G-23 



S.^j Reproduction 



There arc in the literature few published accountc of seaoonal reproductive cycles but 

 the detail that io presented in them has meant that the main patterns identified can be used 

 to provide a reasonable description for those Bpocies for which only limited information is 

 available. 



Hureau (1964) used the factor "Relative Gonad Size" (conad wei^t as a perccntag^e of 

 total weight) from monthly samples to doncribe the gross cycle in the gonads of TromatomuB 

 bemacchii . From those results and the results from several other species of Nototlieniid 

 (Hureau 1970, Evorson 1970) it is possible to outline a poneralised pattern for the ovarian 

 cycle. This in indicated in Fifj. 0.2, and with only sli/^jit adjustment of the (y) axes could 

 be applied to most of the Notothoniids invostip;ated ( Notothenia ncKlecta (from 3cotia Arc), 

 N. ronsi 1 , U. ma.^iollanica , Trcmatomus bomacchii , T. hanaonl ). The exceptions are Notothonia 

 ne.'^'loc ta at Terra Adclit- which produces small diameter ova and therefore does not have such 

 a clearly defined cycle and N_j_ cyanobrancha for which thfere are two spawning periods (those 

 maturing for the first time spavm in January and those that have spawned previously subse- 

 quently spawn in May, (llureau 1970)). 



Information on egg size, fecundity and repawning period for those species of potential 

 commercial importance is given in Table 8.I9 and this has been combined with infonnation for 

 all Antarctic species to describe major spaiming ty^ies (Table 8.20). 



It is a characteristic of Antarctic fish to produce large yolky eggs and this has been 

 discussed by several authors (Harsliall 1953, Andriashev 1965« Permitin 1971, 1973). It is 

 generally considered that large yolky eggs spavmod in the Autumn or early winter months will 

 result in the production of post larvae in the Spring coincident ^^^. th the phy toplankton bloom. 

 These large eg,gs are also generally considered to be pelagic (or benthopelagic in some cases). 

 Tlio release of large eggs in the spring by Trematomus sp. may indicate a much slower develop- 

 ment rate of the eggs and early larvae although there is no proof of this suggestion. 



Table 8.I9. Egg size, fecundity and spavming period for Antarctic fish 



