LABORATORY STUDY OF BEHAVIORAL INTERACTIONS BETWEEN 



THE AMERICAN LOBSTER, HOMARUS AMERICANUS, AND 



THE CALIFORNIA SPINY LOBSTER, PANULIRUS INTERRUPTUS, 



WITH COMPARATIVE OBSERVATIONS ON 



THE ROCK CRAB, CANCER ANTENNARIUS^ 



C. O'Neil Krekorian, David C. Sommerville, and Richard F. Ford^ 



ABSTRACT 



Behavioral interactions between Homarus americanus and Panulirus interruptus, with comparative 

 observations on Cancer antennarius, were studied in order to determine the possible effects an 

 introduced population of H. americanus would have on the southern California population of 

 P. interruptus. Subjects were placed in tanks 3 m in diameter with observational windows 

 equally spaced around the tank perimeter. Three 30-min observation periods were conducted on the 

 lobsters each day for a 5-day precontrol period (H. americanus absent), a 10-day experimental period 

 (H. americanus present), and a 5-day postcontrol period (H. americanus absent). Five replicates 

 of a shelter and no shelter condition were made with five naive P. interruptus and one//, americanus 

 for each replicate. Agonistic action patterns were recorded for actors and reactors, along with various 

 other behaviors, on data sheets partitioned into 1-min intervals. A large percentage of Homarus- 

 initiated behavioral actions in the shelter (44%) and no shelter (39%) conditions involved threat 

 and attack by H. americanus. In //omarus-initiated interactions, P. interruptus was displaced by 

 H. americanus 61% of the time in the shelter condition and 63% of the time in the no shelter 

 condition. Although Panii/irws-initiated interactions occurred much less frequently, the results were 

 similar to the //omarus- initiated interactions in that P. interruptus was ultimately displaced by 

 threatening and attacking//, americanus 92% of the time in the shelter condition and 76% of the time 

 in the no shelter condition. Our results, and those of other studies, are discussed with respect to the 

 potential adverse effects of introducing//, americanus into southern California waters. The evidence 

 suggests that such an introduction is inadvisable. 



At the present time, there is strong interest from 

 the private sector in introducing the American 

 lobster, Homarus americanus, into California 

 waters. This interest arises primarily from the 

 marked downward trend in annual landings of 

 the California spiny lobster, Panulirus inter- 

 ruptus, and the high unit value and continuing 

 demand for lobster species in general and in 

 particular for the American lobster, which 

 supports one of the most valuable fisheries in 

 North America. Conditions along the entire 

 California coast appear well within the limits 

 tolerated by larvae, juveniles, and adults of H. 

 americanus. Thus, with the recent development of 

 successful mass culture techniques (Hughes, 

 1968; Ghelardi and Shoop, 1968; Kensler, 1970), 



'This work is a result of research sponsored by the National 

 Oceanic and Atmospheric Administration Office of Sea Grant, 

 U.S. Department of Commerce, under Grants No. USDC 

 2-35208 and USDC 04-3-158-22. 



^Biological Sciences, San Diego State University, San Diego, 

 CA 92115. 



the species probably could be established, at 

 least by means of continued stocking (Ghelardi 

 and Shoop, 1972). 



Despite the apparent value of the American 

 lobster as a Pacific Coast fishery, there are 

 several potential detrimental effects of intro- 

 ducing it into the Pacific which must be considered 

 (Rathbun, 1888; Ghelardi, 1967). These are: 1) the 

 introduction of disease, parasitic organisms, or 

 other microfauna and microflora harmful to 

 native species and 2) the elimination or reduc- 

 tion in abundance of ecologically similar forms, 

 such as P. interruptus, in areas where//, ameri- 

 canus might become established. 



Introductions of some foreign animals and ~ 

 plants have had very serious effects on native 

 species (Elton, 1958). Thus, there is a great need 

 for effective evaluation and control of exotic 

 species introductions, as recently discussed by 

 Lachner, Robins, and Courtenay (1970). There 

 have been at least 23 attempts to introduce 



Manuscript accepted December 1973. 

 FISHERY BULLETIN: VOL. 72, NO. 4, 1974. 



1146 



