Clarke et a\. Prevalence of the nematode Philometra saltan ix in the ovaries of Pomatomus saltalnx 



123 



Although most studies indicate the occurrence of these 

 nematodes to be lower than in bluefish, in a later study 

 Moravec et al. (1997) reported prevalence of Philometra 

 margolisi in the gonads of Epinephelus morio to be as 

 high as 88% with an intensity of up to 84 nematodes. 

 Additionally, although most studies report the absence 

 of male worms (Hesp et al., 2002), we found up to 20 

 males in the ovary of one female fish. The high per- 

 centage of adult female bluefish that are infected may 

 indicate that Philometra saltatrix are significantly af- 

 fecting the reproductive success of bluefish. 



Despite some studies showing deleterious effects of 

 other parasites on fish ovaries (see for example, Adler- 

 stein and Dorn, 1998), studies on the effects of philome- 

 trids on fish ovaries remain scarce. Indeed, in a recent 

 review of histopathological assessments of gonadal tis- 

 sue in wild fishes, Blazer (2002) made no mention of 

 Philometra spp., despite the fact that it is probably the 

 most common adult helminth observed in fish gonads. 

 Annigeri (1962) described damage to ovaries of Oto- 

 lithiis argenteiis by an unidentified philometrid, and 

 Ramachandran (1975) mentioned necrosis in the ovaries 

 of Mugil cephalus caused by Philometra cephalus. The 

 infection of testes of pink snapper Pagriis auratus by 

 Philometra lateolabracis resulted in partial or extensive 

 atrophy of those gonads (Hine and Anderson 1981). 

 Oliva et al. (1992) alluded briefly to lower fecundity 

 in Paralabrax humeralis as a result of infection with 

 Philometra but provided no data in support of this as- 

 sertion. Hesp et al. (2002) studied the dynamics and 

 effects of P. lateolabracis in the gonads of the Austra- 

 lian predatory marine fish Glaucosoma hebraicum, but 

 did not observe significant pathological abnormalities 

 associated with infection. 



Histopathological changes associated with philome- 

 trid infection in bluefish were significant. The hem- 

 orrhaging, edema, inflammation, atresia, and necro- 

 sis observed most likely reduce oocyte number and 

 quality, leading to lower fecundity. The presence of 

 erythrocytes in the guts of nematodes indicates that 

 the parasites were feeding on the blood of the host; 

 this diversion of nutrients to the parasite may exacer- 

 bate the impacts of the worm on ovarian tissue. Fur- 

 thermore, intense infections can reduce the effective 

 volume of the ovary and thus lead to lower fecundity 

 (Fig. 5, A and B). 



The high prevalence, intensity, and pathological dam- 

 age observed could be an important factor in recruit- 

 ment variation in bluefish. Although modest interannual 

 differences in prevalence and timing of infection were 

 observed in this study (Fig. 4), Philometra saltatrix was 

 not observed by researchers conducting studies of the 

 GSI of bluefish from NY waters in the 1980s (Chiarella 

 and Conover, 1990; Conover, personal observ. ). Hence, 

 it is possible that the abundance of Philometra may 

 fluctuate greatly over long time scales. The reason for 

 the current prevalence of the worm and its effect on 

 bluefish recruitment is unknown. Future studies of 

 this host-parasite system should seek to account for 

 temporal variations of this kind. 



Acknowledgments 



We thank R. Knotoff and numerous other commercial 

 fishermen from Shinnecock Inlet, NY, for helping us 

 to obtain samples. B. Burns and J. Pearce of the NC 

 Division of Marine Fisheries helped collect North Caro- 

 lina bluefish. We thank R. Clarke, C. Knakal, and S. 

 Abrams for laboratory and field assistance. We also 

 thank two anonymous reviewers for helpful comments 

 on the manuscript. Funding was provided by the Rut- 

 gers/NOAA Bluefish-Striped Bass Research Program 

 and the New York State Department of Environmental 

 Conservation. 



Literature cited 



Able K. W., P. Rowe, M. Burlas, and D. Byrne. 



2003. Use of ocean and estuarine habitats by young-of- 

 year bluefish iPomatonuis saltatrix) in the New York 

 Bight. Fish. Bull. 101:201-214. 

 Adlerstein, S. A., and M. W. Dorn. 



1998. The effect of Kudoa paniformis infection on the 

 reproductive effort of female Pacific hake. Can. J. Zool. 

 76:2285-2289. 

 Annigeri, G. G. 



1962. A viviparous nematode, Philometra sp., in the 

 ovaries of Otolithua argenteus (Cuvier). J. Mar. Biol. 

 Assoc. (India) 3:263-265. 

 Blazer, V. S. 



2002. Histopathological assessment of gonadal tissue in 

 wild fishes. Fish Physiol. Biochem. 26: 85-101. 

 Chiarella, L., and D. O. Conover. 



1990. Spawning season and first year growth of adult 

 bluefish (Pomatomus saltatrix) from the New York 

 Bight. Trans. Am. Fish. Soc. 119:455-462. 

 Collins, M. R., and B. W. Slender. 



1987. Larval king mackerel (Scomberomorus caralla), 

 Spanish mackerel, (S. maculatus) and bluefish (Poma- 

 tomus saltatrix) off the southeast coast of the United 

 States, 1973-1980. Bull. Mar. Sci. 41:822-834. 



Friedland, K. D., G. C. Garman, A. J. Bejda, A. L. Studholme, 

 and B. 011a. 



1988. Interannual variation in diet and condition in 

 juvenile bluefish during estuarine residency. Trans. 

 Am. Fish. Soc. 117:474-479. 



Graves, J. E., J. R. McDowell, A. M. Beardsley, and D. R. Scoles 

 1992. Stock structure of the bluefish Pomatomus sal- 

 tatrix along the mid-Atlantic coast. Fish Bull. 90 

 (4):703-710. 

 Hare, J., and R. K. Cowen. 



1997. Size, growth, development, and survival of the 

 planktonic larvae of Pomatomus saltatrix. Ecology 

 78:2415-2431. 

 Hesp, S. A., R. P. Hobbs, and I. C. Potter. 



2002. Infection of the gonads of Glaucosoma hebraicum 

 by the nematode Philometra lateolabracis: occurrence 

 and host response. J. Fish Biol. 60:663-673. 

 Hine, P. M., and C. D. Anderson. 



1981. Diseases of the gonads and kidneys of New Zealand 

 snapper, Chrysophrys auratus Forster (F. Sparidae). In 

 Wildlife diseases of the Pacific Basin and other coun- 

 tries (M. E. Fowler, ed.), p. 166-170. Academic Press, 

 London. 



