FISHERY BULLETIN: VOL. 83, NO. 3 







5 



(26) 



^=:^ 



X- 



11 



(309) 



Figure 7. -The average numbers ofT. coryjihaenne in skipjack tuna 44 to 58.9 cm long in samples of over 22 fish. Note that the iiumi)er in- 

 creased to the east. (In parentheses, number of fish sampled.) 



Several other parasites thought to be short-Hved, 

 such as R. tereba, did not show up in the test, 

 presumably because their infective stages were 

 relatively evenly distributed in the tropical Pacific. 



In New Zealand, parasites showing close associa- 

 tion with particular schools (using both tests) were L. 

 multisacculatum (No. 5), S. filiferum (No. 6), 

 Philometra sp. (No. 7), Coeliodidymocystis (No. 11), 

 T. coryphaenae (No. 12), R. terebra (No. 18), and D. 

 intestinomuscularifi (No. 19). Syncoelium filiferum 

 and R. terebra were both thought to be temporary 

 parasites that could be gained in New Zealand or ad- 

 jacent waters (Norfolk Island). The origin of the 

 Philometra was unknown. Their number reflected 

 the state of maturity of the fish and this varied be- 

 tween schools. However, we were left with three 

 didymozoids and T. coryphaenae, all of which dif- 

 fered markedly between schools in eastern New 



Zealand. One of the didymozoids, L. multisaccula- 

 tum, a normally rare tropical parasite, was found on 

 all five fish from one school (numbers per fish 1, 2, 8, 

 3, and 1). As the three didymozoids and T. cot^- 

 phaenae are essentially tropical parasites, the schools 

 had evidently not fully mixed while in temperate 

 waters. 



If this is true, these four parasites could not have 

 been picked up uniformly across the Pacific. Evi- 

 dence is given above that D. intestinmnuscularis 

 (No. 19) was not picked up uniformly even within the 

 Marquesas. For the other species, a comparison of 

 their mean numbers per fish per school in different 

 areas of the tropical Pacific showed that Coeliodidy- 

 m.ocystis sp. and particularly T. coryphaenae were in- 

 deed more abundant in some areas than others. 

 Lobatozoum multisacculatum was too rare for any 

 conclusions to be drawn in this respect. 



352 



