The present paper deals with the digenetic trematodes collected by the author from fishes of Tomales Bay (including Dillon Beach) during the summers of 1967 and 1968. Also included in this study are several trematodes collected by the late Alden E. Noble (hereinafter referred to as the “Noble Collection”) at Hopkins Marine Station, Monterey Bay in 1936 and 1937. Unfortunately the majority of the slides in the “Noble Collection” have been lost with the exception of specimens of the Family Meniuridae and a few representatives of other digenea that were in the personal collection of Dr. F.M. Nahhas. A few vials containing unprocessed material were also still available but their contents were in poor condition as evidenced by the stained material prepared from them. The records for the “Noble Collection” were intact and various notations were included in the descriptions of these species. These records show an original collection consisting of 170 individuals representing 69 species of fishes. Twenty species represented by 27 fishes were negative for digenetic trematodes, and of the remaining 49, slides of trematodes were found that were obtained from but 25 species. The Tomales Bay material consisted of 495 individual fishes representing 33 species. Of these, 11 species represented by 35 individuals were negative for digenea. Four species of fish that barbored trematodes were common to both localities.

An effort is here made to assemble all of our knowledge of all adult trematodes which have been found in the fishes of the Pacific Marine Station Area. This includes publications, unpublished material such as graduate theses, and specimens herein described for the first time. It is hoped that this endeavor will facilitate further investigation in trematodology and that this paper will be an aid in identification of trematodes subsequently discovered.

This study deals with the cercarial fauna of marine mollusks in the littoral zone and estuaries of the California coast between Duxbury Reef and Fort Ross. The investigation began in June, 1968 at the Pacific Marine Station, Dillon Beach, California and continued through July, 1969, with monthly collections at various localities (see map). Two major objectives were aimed at: first, to continue a survey of the cercariae of the area begun by Fisk (194) and second, to establish a basis for future life history studies.

To date there has been only on major study concerned with parasites of freshwater fishes of California. E. C. Haderlie (1953) summarized investigations up to that year and conducted a general survey of the monogenetic and digenetic trematodes, cestodes, nematodes, acanthocephalans, copepods, and hirudinians of fishes of Northern California. From 2010 fishes representing 36 species of 11 families examined over a three-year period, he obtained a total of 59 species of helminth parasites, copepods, and hirudinians, which include 20 species of digenea and 16 species of cestodes. In addition to the taxonomic study, Haderlie attempted to correlate the relative occurrence of the parasites with various ecological habitats. These data are incomplete, except for a general ecological discussion of the parasites taken from Clear Lake and its contributing streams. In the Sacramento-San Joaquin area the monogenetic trematodes are the only group that has been extensively studied. This work has been done by Dr. J. D. Mizelle of Sacramento State College. The primary purpose of the current investigation is to gain some knowledge of the species of endoparasites of fishes of the San Joaquin Delta. Two hundred and thirty sic fish were examined, including diadromous, potamodramous, anandromous, and territorial species of San Joaquin Delta. This has resulted in the recovery of two previously described and one new adult digenea, three metacercariae, two adult and three larval cestodes,and two cestodarians. Not included in this study are the Acanthocephala and Nematoda. A few cestodes are also not included because of their poor condition. The Host-Parasite List (p. 49) of this paper gives a summary of the fishes examined by Haderlie (H) and the present author (E) with the number of each species examined and the species of trematodes and cestodes recovered.

This report summarizes the results of a study on the life cycle of a member of the trematode family Acanthooolpidae, genus Stephanostomum Looss, 1899, which was carried on during the summers of 1948, 1949, 1951, and the winter of 1948-49 at the Marine Station of the College or the Pacific at Dillon Beach, California. Only one previous experimental work has been done on the life cycle of any member of this family. Martin (1939) reported the life cycle of Stephanostomum tenue (Linton) which he had obtained at Woods Hole, Massachusetts. Modifications of his technical procedures have been used in this study. It is hoped that this endeavor will further facilitate investigations in life cycle studies. The results obtained may be of economic value because the adult members of the family are parasitic in marine fishes, many of which are of commercial importance.