pronounced with most individuals occurring in schools ranging from 2- 20 individuals . The features of the polarized schools and maintenance of this state in subsequent months are described and discussed . xvi It is shown here that the putitora species feeds in marginal areas of the lake and the streams during the morning and the afternoon but may also feed at night . Gut analysis revealed presence of macrovegation, algae, animal food and detritus. Macrovegetation and algae together constitute the most abundant food items. Seasonal variations in the composition of the diet have been examined. The animal food component increases noticeably in the summer (June). Food preferences have been determined on the basis: of numerical analysis and frequency method . The former shows that Spi~oglj~a and Valli6na~ia interchange during the year as the dominant items . The latter revealed the following order of preference; waterboatman and waterbug (insects ) , H ljd~illa, S pi~o 9lj~a, ValLi. 6 na~ia and Ulo;th~ ,LX (decreasing order of the first five items). The study collectively shows that the mahaseer is an omnivore with a primarily herbivorous habit. The value of the relative length of the gut (RLG ) also supports the above conclusion . The absence of a true stomach, presence of pharyngeal teeth and small gill rakers have been noted and discussed in relation to the feeding habits of the putitora mahaseer .