SERFLING and FORD: ECOLOGICAL STUDIES OF PANULIRUS INTERRUPTUS 



terruptus than the nonlighted artificial habitat 

 system utilized by Witham et al. (1968). 



This suggests that natural seaweed habitat 

 traps filled with native flora characteristic of 

 juvenile habitats, in combination with nocturnal 

 illumination, could prove to be a more successful 

 means of sampling the pueruli of other spiny lob- 

 ster species as well. If so, use of this modified 

 sampling technique might indicate that the abun- 

 dances of P. argus pueruli in Florida and those of 

 P. longipes cygnus in Australia actually are much 

 greater than previously estimated by Witham et 

 al. (1968), Sweat (1968), and Phillips (1972). 



Implications for Aquaculture and 

 Fishery Management 



If the small numbers of pueruli captured during 

 this study are representative of puerulus 

 availability throughout the geographic range of P. 

 interruptus, large-scale collecting of this stage for 

 purposes of aquaculture and restocking is not 

 feasible and probably could not be justified. 

 However, other locations, particularly those closer 

 to the center of adult and larval concentrations, 

 such as the Bahia Sebastian Vizcaino-Isla Cedros 

 area off Baja California (Figure 9), should be 

 investigated as potential sites for such large-scale 

 collecting operations, as well as for purposes of 

 locating the primary areas of puerulus settle- 

 ment. 



It also seems reasonable that the habitat trap 

 collecting system developed in this study, if stan- 

 dardized and employed on a wider geographic 

 scale, could prove useful for monitoring fluctua- 

 tions in year class recruitment of pueruli, and 

 thereby provide a means of predicting fluctuations 

 in the size of the demersal population in following 

 years. For example, an extension of our study by 

 Parker (1972) during the years 1970-71 indicates 

 that puerulus settlement at the Scripps Institution 

 pier was much less than we observed during the 

 same months in 1969. If this reduced recruitment 

 was representative of a wider geographic area, 

 then the size of the adult population available to 

 the commercial fishery within the succeeding 5-8 

 yr might be expected to show corresponding 

 changes. 



SUMMARY 



Basic ecological and behavioral information was 

 obtained about the recruitment process, habitat 



preferences, and general abundance of the 

 puerulus larval stage of Panulirus interruptus. 



Pueruli of P. interruptus exhibit a strong posi- 

 tive phototactic response, and could be lured to a 

 bright underwater night-light from the surface 

 water surrounding the Scripps Institution of 

 Oceanography pier. 



Direct observations of free swimming pueruli 

 by this method demonstrated that this stage is 

 typically pelagic rather than benthic, and swims at 

 the surface in a continuous and directed manner. 

 Estimates of swimming speed were obtained. 



The surface swimming behavior of this stage 

 indicates that it probably can be properly sampled 

 quantitatively only by large nets towed horizon- 

 tally at the surface. This may explain why few 

 pueruli have been taken by other conventional 

 sampling methods. Paired neuston nets were 

 developed specifically for this purpose and pueruli 

 seemed to be sampled effectively in this manner 

 during preliminary evaluations. 



Puerulus larvae also were collected effectively 

 in floating habitat traps containing the surfgrass, 

 Phyllospadix torreyi. A variety of natural seaweed 

 habitat trap designs were tested, and all appeared 

 to be about equally effective in collecting pueruli; 

 however, a nylon bag habitat trap proved best in 

 terms of cost and durability. All natural seaweed 

 habitat traps were markedly superior in collecting 

 pueruli compared to the Witham habitat trap 

 design, formed of synthetic fibrous material. 



Habitat traps maintained under the lighted end 

 of Scripps Institution pier collected many more 

 pueruli than those not subject to such artificial 

 illumination. The failure of habitat traps placed 

 offshore to collect any pueruli may have been due 

 to the availability of abundant seaweed flotsam in 

 the areas where they were maintained, as well as 

 lack of artificial illumination. Both the presence of 

 intertidal plants (particularly Phyllospadix) and 

 nocturnal illumination appear to play significant 

 roles in the settlement of puerulus larvae in habi- 

 tat traps. 



The results of night-lighting and habitat trap 

 sampling indicate that off San Diego, Calif., the 

 seasonal influx and settlement of puerulus larvae 

 is continuous, beginning in May and ending in 

 September. 



Estimates based on a comparison of the peak 

 periods of abundance for pueruli and the preced- 

 ing final phyllosoma larval stage suggest that the 

 puerulus stage of P. interruptus has a duration of 

 approximately 2V2 mo. This is followed by 



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