2 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



METHODS AND MATERIALS 



Benthic samples, primarily from the canyon axes, were collected 

 either with an orange-peel grab or a Campbell (modified Van Veen) 

 grab from 1952 to 1962 in the following canyons from north to south 

 along the mainland shelf: Monterey, Hueneme, Mugu, Dume, Santa 

 Monica, Redondo, San Pedro Sea Valley, Newport, La Jolla and Coro- 

 nado. The following insular canyons were sampled : Santa Cruz, Santa 

 Catalina, Tanner and San Clcmente Rift Valley. Samples were also 

 taken in the San Diego Trough. These 201 samples, plus a few addi- 

 tional basin and slope samples, supplement the basin samples discussed 

 by Hartman and Barnard (1958, 1960) to form the basis of the present 

 treatment of the amphipod fauna. Hartman (1963) has already dis- 

 cussed the polychaetes and general faunistic condition of the canyon 

 samples. 



The orange-peel grab collected at each station a plug of sediment 

 with a surface area of about 0.25 m^ and the Campbell grab about 

 0.55 m^. The depth of penetration of the grabs varies but this is consid- 

 ered to be inconsequential in the collecting of Amphipoda as most of the 

 organisms are presumed to inhabit the upper few centimeters of the sub- 

 strate. A few listriella Amphipoda may inhabit the deeply thrust tubes 

 of maldanid polychaetes. Deeply burrowing organisms of groups other 

 than Amphipoda are of course sampled erratically by benthic grabs, de- 

 pending on the compactness of the substrate. Therefore, the values of 

 standing crop and frequency of organisms are only approximate; abso- 

 lute values await the invention of a perfect sampler. Equation of sam- 

 ples according to their areal coverage is acceptable in view of the com- 

 monly practiced comparison of various marine communities in the litera- 

 ture regardless of type of sampler. 



After recovery, samples were washed aboard ship (R/V VELERO 

 IV) through a screen of 0.7 mm mesh and the residues preserved for 

 sorting in the laboratory. Sedimentary volumes of samples are reported 

 by Hartman (1963). 



The faunal composition of canyon samples is extremely variable and 

 can be associated only sketchily with depth and assumed thermal prov- 

 inces, sediments, geomorphology and distances from shore (as based on 

 USHO charts). Mapping and sampling of canyons must be continued on 

 a larger scale than at present but restricted to smaller regions and shorter 

 time scales before valid correlations can be made between biotas and en- 

 vironmental parameters. 



Usage of the term "community" in this paper conforms to the Peter- 

 sen concept (Thorson, 1957). 



