Table 10. Molluscs at Mugu Lagoon and Mission Bay found live in either marsh 

 or tidal creek habitats by Macdonald (1969, cf. Table U, p. 62). Rare 

 species are excluded. Data are mean no./m . 



Gastropoda 

 Subclass Prosobranchia 

 Assiminea californica (Tryon) 

 Cerithidea californica (Haldeman) 

 Nassarius tegula (Reeve) 



Subclass Opisthobranchiata 

 Acteocina sp. cf . A. culcitella (Gould) 



Subclass Pulmonata 

 Melampus olivaceus Carpenter 



Mugu Lagoon Mission Bay 

 Marsh Creek Marsh Creek 



16 



88 



22 



771 



Pelecypoda 

 Subclass Pteriomorphia 

 Modiolus (Brachiodontes) senhousei (Benson) 



Subclass Teleodesmata 

 Chione fluctifraga (Sowerby) 

 Macoma nasuta (Conrad) 

 Protothaca staminea (Conrad) 

 Tagelus californianus (Conrad) 





 

 

 



7 

 

 2 

 3 



refuges for invertebrates, and raises the 

 question of why birds spend less time 

 there than on intertidal flats. Crabs are 

 also snail predators, but their effect 

 appeared to be limited by the availability 

 of refuges for the crab. At Goleta 

 Slough, McCloy (1979) demonstrated higher 

 hornsnail mortality near an area of 

 artificial rock substrate, where shore 

 crabs ( Pachygrapsus crassipes ) found 

 shelter. Again, a seemingly minor 

 alteration of the marsh channel had an 

 unexpected impact on a variety of 

 populations within the ecosystem. 



Hornsnails ( Cerithidea californica ) 

 are of importance to marsh ecosystems in 

 other ways as well, because they host a 

 large number of flukes whose cercariae 

 larvae parasitize shorebirds, fiddler 

 crabs ( Ilea crenulata ) , killifish ( Fundulus 

 parvipinnis ) , and mudsuckers ( Gillichthys 

 mirabilis ) . Cercariae sometimes burrow 

 into human skin and cause an annoying 

 itch. They are especially easy to 

 contract in late summer while wading for 



long periods of time through water or 

 tidal creeks in the marsh. 



Crustacea 



Crabs are the most conspicuous 

 crustaceans of the marsh, but they tend to 

 evade study by burrowing. More elusive 

 still are the salt marsh amphipods 

 ( Orchestia traskiana and 0. californica ) 

 and isopods which enter the high marsh 

 from more terrestrial habitats (Macdonald 

 1977b). These crustaceans are most 

 abundant under rafted debris. Ghost 

 shrimps ( Callianassa californiensis ) are 

 well known because of their utility as 

 bait. However, they are more common in 

 channel sediments than in the marsh. All 

 of these crustaceans are important to 

 marsh food chains since they seem to be 

 omnivores and are all utilized by birds 

 and (at least in their larval forms) by 

 fish. However, only the crabs (Figure 39) 

 have been studied in detail in southern 

 California (Kutilek 1968, Betz 1978, 

 Willason 1980). 



61 



