EFFECTS OF EXPOSURE AND CONFINEMENT ON 

 SPINY LOBSTERS, PANULIRUS ARGUS, USED AS ATTRACTANTS 



IN THE FLORIDA TRAP FISHERY 



John H. Hunt, 1 William G. Lyons, 2 and Frank S. Kennedy, Jr. 2 



ABSTRACT 



Traps in the south Florida spiny lobster fishery are baited with live sublegal-sized lobsters (shorts), many 

 of which are exposed for considerable periods aboard vessels before being placed in traps and returned 

 to the sea. Average mortality rate of lobsters exposed Vz, 1, 2, and 4 hours in controlled field tests was 

 26.3% after 4 weeks of confinement. About 42% of observed mortality occurred within 1 week after ex- 

 posure, indicating exposure to be a primary cause of death. Neither air temperature during exposure 

 nor periodic dampening with seawater had significant effects on mortality rate Mortality among confin- 

 ed lobsters increased markedly in the Atlantic oceanside but not in Florida Bay during the fourth week 

 of confinement following exposure, probably because more natural food organisms entering traps from 

 nearby seagrass beds delayed starvation at the latter site. Mortality caused by baiting traps with shorts 

 may produce economic losses in dockside landings estimated to range from $1.5 to $9.0 million annually. 



The fishery for spiny lobster, Panulirus argus, in 

 south Florida utilizes a method of baiting traps that 

 is apparently unique among fisheries worldwide 

 Sublegal [<76 mm carapace length (CL)] lobsters, 

 locally called "shorts", are confined in traps as living 

 attractants for legal-sized lobsters. Shorts have been 

 demonstrated to be effective attractants of other 

 lobsters (Yang and Obert 1978; Lyons and Kennedy 

 1981; Kennedy 1982). Some use of shorts as bait 

 in the Florida fishery occurred as early as the 1950's 

 (Cope 1959), but use increased appreciably after 

 1965 when the minimum legal size was reduced from 

 1 lb (about 79-80 mm CL) to 3 in (76 mm) CL, 

 and the fishery expanded from Atlantic oceanside 

 reefs and flats into Florida Bay where availability 

 of shorts is considerably greater (Lyons et al. 1981). 

 The practice was widespread but illegal during 

 early years of its use (Wolff erts 1974) and only 

 received legal sanction in 1977. Today, bonded 

 fishermen are allowed to possess as many as 200 

 shorts aboard a vessel for use as bait. Shorts are 

 customarily kept in wooden boxes on deck until 

 replaced in traps, and exposure times vary from 

 several minutes to 1 h or more As many as 1 million 

 shorts may be confined in traps as bait during peak 

 portions of the harvest season (Lyons and Kennedy 

 1981). 



'Florida Department of Natural Resources, Bureau of Marine 

 Research, Marathon, FL 33050. 



2 Florida Department of Natural Resources, Bureau of Marine 

 Research, St. Petersburg, FL 33701. 



During 1979, the Florida Department of Natural 

 Resources initiated a study in which baiting prac- 

 tices in the fishery were mimicked under controlled 

 conditions to determine whether starvation occurred 

 among lobsters confined in traps for long periods. 

 So much mortality occurred among tested lobsters 

 during the first 2 wk of confinement that the study 

 was redirected toward causes of that mortality. Ex- 

 posure was strongly implicated by preliminary 

 results (Lyons and Kennedy 1981). Spokesmen for 

 the fishing industry suggested that observed mor- 

 tality was caused by other factors related to ex- 

 perimental design, prompting expansion of the pro- 

 gram to test those factors. 



This report presents results and conclusions from 

 that expanded program. The relationship between 

 exposure and mortality is examined, including in- 

 fluences of season and location. Mortality rates of 

 lobsters held dry or periodically dampened prior to 

 placement in traps are also compared. Results from 

 this study are used in a model which estimates the 

 relative importance of baiting mortality to economics 

 of the fishery. 



METHODS 



Mortality rates of spiny lobsters used to bait traps 

 were measured in Florida Bay 3 km north of Vaca 

 Key and in the Atlantic Ocean 6 km south of Vaca 

 Key. The Florida Bay site was located in shallow 

 water (~3 m) with a muddy sand substrate overlain 

 by seagrass beds. The ocean site was located in 



Manuscript accepted March 1985. 



FISHERY BULLETIN: VOL. 84, NO. 1. 1986. 



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