FISHERY BULLETIN: VOL. 73, NO. 2 



turnal illumination plays a major role in the suc- 

 cessful use of these habitat traps for pueruli of P. 

 interrupt us. The fact that no pueruli were caught 

 in the unlighted habitat traps maintained 

 offshore, as discussed in the next section, provides 

 additional strong support for this conclusion. 



Habitat Traps Maintained Offshore 



Unlighted habitat traps of the "bag" and 

 "screen" designs were anchored in water 3- to 15- 

 m deep in the San Diego area off Point Loma, La 

 Jolla, and off the northeast shore of Catalina 

 Island, Calif., at the positions shown in Figure 6a, 

 b. This was done to monitor the recruitment of 

 pueruli at other locations along the San Diego 

 coastline, and on the leeward side of a large 

 offshore island, as well as to determine the im- 

 portance of lights in attracting pueruli by com- 

 paring these unlighted traps with those placed 

 under the Scripps Institution pier lights. The traps 

 placed offshore were checked and refilled with 

 fresh Phyllospadix and red algae every 10-15 days 

 during August and September 1969. Many were 

 lost, apparently because of entanglement with 

 kelp and boat propellers. However, the large 

 number maintained successfully failed to collect 

 any pueruli, despite the fact that puerulus 

 settlement at the Scripps Institution pier was 

 relatively high during this same period. The four 

 traps maintained at Catalina Island were situated 

 directly above a shallow rocky area, approximately 

 2-6 m in depth, where we had observed many small 

 first year juvenile lobsters the previous winter. We 

 presumed that the presence of these young 

 juveniles indicated that this was an area of high 

 puerulus recruitment. Thus, failure of the 

 unlighted traps to collect pueruli at this location 

 was particularly surprising. 



The failure of these offshore habitat traps may 

 have been due not only to the lack of nocturnal 

 illumination, but also to the presence of large 

 quantities of Phyllospadix and algal flotsam in the 

 areas where they were maintained. The 

 probability of a puerulus settling in a seaweed 

 habitat trap under such conditions would be small, 

 considering the large volume of seemingly equally 

 suitable patches of floating surfgrass and algae 

 present in these areas. In contrast, relatively few 

 masses of plant flotsam of this kind were observed 

 in the area around the Scripps Institution pier. 



In an attempt to evaluate this, many clumps of 

 floating Phyllospadix were collected and examined 



nr — f 



^^^. 



Bird Rock 



Isthmus Raef 



(a) 



(b) 



SCRIPPS INSTITUTION PlER 



LA JOLLA 



PACIFIC 



OCEAN 



MISSION BAY 



MISSION BAY 

 CHANNEL 



Figure 6.-Locations of sampling areas off northeastern Ca- 

 talina Island (a) and San Diego (b) for puerulus and early 

 juvenile Panulirus interruptus. 



for pueruli while deploying and checking the 

 offshore habitat traps. No pueruli were found in 

 this manner, but only a relatively small percen- 

 tage of this material was examined relative to that 

 present, thus leaving the question open to further 

 investigation. 



Neuston Net Sampling 

 Semiquantitative sampling with the paired 



368 



