Bay indicate that modified harbors do not 

 retain the natural habitat values of less 

 altered wetlands (Horn and Allen 1981). 



The egg and larval studies (Table 13) 

 document that southern California bays and 

 estuaries are breeding grounds for the 

 resident gobies and silversides, as well 

 as for the transient croaker and anchovy 

 families, diamond turbot, and Pacific 

 sardines. The high density of Pacific 

 sardine eggs in Tijuana Estuary (Table 12) 

 was unexpected. This is the first report 

 of the species in an enclosed estuary 

 (about 60 ha [150 ac] of channels). 



Most of the fish common to southern 

 California bays and estuaries are low in 

 the trophic level, consuming either 

 plants, detritus, or small invertebrates. 

 They are in turn fed upon by larger fish, 

 many of which are commercially important. 

 In fact, mudsuckers and topsmelt are 

 commonly collected for use as fish bait. 



Ecological Roles 



Perhaps the best example of an 

 estuarine resident fish is the arrow goby 

 (Figure 42). This small fish (average 

 adult length 5 cm; Miller and Lea 1972) 

 resides in the shallow water of mudflats. 

 It lives freely or in burrows with 

 commensal hosts of one or all of the 

 following invertebrates: ghost shrimp 

 ( Callianassa spp.), the echiuroid worm 

 ( Urechis caupo) , and the blue mud crab 

 ( Upogebia pugettensis ) . Arrow gq^ies 

 reached densities of up to 20/m in 

 Anaheim Bay (MacDonald 1975). This 

 species attaches its eggs to the walls of 

 the burrow, thus explaining its absence 

 from egg collections when larvae are so 

 abundant. According to MacDonald (1975), 

 they recede into burrows at low tide and, 

 if a film of water is present, will 

 journey from one burrow to another. 

 MacGinitie and MacGinitie (19'^9) found 28 

 individuals in one burrow. 



Arrow gobies have a wide dietary 

 range but preferred polychaetes and 

 copepods in Allen's (1980) study of 



Newport Bay, while MacDonald (1975) 

 describe them also as benthic carnivores 

 and included oligochaetes and nematodes in 

 their diet. The arrow goby is an 

 important source of food for the 

 California halibut and staghorn sculpin 



tlacGinitie and MacGinitie 19A9, Brothers 

 1975, MacDonald 1975). Other Fish 

 predators include white croaker 

 ( Genyonemus lineatus ) , diamond turbot, 

 deepbody anchovy ( Anchoa compressa ) , and 

 California killifish, MacGinitie and 

 MacGinitie (19^9) suggested that arrow 

 gobies may be an important food source for 

 willets, godwits and curlews, which are 

 capable of probing the burrows at low 

 tide. Topsmelt, shadow gobies and 

 California killifish are considered 

 competitors as well as predators 

 (MacDonald 1975). 



The long-jaw mudsucker (Figure 43) 

 has been collected from the burrows of the 

 yellow shore crab ( Hemigrapsis 

 oregonensis ) . Presumably these 

 larger-bodied gobies (up to 20 cm; Miller 

 and Lea 1972) cannot enter the burrows of 

 the commensal hosts of the arrow goby. 

 Ghost shrimp and yellow shore crabs appear 

 to be important food items (MacDonald 

 1975). 



Staghorn sculpin (Figure 44) appear 

 to have a preference for decapod 

 crustaceans (Tasto 1975). The most common 

 prey items were yellow shore crab, ghost 

 shrimp and pea crabs ( Pinnixia sp.) in his 

 Anaheim Bay study. Arrow goby remains 

 were found in 10% of the guts analyzed. 

 The staghorn sculpin is preyed upon by the 

 Caspian tern, great blue heron, and a 

 variety of gulls, cormorants and waterfowl 

 (Tasto 1975). 



Topsmelt (Figure 45) are 

 opportunistic feeders. Allen (1980) found 

 that diet was related to size and season. 

 Individuals smaller than 5 cm preferred 

 copepods in spring but converted to 

 floating algae ( Enteromorpha sp., 

 Chaetomorpha sp. and Ulva lobata ) during 

 the summer. When algae declined in fall, 

 the small topsmelt reverted to a copepod 

 diet. Larger individuals (5 to 10 cm) fed 



74 



