FISHERY BULLETIN: VOL. 73, NO. 2 



provided a more accurate means of evaluating 

 possible correlations between puerulus recruit- 

 ment and changing environmental factors than by 

 merely recording the date on which the habitat 

 trap was examined, as done by Witham et al. 

 (1968) and Sweat (1968). In his later study, Parker 

 (1972) provided a more detailed description of the 

 pigmentation and transformation of the puerulus 

 and postpuerulus stages of P. interruptus. 



Laboratory observations indicated that once the 

 puerulus settled in a suitable substrate, its trans- 

 formation into a postpuerulus proceeded without 

 delay. However, a few individuals which were held 

 in containers without fresh Phyllospadix, algae, or 

 rocks containing epifauna, remained as trans- 

 parent pueruli for 2-3 wk until death, suggesting 

 strongly that the presence of such suitable habitat 

 features is necessary to induce transformation to 

 the postpuerulus stage. 



After settlement, pueruli became photonegative 

 and were never again seen swimming. In order to 

 test the related question of whether or not a 

 settled puerulus might desert a habitat trap upon 

 its removal from the water, and thus produce 

 unreliable trap catch data, one seaweed frame 

 habitat trap and one Witham trap containing 

 known numbers of pueruli were returned to the 

 water for 5-10 min on two different occasions, and 

 then retrieved. No individuals left either the 



Witham or seaweed traps. This, and the laboratory 

 observations described above, indicate that the 

 number of individuals found in a habitat trap 

 probably is a reliable estimate of the number that 

 settled there. 



Comparison of Habitat Trap Types 



Habitat traps were mounted either singly or in 

 groups of two or three from one main support bar 

 in order that at least six different types could be 

 tested simultaneously from the three available 

 Scripps Institution pier positions (position A, B, or 

 C, as shown in Figure 1). The exact pier position 

 and combinations of traps were alternated from 

 time to time, as indicated in Table 2, in order to 

 compensate for possible variations in unknown 

 factors influencing puerulus settlement, such as 

 current direction, eddies near the pilings, and 

 differences in daytime or nighttime light intensi- 

 ties. The results of comparative habitat trap 

 design studies conducted during the summer of 

 1969 are summarized in Table 2. These results in- 

 dicate that all habitat traps containing natural 

 seaweed proved markedly superior to the Witham 

 artificial habitat trap for this species (Figure 2C). 



Only 5 pueruli were collected by two Witham 

 habitat traps {x = 2.5 per trap), while 97 pueruli 

 were collected by four seaweed habitats (x = 24.2 



Table 2.-Results of a comparison of the catch effectiveness of habitat traps suspended off the Scripps Institution pier. The catches of 

 pueruli per trap are also recorded in terms of the specific location of the trap at the pier (a, b, or c). Positions A and B were lighted, while 

 position C was unlighted, as shown in Figure 1. For descriptions of the habitat trap designs, see Figure 2 and text. 



'Habitat trap not in position at tfiis time. 



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