FISHERY BULLETIN: VOL. 73, NO. 2 



stage prompted the development of novel equip- 

 ment and techniques. These included underwater 

 night-lights of high intensity, floating artificial 

 and natural seaweed habitat traps, and a special 

 paired neuston net, which are described in the 

 following sections. 



Underwater Night-Lights 



Most of the night-light observations and collec- 

 tions were made from an adjustable ladder plat- 

 form near the end of the Scripps Institution pier, 

 at the position shown in Figure 1, under a variety 

 of environmental conditions. A standard motion 

 picture projection lamp of either 500 or 1,000 W 

 was waterproofed at the electrical connection with 

 silicone sealant. The light was mounted on a pole 

 and lowered 30-50 cm below the surface. This unit 

 illuminated a spherical area 5-8 m in diameter, 

 depending on water turbidity. When suspended in 

 this way it provided much greater illumination 

 than when suspended just above the surface. 

 Pueruli attracted to the light were removed with a 

 dip net and maintained alive for further studies. 



PACIFIC OCEAN 



HABITAT 

 POSITIONS 



-SHORE 



UNLIGHTEO 



^' V-' '■■»- 



T< y 



SCRIPPS INST PIER 



■300M- 



NIGHT-LIGHT -^ 



OBSERVATION AREA 



AREA ILLUMINATED' 

 BY PIER LIGHTS 



Figure l.-Standard positions of puerulus habitat traps placed 

 on the Scripps Institution pier, and the position from which 

 night-light observations and collections of pueruli were made. 



several models of the "Witham" habitat design 

 used by Witham et al. (1968) for collecting P. argus 

 pueruli (Figure 2C). This trap was constructed of a 

 synthetic fibrous material labeled "Conservation 

 Web #200," manufactured by Minnesota 

 Manufacturing and Mining Company.' The traps 

 we developed and tested consisted of wood frames 

 which contained either synthetic materials, e.g., 

 burlap, foam rubber, nylon mop, and plastic screen 

 and netting, or fresh natural seaweeds, held 

 within either plastic cage sides (Figure 2A, B), or 

 within net bags or wire screen (Figure 2D, E). 



Seaweed Habitat Traps 



Pueruli placed in aquaria quickly settled and 

 remained hidden in a variety of intertidal rock and 

 plant substrates, but showed a preference for the 

 surf grass Phyllospadix torreyi. They would con- 

 tinue to cling to any of these substrates, even 

 when removed from the water. In an attempt to 

 take advantage of this behavior, a variety of con- 

 tainers (Figure 2) for holding Phyllospadix and 

 various species of red algae were floated under the 

 lighted end of the Scripps Institution pier at the 

 positions shown in Figure 1. The pier lights (three 

 200 W incandescent flood lamps mounted 

 approximately 15 m above the water) apparently 

 attracted pueruli to the pier, and the seaweed 

 habitat traps provided convenient refuges in 

 which they settled. The traps were retrieved and 

 examined for pueruli every 4-6 days, providing a 

 standard sampling system which could be operat- 

 ed continuously. The same types of habitat traps 

 were also maintained on buoyed lines at several 

 coastal locations in water 3-30 m deep, as discussed 

 in a later section. 



A variety of natural and artificial seaweed 

 habitat trap designs, shown in Figure 2, were 

 tested initially to develop a type most suitable for 

 attracting pueruli. Included in the evaluation were 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



WITHAM 



DOUBLE FRAME 



SINGLE FRAME 



SCRKKN 



Figure 2.— Floating habitat trap designs employed in sampling 

 puerulus larvae of Panulirus interruptus. 



362 



