FISHERY BULLETIN. VOL. 78, NO. 4 



Impact of Blacksmith Foraging 



Most of the food consumed by blacksmith comes 

 from outside the reef community. Blacksmith 

 diets, of course, depend on the composition of 

 the plankton, but consist largely of larvaceans, 

 cladocerans, and copepods. The same items dom- 

 inate the diet of blacksmith off Santa Catalina 

 Island (Hobson and Chess 1976). Some copepods 

 may be members of the reef community (as dis- 

 cussed above), but the small calanoids in the 

 blacksmith's diet are more likely a part of the drift 

 plankton; residential forms probably would not 

 occur during the day in the exposed, current-swept 

 midwater areas of the incurrent end of the reef. 



Too little is known about the total population 

 and daily food consumption of blacksmith, and 

 about the amount of plankton that passes over the 

 reef, to accurately assess the effect of blacksmith 

 foraging on incoming zooplankton. However, sev- 

 eral lines of evidence indicate that blacksmith are 

 major predators. The dominant items in their 

 diets are those that showed the greatest decrease 

 in abundance. Also, individual blacksmith con- 

 sume a large amount of food each day. The guts of 

 blacksmith are empty at dawn (Hobson and Chess 

 1976; Bray unpubl. data), so guts of individuals 

 collected at dusk contain food that was consumed 

 that day. The number of plankters in the stomach 

 of 14 blacksmith (124-178 mm SL) that were 

 speared as they sheltered at dusk averaged 1,455 

 items, 957c of which were larvaceans and small 

 copepods. And these data underestimate the total 

 number consumed. They exclude intestinal items, 

 even though these largely unidentifiable remains 

 weighed an average of 2.2 times the contents of 

 the stomach, and they ignore items evacuated 

 before dusk. Thus, considering that blacksmith 

 composed over 42% of the 7,800 fish tallied, I 

 conclude along with Limbaugh (1955) that they 

 materially affect the plankton that is swept across 

 southern California kelp beds. 



ACKNOWLEDGMENTS 



I thank Alfred Ebeling for his guidance and 

 support throughout this project. Many people 

 generously assisted me in the field, but I especially 

 appreciate the help of Jeff Bovee and Philippe 

 Vigneaud. Discussions with Tom Bailey and Ralph 

 Larson provided many ideas. Norm Lammer and 

 Jack Kisch kept the boats running. Larry Leamy 

 helped with the statistics, and Laurie Farmer, 



Esther Escandon, and Michelle Smith assisted in 

 gut analyses and preparation of the final manu- 

 script. Alice Alldredge, Joseph Connell, and 

 Michael Neushul offered excellent suggestions 

 during the project and, along with Edmund Hob- 

 son and an anonymous referee, critically reviewed 

 earlier drafts. Finally, I thank my wife, Cindy, for 

 her help, encouragement, and tolerance. Finan- 

 cial support was provided by NOAA, Office of Sea 

 Grant, Department of Commerce, under grants 

 2-35208-6 and 04-3-158-22 (Project R-FA-14), by 

 NSF grants GA 38588 and OCE 76-23301, and Sea 

 Grants GH 43 and GH 95, all to Alfred Ebeling. 

 Additional funding at the University of Califor- 

 nia, Santa Barbara, was provided by Henry Offen, 

 Director of the Marine Science Institute. 



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