FISHERY BULLETIN: VOL. 80. NO. 4 



the behavior of males than females, but no dis- 

 turbance was noted if the observer moved no 

 closer than about 4-8 m. Only during early 

 phases of the spawning rush would rapid move- 

 ments by a diver cause the female to abort the 

 spawning rush. Once the spawning rush had 

 reached an advanced point, however, the obser- 

 ver could approach quickly without interrupt- 

 ing. Fish frequently observed seemed to become 

 accustomed to the observers. 



Motion pictures (16 mm) were made of differ- 

 ent aspects of spawning behavior. These were 

 analyzed frame-by-frame to determine the dura- 

 tion of each act and the orientation of the fish 

 during the rapid spawning rush. 



Collection and Rearing of Eggs 



Eggs were collected with fine mesh dip nets 

 (sold as "brine shrimp nets") 10 by 15 cm with 

 mesh openings of about 100 ju in diameter. After 

 some practice, an observer could follow a pair on 

 their spawning run and quickly locate the dif- 

 fuse cloud of gametes when they were released. 

 The cloud was either constantly observed or 

 squirted with ink mixed with seawater from a 

 plastic bottle to provide a reference mark. About 

 45 s to 1 min were needed to assure fertilization. 

 After that time, eggs were collected by passing 

 the net through the water where the eggs oc- 

 curred. In one smooth motion, the net was then 

 everted into a plastic bag and the bag was filled 

 with water from the area where the gametes 

 occurred, in hope of obtaining more sperm in the 

 water and thereby increasing the chances of fer- 

 tilization. Eggs collected before 45 s had elapsed 

 generally were not fertile. Since the ability to see 

 the cloud of gametes decreases with each second, 

 the collection of planktonic eggs with a small 

 hand net is a contest between the time required 

 for fertilization and the ability of the collector to 

 discern the location of the eggs. Although the ink 

 helps to locate the eggs, it quickly disperses or 

 tends to rise or sink because of the differences in 

 density. I found it valuable to remain about 0.5- 

 1.0 m away from the cloud, once it had been 

 located, and focus on sediment particles, opaque 

 eggs, or larger zooplankton rather than trying to 

 follow the rapidly dispersing cloud. If the bag is 

 clear plastic, the eggs, once inside, can be seen 

 easily. It helps to face the sun (underwater) and 

 backlight the eggs by blocking out the sun di- 

 rectly to the eyes with a hand behind the bag. 



The eggs in the bags were transported to the 



laboratory in buckets partially filled with sea- 

 water, and were released into aerated closed- 

 circuit 80 1 aquaria within about 90 min of being 

 collected. Rearing methods followed Houde and 

 Tanaguchi (1977). The aquarium was constantly 

 illuminated by a twin 20-watt fluorescent lamp. 

 A culture of Chlorella was introduced at hatch- 

 ing. Later larvae were fed wild zooplankton col- 

 lected with 53 n mesh nets. Temperatures were 

 maintained at 25°-27°C. 



Selected eggs and larvae were preserved in 3% 

 Formalin 2 . Larvae were illustrated from pre- 

 served specimens by a camera lucida attachment 

 on a dissecting microscope. 



The Study Site 



The study site was located on the insular shelf 

 edge 16 km ESE of La Parguera, Puerto Rico 

 (approximate position: lat. 17°54'N, long. 

 66°57'W). It is typical of most reefs off the south 

 coast of Puerto Rico and the Virgin Islands (Mac- 

 Intyre 1972; Adey et al. 1977). It is an elevated 

 ridge about 100-150 m wide, paralleling the 

 actual shelf break, and has a rocky substrate 

 with abundant coral, particularly on the sea- 

 ward and inshore flanks. Minimum depth is 

 about 16 m. Near the study area the seaward por- 

 tion slopes gently to about 18-19 m depth, then 

 plunges downward at an angle of about 60° to 

 oceanic depths. The inshore side slopes down- 

 ward at about 10° until it meets a nearly level 

 sandy-rubble plain. This slope, termed the "moat 

 slope," is where most spawning activity by L. 

 maximus was observed. 



Water temperatures varied between 24° and 

 27°C, visibility between 50 and 10 m. The area is 

 within the trade wind belt of the Atlantic tropics 

 and is consistently exposed to easterly winds of 

 moderate force (Glynn 1973). Waves usually con- 

 sisted of a small wind produced chop associated 

 with larger swells. Wave heights of 1-2 m were 

 common, but seldom exceeded 2 m. Complete 

 calms would occasionally occur, most often dur- 

 ing winter. These calms were associated with 

 lee-shore conditions on the southwestern coast 

 and occurred only a few percent of the time. Cur- 

 rents were generally east to west, paralleling the 

 shelf edge, but occasionally they were completely 

 reversed or ran strongly off or onto the shelf. 

 Clearest water occurred when strong southeast- 



-Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



854 



