No abstract

Monogeneans of the superfamily Capsa)oidca have been a severe problem in maintaining both teleosts and elasmobranchs in eaptivity. Infestations of Benedeniella posterocolpa on the skin of the cownose ray, Rhinoptera bonasus, provided an excellent model for testing the effects of triehlorfon (0-7ppm), praziquantel (20ppm) and eopper sulphate (0-25 ppm) on adult monogeneans in situ, and on adult monogeneans. oncomiraeidia and eggs in vitro. One treatment with praziquantel eliminated i(K)% of the worms from the skin of rays. Two treatments with triehlorfon only eliminated 81% of the worms. Praziquantel killed all worms tested in vitro within 6h and prevented egg deposition. Triehlorfon killed all worms within 21 h, but some eggs were deposited. Copper sulphate had little effeet on worms in vitro. Both triehlorfon and praziquantel immobilized oneomiraeidia while copper sulphate had httle effeet. Eggs were relatively resistant to these chemieals; however, triehlorfon and praziquantel were the most effective in killing eggs.

The parasite communities ofjuvenile spot, Leiostomu.F.uanthurus Lacepi.de, and Atlantic croaker, Micropogonias undulutus (Linnaeus), changed with size, season. and geographical area. A total of 2 1 parasitic species occurred in juvenile spot and 19 occurred in juvenile croaker from Chesapeake Bay and Pamlico Sound. More parasitic species were acquired as juveniles grew, diversified their diets, and consumed larger numbers of intermediate hosts. They were also exposed to infective larvae of parasites with direct lifecycles over long periods of time. Equibility and, thus, diversity were depressed because of large numbers of Diplornonorchis /eio.rtomi Hopkins, I941 that dominated the parasite communities of both species. Although spot and croaker from both estuaries shared eight and six parasites, respectively, many of these non-specific parasites (generalists) were more common in both spot and croaker from one estuary than from the other. All species occurring in both hosts have indirect life cycles suggesting that the availability of certain intermediate hosts as prey was an important determinant of infection. Estuary of residence was clearly as important as host species identity in determining parasite community structure.

We describe spatial patterns in fish abundance across the lagoonal patch reef system at Glover's Reef Atoll in Belize, and assess the relative influence of physical, biological, and abiotic structural variables on these patterns. Physical factors-specifically, distance from reef channels, current flow, and temperature-play a significant role in structuring overall patterns in fish abundance across the lagoon. The types of variables that best explained trends in abundance of specific groups of fishes were related to feeding habits of these groups. For example, fishes dependent on primary and secondary sources of productivity (herbivores and planktivores) were most highly influenced by physical factors. Abundances of benthophagous fishes were best predicted by benthic habitat variables such as coral cover, while abundance of piscivorous fish groups was best predicted by abiotic structural habitat variables such as reef area. While data on physical oceanographic properties are not normally considered in relation to abundance patterns of reef fishes, we find that such factors are good predictors of abundance for these species. Where physical data are not available, simple distance metrics may serve as reasonable proxies for physical oceanographic processes.

Twenty‐three species of metazoan parasites were recorded from adult spot and 26 from adult croaker. Of the 33 parasitic species found, 17 occurred in both spot and croaker. No significant differences in intensity of parasites occurred between sexes of either spot or croaker. All of the parasites had over‐dispersed, or clumped, distributions among hosts. Adult spot and croaker collected offshore had much greater species‐richness, diversity, and total number of individual parasites than juvenile fishes collected in adjoining estuaries during another study. The juvenile spot and croaker had less time to acquire parasites and inhabited less diverse and more confined habitats in inshore estuaries, which resulted in less diverse parasite communities than offshore fishes. The number of species and diversity of parasites in adult fish was greater in croaker than spot. However, when only gastrointestinal helminths were considered, spot had greater species‐richness as well as greater numbers of individual helminths, suggesting that they had a more diverse diet and that they fed on more infected intermediate hosts than croaker. In both adult spot and croaker the mean number of parasitic species was greater than those of freshwater fishes and fewer than those for birds and mammals. The total number of individual parasites was similar to that of freshwater fishes. The opportunistic diet and the migratory habits of both spot and croaker contribute to their diverse parasite faunas. Comparison of adult spot and croaker parasite faunas collected offshore indicated that their respective parasite component communities were distinct and that similar parasite infracommunity variability existed in both hosts and that their communities were not ‘random’ samples, but restricted subsets of the compound community. Although the parasite dominance hierarchy in adults of both species varied slightly between areas and seasons sampled, there appeared to be a predictable dominant species that was accompanied by subordinate, less predictable species. However, the variability in both relative intensities and presence‐absence of parasites within communities resulting from their diverse diets make them less predictable than those of other vertebrates with less diverse diets such as the lesser scaup duck and more like those of other marine fishes.