data distributions are detailed by Elliott (1971). When animals are 

 aggregated (patchy) in samples, a small sample unit is more effective 

 than a large one (Beall, 1939; Finney, 1946; Elliott, 1971; Gerard and 

 Berthet, 1971); the major reasons are: (a) More samples can be taken 

 from a given bottom area, thus for the same analytical effort statistical 

 error is reduced by increased replication; (b) several small sampling 

 units can assess a wider range of the habitat mosaic than a few large 

 samples; and (c) greater ease of handling, screening, and sorting of 

 smaller samples. However, the sampling unit (core sample, etc.) 

 should be large enough to capture enough organisms of interest in each 

 sample so that sets of data are not extremely skewed towards zero 

 values (see Elliott, 1971). In our biological sampling we have empha- 

 sized extensive replication with small-size sampling units. 



III. MATERIALS AND METHODS 



Three permanent reference points (stations A, B, and C) were 

 established along the beach at Imperial Beach, California (Fig. 1). 

 Station A was located near the beginning of the dredge-disposal area. 

 Proceeding downcoast, station B was located at the terminus of the 

 dredge disposal, 1.188 kilometers downcoast, and station C was esta- 

 blished as a control site, 954 meters downcoast of station B. At each 

 reference point sampling was conducted intertidally as well as directly 

 offshore in 3.7 and 6.1 meters of water below mean lower low water 

 (MLLW) . The station reference points are shown in Figure 1 and are 

 described as follows: 



(a) Station A (northern dredge-disposal site) - 

 located directly off of Carnation Avenue; station 

 origin on fence approximately 171 meters south from 

 groin No. 1 (start of dredge-disposal zone); located 

 732 meters north of the municipal pier. 



(b) Station B (dredge-disposal terminus) - 

 located just south of Coronado Avenue near Black 

 Avenue; station origin approximately 1.359 kilo- 

 meters south of groin No. 1; located 412 meters south 

 of the municipal fishing pier. 



(c) Station C (southern control site) - 

 located south of Encanto Avenue; station origin is 

 sixth house north of the terminus of First Street; 

 located approximately 2.313 kilometers sputh of 

 groin No. 1 or 1.426 kilometers south of the 

 municipal fishing pier. This station was 1.125 

 kilometers north from the mouth of the 



Tijuana River. 



Nine sampling locations were established witfiin the three stations, 

 three per station--one intertidally, and one each at the 3.7- and 6.1- 



20 



