FISHERY BULLETIN: VOL. 78, NO. 2 



Table 3. — Gradation of adult morphological characters in the five species of paraphoxid amphipods in Monterey 



Bay, Calif. 



'Higher ratio indicates more foliose uropod used in swimming. 



Table 4. — Abundance of crustaceans caught in funnel traps at 

 station M-2 (9 m) in Monterey Bay, Calif. (410 trap days). 



semblage at M-1 were mobile deposit feeders. The 

 most abundant polychaetes at M-2 (9 m) were 

 species that maintained larger populations in 

 deeper water. The one exception, Armandia bre- 

 vis, had a low frequency of occurrence (Table 2), 

 was highly opportunistic, and primarily lived in 

 more protected areas (Oliver 1979). 



Polychaete Zone 



The polychaete zone (Table 2) was characterized 

 by animals that require a more stable substratum 

 to establish and maintain burrows and tubes. 

 Most of the polychaetes living exclusively in the 

 shallow crustacean zone did not have permanent 

 tubes or burrows (Table 2). This was true of all the 

 crustaceans. The gradual change in ripple mark 

 and vertical sedimentary structure discussed pre- 

 viously reflected this increase in substrate stabil- 

 ity. There were several other distinct visual 

 changes between the two zones. The most con- 

 spicuous were the increase in burrow openings 

 and tube fragments and the density of large 

 siphons of the goeduck, Panopea generosa, which 

 was first encountered in the transition area (14 m). 



Polychaetes 



The polychaetes Magelona sacculata and Noth- 

 ria elegans were abundant at the deeper stations 

 (Table 2). The onuphid N. elegans lived in a verti- 



cal tube constructed of clean sand. Laboratory ob- 

 servations and gut contents indicated that N. ele- 

 gans was a surface-deposit feeder, scavenger, and 

 predator. Magelona sacculata lived in a burrow 

 and was a surface-deposit and suspension feeder. 

 The gut contents of 25 M. sacculata were mainly 

 amorphous organic matter with very little sand. 



Many other polychaetes were generally more 

 abundant in deeper water. These included the 

 spionids Prionospio cirrifera and P. pygmaea and 

 the large terebellid Amaeana occidentalis (Table 

 2). Amaeana occidentalis constructed a burrow 

 with a mucus-impregnated wall and was capable 

 of extensive burrowing activity in the laboratory. 

 The mouth v/as often positioned a centimeter or 

 more below the substrate surface with the tenta- 

 cles extended through the sediment and into the 

 overlying water. The gut contents of A. occiden- 

 talis and Prionospio spp. were similar to those of 

 M. sacculata. Apparently, they scrape fine mate- 

 rial from the sediment-water interface and catch 

 suspended particles. 



In general, a higher proportion of animals was 

 found in lower vertical sediment strata from the 

 polychaete zone (> 14 m depth) compared with the 

 crustacean zone (Figures 5,6). This was expected 

 due to the greater number of tube- and burrow- 

 dwelling inhabitants. Coincident with this in- 

 crease was an increase in known or suspected 

 commensal or symbiont animals. These included 

 the pinnotherid crabs Scleroplax granulata (Fig- 

 ure 4) and Pinnixa franciscana and several species 

 of polynoid polychaetes. Although Day (1967) de- 

 scribed the paraonid polychaetes as shallow sur- 

 face burrowers, almost half of the individuals of 

 the three local species (Aricidea suecica, Aedicira 

 pacifica, and Paraonides platybranchia) were 

 found below 10 cm in the sediment (9 individuals 

 in 0-10 cm and 7 in 10-20 cm). 



Several rather small species also burrowed deep 

 into the sediment. The capitellid polychaete 

 Mediomastus californiensis was generally <1 cm 

 long after preservation and was found throughout 

 the sediment column (Figure 4). Additionally, the 



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